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https://github.com/c64scene-ar/llvm-6502.git
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c2945e44d5
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164090 91177308-0d34-0410-b5e6-96231b3b80d8
4218 lines
149 KiB
C++
4218 lines
149 KiB
C++
//===- ObjCARC.cpp - ObjC ARC Optimization --------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines ObjC ARC optimizations. ARC stands for
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// Automatic Reference Counting and is a system for managing reference counts
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// for objects in Objective C.
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//
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// The optimizations performed include elimination of redundant, partially
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// redundant, and inconsequential reference count operations, elimination of
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// redundant weak pointer operations, pattern-matching and replacement of
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// low-level operations into higher-level operations, and numerous minor
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// simplifications.
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//
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// This file also defines a simple ARC-aware AliasAnalysis.
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//
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// WARNING: This file knows about certain library functions. It recognizes them
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// by name, and hardwires knowledge of their semantics.
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//
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// WARNING: This file knows about how certain Objective-C library functions are
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// used. Naive LLVM IR transformations which would otherwise be
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// behavior-preserving may break these assumptions.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "objc-arc"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/ADT/DenseMap.h"
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using namespace llvm;
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// A handy option to enable/disable all optimizations in this file.
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static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
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//===----------------------------------------------------------------------===//
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// Misc. Utilities
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//===----------------------------------------------------------------------===//
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namespace {
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/// MapVector - An associative container with fast insertion-order
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/// (deterministic) iteration over its elements. Plus the special
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/// blot operation.
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template<class KeyT, class ValueT>
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class MapVector {
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/// Map - Map keys to indices in Vector.
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typedef DenseMap<KeyT, size_t> MapTy;
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MapTy Map;
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/// Vector - Keys and values.
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typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
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VectorTy Vector;
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public:
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typedef typename VectorTy::iterator iterator;
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typedef typename VectorTy::const_iterator const_iterator;
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iterator begin() { return Vector.begin(); }
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iterator end() { return Vector.end(); }
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const_iterator begin() const { return Vector.begin(); }
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const_iterator end() const { return Vector.end(); }
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#ifdef XDEBUG
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~MapVector() {
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assert(Vector.size() >= Map.size()); // May differ due to blotting.
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for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
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I != E; ++I) {
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assert(I->second < Vector.size());
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assert(Vector[I->second].first == I->first);
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}
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for (typename VectorTy::const_iterator I = Vector.begin(),
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E = Vector.end(); I != E; ++I)
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assert(!I->first ||
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(Map.count(I->first) &&
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Map[I->first] == size_t(I - Vector.begin())));
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}
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#endif
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ValueT &operator[](const KeyT &Arg) {
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std::pair<typename MapTy::iterator, bool> Pair =
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Map.insert(std::make_pair(Arg, size_t(0)));
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if (Pair.second) {
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size_t Num = Vector.size();
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Pair.first->second = Num;
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Vector.push_back(std::make_pair(Arg, ValueT()));
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return Vector[Num].second;
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}
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return Vector[Pair.first->second].second;
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}
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std::pair<iterator, bool>
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insert(const std::pair<KeyT, ValueT> &InsertPair) {
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std::pair<typename MapTy::iterator, bool> Pair =
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Map.insert(std::make_pair(InsertPair.first, size_t(0)));
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if (Pair.second) {
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size_t Num = Vector.size();
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Pair.first->second = Num;
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Vector.push_back(InsertPair);
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return std::make_pair(Vector.begin() + Num, true);
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}
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return std::make_pair(Vector.begin() + Pair.first->second, false);
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}
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const_iterator find(const KeyT &Key) const {
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typename MapTy::const_iterator It = Map.find(Key);
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if (It == Map.end()) return Vector.end();
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return Vector.begin() + It->second;
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}
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/// blot - This is similar to erase, but instead of removing the element
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/// from the vector, it just zeros out the key in the vector. This leaves
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/// iterators intact, but clients must be prepared for zeroed-out keys when
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/// iterating.
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void blot(const KeyT &Key) {
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typename MapTy::iterator It = Map.find(Key);
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if (It == Map.end()) return;
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Vector[It->second].first = KeyT();
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Map.erase(It);
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}
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void clear() {
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Map.clear();
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Vector.clear();
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}
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};
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}
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//===----------------------------------------------------------------------===//
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// ARC Utilities.
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//===----------------------------------------------------------------------===//
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#include "llvm/Intrinsics.h"
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#include "llvm/Module.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/ADT/StringSwitch.h"
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namespace {
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/// InstructionClass - A simple classification for instructions.
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enum InstructionClass {
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IC_Retain, ///< objc_retain
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IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
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IC_RetainBlock, ///< objc_retainBlock
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IC_Release, ///< objc_release
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IC_Autorelease, ///< objc_autorelease
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IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
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IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
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IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
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IC_NoopCast, ///< objc_retainedObject, etc.
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IC_FusedRetainAutorelease, ///< objc_retainAutorelease
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IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
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IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
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IC_StoreWeak, ///< objc_storeWeak (primitive)
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IC_InitWeak, ///< objc_initWeak (derived)
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IC_LoadWeak, ///< objc_loadWeak (derived)
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IC_MoveWeak, ///< objc_moveWeak (derived)
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IC_CopyWeak, ///< objc_copyWeak (derived)
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IC_DestroyWeak, ///< objc_destroyWeak (derived)
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IC_StoreStrong, ///< objc_storeStrong (derived)
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IC_CallOrUser, ///< could call objc_release and/or "use" pointers
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IC_Call, ///< could call objc_release
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IC_User, ///< could "use" a pointer
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IC_None ///< anything else
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};
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}
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/// IsPotentialUse - Test whether the given value is possible a
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/// reference-counted pointer.
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static bool IsPotentialUse(const Value *Op) {
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// Pointers to static or stack storage are not reference-counted pointers.
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if (isa<Constant>(Op) || isa<AllocaInst>(Op))
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return false;
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// Special arguments are not reference-counted.
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if (const Argument *Arg = dyn_cast<Argument>(Op))
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if (Arg->hasByValAttr() ||
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Arg->hasNestAttr() ||
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Arg->hasStructRetAttr())
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return false;
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// Only consider values with pointer types.
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// It seemes intuitive to exclude function pointer types as well, since
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// functions are never reference-counted, however clang occasionally
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// bitcasts reference-counted pointers to function-pointer type
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// temporarily.
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PointerType *Ty = dyn_cast<PointerType>(Op->getType());
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if (!Ty)
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return false;
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// Conservatively assume anything else is a potential use.
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return true;
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}
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/// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind
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/// of construct CS is.
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static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
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for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
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I != E; ++I)
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if (IsPotentialUse(*I))
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return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
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return CS.onlyReadsMemory() ? IC_None : IC_Call;
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}
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/// GetFunctionClass - Determine if F is one of the special known Functions.
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/// If it isn't, return IC_CallOrUser.
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static InstructionClass GetFunctionClass(const Function *F) {
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Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
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// No arguments.
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if (AI == AE)
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return StringSwitch<InstructionClass>(F->getName())
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.Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
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.Default(IC_CallOrUser);
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// One argument.
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const Argument *A0 = AI++;
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if (AI == AE)
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// Argument is a pointer.
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if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
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Type *ETy = PTy->getElementType();
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// Argument is i8*.
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if (ETy->isIntegerTy(8))
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return StringSwitch<InstructionClass>(F->getName())
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.Case("objc_retain", IC_Retain)
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.Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
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.Case("objc_retainBlock", IC_RetainBlock)
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.Case("objc_release", IC_Release)
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.Case("objc_autorelease", IC_Autorelease)
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.Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
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.Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
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.Case("objc_retainedObject", IC_NoopCast)
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.Case("objc_unretainedObject", IC_NoopCast)
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.Case("objc_unretainedPointer", IC_NoopCast)
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.Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
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.Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
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.Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
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.Default(IC_CallOrUser);
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// Argument is i8**
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if (PointerType *Pte = dyn_cast<PointerType>(ETy))
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if (Pte->getElementType()->isIntegerTy(8))
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return StringSwitch<InstructionClass>(F->getName())
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.Case("objc_loadWeakRetained", IC_LoadWeakRetained)
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.Case("objc_loadWeak", IC_LoadWeak)
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.Case("objc_destroyWeak", IC_DestroyWeak)
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.Default(IC_CallOrUser);
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}
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// Two arguments, first is i8**.
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const Argument *A1 = AI++;
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if (AI == AE)
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if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
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if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
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if (Pte->getElementType()->isIntegerTy(8))
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if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
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Type *ETy1 = PTy1->getElementType();
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// Second argument is i8*
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if (ETy1->isIntegerTy(8))
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return StringSwitch<InstructionClass>(F->getName())
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.Case("objc_storeWeak", IC_StoreWeak)
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.Case("objc_initWeak", IC_InitWeak)
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.Case("objc_storeStrong", IC_StoreStrong)
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.Default(IC_CallOrUser);
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// Second argument is i8**.
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if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
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if (Pte1->getElementType()->isIntegerTy(8))
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return StringSwitch<InstructionClass>(F->getName())
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.Case("objc_moveWeak", IC_MoveWeak)
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.Case("objc_copyWeak", IC_CopyWeak)
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.Default(IC_CallOrUser);
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}
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// Anything else.
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return IC_CallOrUser;
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}
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/// GetInstructionClass - Determine what kind of construct V is.
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static InstructionClass GetInstructionClass(const Value *V) {
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if (const Instruction *I = dyn_cast<Instruction>(V)) {
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// Any instruction other than bitcast and gep with a pointer operand have a
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// use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
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// to a subsequent use, rather than using it themselves, in this sense.
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// As a short cut, several other opcodes are known to have no pointer
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// operands of interest. And ret is never followed by a release, so it's
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// not interesting to examine.
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switch (I->getOpcode()) {
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case Instruction::Call: {
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const CallInst *CI = cast<CallInst>(I);
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// Check for calls to special functions.
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if (const Function *F = CI->getCalledFunction()) {
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InstructionClass Class = GetFunctionClass(F);
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if (Class != IC_CallOrUser)
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return Class;
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// None of the intrinsic functions do objc_release. For intrinsics, the
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// only question is whether or not they may be users.
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switch (F->getIntrinsicID()) {
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case Intrinsic::returnaddress: case Intrinsic::frameaddress:
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case Intrinsic::stacksave: case Intrinsic::stackrestore:
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case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
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case Intrinsic::objectsize: case Intrinsic::prefetch:
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case Intrinsic::stackprotector:
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case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
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case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
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case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
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case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
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case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
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case Intrinsic::invariant_start: case Intrinsic::invariant_end:
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// Don't let dbg info affect our results.
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case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
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// Short cut: Some intrinsics obviously don't use ObjC pointers.
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return IC_None;
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default:
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break;
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}
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}
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return GetCallSiteClass(CI);
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}
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case Instruction::Invoke:
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return GetCallSiteClass(cast<InvokeInst>(I));
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case Instruction::BitCast:
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case Instruction::GetElementPtr:
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case Instruction::Select: case Instruction::PHI:
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case Instruction::Ret: case Instruction::Br:
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case Instruction::Switch: case Instruction::IndirectBr:
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case Instruction::Alloca: case Instruction::VAArg:
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case Instruction::Add: case Instruction::FAdd:
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case Instruction::Sub: case Instruction::FSub:
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case Instruction::Mul: case Instruction::FMul:
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case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
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case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
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case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
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case Instruction::And: case Instruction::Or: case Instruction::Xor:
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case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
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case Instruction::IntToPtr: case Instruction::FCmp:
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case Instruction::FPTrunc: case Instruction::FPExt:
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case Instruction::FPToUI: case Instruction::FPToSI:
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case Instruction::UIToFP: case Instruction::SIToFP:
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case Instruction::InsertElement: case Instruction::ExtractElement:
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case Instruction::ShuffleVector:
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case Instruction::ExtractValue:
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break;
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case Instruction::ICmp:
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// Comparing a pointer with null, or any other constant, isn't an
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// interesting use, because we don't care what the pointer points to, or
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// about the values of any other dynamic reference-counted pointers.
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if (IsPotentialUse(I->getOperand(1)))
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return IC_User;
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break;
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default:
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// For anything else, check all the operands.
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// Note that this includes both operands of a Store: while the first
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// operand isn't actually being dereferenced, it is being stored to
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// memory where we can no longer track who might read it and dereference
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// it, so we have to consider it potentially used.
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for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
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OI != OE; ++OI)
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if (IsPotentialUse(*OI))
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return IC_User;
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}
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}
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// Otherwise, it's totally inert for ARC purposes.
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return IC_None;
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}
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/// GetBasicInstructionClass - Determine what kind of construct V is. This is
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/// similar to GetInstructionClass except that it only detects objc runtine
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/// calls. This allows it to be faster.
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static InstructionClass GetBasicInstructionClass(const Value *V) {
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if (const CallInst *CI = dyn_cast<CallInst>(V)) {
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if (const Function *F = CI->getCalledFunction())
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return GetFunctionClass(F);
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// Otherwise, be conservative.
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return IC_CallOrUser;
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}
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// Otherwise, be conservative.
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return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
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}
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/// IsRetain - Test if the given class is objc_retain or
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/// equivalent.
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static bool IsRetain(InstructionClass Class) {
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return Class == IC_Retain ||
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Class == IC_RetainRV;
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}
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/// IsAutorelease - Test if the given class is objc_autorelease or
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/// equivalent.
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static bool IsAutorelease(InstructionClass Class) {
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return Class == IC_Autorelease ||
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Class == IC_AutoreleaseRV;
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}
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/// IsForwarding - Test if the given class represents instructions which return
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/// their argument verbatim.
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static bool IsForwarding(InstructionClass Class) {
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// objc_retainBlock technically doesn't always return its argument
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// verbatim, but it doesn't matter for our purposes here.
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return Class == IC_Retain ||
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Class == IC_RetainRV ||
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Class == IC_Autorelease ||
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Class == IC_AutoreleaseRV ||
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Class == IC_RetainBlock ||
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Class == IC_NoopCast;
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}
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/// IsNoopOnNull - Test if the given class represents instructions which do
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/// nothing if passed a null pointer.
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static bool IsNoopOnNull(InstructionClass Class) {
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return Class == IC_Retain ||
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Class == IC_RetainRV ||
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Class == IC_Release ||
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Class == IC_Autorelease ||
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Class == IC_AutoreleaseRV ||
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Class == IC_RetainBlock;
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}
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|
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/// IsAlwaysTail - Test if the given class represents instructions which are
|
|
/// always safe to mark with the "tail" keyword.
|
|
static bool IsAlwaysTail(InstructionClass Class) {
|
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// IC_RetainBlock may be given a stack argument.
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return Class == IC_Retain ||
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Class == IC_RetainRV ||
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Class == IC_Autorelease ||
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Class == IC_AutoreleaseRV;
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}
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/// IsNoThrow - Test if the given class represents instructions which are always
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/// safe to mark with the nounwind attribute..
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static bool IsNoThrow(InstructionClass Class) {
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// objc_retainBlock is not nounwind because it calls user copy constructors
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// which could theoretically throw.
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return Class == IC_Retain ||
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Class == IC_RetainRV ||
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Class == IC_Release ||
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Class == IC_Autorelease ||
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Class == IC_AutoreleaseRV ||
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Class == IC_AutoreleasepoolPush ||
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Class == IC_AutoreleasepoolPop;
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}
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|
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/// EraseInstruction - Erase the given instruction. Many ObjC calls return their
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/// argument verbatim, so if it's such a call and the return value has users,
|
|
/// replace them with the argument value.
|
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static void EraseInstruction(Instruction *CI) {
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Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
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bool Unused = CI->use_empty();
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if (!Unused) {
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// Replace the return value with the argument.
|
|
assert(IsForwarding(GetBasicInstructionClass(CI)) &&
|
|
"Can't delete non-forwarding instruction with users!");
|
|
CI->replaceAllUsesWith(OldArg);
|
|
}
|
|
|
|
CI->eraseFromParent();
|
|
|
|
if (Unused)
|
|
RecursivelyDeleteTriviallyDeadInstructions(OldArg);
|
|
}
|
|
|
|
/// GetUnderlyingObjCPtr - This is a wrapper around getUnderlyingObject which
|
|
/// also knows how to look through objc_retain and objc_autorelease calls, which
|
|
/// we know to return their argument verbatim.
|
|
static const Value *GetUnderlyingObjCPtr(const Value *V) {
|
|
for (;;) {
|
|
V = GetUnderlyingObject(V);
|
|
if (!IsForwarding(GetBasicInstructionClass(V)))
|
|
break;
|
|
V = cast<CallInst>(V)->getArgOperand(0);
|
|
}
|
|
|
|
return V;
|
|
}
|
|
|
|
/// StripPointerCastsAndObjCCalls - This is a wrapper around
|
|
/// Value::stripPointerCasts which also knows how to look through objc_retain
|
|
/// and objc_autorelease calls, which we know to return their argument verbatim.
|
|
static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
|
|
for (;;) {
|
|
V = V->stripPointerCasts();
|
|
if (!IsForwarding(GetBasicInstructionClass(V)))
|
|
break;
|
|
V = cast<CallInst>(V)->getArgOperand(0);
|
|
}
|
|
return V;
|
|
}
|
|
|
|
/// StripPointerCastsAndObjCCalls - This is a wrapper around
|
|
/// Value::stripPointerCasts which also knows how to look through objc_retain
|
|
/// and objc_autorelease calls, which we know to return their argument verbatim.
|
|
static Value *StripPointerCastsAndObjCCalls(Value *V) {
|
|
for (;;) {
|
|
V = V->stripPointerCasts();
|
|
if (!IsForwarding(GetBasicInstructionClass(V)))
|
|
break;
|
|
V = cast<CallInst>(V)->getArgOperand(0);
|
|
}
|
|
return V;
|
|
}
|
|
|
|
/// GetObjCArg - Assuming the given instruction is one of the special calls such
|
|
/// as objc_retain or objc_release, return the argument value, stripped of no-op
|
|
/// casts and forwarding calls.
|
|
static Value *GetObjCArg(Value *Inst) {
|
|
return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
|
|
}
|
|
|
|
/// IsObjCIdentifiedObject - This is similar to AliasAnalysis'
|
|
/// isObjCIdentifiedObject, except that it uses special knowledge of
|
|
/// ObjC conventions...
|
|
static bool IsObjCIdentifiedObject(const Value *V) {
|
|
// Assume that call results and arguments have their own "provenance".
|
|
// Constants (including GlobalVariables) and Allocas are never
|
|
// reference-counted.
|
|
if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
|
|
isa<Argument>(V) || isa<Constant>(V) ||
|
|
isa<AllocaInst>(V))
|
|
return true;
|
|
|
|
if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
|
|
const Value *Pointer =
|
|
StripPointerCastsAndObjCCalls(LI->getPointerOperand());
|
|
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
|
|
// A constant pointer can't be pointing to an object on the heap. It may
|
|
// be reference-counted, but it won't be deleted.
|
|
if (GV->isConstant())
|
|
return true;
|
|
StringRef Name = GV->getName();
|
|
// These special variables are known to hold values which are not
|
|
// reference-counted pointers.
|
|
if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
|
|
Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
|
|
Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
|
|
Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
|
|
Name.startswith("\01l_objc_msgSend_fixup_"))
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// FindSingleUseIdentifiedObject - This is similar to
|
|
/// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value
|
|
/// with multiple uses.
|
|
static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
|
|
if (Arg->hasOneUse()) {
|
|
if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
|
|
return FindSingleUseIdentifiedObject(BC->getOperand(0));
|
|
if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
|
|
if (GEP->hasAllZeroIndices())
|
|
return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
|
|
if (IsForwarding(GetBasicInstructionClass(Arg)))
|
|
return FindSingleUseIdentifiedObject(
|
|
cast<CallInst>(Arg)->getArgOperand(0));
|
|
if (!IsObjCIdentifiedObject(Arg))
|
|
return 0;
|
|
return Arg;
|
|
}
|
|
|
|
// If we found an identifiable object but it has multiple uses, but they are
|
|
// trivial uses, we can still consider this to be a single-use value.
|
|
if (IsObjCIdentifiedObject(Arg)) {
|
|
for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
|
|
UI != UE; ++UI) {
|
|
const User *U = *UI;
|
|
if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
|
|
return 0;
|
|
}
|
|
|
|
return Arg;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// ModuleHasARC - Test if the given module looks interesting to run ARC
|
|
/// optimization on.
|
|
static bool ModuleHasARC(const Module &M) {
|
|
return
|
|
M.getNamedValue("objc_retain") ||
|
|
M.getNamedValue("objc_release") ||
|
|
M.getNamedValue("objc_autorelease") ||
|
|
M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
|
|
M.getNamedValue("objc_retainBlock") ||
|
|
M.getNamedValue("objc_autoreleaseReturnValue") ||
|
|
M.getNamedValue("objc_autoreleasePoolPush") ||
|
|
M.getNamedValue("objc_loadWeakRetained") ||
|
|
M.getNamedValue("objc_loadWeak") ||
|
|
M.getNamedValue("objc_destroyWeak") ||
|
|
M.getNamedValue("objc_storeWeak") ||
|
|
M.getNamedValue("objc_initWeak") ||
|
|
M.getNamedValue("objc_moveWeak") ||
|
|
M.getNamedValue("objc_copyWeak") ||
|
|
M.getNamedValue("objc_retainedObject") ||
|
|
M.getNamedValue("objc_unretainedObject") ||
|
|
M.getNamedValue("objc_unretainedPointer");
|
|
}
|
|
|
|
/// DoesObjCBlockEscape - Test whether the given pointer, which is an
|
|
/// Objective C block pointer, does not "escape". This differs from regular
|
|
/// escape analysis in that a use as an argument to a call is not considered
|
|
/// an escape.
|
|
static bool DoesObjCBlockEscape(const Value *BlockPtr) {
|
|
// Walk the def-use chains.
|
|
SmallVector<const Value *, 4> Worklist;
|
|
Worklist.push_back(BlockPtr);
|
|
do {
|
|
const Value *V = Worklist.pop_back_val();
|
|
for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
|
|
UI != UE; ++UI) {
|
|
const User *UUser = *UI;
|
|
// Special - Use by a call (callee or argument) is not considered
|
|
// to be an escape.
|
|
switch (GetBasicInstructionClass(UUser)) {
|
|
case IC_StoreWeak:
|
|
case IC_InitWeak:
|
|
case IC_StoreStrong:
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
// These special functions make copies of their pointer arguments.
|
|
return true;
|
|
case IC_User:
|
|
case IC_None:
|
|
// Use by an instruction which copies the value is an escape if the
|
|
// result is an escape.
|
|
if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
|
|
isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
|
|
Worklist.push_back(UUser);
|
|
continue;
|
|
}
|
|
// Use by a load is not an escape.
|
|
if (isa<LoadInst>(UUser))
|
|
continue;
|
|
// Use by a store is not an escape if the use is the address.
|
|
if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
|
|
if (V != SI->getValueOperand())
|
|
continue;
|
|
break;
|
|
default:
|
|
// Regular calls and other stuff are not considered escapes.
|
|
continue;
|
|
}
|
|
// Otherwise, conservatively assume an escape.
|
|
return true;
|
|
}
|
|
} while (!Worklist.empty());
|
|
|
|
// No escapes found.
|
|
return false;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ARC AliasAnalysis.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Analysis/Passes.h"
|
|
|
|
namespace {
|
|
/// ObjCARCAliasAnalysis - This is a simple alias analysis
|
|
/// implementation that uses knowledge of ARC constructs to answer queries.
|
|
///
|
|
/// TODO: This class could be generalized to know about other ObjC-specific
|
|
/// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
|
|
/// even though their offsets are dynamic.
|
|
class ObjCARCAliasAnalysis : public ImmutablePass,
|
|
public AliasAnalysis {
|
|
public:
|
|
static char ID; // Class identification, replacement for typeinfo
|
|
ObjCARCAliasAnalysis() : ImmutablePass(ID) {
|
|
initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
private:
|
|
virtual void initializePass() {
|
|
InitializeAliasAnalysis(this);
|
|
}
|
|
|
|
/// getAdjustedAnalysisPointer - This method is used when a pass implements
|
|
/// an analysis interface through multiple inheritance. If needed, it
|
|
/// should override this to adjust the this pointer as needed for the
|
|
/// specified pass info.
|
|
virtual void *getAdjustedAnalysisPointer(const void *PI) {
|
|
if (PI == &AliasAnalysis::ID)
|
|
return static_cast<AliasAnalysis *>(this);
|
|
return this;
|
|
}
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
virtual AliasResult alias(const Location &LocA, const Location &LocB);
|
|
virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
|
|
virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
|
|
virtual ModRefBehavior getModRefBehavior(const Function *F);
|
|
virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
|
|
const Location &Loc);
|
|
virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
|
|
ImmutableCallSite CS2);
|
|
};
|
|
} // End of anonymous namespace
|
|
|
|
// Register this pass...
|
|
char ObjCARCAliasAnalysis::ID = 0;
|
|
INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
|
|
"ObjC-ARC-Based Alias Analysis", false, true, false)
|
|
|
|
ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
|
|
return new ObjCARCAliasAnalysis();
|
|
}
|
|
|
|
void
|
|
ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesAll();
|
|
AliasAnalysis::getAnalysisUsage(AU);
|
|
}
|
|
|
|
AliasAnalysis::AliasResult
|
|
ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
|
|
if (!EnableARCOpts)
|
|
return AliasAnalysis::alias(LocA, LocB);
|
|
|
|
// First, strip off no-ops, including ObjC-specific no-ops, and try making a
|
|
// precise alias query.
|
|
const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
|
|
const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
|
|
AliasResult Result =
|
|
AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
|
|
Location(SB, LocB.Size, LocB.TBAATag));
|
|
if (Result != MayAlias)
|
|
return Result;
|
|
|
|
// If that failed, climb to the underlying object, including climbing through
|
|
// ObjC-specific no-ops, and try making an imprecise alias query.
|
|
const Value *UA = GetUnderlyingObjCPtr(SA);
|
|
const Value *UB = GetUnderlyingObjCPtr(SB);
|
|
if (UA != SA || UB != SB) {
|
|
Result = AliasAnalysis::alias(Location(UA), Location(UB));
|
|
// We can't use MustAlias or PartialAlias results here because
|
|
// GetUnderlyingObjCPtr may return an offsetted pointer value.
|
|
if (Result == NoAlias)
|
|
return NoAlias;
|
|
}
|
|
|
|
// If that failed, fail. We don't need to chain here, since that's covered
|
|
// by the earlier precise query.
|
|
return MayAlias;
|
|
}
|
|
|
|
bool
|
|
ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
|
|
bool OrLocal) {
|
|
if (!EnableARCOpts)
|
|
return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
|
|
|
|
// First, strip off no-ops, including ObjC-specific no-ops, and try making
|
|
// a precise alias query.
|
|
const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
|
|
if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
|
|
OrLocal))
|
|
return true;
|
|
|
|
// If that failed, climb to the underlying object, including climbing through
|
|
// ObjC-specific no-ops, and try making an imprecise alias query.
|
|
const Value *U = GetUnderlyingObjCPtr(S);
|
|
if (U != S)
|
|
return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
|
|
|
|
// If that failed, fail. We don't need to chain here, since that's covered
|
|
// by the earlier precise query.
|
|
return false;
|
|
}
|
|
|
|
AliasAnalysis::ModRefBehavior
|
|
ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
|
|
// We have nothing to do. Just chain to the next AliasAnalysis.
|
|
return AliasAnalysis::getModRefBehavior(CS);
|
|
}
|
|
|
|
AliasAnalysis::ModRefBehavior
|
|
ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
|
|
if (!EnableARCOpts)
|
|
return AliasAnalysis::getModRefBehavior(F);
|
|
|
|
switch (GetFunctionClass(F)) {
|
|
case IC_NoopCast:
|
|
return DoesNotAccessMemory;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return AliasAnalysis::getModRefBehavior(F);
|
|
}
|
|
|
|
AliasAnalysis::ModRefResult
|
|
ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
|
|
if (!EnableARCOpts)
|
|
return AliasAnalysis::getModRefInfo(CS, Loc);
|
|
|
|
switch (GetBasicInstructionClass(CS.getInstruction())) {
|
|
case IC_Retain:
|
|
case IC_RetainRV:
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
case IC_NoopCast:
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_FusedRetainAutorelease:
|
|
case IC_FusedRetainAutoreleaseRV:
|
|
// These functions don't access any memory visible to the compiler.
|
|
// Note that this doesn't include objc_retainBlock, because it updates
|
|
// pointers when it copies block data.
|
|
return NoModRef;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return AliasAnalysis::getModRefInfo(CS, Loc);
|
|
}
|
|
|
|
AliasAnalysis::ModRefResult
|
|
ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
|
|
ImmutableCallSite CS2) {
|
|
// TODO: Theoretically we could check for dependencies between objc_* calls
|
|
// and OnlyAccessesArgumentPointees calls or other well-behaved calls.
|
|
return AliasAnalysis::getModRefInfo(CS1, CS2);
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ARC expansion.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Support/InstIterator.h"
|
|
#include "llvm/Transforms/Scalar.h"
|
|
|
|
namespace {
|
|
/// ObjCARCExpand - Early ARC transformations.
|
|
class ObjCARCExpand : public FunctionPass {
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
virtual bool doInitialization(Module &M);
|
|
virtual bool runOnFunction(Function &F);
|
|
|
|
/// Run - A flag indicating whether this optimization pass should run.
|
|
bool Run;
|
|
|
|
public:
|
|
static char ID;
|
|
ObjCARCExpand() : FunctionPass(ID) {
|
|
initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
};
|
|
}
|
|
|
|
char ObjCARCExpand::ID = 0;
|
|
INITIALIZE_PASS(ObjCARCExpand,
|
|
"objc-arc-expand", "ObjC ARC expansion", false, false)
|
|
|
|
Pass *llvm::createObjCARCExpandPass() {
|
|
return new ObjCARCExpand();
|
|
}
|
|
|
|
void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesCFG();
|
|
}
|
|
|
|
bool ObjCARCExpand::doInitialization(Module &M) {
|
|
Run = ModuleHasARC(M);
|
|
return false;
|
|
}
|
|
|
|
bool ObjCARCExpand::runOnFunction(Function &F) {
|
|
if (!EnableARCOpts)
|
|
return false;
|
|
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
if (!Run)
|
|
return false;
|
|
|
|
bool Changed = false;
|
|
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
|
|
Instruction *Inst = &*I;
|
|
|
|
switch (GetBasicInstructionClass(Inst)) {
|
|
case IC_Retain:
|
|
case IC_RetainRV:
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
case IC_FusedRetainAutorelease:
|
|
case IC_FusedRetainAutoreleaseRV:
|
|
// These calls return their argument verbatim, as a low-level
|
|
// optimization. However, this makes high-level optimizations
|
|
// harder. Undo any uses of this optimization that the front-end
|
|
// emitted here. We'll redo them in the contract pass.
|
|
Changed = true;
|
|
Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0));
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ARC autorelease pool elimination.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Constants.h"
|
|
#include "llvm/ADT/STLExtras.h"
|
|
|
|
namespace {
|
|
/// ObjCARCAPElim - Autorelease pool elimination.
|
|
class ObjCARCAPElim : public ModulePass {
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
virtual bool runOnModule(Module &M);
|
|
|
|
static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0);
|
|
static bool OptimizeBB(BasicBlock *BB);
|
|
|
|
public:
|
|
static char ID;
|
|
ObjCARCAPElim() : ModulePass(ID) {
|
|
initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
};
|
|
}
|
|
|
|
char ObjCARCAPElim::ID = 0;
|
|
INITIALIZE_PASS(ObjCARCAPElim,
|
|
"objc-arc-apelim",
|
|
"ObjC ARC autorelease pool elimination",
|
|
false, false)
|
|
|
|
Pass *llvm::createObjCARCAPElimPass() {
|
|
return new ObjCARCAPElim();
|
|
}
|
|
|
|
void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesCFG();
|
|
}
|
|
|
|
/// MayAutorelease - Interprocedurally determine if calls made by the
|
|
/// given call site can possibly produce autoreleases.
|
|
bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) {
|
|
if (const Function *Callee = CS.getCalledFunction()) {
|
|
if (Callee->isDeclaration() || Callee->mayBeOverridden())
|
|
return true;
|
|
for (Function::const_iterator I = Callee->begin(), E = Callee->end();
|
|
I != E; ++I) {
|
|
const BasicBlock *BB = I;
|
|
for (BasicBlock::const_iterator J = BB->begin(), F = BB->end();
|
|
J != F; ++J)
|
|
if (ImmutableCallSite JCS = ImmutableCallSite(J))
|
|
// This recursion depth limit is arbitrary. It's just great
|
|
// enough to cover known interesting testcases.
|
|
if (Depth < 3 &&
|
|
!JCS.onlyReadsMemory() &&
|
|
MayAutorelease(JCS, Depth + 1))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) {
|
|
bool Changed = false;
|
|
|
|
Instruction *Push = 0;
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
|
|
Instruction *Inst = I++;
|
|
switch (GetBasicInstructionClass(Inst)) {
|
|
case IC_AutoreleasepoolPush:
|
|
Push = Inst;
|
|
break;
|
|
case IC_AutoreleasepoolPop:
|
|
// If this pop matches a push and nothing in between can autorelease,
|
|
// zap the pair.
|
|
if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) {
|
|
Changed = true;
|
|
Inst->eraseFromParent();
|
|
Push->eraseFromParent();
|
|
}
|
|
Push = 0;
|
|
break;
|
|
case IC_CallOrUser:
|
|
if (MayAutorelease(ImmutableCallSite(Inst)))
|
|
Push = 0;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
bool ObjCARCAPElim::runOnModule(Module &M) {
|
|
if (!EnableARCOpts)
|
|
return false;
|
|
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
if (!ModuleHasARC(M))
|
|
return false;
|
|
|
|
// Find the llvm.global_ctors variable, as the first step in
|
|
// identifying the global constructors. In theory, unnecessary autorelease
|
|
// pools could occur anywhere, but in practice it's pretty rare. Global
|
|
// ctors are a place where autorelease pools get inserted automatically,
|
|
// so it's pretty common for them to be unnecessary, and it's pretty
|
|
// profitable to eliminate them.
|
|
GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
|
|
if (!GV)
|
|
return false;
|
|
|
|
assert(GV->hasDefinitiveInitializer() &&
|
|
"llvm.global_ctors is uncooperative!");
|
|
|
|
bool Changed = false;
|
|
|
|
// Dig the constructor functions out of GV's initializer.
|
|
ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
|
|
for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
|
|
OI != OE; ++OI) {
|
|
Value *Op = *OI;
|
|
// llvm.global_ctors is an array of pairs where the second members
|
|
// are constructor functions.
|
|
Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
|
|
// If the user used a constructor function with the wrong signature and
|
|
// it got bitcasted or whatever, look the other way.
|
|
if (!F)
|
|
continue;
|
|
// Only look at function definitions.
|
|
if (F->isDeclaration())
|
|
continue;
|
|
// Only look at functions with one basic block.
|
|
if (llvm::next(F->begin()) != F->end())
|
|
continue;
|
|
// Ok, a single-block constructor function definition. Try to optimize it.
|
|
Changed |= OptimizeBB(F->begin());
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ARC optimization.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// TODO: On code like this:
|
|
//
|
|
// objc_retain(%x)
|
|
// stuff_that_cannot_release()
|
|
// objc_autorelease(%x)
|
|
// stuff_that_cannot_release()
|
|
// objc_retain(%x)
|
|
// stuff_that_cannot_release()
|
|
// objc_autorelease(%x)
|
|
//
|
|
// The second retain and autorelease can be deleted.
|
|
|
|
// TODO: It should be possible to delete
|
|
// objc_autoreleasePoolPush and objc_autoreleasePoolPop
|
|
// pairs if nothing is actually autoreleased between them. Also, autorelease
|
|
// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
|
|
// after inlining) can be turned into plain release calls.
|
|
|
|
// TODO: Critical-edge splitting. If the optimial insertion point is
|
|
// a critical edge, the current algorithm has to fail, because it doesn't
|
|
// know how to split edges. It should be possible to make the optimizer
|
|
// think in terms of edges, rather than blocks, and then split critical
|
|
// edges on demand.
|
|
|
|
// TODO: OptimizeSequences could generalized to be Interprocedural.
|
|
|
|
// TODO: Recognize that a bunch of other objc runtime calls have
|
|
// non-escaping arguments and non-releasing arguments, and may be
|
|
// non-autoreleasing.
|
|
|
|
// TODO: Sink autorelease calls as far as possible. Unfortunately we
|
|
// usually can't sink them past other calls, which would be the main
|
|
// case where it would be useful.
|
|
|
|
// TODO: The pointer returned from objc_loadWeakRetained is retained.
|
|
|
|
// TODO: Delete release+retain pairs (rare).
|
|
|
|
#include "llvm/LLVMContext.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
|
|
STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
|
|
STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
|
|
STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
|
|
STATISTIC(NumRets, "Number of return value forwarding "
|
|
"retain+autoreleaes eliminated");
|
|
STATISTIC(NumRRs, "Number of retain+release paths eliminated");
|
|
STATISTIC(NumPeeps, "Number of calls peephole-optimized");
|
|
|
|
namespace {
|
|
/// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it
|
|
/// uses many of the same techniques, except it uses special ObjC-specific
|
|
/// reasoning about pointer relationships.
|
|
class ProvenanceAnalysis {
|
|
AliasAnalysis *AA;
|
|
|
|
typedef std::pair<const Value *, const Value *> ValuePairTy;
|
|
typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
|
|
CachedResultsTy CachedResults;
|
|
|
|
bool relatedCheck(const Value *A, const Value *B);
|
|
bool relatedSelect(const SelectInst *A, const Value *B);
|
|
bool relatedPHI(const PHINode *A, const Value *B);
|
|
|
|
void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
|
|
ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
|
|
|
|
public:
|
|
ProvenanceAnalysis() {}
|
|
|
|
void setAA(AliasAnalysis *aa) { AA = aa; }
|
|
|
|
AliasAnalysis *getAA() const { return AA; }
|
|
|
|
bool related(const Value *A, const Value *B);
|
|
|
|
void clear() {
|
|
CachedResults.clear();
|
|
}
|
|
};
|
|
}
|
|
|
|
bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
|
|
// If the values are Selects with the same condition, we can do a more precise
|
|
// check: just check for relations between the values on corresponding arms.
|
|
if (const SelectInst *SB = dyn_cast<SelectInst>(B))
|
|
if (A->getCondition() == SB->getCondition())
|
|
return related(A->getTrueValue(), SB->getTrueValue()) ||
|
|
related(A->getFalseValue(), SB->getFalseValue());
|
|
|
|
// Check both arms of the Select node individually.
|
|
return related(A->getTrueValue(), B) ||
|
|
related(A->getFalseValue(), B);
|
|
}
|
|
|
|
bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
|
|
// If the values are PHIs in the same block, we can do a more precise as well
|
|
// as efficient check: just check for relations between the values on
|
|
// corresponding edges.
|
|
if (const PHINode *PNB = dyn_cast<PHINode>(B))
|
|
if (PNB->getParent() == A->getParent()) {
|
|
for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
|
|
if (related(A->getIncomingValue(i),
|
|
PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
// Check each unique source of the PHI node against B.
|
|
SmallPtrSet<const Value *, 4> UniqueSrc;
|
|
for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
|
|
const Value *PV1 = A->getIncomingValue(i);
|
|
if (UniqueSrc.insert(PV1) && related(PV1, B))
|
|
return true;
|
|
}
|
|
|
|
// All of the arms checked out.
|
|
return false;
|
|
}
|
|
|
|
/// isStoredObjCPointer - Test if the value of P, or any value covered by its
|
|
/// provenance, is ever stored within the function (not counting callees).
|
|
static bool isStoredObjCPointer(const Value *P) {
|
|
SmallPtrSet<const Value *, 8> Visited;
|
|
SmallVector<const Value *, 8> Worklist;
|
|
Worklist.push_back(P);
|
|
Visited.insert(P);
|
|
do {
|
|
P = Worklist.pop_back_val();
|
|
for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
|
|
UI != UE; ++UI) {
|
|
const User *Ur = *UI;
|
|
if (isa<StoreInst>(Ur)) {
|
|
if (UI.getOperandNo() == 0)
|
|
// The pointer is stored.
|
|
return true;
|
|
// The pointed is stored through.
|
|
continue;
|
|
}
|
|
if (isa<CallInst>(Ur))
|
|
// The pointer is passed as an argument, ignore this.
|
|
continue;
|
|
if (isa<PtrToIntInst>(P))
|
|
// Assume the worst.
|
|
return true;
|
|
if (Visited.insert(Ur))
|
|
Worklist.push_back(Ur);
|
|
}
|
|
} while (!Worklist.empty());
|
|
|
|
// Everything checked out.
|
|
return false;
|
|
}
|
|
|
|
bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
|
|
// Skip past provenance pass-throughs.
|
|
A = GetUnderlyingObjCPtr(A);
|
|
B = GetUnderlyingObjCPtr(B);
|
|
|
|
// Quick check.
|
|
if (A == B)
|
|
return true;
|
|
|
|
// Ask regular AliasAnalysis, for a first approximation.
|
|
switch (AA->alias(A, B)) {
|
|
case AliasAnalysis::NoAlias:
|
|
return false;
|
|
case AliasAnalysis::MustAlias:
|
|
case AliasAnalysis::PartialAlias:
|
|
return true;
|
|
case AliasAnalysis::MayAlias:
|
|
break;
|
|
}
|
|
|
|
bool AIsIdentified = IsObjCIdentifiedObject(A);
|
|
bool BIsIdentified = IsObjCIdentifiedObject(B);
|
|
|
|
// An ObjC-Identified object can't alias a load if it is never locally stored.
|
|
if (AIsIdentified) {
|
|
// Check for an obvious escape.
|
|
if (isa<LoadInst>(B))
|
|
return isStoredObjCPointer(A);
|
|
if (BIsIdentified) {
|
|
// Check for an obvious escape.
|
|
if (isa<LoadInst>(A))
|
|
return isStoredObjCPointer(B);
|
|
// Both pointers are identified and escapes aren't an evident problem.
|
|
return false;
|
|
}
|
|
} else if (BIsIdentified) {
|
|
// Check for an obvious escape.
|
|
if (isa<LoadInst>(A))
|
|
return isStoredObjCPointer(B);
|
|
}
|
|
|
|
// Special handling for PHI and Select.
|
|
if (const PHINode *PN = dyn_cast<PHINode>(A))
|
|
return relatedPHI(PN, B);
|
|
if (const PHINode *PN = dyn_cast<PHINode>(B))
|
|
return relatedPHI(PN, A);
|
|
if (const SelectInst *S = dyn_cast<SelectInst>(A))
|
|
return relatedSelect(S, B);
|
|
if (const SelectInst *S = dyn_cast<SelectInst>(B))
|
|
return relatedSelect(S, A);
|
|
|
|
// Conservative.
|
|
return true;
|
|
}
|
|
|
|
bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
|
|
// Begin by inserting a conservative value into the map. If the insertion
|
|
// fails, we have the answer already. If it succeeds, leave it there until we
|
|
// compute the real answer to guard against recursive queries.
|
|
if (A > B) std::swap(A, B);
|
|
std::pair<CachedResultsTy::iterator, bool> Pair =
|
|
CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
|
|
if (!Pair.second)
|
|
return Pair.first->second;
|
|
|
|
bool Result = relatedCheck(A, B);
|
|
CachedResults[ValuePairTy(A, B)] = Result;
|
|
return Result;
|
|
}
|
|
|
|
namespace {
|
|
// Sequence - A sequence of states that a pointer may go through in which an
|
|
// objc_retain and objc_release are actually needed.
|
|
enum Sequence {
|
|
S_None,
|
|
S_Retain, ///< objc_retain(x)
|
|
S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
|
|
S_Use, ///< any use of x
|
|
S_Stop, ///< like S_Release, but code motion is stopped
|
|
S_Release, ///< objc_release(x)
|
|
S_MovableRelease ///< objc_release(x), !clang.imprecise_release
|
|
};
|
|
}
|
|
|
|
static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
|
|
// The easy cases.
|
|
if (A == B)
|
|
return A;
|
|
if (A == S_None || B == S_None)
|
|
return S_None;
|
|
|
|
if (A > B) std::swap(A, B);
|
|
if (TopDown) {
|
|
// Choose the side which is further along in the sequence.
|
|
if ((A == S_Retain || A == S_CanRelease) &&
|
|
(B == S_CanRelease || B == S_Use))
|
|
return B;
|
|
} else {
|
|
// Choose the side which is further along in the sequence.
|
|
if ((A == S_Use || A == S_CanRelease) &&
|
|
(B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
|
|
return A;
|
|
// If both sides are releases, choose the more conservative one.
|
|
if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
|
|
return A;
|
|
if (A == S_Release && B == S_MovableRelease)
|
|
return A;
|
|
}
|
|
|
|
return S_None;
|
|
}
|
|
|
|
namespace {
|
|
/// RRInfo - Unidirectional information about either a
|
|
/// retain-decrement-use-release sequence or release-use-decrement-retain
|
|
/// reverese sequence.
|
|
struct RRInfo {
|
|
/// KnownSafe - After an objc_retain, the reference count of the referenced
|
|
/// object is known to be positive. Similarly, before an objc_release, the
|
|
/// reference count of the referenced object is known to be positive. If
|
|
/// there are retain-release pairs in code regions where the retain count
|
|
/// is known to be positive, they can be eliminated, regardless of any side
|
|
/// effects between them.
|
|
///
|
|
/// Also, a retain+release pair nested within another retain+release
|
|
/// pair all on the known same pointer value can be eliminated, regardless
|
|
/// of any intervening side effects.
|
|
///
|
|
/// KnownSafe is true when either of these conditions is satisfied.
|
|
bool KnownSafe;
|
|
|
|
/// IsRetainBlock - True if the Calls are objc_retainBlock calls (as
|
|
/// opposed to objc_retain calls).
|
|
bool IsRetainBlock;
|
|
|
|
/// IsTailCallRelease - True of the objc_release calls are all marked
|
|
/// with the "tail" keyword.
|
|
bool IsTailCallRelease;
|
|
|
|
/// ReleaseMetadata - If the Calls are objc_release calls and they all have
|
|
/// a clang.imprecise_release tag, this is the metadata tag.
|
|
MDNode *ReleaseMetadata;
|
|
|
|
/// Calls - For a top-down sequence, the set of objc_retains or
|
|
/// objc_retainBlocks. For bottom-up, the set of objc_releases.
|
|
SmallPtrSet<Instruction *, 2> Calls;
|
|
|
|
/// ReverseInsertPts - The set of optimal insert positions for
|
|
/// moving calls in the opposite sequence.
|
|
SmallPtrSet<Instruction *, 2> ReverseInsertPts;
|
|
|
|
RRInfo() :
|
|
KnownSafe(false), IsRetainBlock(false),
|
|
IsTailCallRelease(false),
|
|
ReleaseMetadata(0) {}
|
|
|
|
void clear();
|
|
};
|
|
}
|
|
|
|
void RRInfo::clear() {
|
|
KnownSafe = false;
|
|
IsRetainBlock = false;
|
|
IsTailCallRelease = false;
|
|
ReleaseMetadata = 0;
|
|
Calls.clear();
|
|
ReverseInsertPts.clear();
|
|
}
|
|
|
|
namespace {
|
|
/// PtrState - This class summarizes several per-pointer runtime properties
|
|
/// which are propogated through the flow graph.
|
|
class PtrState {
|
|
/// KnownPositiveRefCount - True if the reference count is known to
|
|
/// be incremented.
|
|
bool KnownPositiveRefCount;
|
|
|
|
/// Partial - True of we've seen an opportunity for partial RR elimination,
|
|
/// such as pushing calls into a CFG triangle or into one side of a
|
|
/// CFG diamond.
|
|
bool Partial;
|
|
|
|
/// Seq - The current position in the sequence.
|
|
Sequence Seq : 8;
|
|
|
|
public:
|
|
/// RRI - Unidirectional information about the current sequence.
|
|
/// TODO: Encapsulate this better.
|
|
RRInfo RRI;
|
|
|
|
PtrState() : KnownPositiveRefCount(false), Partial(false),
|
|
Seq(S_None) {}
|
|
|
|
void SetKnownPositiveRefCount() {
|
|
KnownPositiveRefCount = true;
|
|
}
|
|
|
|
void ClearRefCount() {
|
|
KnownPositiveRefCount = false;
|
|
}
|
|
|
|
bool IsKnownIncremented() const {
|
|
return KnownPositiveRefCount;
|
|
}
|
|
|
|
void SetSeq(Sequence NewSeq) {
|
|
Seq = NewSeq;
|
|
}
|
|
|
|
Sequence GetSeq() const {
|
|
return Seq;
|
|
}
|
|
|
|
void ClearSequenceProgress() {
|
|
ResetSequenceProgress(S_None);
|
|
}
|
|
|
|
void ResetSequenceProgress(Sequence NewSeq) {
|
|
Seq = NewSeq;
|
|
Partial = false;
|
|
RRI.clear();
|
|
}
|
|
|
|
void Merge(const PtrState &Other, bool TopDown);
|
|
};
|
|
}
|
|
|
|
void
|
|
PtrState::Merge(const PtrState &Other, bool TopDown) {
|
|
Seq = MergeSeqs(Seq, Other.Seq, TopDown);
|
|
KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
|
|
|
|
// We can't merge a plain objc_retain with an objc_retainBlock.
|
|
if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
|
|
Seq = S_None;
|
|
|
|
// If we're not in a sequence (anymore), drop all associated state.
|
|
if (Seq == S_None) {
|
|
Partial = false;
|
|
RRI.clear();
|
|
} else if (Partial || Other.Partial) {
|
|
// If we're doing a merge on a path that's previously seen a partial
|
|
// merge, conservatively drop the sequence, to avoid doing partial
|
|
// RR elimination. If the branch predicates for the two merge differ,
|
|
// mixing them is unsafe.
|
|
ClearSequenceProgress();
|
|
} else {
|
|
// Conservatively merge the ReleaseMetadata information.
|
|
if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
|
|
RRI.ReleaseMetadata = 0;
|
|
|
|
RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
|
|
RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
|
|
Other.RRI.IsTailCallRelease;
|
|
RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
|
|
|
|
// Merge the insert point sets. If there are any differences,
|
|
// that makes this a partial merge.
|
|
Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
I = Other.RRI.ReverseInsertPts.begin(),
|
|
E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
|
|
Partial |= RRI.ReverseInsertPts.insert(*I);
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
/// BBState - Per-BasicBlock state.
|
|
class BBState {
|
|
/// TopDownPathCount - The number of unique control paths from the entry
|
|
/// which can reach this block.
|
|
unsigned TopDownPathCount;
|
|
|
|
/// BottomUpPathCount - The number of unique control paths to exits
|
|
/// from this block.
|
|
unsigned BottomUpPathCount;
|
|
|
|
/// MapTy - A type for PerPtrTopDown and PerPtrBottomUp.
|
|
typedef MapVector<const Value *, PtrState> MapTy;
|
|
|
|
/// PerPtrTopDown - The top-down traversal uses this to record information
|
|
/// known about a pointer at the bottom of each block.
|
|
MapTy PerPtrTopDown;
|
|
|
|
/// PerPtrBottomUp - The bottom-up traversal uses this to record information
|
|
/// known about a pointer at the top of each block.
|
|
MapTy PerPtrBottomUp;
|
|
|
|
/// Preds, Succs - Effective successors and predecessors of the current
|
|
/// block (this ignores ignorable edges and ignored backedges).
|
|
SmallVector<BasicBlock *, 2> Preds;
|
|
SmallVector<BasicBlock *, 2> Succs;
|
|
|
|
public:
|
|
BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
|
|
|
|
typedef MapTy::iterator ptr_iterator;
|
|
typedef MapTy::const_iterator ptr_const_iterator;
|
|
|
|
ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
|
|
ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
|
|
ptr_const_iterator top_down_ptr_begin() const {
|
|
return PerPtrTopDown.begin();
|
|
}
|
|
ptr_const_iterator top_down_ptr_end() const {
|
|
return PerPtrTopDown.end();
|
|
}
|
|
|
|
ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
|
|
ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
|
|
ptr_const_iterator bottom_up_ptr_begin() const {
|
|
return PerPtrBottomUp.begin();
|
|
}
|
|
ptr_const_iterator bottom_up_ptr_end() const {
|
|
return PerPtrBottomUp.end();
|
|
}
|
|
|
|
/// SetAsEntry - Mark this block as being an entry block, which has one
|
|
/// path from the entry by definition.
|
|
void SetAsEntry() { TopDownPathCount = 1; }
|
|
|
|
/// SetAsExit - Mark this block as being an exit block, which has one
|
|
/// path to an exit by definition.
|
|
void SetAsExit() { BottomUpPathCount = 1; }
|
|
|
|
PtrState &getPtrTopDownState(const Value *Arg) {
|
|
return PerPtrTopDown[Arg];
|
|
}
|
|
|
|
PtrState &getPtrBottomUpState(const Value *Arg) {
|
|
return PerPtrBottomUp[Arg];
|
|
}
|
|
|
|
void clearBottomUpPointers() {
|
|
PerPtrBottomUp.clear();
|
|
}
|
|
|
|
void clearTopDownPointers() {
|
|
PerPtrTopDown.clear();
|
|
}
|
|
|
|
void InitFromPred(const BBState &Other);
|
|
void InitFromSucc(const BBState &Other);
|
|
void MergePred(const BBState &Other);
|
|
void MergeSucc(const BBState &Other);
|
|
|
|
/// GetAllPathCount - Return the number of possible unique paths from an
|
|
/// entry to an exit which pass through this block. This is only valid
|
|
/// after both the top-down and bottom-up traversals are complete.
|
|
unsigned GetAllPathCount() const {
|
|
assert(TopDownPathCount != 0);
|
|
assert(BottomUpPathCount != 0);
|
|
return TopDownPathCount * BottomUpPathCount;
|
|
}
|
|
|
|
// Specialized CFG utilities.
|
|
typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
|
|
edge_iterator pred_begin() { return Preds.begin(); }
|
|
edge_iterator pred_end() { return Preds.end(); }
|
|
edge_iterator succ_begin() { return Succs.begin(); }
|
|
edge_iterator succ_end() { return Succs.end(); }
|
|
|
|
void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); }
|
|
void addPred(BasicBlock *Pred) { Preds.push_back(Pred); }
|
|
|
|
bool isExit() const { return Succs.empty(); }
|
|
};
|
|
}
|
|
|
|
void BBState::InitFromPred(const BBState &Other) {
|
|
PerPtrTopDown = Other.PerPtrTopDown;
|
|
TopDownPathCount = Other.TopDownPathCount;
|
|
}
|
|
|
|
void BBState::InitFromSucc(const BBState &Other) {
|
|
PerPtrBottomUp = Other.PerPtrBottomUp;
|
|
BottomUpPathCount = Other.BottomUpPathCount;
|
|
}
|
|
|
|
/// MergePred - The top-down traversal uses this to merge information about
|
|
/// predecessors to form the initial state for a new block.
|
|
void BBState::MergePred(const BBState &Other) {
|
|
// Other.TopDownPathCount can be 0, in which case it is either dead or a
|
|
// loop backedge. Loop backedges are special.
|
|
TopDownPathCount += Other.TopDownPathCount;
|
|
|
|
// Check for overflow. If we have overflow, fall back to conservative behavior.
|
|
if (TopDownPathCount < Other.TopDownPathCount) {
|
|
clearTopDownPointers();
|
|
return;
|
|
}
|
|
|
|
// For each entry in the other set, if our set has an entry with the same key,
|
|
// merge the entries. Otherwise, copy the entry and merge it with an empty
|
|
// entry.
|
|
for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
|
|
ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
|
|
std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
|
|
Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
|
|
/*TopDown=*/true);
|
|
}
|
|
|
|
// For each entry in our set, if the other set doesn't have an entry with the
|
|
// same key, force it to merge with an empty entry.
|
|
for (ptr_iterator MI = top_down_ptr_begin(),
|
|
ME = top_down_ptr_end(); MI != ME; ++MI)
|
|
if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
|
|
MI->second.Merge(PtrState(), /*TopDown=*/true);
|
|
}
|
|
|
|
/// MergeSucc - The bottom-up traversal uses this to merge information about
|
|
/// successors to form the initial state for a new block.
|
|
void BBState::MergeSucc(const BBState &Other) {
|
|
// Other.BottomUpPathCount can be 0, in which case it is either dead or a
|
|
// loop backedge. Loop backedges are special.
|
|
BottomUpPathCount += Other.BottomUpPathCount;
|
|
|
|
// Check for overflow. If we have overflow, fall back to conservative behavior.
|
|
if (BottomUpPathCount < Other.BottomUpPathCount) {
|
|
clearBottomUpPointers();
|
|
return;
|
|
}
|
|
|
|
// For each entry in the other set, if our set has an entry with the
|
|
// same key, merge the entries. Otherwise, copy the entry and merge
|
|
// it with an empty entry.
|
|
for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
|
|
ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
|
|
std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
|
|
Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
|
|
/*TopDown=*/false);
|
|
}
|
|
|
|
// For each entry in our set, if the other set doesn't have an entry
|
|
// with the same key, force it to merge with an empty entry.
|
|
for (ptr_iterator MI = bottom_up_ptr_begin(),
|
|
ME = bottom_up_ptr_end(); MI != ME; ++MI)
|
|
if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
|
|
MI->second.Merge(PtrState(), /*TopDown=*/false);
|
|
}
|
|
|
|
namespace {
|
|
/// ObjCARCOpt - The main ARC optimization pass.
|
|
class ObjCARCOpt : public FunctionPass {
|
|
bool Changed;
|
|
ProvenanceAnalysis PA;
|
|
|
|
/// Run - A flag indicating whether this optimization pass should run.
|
|
bool Run;
|
|
|
|
/// RetainRVCallee, etc. - Declarations for ObjC runtime
|
|
/// functions, for use in creating calls to them. These are initialized
|
|
/// lazily to avoid cluttering up the Module with unused declarations.
|
|
Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee,
|
|
*RetainCallee, *RetainBlockCallee, *AutoreleaseCallee;
|
|
|
|
/// UsedInThisFunciton - Flags which determine whether each of the
|
|
/// interesting runtine functions is in fact used in the current function.
|
|
unsigned UsedInThisFunction;
|
|
|
|
/// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release
|
|
/// metadata.
|
|
unsigned ImpreciseReleaseMDKind;
|
|
|
|
/// CopyOnEscapeMDKind - The Metadata Kind for clang.arc.copy_on_escape
|
|
/// metadata.
|
|
unsigned CopyOnEscapeMDKind;
|
|
|
|
/// NoObjCARCExceptionsMDKind - The Metadata Kind for
|
|
/// clang.arc.no_objc_arc_exceptions metadata.
|
|
unsigned NoObjCARCExceptionsMDKind;
|
|
|
|
Constant *getRetainRVCallee(Module *M);
|
|
Constant *getAutoreleaseRVCallee(Module *M);
|
|
Constant *getReleaseCallee(Module *M);
|
|
Constant *getRetainCallee(Module *M);
|
|
Constant *getRetainBlockCallee(Module *M);
|
|
Constant *getAutoreleaseCallee(Module *M);
|
|
|
|
bool IsRetainBlockOptimizable(const Instruction *Inst);
|
|
|
|
void OptimizeRetainCall(Function &F, Instruction *Retain);
|
|
bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
|
|
void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV);
|
|
void OptimizeIndividualCalls(Function &F);
|
|
|
|
void CheckForCFGHazards(const BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
BBState &MyStates) const;
|
|
bool VisitInstructionBottomUp(Instruction *Inst,
|
|
BasicBlock *BB,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
BBState &MyStates);
|
|
bool VisitBottomUp(BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains);
|
|
bool VisitInstructionTopDown(Instruction *Inst,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
BBState &MyStates);
|
|
bool VisitTopDown(BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
DenseMap<Value *, RRInfo> &Releases);
|
|
bool Visit(Function &F,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases);
|
|
|
|
void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
SmallVectorImpl<Instruction *> &DeadInsts,
|
|
Module *M);
|
|
|
|
bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
Module *M);
|
|
|
|
void OptimizeWeakCalls(Function &F);
|
|
|
|
bool OptimizeSequences(Function &F);
|
|
|
|
void OptimizeReturns(Function &F);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
virtual bool doInitialization(Module &M);
|
|
virtual bool runOnFunction(Function &F);
|
|
virtual void releaseMemory();
|
|
|
|
public:
|
|
static char ID;
|
|
ObjCARCOpt() : FunctionPass(ID) {
|
|
initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
};
|
|
}
|
|
|
|
char ObjCARCOpt::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(ObjCARCOpt,
|
|
"objc-arc", "ObjC ARC optimization", false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
|
|
INITIALIZE_PASS_END(ObjCARCOpt,
|
|
"objc-arc", "ObjC ARC optimization", false, false)
|
|
|
|
Pass *llvm::createObjCARCOptPass() {
|
|
return new ObjCARCOpt();
|
|
}
|
|
|
|
void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.addRequired<ObjCARCAliasAnalysis>();
|
|
AU.addRequired<AliasAnalysis>();
|
|
// ARC optimization doesn't currently split critical edges.
|
|
AU.setPreservesCFG();
|
|
}
|
|
|
|
bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) {
|
|
// Without the magic metadata tag, we have to assume this might be an
|
|
// objc_retainBlock call inserted to convert a block pointer to an id,
|
|
// in which case it really is needed.
|
|
if (!Inst->getMetadata(CopyOnEscapeMDKind))
|
|
return false;
|
|
|
|
// If the pointer "escapes" (not including being used in a call),
|
|
// the copy may be needed.
|
|
if (DoesObjCBlockEscape(Inst))
|
|
return false;
|
|
|
|
// Otherwise, it's not needed.
|
|
return true;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
|
|
if (!RetainRVCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *Params[] = { I8X };
|
|
FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
RetainRVCallee =
|
|
M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
|
|
Attributes);
|
|
}
|
|
return RetainRVCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
|
|
if (!AutoreleaseRVCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *Params[] = { I8X };
|
|
FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
AutoreleaseRVCallee =
|
|
M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
|
|
Attributes);
|
|
}
|
|
return AutoreleaseRVCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
|
|
if (!ReleaseCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
ReleaseCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_release",
|
|
FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
|
|
Attributes);
|
|
}
|
|
return ReleaseCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getRetainCallee(Module *M) {
|
|
if (!RetainCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
RetainCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_retain",
|
|
FunctionType::get(Params[0], Params, /*isVarArg=*/false),
|
|
Attributes);
|
|
}
|
|
return RetainCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
|
|
if (!RetainBlockCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
// objc_retainBlock is not nounwind because it calls user copy constructors
|
|
// which could theoretically throw.
|
|
RetainBlockCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_retainBlock",
|
|
FunctionType::get(Params[0], Params, /*isVarArg=*/false),
|
|
AttrListPtr());
|
|
}
|
|
return RetainBlockCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
|
|
if (!AutoreleaseCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
AutoreleaseCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_autorelease",
|
|
FunctionType::get(Params[0], Params, /*isVarArg=*/false),
|
|
Attributes);
|
|
}
|
|
return AutoreleaseCallee;
|
|
}
|
|
|
|
/// IsPotentialUse - Test whether the given value is possible a
|
|
/// reference-counted pointer, including tests which utilize AliasAnalysis.
|
|
static bool IsPotentialUse(const Value *Op, AliasAnalysis &AA) {
|
|
// First make the rudimentary check.
|
|
if (!IsPotentialUse(Op))
|
|
return false;
|
|
|
|
// Objects in constant memory are not reference-counted.
|
|
if (AA.pointsToConstantMemory(Op))
|
|
return false;
|
|
|
|
// Pointers in constant memory are not pointing to reference-counted objects.
|
|
if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
|
|
if (AA.pointsToConstantMemory(LI->getPointerOperand()))
|
|
return false;
|
|
|
|
// Otherwise assume the worst.
|
|
return true;
|
|
}
|
|
|
|
/// CanAlterRefCount - Test whether the given instruction can result in a
|
|
/// reference count modification (positive or negative) for the pointer's
|
|
/// object.
|
|
static bool
|
|
CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
|
|
ProvenanceAnalysis &PA, InstructionClass Class) {
|
|
switch (Class) {
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
case IC_User:
|
|
// These operations never directly modify a reference count.
|
|
return false;
|
|
default: break;
|
|
}
|
|
|
|
ImmutableCallSite CS = static_cast<const Value *>(Inst);
|
|
assert(CS && "Only calls can alter reference counts!");
|
|
|
|
// See if AliasAnalysis can help us with the call.
|
|
AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
|
|
if (AliasAnalysis::onlyReadsMemory(MRB))
|
|
return false;
|
|
if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
|
|
for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
|
|
I != E; ++I) {
|
|
const Value *Op = *I;
|
|
if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Assume the worst.
|
|
return true;
|
|
}
|
|
|
|
/// CanUse - Test whether the given instruction can "use" the given pointer's
|
|
/// object in a way that requires the reference count to be positive.
|
|
static bool
|
|
CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
|
|
InstructionClass Class) {
|
|
// IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
|
|
if (Class == IC_Call)
|
|
return false;
|
|
|
|
// Consider various instructions which may have pointer arguments which are
|
|
// not "uses".
|
|
if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
|
|
// Comparing a pointer with null, or any other constant, isn't really a use,
|
|
// because we don't care what the pointer points to, or about the values
|
|
// of any other dynamic reference-counted pointers.
|
|
if (!IsPotentialUse(ICI->getOperand(1), *PA.getAA()))
|
|
return false;
|
|
} else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
|
|
// For calls, just check the arguments (and not the callee operand).
|
|
for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
|
|
OE = CS.arg_end(); OI != OE; ++OI) {
|
|
const Value *Op = *OI;
|
|
if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
|
|
return true;
|
|
}
|
|
return false;
|
|
} else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
// Special-case stores, because we don't care about the stored value, just
|
|
// the store address.
|
|
const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
|
|
// If we can't tell what the underlying object was, assume there is a
|
|
// dependence.
|
|
return IsPotentialUse(Op, *PA.getAA()) && PA.related(Op, Ptr);
|
|
}
|
|
|
|
// Check each operand for a match.
|
|
for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
|
|
OI != OE; ++OI) {
|
|
const Value *Op = *OI;
|
|
if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// CanInterruptRV - Test whether the given instruction can autorelease
|
|
/// any pointer or cause an autoreleasepool pop.
|
|
static bool
|
|
CanInterruptRV(InstructionClass Class) {
|
|
switch (Class) {
|
|
case IC_AutoreleasepoolPop:
|
|
case IC_CallOrUser:
|
|
case IC_Call:
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
case IC_FusedRetainAutorelease:
|
|
case IC_FusedRetainAutoreleaseRV:
|
|
return true;
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
/// DependenceKind - There are several kinds of dependence-like concepts in
|
|
/// use here.
|
|
enum DependenceKind {
|
|
NeedsPositiveRetainCount,
|
|
AutoreleasePoolBoundary,
|
|
CanChangeRetainCount,
|
|
RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
|
|
RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
|
|
RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
|
|
};
|
|
}
|
|
|
|
/// Depends - Test if there can be dependencies on Inst through Arg. This
|
|
/// function only tests dependencies relevant for removing pairs of calls.
|
|
static bool
|
|
Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
|
|
ProvenanceAnalysis &PA) {
|
|
// If we've reached the definition of Arg, stop.
|
|
if (Inst == Arg)
|
|
return true;
|
|
|
|
switch (Flavor) {
|
|
case NeedsPositiveRetainCount: {
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
switch (Class) {
|
|
case IC_AutoreleasepoolPop:
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_None:
|
|
return false;
|
|
default:
|
|
return CanUse(Inst, Arg, PA, Class);
|
|
}
|
|
}
|
|
|
|
case AutoreleasePoolBoundary: {
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
switch (Class) {
|
|
case IC_AutoreleasepoolPop:
|
|
case IC_AutoreleasepoolPush:
|
|
// These mark the end and begin of an autorelease pool scope.
|
|
return true;
|
|
default:
|
|
// Nothing else does this.
|
|
return false;
|
|
}
|
|
}
|
|
|
|
case CanChangeRetainCount: {
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
switch (Class) {
|
|
case IC_AutoreleasepoolPop:
|
|
// Conservatively assume this can decrement any count.
|
|
return true;
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_None:
|
|
return false;
|
|
default:
|
|
return CanAlterRefCount(Inst, Arg, PA, Class);
|
|
}
|
|
}
|
|
|
|
case RetainAutoreleaseDep:
|
|
switch (GetBasicInstructionClass(Inst)) {
|
|
case IC_AutoreleasepoolPop:
|
|
case IC_AutoreleasepoolPush:
|
|
// Don't merge an objc_autorelease with an objc_retain inside a different
|
|
// autoreleasepool scope.
|
|
return true;
|
|
case IC_Retain:
|
|
case IC_RetainRV:
|
|
// Check for a retain of the same pointer for merging.
|
|
return GetObjCArg(Inst) == Arg;
|
|
default:
|
|
// Nothing else matters for objc_retainAutorelease formation.
|
|
return false;
|
|
}
|
|
|
|
case RetainAutoreleaseRVDep: {
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
switch (Class) {
|
|
case IC_Retain:
|
|
case IC_RetainRV:
|
|
// Check for a retain of the same pointer for merging.
|
|
return GetObjCArg(Inst) == Arg;
|
|
default:
|
|
// Anything that can autorelease interrupts
|
|
// retainAutoreleaseReturnValue formation.
|
|
return CanInterruptRV(Class);
|
|
}
|
|
}
|
|
|
|
case RetainRVDep:
|
|
return CanInterruptRV(GetBasicInstructionClass(Inst));
|
|
}
|
|
|
|
llvm_unreachable("Invalid dependence flavor");
|
|
}
|
|
|
|
/// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and
|
|
/// find local and non-local dependencies on Arg.
|
|
/// TODO: Cache results?
|
|
static void
|
|
FindDependencies(DependenceKind Flavor,
|
|
const Value *Arg,
|
|
BasicBlock *StartBB, Instruction *StartInst,
|
|
SmallPtrSet<Instruction *, 4> &DependingInstructions,
|
|
SmallPtrSet<const BasicBlock *, 4> &Visited,
|
|
ProvenanceAnalysis &PA) {
|
|
BasicBlock::iterator StartPos = StartInst;
|
|
|
|
SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
|
|
Worklist.push_back(std::make_pair(StartBB, StartPos));
|
|
do {
|
|
std::pair<BasicBlock *, BasicBlock::iterator> Pair =
|
|
Worklist.pop_back_val();
|
|
BasicBlock *LocalStartBB = Pair.first;
|
|
BasicBlock::iterator LocalStartPos = Pair.second;
|
|
BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
|
|
for (;;) {
|
|
if (LocalStartPos == StartBBBegin) {
|
|
pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
|
|
if (PI == PE)
|
|
// If we've reached the function entry, produce a null dependence.
|
|
DependingInstructions.insert(0);
|
|
else
|
|
// Add the predecessors to the worklist.
|
|
do {
|
|
BasicBlock *PredBB = *PI;
|
|
if (Visited.insert(PredBB))
|
|
Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
|
|
} while (++PI != PE);
|
|
break;
|
|
}
|
|
|
|
Instruction *Inst = --LocalStartPos;
|
|
if (Depends(Flavor, Inst, Arg, PA)) {
|
|
DependingInstructions.insert(Inst);
|
|
break;
|
|
}
|
|
}
|
|
} while (!Worklist.empty());
|
|
|
|
// Determine whether the original StartBB post-dominates all of the blocks we
|
|
// visited. If not, insert a sentinal indicating that most optimizations are
|
|
// not safe.
|
|
for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
|
|
E = Visited.end(); I != E; ++I) {
|
|
const BasicBlock *BB = *I;
|
|
if (BB == StartBB)
|
|
continue;
|
|
const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
|
|
for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
|
|
const BasicBlock *Succ = *SI;
|
|
if (Succ != StartBB && !Visited.count(Succ)) {
|
|
DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
static bool isNullOrUndef(const Value *V) {
|
|
return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
|
|
}
|
|
|
|
static bool isNoopInstruction(const Instruction *I) {
|
|
return isa<BitCastInst>(I) ||
|
|
(isa<GetElementPtrInst>(I) &&
|
|
cast<GetElementPtrInst>(I)->hasAllZeroIndices());
|
|
}
|
|
|
|
/// OptimizeRetainCall - Turn objc_retain into
|
|
/// objc_retainAutoreleasedReturnValue if the operand is a return value.
|
|
void
|
|
ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
|
|
ImmutableCallSite CS(GetObjCArg(Retain));
|
|
const Instruction *Call = CS.getInstruction();
|
|
if (!Call) return;
|
|
if (Call->getParent() != Retain->getParent()) return;
|
|
|
|
// Check that the call is next to the retain.
|
|
BasicBlock::const_iterator I = Call;
|
|
++I;
|
|
while (isNoopInstruction(I)) ++I;
|
|
if (&*I != Retain)
|
|
return;
|
|
|
|
// Turn it to an objc_retainAutoreleasedReturnValue..
|
|
Changed = true;
|
|
++NumPeeps;
|
|
cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
|
|
}
|
|
|
|
/// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into
|
|
/// objc_retain if the operand is not a return value. Or, if it can be paired
|
|
/// with an objc_autoreleaseReturnValue, delete the pair and return true.
|
|
bool
|
|
ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
|
|
// Check for the argument being from an immediately preceding call or invoke.
|
|
const Value *Arg = GetObjCArg(RetainRV);
|
|
ImmutableCallSite CS(Arg);
|
|
if (const Instruction *Call = CS.getInstruction()) {
|
|
if (Call->getParent() == RetainRV->getParent()) {
|
|
BasicBlock::const_iterator I = Call;
|
|
++I;
|
|
while (isNoopInstruction(I)) ++I;
|
|
if (&*I == RetainRV)
|
|
return false;
|
|
} else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
|
|
BasicBlock *RetainRVParent = RetainRV->getParent();
|
|
if (II->getNormalDest() == RetainRVParent) {
|
|
BasicBlock::const_iterator I = RetainRVParent->begin();
|
|
while (isNoopInstruction(I)) ++I;
|
|
if (&*I == RetainRV)
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Check for being preceded by an objc_autoreleaseReturnValue on the same
|
|
// pointer. In this case, we can delete the pair.
|
|
BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
|
|
if (I != Begin) {
|
|
do --I; while (I != Begin && isNoopInstruction(I));
|
|
if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
|
|
GetObjCArg(I) == Arg) {
|
|
Changed = true;
|
|
++NumPeeps;
|
|
EraseInstruction(I);
|
|
EraseInstruction(RetainRV);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Turn it to a plain objc_retain.
|
|
Changed = true;
|
|
++NumPeeps;
|
|
cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
|
|
return false;
|
|
}
|
|
|
|
/// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into
|
|
/// objc_autorelease if the result is not used as a return value.
|
|
void
|
|
ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) {
|
|
// Check for a return of the pointer value.
|
|
const Value *Ptr = GetObjCArg(AutoreleaseRV);
|
|
SmallVector<const Value *, 2> Users;
|
|
Users.push_back(Ptr);
|
|
do {
|
|
Ptr = Users.pop_back_val();
|
|
for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
|
|
UI != UE; ++UI) {
|
|
const User *I = *UI;
|
|
if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
|
|
return;
|
|
if (isa<BitCastInst>(I))
|
|
Users.push_back(I);
|
|
}
|
|
} while (!Users.empty());
|
|
|
|
Changed = true;
|
|
++NumPeeps;
|
|
cast<CallInst>(AutoreleaseRV)->
|
|
setCalledFunction(getAutoreleaseCallee(F.getParent()));
|
|
}
|
|
|
|
/// OptimizeIndividualCalls - Visit each call, one at a time, and make
|
|
/// simplifications without doing any additional analysis.
|
|
void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
|
|
// Reset all the flags in preparation for recomputing them.
|
|
UsedInThisFunction = 0;
|
|
|
|
// Visit all objc_* calls in F.
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
|
|
Instruction *Inst = &*I++;
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
|
|
switch (Class) {
|
|
default: break;
|
|
|
|
// Delete no-op casts. These function calls have special semantics, but
|
|
// the semantics are entirely implemented via lowering in the front-end,
|
|
// so by the time they reach the optimizer, they are just no-op calls
|
|
// which return their argument.
|
|
//
|
|
// There are gray areas here, as the ability to cast reference-counted
|
|
// pointers to raw void* and back allows code to break ARC assumptions,
|
|
// however these are currently considered to be unimportant.
|
|
case IC_NoopCast:
|
|
Changed = true;
|
|
++NumNoops;
|
|
EraseInstruction(Inst);
|
|
continue;
|
|
|
|
// If the pointer-to-weak-pointer is null, it's undefined behavior.
|
|
case IC_StoreWeak:
|
|
case IC_LoadWeak:
|
|
case IC_LoadWeakRetained:
|
|
case IC_InitWeak:
|
|
case IC_DestroyWeak: {
|
|
CallInst *CI = cast<CallInst>(Inst);
|
|
if (isNullOrUndef(CI->getArgOperand(0))) {
|
|
Changed = true;
|
|
Type *Ty = CI->getArgOperand(0)->getType();
|
|
new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
|
|
Constant::getNullValue(Ty),
|
|
CI);
|
|
CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
|
|
CI->eraseFromParent();
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
case IC_CopyWeak:
|
|
case IC_MoveWeak: {
|
|
CallInst *CI = cast<CallInst>(Inst);
|
|
if (isNullOrUndef(CI->getArgOperand(0)) ||
|
|
isNullOrUndef(CI->getArgOperand(1))) {
|
|
Changed = true;
|
|
Type *Ty = CI->getArgOperand(0)->getType();
|
|
new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
|
|
Constant::getNullValue(Ty),
|
|
CI);
|
|
CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
|
|
CI->eraseFromParent();
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
case IC_Retain:
|
|
OptimizeRetainCall(F, Inst);
|
|
break;
|
|
case IC_RetainRV:
|
|
if (OptimizeRetainRVCall(F, Inst))
|
|
continue;
|
|
break;
|
|
case IC_AutoreleaseRV:
|
|
OptimizeAutoreleaseRVCall(F, Inst);
|
|
break;
|
|
}
|
|
|
|
// objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
|
|
if (IsAutorelease(Class) && Inst->use_empty()) {
|
|
CallInst *Call = cast<CallInst>(Inst);
|
|
const Value *Arg = Call->getArgOperand(0);
|
|
Arg = FindSingleUseIdentifiedObject(Arg);
|
|
if (Arg) {
|
|
Changed = true;
|
|
++NumAutoreleases;
|
|
|
|
// Create the declaration lazily.
|
|
LLVMContext &C = Inst->getContext();
|
|
CallInst *NewCall =
|
|
CallInst::Create(getReleaseCallee(F.getParent()),
|
|
Call->getArgOperand(0), "", Call);
|
|
NewCall->setMetadata(ImpreciseReleaseMDKind,
|
|
MDNode::get(C, ArrayRef<Value *>()));
|
|
EraseInstruction(Call);
|
|
Inst = NewCall;
|
|
Class = IC_Release;
|
|
}
|
|
}
|
|
|
|
// For functions which can never be passed stack arguments, add
|
|
// a tail keyword.
|
|
if (IsAlwaysTail(Class)) {
|
|
Changed = true;
|
|
cast<CallInst>(Inst)->setTailCall();
|
|
}
|
|
|
|
// Set nounwind as needed.
|
|
if (IsNoThrow(Class)) {
|
|
Changed = true;
|
|
cast<CallInst>(Inst)->setDoesNotThrow();
|
|
}
|
|
|
|
if (!IsNoopOnNull(Class)) {
|
|
UsedInThisFunction |= 1 << Class;
|
|
continue;
|
|
}
|
|
|
|
const Value *Arg = GetObjCArg(Inst);
|
|
|
|
// ARC calls with null are no-ops. Delete them.
|
|
if (isNullOrUndef(Arg)) {
|
|
Changed = true;
|
|
++NumNoops;
|
|
EraseInstruction(Inst);
|
|
continue;
|
|
}
|
|
|
|
// Keep track of which of retain, release, autorelease, and retain_block
|
|
// are actually present in this function.
|
|
UsedInThisFunction |= 1 << Class;
|
|
|
|
// If Arg is a PHI, and one or more incoming values to the
|
|
// PHI are null, and the call is control-equivalent to the PHI, and there
|
|
// are no relevant side effects between the PHI and the call, the call
|
|
// could be pushed up to just those paths with non-null incoming values.
|
|
// For now, don't bother splitting critical edges for this.
|
|
SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
|
|
Worklist.push_back(std::make_pair(Inst, Arg));
|
|
do {
|
|
std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
|
|
Inst = Pair.first;
|
|
Arg = Pair.second;
|
|
|
|
const PHINode *PN = dyn_cast<PHINode>(Arg);
|
|
if (!PN) continue;
|
|
|
|
// Determine if the PHI has any null operands, or any incoming
|
|
// critical edges.
|
|
bool HasNull = false;
|
|
bool HasCriticalEdges = false;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
Value *Incoming =
|
|
StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
|
|
if (isNullOrUndef(Incoming))
|
|
HasNull = true;
|
|
else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
|
|
.getNumSuccessors() != 1) {
|
|
HasCriticalEdges = true;
|
|
break;
|
|
}
|
|
}
|
|
// If we have null operands and no critical edges, optimize.
|
|
if (!HasCriticalEdges && HasNull) {
|
|
SmallPtrSet<Instruction *, 4> DependingInstructions;
|
|
SmallPtrSet<const BasicBlock *, 4> Visited;
|
|
|
|
// Check that there is nothing that cares about the reference
|
|
// count between the call and the phi.
|
|
switch (Class) {
|
|
case IC_Retain:
|
|
case IC_RetainBlock:
|
|
// These can always be moved up.
|
|
break;
|
|
case IC_Release:
|
|
// These can't be moved across things that care about the retain
|
|
// count.
|
|
FindDependencies(NeedsPositiveRetainCount, Arg,
|
|
Inst->getParent(), Inst,
|
|
DependingInstructions, Visited, PA);
|
|
break;
|
|
case IC_Autorelease:
|
|
// These can't be moved across autorelease pool scope boundaries.
|
|
FindDependencies(AutoreleasePoolBoundary, Arg,
|
|
Inst->getParent(), Inst,
|
|
DependingInstructions, Visited, PA);
|
|
break;
|
|
case IC_RetainRV:
|
|
case IC_AutoreleaseRV:
|
|
// Don't move these; the RV optimization depends on the autoreleaseRV
|
|
// being tail called, and the retainRV being immediately after a call
|
|
// (which might still happen if we get lucky with codegen layout, but
|
|
// it's not worth taking the chance).
|
|
continue;
|
|
default:
|
|
llvm_unreachable("Invalid dependence flavor");
|
|
}
|
|
|
|
if (DependingInstructions.size() == 1 &&
|
|
*DependingInstructions.begin() == PN) {
|
|
Changed = true;
|
|
++NumPartialNoops;
|
|
// Clone the call into each predecessor that has a non-null value.
|
|
CallInst *CInst = cast<CallInst>(Inst);
|
|
Type *ParamTy = CInst->getArgOperand(0)->getType();
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
Value *Incoming =
|
|
StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
|
|
if (!isNullOrUndef(Incoming)) {
|
|
CallInst *Clone = cast<CallInst>(CInst->clone());
|
|
Value *Op = PN->getIncomingValue(i);
|
|
Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
|
|
if (Op->getType() != ParamTy)
|
|
Op = new BitCastInst(Op, ParamTy, "", InsertPos);
|
|
Clone->setArgOperand(0, Op);
|
|
Clone->insertBefore(InsertPos);
|
|
Worklist.push_back(std::make_pair(Clone, Incoming));
|
|
}
|
|
}
|
|
// Erase the original call.
|
|
EraseInstruction(CInst);
|
|
continue;
|
|
}
|
|
}
|
|
} while (!Worklist.empty());
|
|
}
|
|
}
|
|
|
|
/// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible
|
|
/// control flow, or other CFG structures where moving code across the edge
|
|
/// would result in it being executed more.
|
|
void
|
|
ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
BBState &MyStates) const {
|
|
// If any top-down local-use or possible-dec has a succ which is earlier in
|
|
// the sequence, forget it.
|
|
for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(),
|
|
E = MyStates.top_down_ptr_end(); I != E; ++I)
|
|
switch (I->second.GetSeq()) {
|
|
default: break;
|
|
case S_Use: {
|
|
const Value *Arg = I->first;
|
|
const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
|
|
bool SomeSuccHasSame = false;
|
|
bool AllSuccsHaveSame = true;
|
|
PtrState &S = I->second;
|
|
succ_const_iterator SI(TI), SE(TI, false);
|
|
|
|
// If the terminator is an invoke marked with the
|
|
// clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
|
|
// ignored, for ARC purposes.
|
|
if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
|
|
--SE;
|
|
|
|
for (; SI != SE; ++SI) {
|
|
Sequence SuccSSeq = S_None;
|
|
bool SuccSRRIKnownSafe = false;
|
|
// If VisitBottomUp has pointer information for this successor, take
|
|
// what we know about it.
|
|
DenseMap<const BasicBlock *, BBState>::iterator BBI =
|
|
BBStates.find(*SI);
|
|
assert(BBI != BBStates.end());
|
|
const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
|
|
SuccSSeq = SuccS.GetSeq();
|
|
SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
|
|
switch (SuccSSeq) {
|
|
case S_None:
|
|
case S_CanRelease: {
|
|
if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
}
|
|
continue;
|
|
}
|
|
case S_Use:
|
|
SomeSuccHasSame = true;
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
|
|
AllSuccsHaveSame = false;
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
}
|
|
// If the state at the other end of any of the successor edges
|
|
// matches the current state, require all edges to match. This
|
|
// guards against loops in the middle of a sequence.
|
|
if (SomeSuccHasSame && !AllSuccsHaveSame)
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
}
|
|
case S_CanRelease: {
|
|
const Value *Arg = I->first;
|
|
const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
|
|
bool SomeSuccHasSame = false;
|
|
bool AllSuccsHaveSame = true;
|
|
PtrState &S = I->second;
|
|
succ_const_iterator SI(TI), SE(TI, false);
|
|
|
|
// If the terminator is an invoke marked with the
|
|
// clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
|
|
// ignored, for ARC purposes.
|
|
if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
|
|
--SE;
|
|
|
|
for (; SI != SE; ++SI) {
|
|
Sequence SuccSSeq = S_None;
|
|
bool SuccSRRIKnownSafe = false;
|
|
// If VisitBottomUp has pointer information for this successor, take
|
|
// what we know about it.
|
|
DenseMap<const BasicBlock *, BBState>::iterator BBI =
|
|
BBStates.find(*SI);
|
|
assert(BBI != BBStates.end());
|
|
const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
|
|
SuccSSeq = SuccS.GetSeq();
|
|
SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
|
|
switch (SuccSSeq) {
|
|
case S_None: {
|
|
if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
}
|
|
continue;
|
|
}
|
|
case S_CanRelease:
|
|
SomeSuccHasSame = true;
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
case S_Use:
|
|
if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
|
|
AllSuccsHaveSame = false;
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
}
|
|
// If the state at the other end of any of the successor edges
|
|
// matches the current state, require all edges to match. This
|
|
// guards against loops in the middle of a sequence.
|
|
if (SomeSuccHasSame && !AllSuccsHaveSame)
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
|
|
BasicBlock *BB,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
BBState &MyStates) {
|
|
bool NestingDetected = false;
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
const Value *Arg = 0;
|
|
|
|
switch (Class) {
|
|
case IC_Release: {
|
|
Arg = GetObjCArg(Inst);
|
|
|
|
PtrState &S = MyStates.getPtrBottomUpState(Arg);
|
|
|
|
// If we see two releases in a row on the same pointer. If so, make
|
|
// a note, and we'll cicle back to revisit it after we've
|
|
// hopefully eliminated the second release, which may allow us to
|
|
// eliminate the first release too.
|
|
// Theoretically we could implement removal of nested retain+release
|
|
// pairs by making PtrState hold a stack of states, but this is
|
|
// simple and avoids adding overhead for the non-nested case.
|
|
if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease)
|
|
NestingDetected = true;
|
|
|
|
MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
|
|
S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release);
|
|
S.RRI.ReleaseMetadata = ReleaseMetadata;
|
|
S.RRI.KnownSafe = S.IsKnownIncremented();
|
|
S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
|
|
S.RRI.Calls.insert(Inst);
|
|
|
|
S.SetKnownPositiveRefCount();
|
|
break;
|
|
}
|
|
case IC_RetainBlock:
|
|
// An objc_retainBlock call with just a use may need to be kept,
|
|
// because it may be copying a block from the stack to the heap.
|
|
if (!IsRetainBlockOptimizable(Inst))
|
|
break;
|
|
// FALLTHROUGH
|
|
case IC_Retain:
|
|
case IC_RetainRV: {
|
|
Arg = GetObjCArg(Inst);
|
|
|
|
PtrState &S = MyStates.getPtrBottomUpState(Arg);
|
|
S.SetKnownPositiveRefCount();
|
|
|
|
switch (S.GetSeq()) {
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
case S_Use:
|
|
S.RRI.ReverseInsertPts.clear();
|
|
// FALL THROUGH
|
|
case S_CanRelease:
|
|
// Don't do retain+release tracking for IC_RetainRV, because it's
|
|
// better to let it remain as the first instruction after a call.
|
|
if (Class != IC_RetainRV) {
|
|
S.RRI.IsRetainBlock = Class == IC_RetainBlock;
|
|
Retains[Inst] = S.RRI;
|
|
}
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
case S_None:
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
return NestingDetected;
|
|
}
|
|
case IC_AutoreleasepoolPop:
|
|
// Conservatively, clear MyStates for all known pointers.
|
|
MyStates.clearBottomUpPointers();
|
|
return NestingDetected;
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_None:
|
|
// These are irrelevant.
|
|
return NestingDetected;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
// Consider any other possible effects of this instruction on each
|
|
// pointer being tracked.
|
|
for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
|
|
ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
|
|
const Value *Ptr = MI->first;
|
|
if (Ptr == Arg)
|
|
continue; // Handled above.
|
|
PtrState &S = MI->second;
|
|
Sequence Seq = S.GetSeq();
|
|
|
|
// Check for possible releases.
|
|
if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
|
|
S.ClearRefCount();
|
|
switch (Seq) {
|
|
case S_Use:
|
|
S.SetSeq(S_CanRelease);
|
|
continue;
|
|
case S_CanRelease:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
case S_Stop:
|
|
case S_None:
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
}
|
|
|
|
// Check for possible direct uses.
|
|
switch (Seq) {
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
if (CanUse(Inst, Ptr, PA, Class)) {
|
|
assert(S.RRI.ReverseInsertPts.empty());
|
|
// If this is an invoke instruction, we're scanning it as part of
|
|
// one of its successor blocks, since we can't insert code after it
|
|
// in its own block, and we don't want to split critical edges.
|
|
if (isa<InvokeInst>(Inst))
|
|
S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
|
|
else
|
|
S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
|
|
S.SetSeq(S_Use);
|
|
} else if (Seq == S_Release &&
|
|
(Class == IC_User || Class == IC_CallOrUser)) {
|
|
// Non-movable releases depend on any possible objc pointer use.
|
|
S.SetSeq(S_Stop);
|
|
assert(S.RRI.ReverseInsertPts.empty());
|
|
// As above; handle invoke specially.
|
|
if (isa<InvokeInst>(Inst))
|
|
S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
|
|
else
|
|
S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
|
|
}
|
|
break;
|
|
case S_Stop:
|
|
if (CanUse(Inst, Ptr, PA, Class))
|
|
S.SetSeq(S_Use);
|
|
break;
|
|
case S_CanRelease:
|
|
case S_Use:
|
|
case S_None:
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
}
|
|
|
|
return NestingDetected;
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains) {
|
|
bool NestingDetected = false;
|
|
BBState &MyStates = BBStates[BB];
|
|
|
|
// Merge the states from each successor to compute the initial state
|
|
// for the current block.
|
|
BBState::edge_iterator SI(MyStates.succ_begin()),
|
|
SE(MyStates.succ_end());
|
|
if (SI != SE) {
|
|
const BasicBlock *Succ = *SI;
|
|
DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
|
|
assert(I != BBStates.end());
|
|
MyStates.InitFromSucc(I->second);
|
|
++SI;
|
|
for (; SI != SE; ++SI) {
|
|
Succ = *SI;
|
|
I = BBStates.find(Succ);
|
|
assert(I != BBStates.end());
|
|
MyStates.MergeSucc(I->second);
|
|
}
|
|
}
|
|
|
|
// Visit all the instructions, bottom-up.
|
|
for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
|
|
Instruction *Inst = llvm::prior(I);
|
|
|
|
// Invoke instructions are visited as part of their successors (below).
|
|
if (isa<InvokeInst>(Inst))
|
|
continue;
|
|
|
|
NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
|
|
}
|
|
|
|
// If there's a predecessor with an invoke, visit the invoke as if it were
|
|
// part of this block, since we can't insert code after an invoke in its own
|
|
// block, and we don't want to split critical edges.
|
|
for (BBState::edge_iterator PI(MyStates.pred_begin()),
|
|
PE(MyStates.pred_end()); PI != PE; ++PI) {
|
|
BasicBlock *Pred = *PI;
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back()))
|
|
NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates);
|
|
}
|
|
|
|
return NestingDetected;
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
BBState &MyStates) {
|
|
bool NestingDetected = false;
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
const Value *Arg = 0;
|
|
|
|
switch (Class) {
|
|
case IC_RetainBlock:
|
|
// An objc_retainBlock call with just a use may need to be kept,
|
|
// because it may be copying a block from the stack to the heap.
|
|
if (!IsRetainBlockOptimizable(Inst))
|
|
break;
|
|
// FALLTHROUGH
|
|
case IC_Retain:
|
|
case IC_RetainRV: {
|
|
Arg = GetObjCArg(Inst);
|
|
|
|
PtrState &S = MyStates.getPtrTopDownState(Arg);
|
|
|
|
// Don't do retain+release tracking for IC_RetainRV, because it's
|
|
// better to let it remain as the first instruction after a call.
|
|
if (Class != IC_RetainRV) {
|
|
// If we see two retains in a row on the same pointer. If so, make
|
|
// a note, and we'll cicle back to revisit it after we've
|
|
// hopefully eliminated the second retain, which may allow us to
|
|
// eliminate the first retain too.
|
|
// Theoretically we could implement removal of nested retain+release
|
|
// pairs by making PtrState hold a stack of states, but this is
|
|
// simple and avoids adding overhead for the non-nested case.
|
|
if (S.GetSeq() == S_Retain)
|
|
NestingDetected = true;
|
|
|
|
S.ResetSequenceProgress(S_Retain);
|
|
S.RRI.IsRetainBlock = Class == IC_RetainBlock;
|
|
S.RRI.KnownSafe = S.IsKnownIncremented();
|
|
S.RRI.Calls.insert(Inst);
|
|
}
|
|
|
|
S.SetKnownPositiveRefCount();
|
|
|
|
// A retain can be a potential use; procede to the generic checking
|
|
// code below.
|
|
break;
|
|
}
|
|
case IC_Release: {
|
|
Arg = GetObjCArg(Inst);
|
|
|
|
PtrState &S = MyStates.getPtrTopDownState(Arg);
|
|
S.ClearRefCount();
|
|
|
|
switch (S.GetSeq()) {
|
|
case S_Retain:
|
|
case S_CanRelease:
|
|
S.RRI.ReverseInsertPts.clear();
|
|
// FALL THROUGH
|
|
case S_Use:
|
|
S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
|
|
S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
|
|
Releases[Inst] = S.RRI;
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
case S_None:
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
llvm_unreachable("top-down pointer in release state!");
|
|
}
|
|
break;
|
|
}
|
|
case IC_AutoreleasepoolPop:
|
|
// Conservatively, clear MyStates for all known pointers.
|
|
MyStates.clearTopDownPointers();
|
|
return NestingDetected;
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_None:
|
|
// These are irrelevant.
|
|
return NestingDetected;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
// Consider any other possible effects of this instruction on each
|
|
// pointer being tracked.
|
|
for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
|
|
ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
|
|
const Value *Ptr = MI->first;
|
|
if (Ptr == Arg)
|
|
continue; // Handled above.
|
|
PtrState &S = MI->second;
|
|
Sequence Seq = S.GetSeq();
|
|
|
|
// Check for possible releases.
|
|
if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
|
|
S.ClearRefCount();
|
|
switch (Seq) {
|
|
case S_Retain:
|
|
S.SetSeq(S_CanRelease);
|
|
assert(S.RRI.ReverseInsertPts.empty());
|
|
S.RRI.ReverseInsertPts.insert(Inst);
|
|
|
|
// One call can't cause a transition from S_Retain to S_CanRelease
|
|
// and S_CanRelease to S_Use. If we've made the first transition,
|
|
// we're done.
|
|
continue;
|
|
case S_Use:
|
|
case S_CanRelease:
|
|
case S_None:
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
llvm_unreachable("top-down pointer in release state!");
|
|
}
|
|
}
|
|
|
|
// Check for possible direct uses.
|
|
switch (Seq) {
|
|
case S_CanRelease:
|
|
if (CanUse(Inst, Ptr, PA, Class))
|
|
S.SetSeq(S_Use);
|
|
break;
|
|
case S_Retain:
|
|
case S_Use:
|
|
case S_None:
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
llvm_unreachable("top-down pointer in release state!");
|
|
}
|
|
}
|
|
|
|
return NestingDetected;
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::VisitTopDown(BasicBlock *BB,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
DenseMap<Value *, RRInfo> &Releases) {
|
|
bool NestingDetected = false;
|
|
BBState &MyStates = BBStates[BB];
|
|
|
|
// Merge the states from each predecessor to compute the initial state
|
|
// for the current block.
|
|
BBState::edge_iterator PI(MyStates.pred_begin()),
|
|
PE(MyStates.pred_end());
|
|
if (PI != PE) {
|
|
const BasicBlock *Pred = *PI;
|
|
DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
|
|
assert(I != BBStates.end());
|
|
MyStates.InitFromPred(I->second);
|
|
++PI;
|
|
for (; PI != PE; ++PI) {
|
|
Pred = *PI;
|
|
I = BBStates.find(Pred);
|
|
assert(I != BBStates.end());
|
|
MyStates.MergePred(I->second);
|
|
}
|
|
}
|
|
|
|
// Visit all the instructions, top-down.
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
Instruction *Inst = I;
|
|
NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
|
|
}
|
|
|
|
CheckForCFGHazards(BB, BBStates, MyStates);
|
|
return NestingDetected;
|
|
}
|
|
|
|
static void
|
|
ComputePostOrders(Function &F,
|
|
SmallVectorImpl<BasicBlock *> &PostOrder,
|
|
SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder,
|
|
unsigned NoObjCARCExceptionsMDKind,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates) {
|
|
/// Visited - The visited set, for doing DFS walks.
|
|
SmallPtrSet<BasicBlock *, 16> Visited;
|
|
|
|
// Do DFS, computing the PostOrder.
|
|
SmallPtrSet<BasicBlock *, 16> OnStack;
|
|
SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack;
|
|
|
|
// Functions always have exactly one entry block, and we don't have
|
|
// any other block that we treat like an entry block.
|
|
BasicBlock *EntryBB = &F.getEntryBlock();
|
|
BBState &MyStates = BBStates[EntryBB];
|
|
MyStates.SetAsEntry();
|
|
TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back());
|
|
SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI)));
|
|
Visited.insert(EntryBB);
|
|
OnStack.insert(EntryBB);
|
|
do {
|
|
dfs_next_succ:
|
|
BasicBlock *CurrBB = SuccStack.back().first;
|
|
TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back());
|
|
succ_iterator SE(TI, false);
|
|
|
|
// If the terminator is an invoke marked with the
|
|
// clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
|
|
// ignored, for ARC purposes.
|
|
if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
|
|
--SE;
|
|
|
|
while (SuccStack.back().second != SE) {
|
|
BasicBlock *SuccBB = *SuccStack.back().second++;
|
|
if (Visited.insert(SuccBB)) {
|
|
TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back());
|
|
SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI)));
|
|
BBStates[CurrBB].addSucc(SuccBB);
|
|
BBState &SuccStates = BBStates[SuccBB];
|
|
SuccStates.addPred(CurrBB);
|
|
OnStack.insert(SuccBB);
|
|
goto dfs_next_succ;
|
|
}
|
|
|
|
if (!OnStack.count(SuccBB)) {
|
|
BBStates[CurrBB].addSucc(SuccBB);
|
|
BBStates[SuccBB].addPred(CurrBB);
|
|
}
|
|
}
|
|
OnStack.erase(CurrBB);
|
|
PostOrder.push_back(CurrBB);
|
|
SuccStack.pop_back();
|
|
} while (!SuccStack.empty());
|
|
|
|
Visited.clear();
|
|
|
|
// Do reverse-CFG DFS, computing the reverse-CFG PostOrder.
|
|
// Functions may have many exits, and there also blocks which we treat
|
|
// as exits due to ignored edges.
|
|
SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack;
|
|
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
|
|
BasicBlock *ExitBB = I;
|
|
BBState &MyStates = BBStates[ExitBB];
|
|
if (!MyStates.isExit())
|
|
continue;
|
|
|
|
MyStates.SetAsExit();
|
|
|
|
PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin()));
|
|
Visited.insert(ExitBB);
|
|
while (!PredStack.empty()) {
|
|
reverse_dfs_next_succ:
|
|
BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end();
|
|
while (PredStack.back().second != PE) {
|
|
BasicBlock *BB = *PredStack.back().second++;
|
|
if (Visited.insert(BB)) {
|
|
PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin()));
|
|
goto reverse_dfs_next_succ;
|
|
}
|
|
}
|
|
ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Visit - Visit the function both top-down and bottom-up.
|
|
bool
|
|
ObjCARCOpt::Visit(Function &F,
|
|
DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases) {
|
|
|
|
// Use reverse-postorder traversals, because we magically know that loops
|
|
// will be well behaved, i.e. they won't repeatedly call retain on a single
|
|
// pointer without doing a release. We can't use the ReversePostOrderTraversal
|
|
// class here because we want the reverse-CFG postorder to consider each
|
|
// function exit point, and we want to ignore selected cycle edges.
|
|
SmallVector<BasicBlock *, 16> PostOrder;
|
|
SmallVector<BasicBlock *, 16> ReverseCFGPostOrder;
|
|
ComputePostOrders(F, PostOrder, ReverseCFGPostOrder,
|
|
NoObjCARCExceptionsMDKind,
|
|
BBStates);
|
|
|
|
// Use reverse-postorder on the reverse CFG for bottom-up.
|
|
bool BottomUpNestingDetected = false;
|
|
for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
|
|
ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend();
|
|
I != E; ++I)
|
|
BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains);
|
|
|
|
// Use reverse-postorder for top-down.
|
|
bool TopDownNestingDetected = false;
|
|
for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
|
|
PostOrder.rbegin(), E = PostOrder.rend();
|
|
I != E; ++I)
|
|
TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases);
|
|
|
|
return TopDownNestingDetected && BottomUpNestingDetected;
|
|
}
|
|
|
|
/// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove.
|
|
void ObjCARCOpt::MoveCalls(Value *Arg,
|
|
RRInfo &RetainsToMove,
|
|
RRInfo &ReleasesToMove,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
SmallVectorImpl<Instruction *> &DeadInsts,
|
|
Module *M) {
|
|
Type *ArgTy = Arg->getType();
|
|
Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
|
|
|
|
// Insert the new retain and release calls.
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
PI = ReleasesToMove.ReverseInsertPts.begin(),
|
|
PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
|
|
Instruction *InsertPt = *PI;
|
|
Value *MyArg = ArgTy == ParamTy ? Arg :
|
|
new BitCastInst(Arg, ParamTy, "", InsertPt);
|
|
CallInst *Call =
|
|
CallInst::Create(RetainsToMove.IsRetainBlock ?
|
|
getRetainBlockCallee(M) : getRetainCallee(M),
|
|
MyArg, "", InsertPt);
|
|
Call->setDoesNotThrow();
|
|
if (RetainsToMove.IsRetainBlock)
|
|
Call->setMetadata(CopyOnEscapeMDKind,
|
|
MDNode::get(M->getContext(), ArrayRef<Value *>()));
|
|
else
|
|
Call->setTailCall();
|
|
}
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
PI = RetainsToMove.ReverseInsertPts.begin(),
|
|
PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
|
|
Instruction *InsertPt = *PI;
|
|
Value *MyArg = ArgTy == ParamTy ? Arg :
|
|
new BitCastInst(Arg, ParamTy, "", InsertPt);
|
|
CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
|
|
"", InsertPt);
|
|
// Attach a clang.imprecise_release metadata tag, if appropriate.
|
|
if (MDNode *M = ReleasesToMove.ReleaseMetadata)
|
|
Call->setMetadata(ImpreciseReleaseMDKind, M);
|
|
Call->setDoesNotThrow();
|
|
if (ReleasesToMove.IsTailCallRelease)
|
|
Call->setTailCall();
|
|
}
|
|
|
|
// Delete the original retain and release calls.
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
AI = RetainsToMove.Calls.begin(),
|
|
AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
|
|
Instruction *OrigRetain = *AI;
|
|
Retains.blot(OrigRetain);
|
|
DeadInsts.push_back(OrigRetain);
|
|
}
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
AI = ReleasesToMove.Calls.begin(),
|
|
AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
|
|
Instruction *OrigRelease = *AI;
|
|
Releases.erase(OrigRelease);
|
|
DeadInsts.push_back(OrigRelease);
|
|
}
|
|
}
|
|
|
|
/// PerformCodePlacement - Identify pairings between the retains and releases,
|
|
/// and delete and/or move them.
|
|
bool
|
|
ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
|
|
&BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
Module *M) {
|
|
bool AnyPairsCompletelyEliminated = false;
|
|
RRInfo RetainsToMove;
|
|
RRInfo ReleasesToMove;
|
|
SmallVector<Instruction *, 4> NewRetains;
|
|
SmallVector<Instruction *, 4> NewReleases;
|
|
SmallVector<Instruction *, 8> DeadInsts;
|
|
|
|
// Visit each retain.
|
|
for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
|
|
E = Retains.end(); I != E; ++I) {
|
|
Value *V = I->first;
|
|
if (!V) continue; // blotted
|
|
|
|
Instruction *Retain = cast<Instruction>(V);
|
|
Value *Arg = GetObjCArg(Retain);
|
|
|
|
// If the object being released is in static or stack storage, we know it's
|
|
// not being managed by ObjC reference counting, so we can delete pairs
|
|
// regardless of what possible decrements or uses lie between them.
|
|
bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
|
|
|
|
// A constant pointer can't be pointing to an object on the heap. It may
|
|
// be reference-counted, but it won't be deleted.
|
|
if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
|
|
if (const GlobalVariable *GV =
|
|
dyn_cast<GlobalVariable>(
|
|
StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
|
|
if (GV->isConstant())
|
|
KnownSafe = true;
|
|
|
|
// If a pair happens in a region where it is known that the reference count
|
|
// is already incremented, we can similarly ignore possible decrements.
|
|
bool KnownSafeTD = true, KnownSafeBU = true;
|
|
|
|
// Connect the dots between the top-down-collected RetainsToMove and
|
|
// bottom-up-collected ReleasesToMove to form sets of related calls.
|
|
// This is an iterative process so that we connect multiple releases
|
|
// to multiple retains if needed.
|
|
unsigned OldDelta = 0;
|
|
unsigned NewDelta = 0;
|
|
unsigned OldCount = 0;
|
|
unsigned NewCount = 0;
|
|
bool FirstRelease = true;
|
|
bool FirstRetain = true;
|
|
NewRetains.push_back(Retain);
|
|
for (;;) {
|
|
for (SmallVectorImpl<Instruction *>::const_iterator
|
|
NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
|
|
Instruction *NewRetain = *NI;
|
|
MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
|
|
assert(It != Retains.end());
|
|
const RRInfo &NewRetainRRI = It->second;
|
|
KnownSafeTD &= NewRetainRRI.KnownSafe;
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
LI = NewRetainRRI.Calls.begin(),
|
|
LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
|
|
Instruction *NewRetainRelease = *LI;
|
|
DenseMap<Value *, RRInfo>::const_iterator Jt =
|
|
Releases.find(NewRetainRelease);
|
|
if (Jt == Releases.end())
|
|
goto next_retain;
|
|
const RRInfo &NewRetainReleaseRRI = Jt->second;
|
|
assert(NewRetainReleaseRRI.Calls.count(NewRetain));
|
|
if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
|
|
OldDelta -=
|
|
BBStates[NewRetainRelease->getParent()].GetAllPathCount();
|
|
|
|
// Merge the ReleaseMetadata and IsTailCallRelease values.
|
|
if (FirstRelease) {
|
|
ReleasesToMove.ReleaseMetadata =
|
|
NewRetainReleaseRRI.ReleaseMetadata;
|
|
ReleasesToMove.IsTailCallRelease =
|
|
NewRetainReleaseRRI.IsTailCallRelease;
|
|
FirstRelease = false;
|
|
} else {
|
|
if (ReleasesToMove.ReleaseMetadata !=
|
|
NewRetainReleaseRRI.ReleaseMetadata)
|
|
ReleasesToMove.ReleaseMetadata = 0;
|
|
if (ReleasesToMove.IsTailCallRelease !=
|
|
NewRetainReleaseRRI.IsTailCallRelease)
|
|
ReleasesToMove.IsTailCallRelease = false;
|
|
}
|
|
|
|
// Collect the optimal insertion points.
|
|
if (!KnownSafe)
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
|
|
RE = NewRetainReleaseRRI.ReverseInsertPts.end();
|
|
RI != RE; ++RI) {
|
|
Instruction *RIP = *RI;
|
|
if (ReleasesToMove.ReverseInsertPts.insert(RIP))
|
|
NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
|
|
}
|
|
NewReleases.push_back(NewRetainRelease);
|
|
}
|
|
}
|
|
}
|
|
NewRetains.clear();
|
|
if (NewReleases.empty()) break;
|
|
|
|
// Back the other way.
|
|
for (SmallVectorImpl<Instruction *>::const_iterator
|
|
NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
|
|
Instruction *NewRelease = *NI;
|
|
DenseMap<Value *, RRInfo>::const_iterator It =
|
|
Releases.find(NewRelease);
|
|
assert(It != Releases.end());
|
|
const RRInfo &NewReleaseRRI = It->second;
|
|
KnownSafeBU &= NewReleaseRRI.KnownSafe;
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
LI = NewReleaseRRI.Calls.begin(),
|
|
LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
|
|
Instruction *NewReleaseRetain = *LI;
|
|
MapVector<Value *, RRInfo>::const_iterator Jt =
|
|
Retains.find(NewReleaseRetain);
|
|
if (Jt == Retains.end())
|
|
goto next_retain;
|
|
const RRInfo &NewReleaseRetainRRI = Jt->second;
|
|
assert(NewReleaseRetainRRI.Calls.count(NewRelease));
|
|
if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
|
|
unsigned PathCount =
|
|
BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
|
|
OldDelta += PathCount;
|
|
OldCount += PathCount;
|
|
|
|
// Merge the IsRetainBlock values.
|
|
if (FirstRetain) {
|
|
RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
|
|
FirstRetain = false;
|
|
} else if (ReleasesToMove.IsRetainBlock !=
|
|
NewReleaseRetainRRI.IsRetainBlock)
|
|
// It's not possible to merge the sequences if one uses
|
|
// objc_retain and the other uses objc_retainBlock.
|
|
goto next_retain;
|
|
|
|
// Collect the optimal insertion points.
|
|
if (!KnownSafe)
|
|
for (SmallPtrSet<Instruction *, 2>::const_iterator
|
|
RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
|
|
RE = NewReleaseRetainRRI.ReverseInsertPts.end();
|
|
RI != RE; ++RI) {
|
|
Instruction *RIP = *RI;
|
|
if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
|
|
PathCount = BBStates[RIP->getParent()].GetAllPathCount();
|
|
NewDelta += PathCount;
|
|
NewCount += PathCount;
|
|
}
|
|
}
|
|
NewRetains.push_back(NewReleaseRetain);
|
|
}
|
|
}
|
|
}
|
|
NewReleases.clear();
|
|
if (NewRetains.empty()) break;
|
|
}
|
|
|
|
// If the pointer is known incremented or nested, we can safely delete the
|
|
// pair regardless of what's between them.
|
|
if (KnownSafeTD || KnownSafeBU) {
|
|
RetainsToMove.ReverseInsertPts.clear();
|
|
ReleasesToMove.ReverseInsertPts.clear();
|
|
NewCount = 0;
|
|
} else {
|
|
// Determine whether the new insertion points we computed preserve the
|
|
// balance of retain and release calls through the program.
|
|
// TODO: If the fully aggressive solution isn't valid, try to find a
|
|
// less aggressive solution which is.
|
|
if (NewDelta != 0)
|
|
goto next_retain;
|
|
}
|
|
|
|
// Determine whether the original call points are balanced in the retain and
|
|
// release calls through the program. If not, conservatively don't touch
|
|
// them.
|
|
// TODO: It's theoretically possible to do code motion in this case, as
|
|
// long as the existing imbalances are maintained.
|
|
if (OldDelta != 0)
|
|
goto next_retain;
|
|
|
|
// Ok, everything checks out and we're all set. Let's move some code!
|
|
Changed = true;
|
|
assert(OldCount != 0 && "Unreachable code?");
|
|
AnyPairsCompletelyEliminated = NewCount == 0;
|
|
NumRRs += OldCount - NewCount;
|
|
MoveCalls(Arg, RetainsToMove, ReleasesToMove,
|
|
Retains, Releases, DeadInsts, M);
|
|
|
|
next_retain:
|
|
NewReleases.clear();
|
|
NewRetains.clear();
|
|
RetainsToMove.clear();
|
|
ReleasesToMove.clear();
|
|
}
|
|
|
|
// Now that we're done moving everything, we can delete the newly dead
|
|
// instructions, as we no longer need them as insert points.
|
|
while (!DeadInsts.empty())
|
|
EraseInstruction(DeadInsts.pop_back_val());
|
|
|
|
return AnyPairsCompletelyEliminated;
|
|
}
|
|
|
|
/// OptimizeWeakCalls - Weak pointer optimizations.
|
|
void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
|
|
// First, do memdep-style RLE and S2L optimizations. We can't use memdep
|
|
// itself because it uses AliasAnalysis and we need to do provenance
|
|
// queries instead.
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
|
|
Instruction *Inst = &*I++;
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
|
|
continue;
|
|
|
|
// Delete objc_loadWeak calls with no users.
|
|
if (Class == IC_LoadWeak && Inst->use_empty()) {
|
|
Inst->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
// TODO: For now, just look for an earlier available version of this value
|
|
// within the same block. Theoretically, we could do memdep-style non-local
|
|
// analysis too, but that would want caching. A better approach would be to
|
|
// use the technique that EarlyCSE uses.
|
|
inst_iterator Current = llvm::prior(I);
|
|
BasicBlock *CurrentBB = Current.getBasicBlockIterator();
|
|
for (BasicBlock::iterator B = CurrentBB->begin(),
|
|
J = Current.getInstructionIterator();
|
|
J != B; --J) {
|
|
Instruction *EarlierInst = &*llvm::prior(J);
|
|
InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
|
|
switch (EarlierClass) {
|
|
case IC_LoadWeak:
|
|
case IC_LoadWeakRetained: {
|
|
// If this is loading from the same pointer, replace this load's value
|
|
// with that one.
|
|
CallInst *Call = cast<CallInst>(Inst);
|
|
CallInst *EarlierCall = cast<CallInst>(EarlierInst);
|
|
Value *Arg = Call->getArgOperand(0);
|
|
Value *EarlierArg = EarlierCall->getArgOperand(0);
|
|
switch (PA.getAA()->alias(Arg, EarlierArg)) {
|
|
case AliasAnalysis::MustAlias:
|
|
Changed = true;
|
|
// If the load has a builtin retain, insert a plain retain for it.
|
|
if (Class == IC_LoadWeakRetained) {
|
|
CallInst *CI =
|
|
CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
|
|
"", Call);
|
|
CI->setTailCall();
|
|
}
|
|
// Zap the fully redundant load.
|
|
Call->replaceAllUsesWith(EarlierCall);
|
|
Call->eraseFromParent();
|
|
goto clobbered;
|
|
case AliasAnalysis::MayAlias:
|
|
case AliasAnalysis::PartialAlias:
|
|
goto clobbered;
|
|
case AliasAnalysis::NoAlias:
|
|
break;
|
|
}
|
|
break;
|
|
}
|
|
case IC_StoreWeak:
|
|
case IC_InitWeak: {
|
|
// If this is storing to the same pointer and has the same size etc.
|
|
// replace this load's value with the stored value.
|
|
CallInst *Call = cast<CallInst>(Inst);
|
|
CallInst *EarlierCall = cast<CallInst>(EarlierInst);
|
|
Value *Arg = Call->getArgOperand(0);
|
|
Value *EarlierArg = EarlierCall->getArgOperand(0);
|
|
switch (PA.getAA()->alias(Arg, EarlierArg)) {
|
|
case AliasAnalysis::MustAlias:
|
|
Changed = true;
|
|
// If the load has a builtin retain, insert a plain retain for it.
|
|
if (Class == IC_LoadWeakRetained) {
|
|
CallInst *CI =
|
|
CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
|
|
"", Call);
|
|
CI->setTailCall();
|
|
}
|
|
// Zap the fully redundant load.
|
|
Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
|
|
Call->eraseFromParent();
|
|
goto clobbered;
|
|
case AliasAnalysis::MayAlias:
|
|
case AliasAnalysis::PartialAlias:
|
|
goto clobbered;
|
|
case AliasAnalysis::NoAlias:
|
|
break;
|
|
}
|
|
break;
|
|
}
|
|
case IC_MoveWeak:
|
|
case IC_CopyWeak:
|
|
// TOOD: Grab the copied value.
|
|
goto clobbered;
|
|
case IC_AutoreleasepoolPush:
|
|
case IC_None:
|
|
case IC_User:
|
|
// Weak pointers are only modified through the weak entry points
|
|
// (and arbitrary calls, which could call the weak entry points).
|
|
break;
|
|
default:
|
|
// Anything else could modify the weak pointer.
|
|
goto clobbered;
|
|
}
|
|
}
|
|
clobbered:;
|
|
}
|
|
|
|
// Then, for each destroyWeak with an alloca operand, check to see if
|
|
// the alloca and all its users can be zapped.
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
|
|
Instruction *Inst = &*I++;
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
if (Class != IC_DestroyWeak)
|
|
continue;
|
|
|
|
CallInst *Call = cast<CallInst>(Inst);
|
|
Value *Arg = Call->getArgOperand(0);
|
|
if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
|
|
for (Value::use_iterator UI = Alloca->use_begin(),
|
|
UE = Alloca->use_end(); UI != UE; ++UI) {
|
|
const Instruction *UserInst = cast<Instruction>(*UI);
|
|
switch (GetBasicInstructionClass(UserInst)) {
|
|
case IC_InitWeak:
|
|
case IC_StoreWeak:
|
|
case IC_DestroyWeak:
|
|
continue;
|
|
default:
|
|
goto done;
|
|
}
|
|
}
|
|
Changed = true;
|
|
for (Value::use_iterator UI = Alloca->use_begin(),
|
|
UE = Alloca->use_end(); UI != UE; ) {
|
|
CallInst *UserInst = cast<CallInst>(*UI++);
|
|
switch (GetBasicInstructionClass(UserInst)) {
|
|
case IC_InitWeak:
|
|
case IC_StoreWeak:
|
|
// These functions return their second argument.
|
|
UserInst->replaceAllUsesWith(UserInst->getArgOperand(1));
|
|
break;
|
|
case IC_DestroyWeak:
|
|
// No return value.
|
|
break;
|
|
default:
|
|
llvm_unreachable("alloca really is used!");
|
|
}
|
|
UserInst->eraseFromParent();
|
|
}
|
|
Alloca->eraseFromParent();
|
|
done:;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// OptimizeSequences - Identify program paths which execute sequences of
|
|
/// retains and releases which can be eliminated.
|
|
bool ObjCARCOpt::OptimizeSequences(Function &F) {
|
|
/// Releases, Retains - These are used to store the results of the main flow
|
|
/// analysis. These use Value* as the key instead of Instruction* so that the
|
|
/// map stays valid when we get around to rewriting code and calls get
|
|
/// replaced by arguments.
|
|
DenseMap<Value *, RRInfo> Releases;
|
|
MapVector<Value *, RRInfo> Retains;
|
|
|
|
/// BBStates, This is used during the traversal of the function to track the
|
|
/// states for each identified object at each block.
|
|
DenseMap<const BasicBlock *, BBState> BBStates;
|
|
|
|
// Analyze the CFG of the function, and all instructions.
|
|
bool NestingDetected = Visit(F, BBStates, Retains, Releases);
|
|
|
|
// Transform.
|
|
return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
|
|
NestingDetected;
|
|
}
|
|
|
|
/// OptimizeReturns - Look for this pattern:
|
|
/// \code
|
|
/// %call = call i8* @something(...)
|
|
/// %2 = call i8* @objc_retain(i8* %call)
|
|
/// %3 = call i8* @objc_autorelease(i8* %2)
|
|
/// ret i8* %3
|
|
/// \endcode
|
|
/// And delete the retain and autorelease.
|
|
///
|
|
/// Otherwise if it's just this:
|
|
/// \code
|
|
/// %3 = call i8* @objc_autorelease(i8* %2)
|
|
/// ret i8* %3
|
|
/// \endcode
|
|
/// convert the autorelease to autoreleaseRV.
|
|
void ObjCARCOpt::OptimizeReturns(Function &F) {
|
|
if (!F.getReturnType()->isPointerTy())
|
|
return;
|
|
|
|
SmallPtrSet<Instruction *, 4> DependingInstructions;
|
|
SmallPtrSet<const BasicBlock *, 4> Visited;
|
|
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
|
|
BasicBlock *BB = FI;
|
|
ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
|
|
if (!Ret) continue;
|
|
|
|
const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
|
|
FindDependencies(NeedsPositiveRetainCount, Arg,
|
|
BB, Ret, DependingInstructions, Visited, PA);
|
|
if (DependingInstructions.size() != 1)
|
|
goto next_block;
|
|
|
|
{
|
|
CallInst *Autorelease =
|
|
dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
|
|
if (!Autorelease)
|
|
goto next_block;
|
|
InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
|
|
if (!IsAutorelease(AutoreleaseClass))
|
|
goto next_block;
|
|
if (GetObjCArg(Autorelease) != Arg)
|
|
goto next_block;
|
|
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
|
|
// Check that there is nothing that can affect the reference
|
|
// count between the autorelease and the retain.
|
|
FindDependencies(CanChangeRetainCount, Arg,
|
|
BB, Autorelease, DependingInstructions, Visited, PA);
|
|
if (DependingInstructions.size() != 1)
|
|
goto next_block;
|
|
|
|
{
|
|
CallInst *Retain =
|
|
dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
|
|
|
|
// Check that we found a retain with the same argument.
|
|
if (!Retain ||
|
|
!IsRetain(GetBasicInstructionClass(Retain)) ||
|
|
GetObjCArg(Retain) != Arg)
|
|
goto next_block;
|
|
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
|
|
// Convert the autorelease to an autoreleaseRV, since it's
|
|
// returning the value.
|
|
if (AutoreleaseClass == IC_Autorelease) {
|
|
Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
|
|
AutoreleaseClass = IC_AutoreleaseRV;
|
|
}
|
|
|
|
// Check that there is nothing that can affect the reference
|
|
// count between the retain and the call.
|
|
// Note that Retain need not be in BB.
|
|
FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
|
|
DependingInstructions, Visited, PA);
|
|
if (DependingInstructions.size() != 1)
|
|
goto next_block;
|
|
|
|
{
|
|
CallInst *Call =
|
|
dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
|
|
|
|
// Check that the pointer is the return value of the call.
|
|
if (!Call || Arg != Call)
|
|
goto next_block;
|
|
|
|
// Check that the call is a regular call.
|
|
InstructionClass Class = GetBasicInstructionClass(Call);
|
|
if (Class != IC_CallOrUser && Class != IC_Call)
|
|
goto next_block;
|
|
|
|
// If so, we can zap the retain and autorelease.
|
|
Changed = true;
|
|
++NumRets;
|
|
EraseInstruction(Retain);
|
|
EraseInstruction(Autorelease);
|
|
}
|
|
}
|
|
}
|
|
|
|
next_block:
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
}
|
|
}
|
|
|
|
bool ObjCARCOpt::doInitialization(Module &M) {
|
|
if (!EnableARCOpts)
|
|
return false;
|
|
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
Run = ModuleHasARC(M);
|
|
if (!Run)
|
|
return false;
|
|
|
|
// Identify the imprecise release metadata kind.
|
|
ImpreciseReleaseMDKind =
|
|
M.getContext().getMDKindID("clang.imprecise_release");
|
|
CopyOnEscapeMDKind =
|
|
M.getContext().getMDKindID("clang.arc.copy_on_escape");
|
|
NoObjCARCExceptionsMDKind =
|
|
M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions");
|
|
|
|
// Intuitively, objc_retain and others are nocapture, however in practice
|
|
// they are not, because they return their argument value. And objc_release
|
|
// calls finalizers which can have arbitrary side effects.
|
|
|
|
// These are initialized lazily.
|
|
RetainRVCallee = 0;
|
|
AutoreleaseRVCallee = 0;
|
|
ReleaseCallee = 0;
|
|
RetainCallee = 0;
|
|
RetainBlockCallee = 0;
|
|
AutoreleaseCallee = 0;
|
|
|
|
return false;
|
|
}
|
|
|
|
bool ObjCARCOpt::runOnFunction(Function &F) {
|
|
if (!EnableARCOpts)
|
|
return false;
|
|
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
if (!Run)
|
|
return false;
|
|
|
|
Changed = false;
|
|
|
|
PA.setAA(&getAnalysis<AliasAnalysis>());
|
|
|
|
// This pass performs several distinct transformations. As a compile-time aid
|
|
// when compiling code that isn't ObjC, skip these if the relevant ObjC
|
|
// library functions aren't declared.
|
|
|
|
// Preliminary optimizations. This also computs UsedInThisFunction.
|
|
OptimizeIndividualCalls(F);
|
|
|
|
// Optimizations for weak pointers.
|
|
if (UsedInThisFunction & ((1 << IC_LoadWeak) |
|
|
(1 << IC_LoadWeakRetained) |
|
|
(1 << IC_StoreWeak) |
|
|
(1 << IC_InitWeak) |
|
|
(1 << IC_CopyWeak) |
|
|
(1 << IC_MoveWeak) |
|
|
(1 << IC_DestroyWeak)))
|
|
OptimizeWeakCalls(F);
|
|
|
|
// Optimizations for retain+release pairs.
|
|
if (UsedInThisFunction & ((1 << IC_Retain) |
|
|
(1 << IC_RetainRV) |
|
|
(1 << IC_RetainBlock)))
|
|
if (UsedInThisFunction & (1 << IC_Release))
|
|
// Run OptimizeSequences until it either stops making changes or
|
|
// no retain+release pair nesting is detected.
|
|
while (OptimizeSequences(F)) {}
|
|
|
|
// Optimizations if objc_autorelease is used.
|
|
if (UsedInThisFunction & ((1 << IC_Autorelease) |
|
|
(1 << IC_AutoreleaseRV)))
|
|
OptimizeReturns(F);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
void ObjCARCOpt::releaseMemory() {
|
|
PA.clear();
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// ARC contraction.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// TODO: ObjCARCContract could insert PHI nodes when uses aren't
|
|
// dominated by single calls.
|
|
|
|
#include "llvm/Operator.h"
|
|
#include "llvm/InlineAsm.h"
|
|
#include "llvm/Analysis/Dominators.h"
|
|
|
|
STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
|
|
|
|
namespace {
|
|
/// ObjCARCContract - Late ARC optimizations. These change the IR in a way
|
|
/// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late.
|
|
class ObjCARCContract : public FunctionPass {
|
|
bool Changed;
|
|
AliasAnalysis *AA;
|
|
DominatorTree *DT;
|
|
ProvenanceAnalysis PA;
|
|
|
|
/// Run - A flag indicating whether this optimization pass should run.
|
|
bool Run;
|
|
|
|
/// StoreStrongCallee, etc. - Declarations for ObjC runtime
|
|
/// functions, for use in creating calls to them. These are initialized
|
|
/// lazily to avoid cluttering up the Module with unused declarations.
|
|
Constant *StoreStrongCallee,
|
|
*RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee;
|
|
|
|
/// RetainRVMarker - The inline asm string to insert between calls and
|
|
/// RetainRV calls to make the optimization work on targets which need it.
|
|
const MDString *RetainRVMarker;
|
|
|
|
/// StoreStrongCalls - The set of inserted objc_storeStrong calls. If
|
|
/// at the end of walking the function we have found no alloca
|
|
/// instructions, these calls can be marked "tail".
|
|
SmallPtrSet<CallInst *, 8> StoreStrongCalls;
|
|
|
|
Constant *getStoreStrongCallee(Module *M);
|
|
Constant *getRetainAutoreleaseCallee(Module *M);
|
|
Constant *getRetainAutoreleaseRVCallee(Module *M);
|
|
|
|
bool ContractAutorelease(Function &F, Instruction *Autorelease,
|
|
InstructionClass Class,
|
|
SmallPtrSet<Instruction *, 4>
|
|
&DependingInstructions,
|
|
SmallPtrSet<const BasicBlock *, 4>
|
|
&Visited);
|
|
|
|
void ContractRelease(Instruction *Release,
|
|
inst_iterator &Iter);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
virtual bool doInitialization(Module &M);
|
|
virtual bool runOnFunction(Function &F);
|
|
|
|
public:
|
|
static char ID;
|
|
ObjCARCContract() : FunctionPass(ID) {
|
|
initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
};
|
|
}
|
|
|
|
char ObjCARCContract::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(ObjCARCContract,
|
|
"objc-arc-contract", "ObjC ARC contraction", false, false)
|
|
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
|
|
INITIALIZE_PASS_END(ObjCARCContract,
|
|
"objc-arc-contract", "ObjC ARC contraction", false, false)
|
|
|
|
Pass *llvm::createObjCARCContractPass() {
|
|
return new ObjCARCContract();
|
|
}
|
|
|
|
void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.addRequired<AliasAnalysis>();
|
|
AU.addRequired<DominatorTree>();
|
|
AU.setPreservesCFG();
|
|
}
|
|
|
|
Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
|
|
if (!StoreStrongCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *I8XX = PointerType::getUnqual(I8X);
|
|
Type *Params[] = { I8XX, I8X };
|
|
|
|
AttrListPtr Attributes = AttrListPtr()
|
|
.addAttr(~0u, Attribute::NoUnwind)
|
|
.addAttr(1, Attribute::NoCapture);
|
|
|
|
StoreStrongCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_storeStrong",
|
|
FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
|
|
Attributes);
|
|
}
|
|
return StoreStrongCallee;
|
|
}
|
|
|
|
Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
|
|
if (!RetainAutoreleaseCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *Params[] = { I8X };
|
|
FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
RetainAutoreleaseCallee =
|
|
M->getOrInsertFunction("objc_retainAutorelease", FTy, Attributes);
|
|
}
|
|
return RetainAutoreleaseCallee;
|
|
}
|
|
|
|
Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
|
|
if (!RetainAutoreleaseRVCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *Params[] = { I8X };
|
|
FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
|
|
AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attribute::NoUnwind);
|
|
RetainAutoreleaseRVCallee =
|
|
M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
|
|
Attributes);
|
|
}
|
|
return RetainAutoreleaseRVCallee;
|
|
}
|
|
|
|
/// ContractAutorelease - Merge an autorelease with a retain into a fused call.
|
|
bool
|
|
ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
|
|
InstructionClass Class,
|
|
SmallPtrSet<Instruction *, 4>
|
|
&DependingInstructions,
|
|
SmallPtrSet<const BasicBlock *, 4>
|
|
&Visited) {
|
|
const Value *Arg = GetObjCArg(Autorelease);
|
|
|
|
// Check that there are no instructions between the retain and the autorelease
|
|
// (such as an autorelease_pop) which may change the count.
|
|
CallInst *Retain = 0;
|
|
if (Class == IC_AutoreleaseRV)
|
|
FindDependencies(RetainAutoreleaseRVDep, Arg,
|
|
Autorelease->getParent(), Autorelease,
|
|
DependingInstructions, Visited, PA);
|
|
else
|
|
FindDependencies(RetainAutoreleaseDep, Arg,
|
|
Autorelease->getParent(), Autorelease,
|
|
DependingInstructions, Visited, PA);
|
|
|
|
Visited.clear();
|
|
if (DependingInstructions.size() != 1) {
|
|
DependingInstructions.clear();
|
|
return false;
|
|
}
|
|
|
|
Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
|
|
DependingInstructions.clear();
|
|
|
|
if (!Retain ||
|
|
GetBasicInstructionClass(Retain) != IC_Retain ||
|
|
GetObjCArg(Retain) != Arg)
|
|
return false;
|
|
|
|
Changed = true;
|
|
++NumPeeps;
|
|
|
|
if (Class == IC_AutoreleaseRV)
|
|
Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
|
|
else
|
|
Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
|
|
|
|
EraseInstruction(Autorelease);
|
|
return true;
|
|
}
|
|
|
|
/// ContractRelease - Attempt to merge an objc_release with a store, load, and
|
|
/// objc_retain to form an objc_storeStrong. This can be a little tricky because
|
|
/// the instructions don't always appear in order, and there may be unrelated
|
|
/// intervening instructions.
|
|
void ObjCARCContract::ContractRelease(Instruction *Release,
|
|
inst_iterator &Iter) {
|
|
LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
|
|
if (!Load || !Load->isSimple()) return;
|
|
|
|
// For now, require everything to be in one basic block.
|
|
BasicBlock *BB = Release->getParent();
|
|
if (Load->getParent() != BB) return;
|
|
|
|
// Walk down to find the store and the release, which may be in either order.
|
|
BasicBlock::iterator I = Load, End = BB->end();
|
|
++I;
|
|
AliasAnalysis::Location Loc = AA->getLocation(Load);
|
|
StoreInst *Store = 0;
|
|
bool SawRelease = false;
|
|
for (; !Store || !SawRelease; ++I) {
|
|
if (I == End)
|
|
return;
|
|
|
|
Instruction *Inst = I;
|
|
if (Inst == Release) {
|
|
SawRelease = true;
|
|
continue;
|
|
}
|
|
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
|
|
// Unrelated retains are harmless.
|
|
if (IsRetain(Class))
|
|
continue;
|
|
|
|
if (Store) {
|
|
// The store is the point where we're going to put the objc_storeStrong,
|
|
// so make sure there are no uses after it.
|
|
if (CanUse(Inst, Load, PA, Class))
|
|
return;
|
|
} else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
|
|
// We are moving the load down to the store, so check for anything
|
|
// else which writes to the memory between the load and the store.
|
|
Store = dyn_cast<StoreInst>(Inst);
|
|
if (!Store || !Store->isSimple()) return;
|
|
if (Store->getPointerOperand() != Loc.Ptr) return;
|
|
}
|
|
}
|
|
|
|
Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
|
|
|
|
// Walk up to find the retain.
|
|
I = Store;
|
|
BasicBlock::iterator Begin = BB->begin();
|
|
while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
|
|
--I;
|
|
Instruction *Retain = I;
|
|
if (GetBasicInstructionClass(Retain) != IC_Retain) return;
|
|
if (GetObjCArg(Retain) != New) return;
|
|
|
|
Changed = true;
|
|
++NumStoreStrongs;
|
|
|
|
LLVMContext &C = Release->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *I8XX = PointerType::getUnqual(I8X);
|
|
|
|
Value *Args[] = { Load->getPointerOperand(), New };
|
|
if (Args[0]->getType() != I8XX)
|
|
Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
|
|
if (Args[1]->getType() != I8X)
|
|
Args[1] = new BitCastInst(Args[1], I8X, "", Store);
|
|
CallInst *StoreStrong =
|
|
CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
|
|
Args, "", Store);
|
|
StoreStrong->setDoesNotThrow();
|
|
StoreStrong->setDebugLoc(Store->getDebugLoc());
|
|
|
|
// We can't set the tail flag yet, because we haven't yet determined
|
|
// whether there are any escaping allocas. Remember this call, so that
|
|
// we can set the tail flag once we know it's safe.
|
|
StoreStrongCalls.insert(StoreStrong);
|
|
|
|
if (&*Iter == Store) ++Iter;
|
|
Store->eraseFromParent();
|
|
Release->eraseFromParent();
|
|
EraseInstruction(Retain);
|
|
if (Load->use_empty())
|
|
Load->eraseFromParent();
|
|
}
|
|
|
|
bool ObjCARCContract::doInitialization(Module &M) {
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
Run = ModuleHasARC(M);
|
|
if (!Run)
|
|
return false;
|
|
|
|
// These are initialized lazily.
|
|
StoreStrongCallee = 0;
|
|
RetainAutoreleaseCallee = 0;
|
|
RetainAutoreleaseRVCallee = 0;
|
|
|
|
// Initialize RetainRVMarker.
|
|
RetainRVMarker = 0;
|
|
if (NamedMDNode *NMD =
|
|
M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
|
|
if (NMD->getNumOperands() == 1) {
|
|
const MDNode *N = NMD->getOperand(0);
|
|
if (N->getNumOperands() == 1)
|
|
if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
|
|
RetainRVMarker = S;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool ObjCARCContract::runOnFunction(Function &F) {
|
|
if (!EnableARCOpts)
|
|
return false;
|
|
|
|
// If nothing in the Module uses ARC, don't do anything.
|
|
if (!Run)
|
|
return false;
|
|
|
|
Changed = false;
|
|
AA = &getAnalysis<AliasAnalysis>();
|
|
DT = &getAnalysis<DominatorTree>();
|
|
|
|
PA.setAA(&getAnalysis<AliasAnalysis>());
|
|
|
|
// Track whether it's ok to mark objc_storeStrong calls with the "tail"
|
|
// keyword. Be conservative if the function has variadic arguments.
|
|
// It seems that functions which "return twice" are also unsafe for the
|
|
// "tail" argument, because they are setjmp, which could need to
|
|
// return to an earlier stack state.
|
|
bool TailOkForStoreStrongs = !F.isVarArg() &&
|
|
!F.callsFunctionThatReturnsTwice();
|
|
|
|
// For ObjC library calls which return their argument, replace uses of the
|
|
// argument with uses of the call return value, if it dominates the use. This
|
|
// reduces register pressure.
|
|
SmallPtrSet<Instruction *, 4> DependingInstructions;
|
|
SmallPtrSet<const BasicBlock *, 4> Visited;
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
|
|
Instruction *Inst = &*I++;
|
|
|
|
// Only these library routines return their argument. In particular,
|
|
// objc_retainBlock does not necessarily return its argument.
|
|
InstructionClass Class = GetBasicInstructionClass(Inst);
|
|
switch (Class) {
|
|
case IC_Retain:
|
|
case IC_FusedRetainAutorelease:
|
|
case IC_FusedRetainAutoreleaseRV:
|
|
break;
|
|
case IC_Autorelease:
|
|
case IC_AutoreleaseRV:
|
|
if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
|
|
continue;
|
|
break;
|
|
case IC_RetainRV: {
|
|
// If we're compiling for a target which needs a special inline-asm
|
|
// marker to do the retainAutoreleasedReturnValue optimization,
|
|
// insert it now.
|
|
if (!RetainRVMarker)
|
|
break;
|
|
BasicBlock::iterator BBI = Inst;
|
|
BasicBlock *InstParent = Inst->getParent();
|
|
|
|
// Step up to see if the call immediately precedes the RetainRV call.
|
|
// If it's an invoke, we have to cross a block boundary. And we have
|
|
// to carefully dodge no-op instructions.
|
|
do {
|
|
if (&*BBI == InstParent->begin()) {
|
|
BasicBlock *Pred = InstParent->getSinglePredecessor();
|
|
if (!Pred)
|
|
goto decline_rv_optimization;
|
|
BBI = Pred->getTerminator();
|
|
break;
|
|
}
|
|
--BBI;
|
|
} while (isNoopInstruction(BBI));
|
|
|
|
if (&*BBI == GetObjCArg(Inst)) {
|
|
Changed = true;
|
|
InlineAsm *IA =
|
|
InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
|
|
/*isVarArg=*/false),
|
|
RetainRVMarker->getString(),
|
|
/*Constraints=*/"", /*hasSideEffects=*/true);
|
|
CallInst::Create(IA, "", Inst);
|
|
}
|
|
decline_rv_optimization:
|
|
break;
|
|
}
|
|
case IC_InitWeak: {
|
|
// objc_initWeak(p, null) => *p = null
|
|
CallInst *CI = cast<CallInst>(Inst);
|
|
if (isNullOrUndef(CI->getArgOperand(1))) {
|
|
Value *Null =
|
|
ConstantPointerNull::get(cast<PointerType>(CI->getType()));
|
|
Changed = true;
|
|
new StoreInst(Null, CI->getArgOperand(0), CI);
|
|
CI->replaceAllUsesWith(Null);
|
|
CI->eraseFromParent();
|
|
}
|
|
continue;
|
|
}
|
|
case IC_Release:
|
|
ContractRelease(Inst, I);
|
|
continue;
|
|
case IC_User:
|
|
// Be conservative if the function has any alloca instructions.
|
|
// Technically we only care about escaping alloca instructions,
|
|
// but this is sufficient to handle some interesting cases.
|
|
if (isa<AllocaInst>(Inst))
|
|
TailOkForStoreStrongs = false;
|
|
continue;
|
|
default:
|
|
continue;
|
|
}
|
|
|
|
// Don't use GetObjCArg because we don't want to look through bitcasts
|
|
// and such; to do the replacement, the argument must have type i8*.
|
|
const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
|
|
for (;;) {
|
|
// If we're compiling bugpointed code, don't get in trouble.
|
|
if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
|
|
break;
|
|
// Look through the uses of the pointer.
|
|
for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
|
|
UI != UE; ) {
|
|
Use &U = UI.getUse();
|
|
unsigned OperandNo = UI.getOperandNo();
|
|
++UI; // Increment UI now, because we may unlink its element.
|
|
|
|
// If the call's return value dominates a use of the call's argument
|
|
// value, rewrite the use to use the return value. We check for
|
|
// reachability here because an unreachable call is considered to
|
|
// trivially dominate itself, which would lead us to rewriting its
|
|
// argument in terms of its return value, which would lead to
|
|
// infinite loops in GetObjCArg.
|
|
if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
|
|
Changed = true;
|
|
Instruction *Replacement = Inst;
|
|
Type *UseTy = U.get()->getType();
|
|
if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
|
|
// For PHI nodes, insert the bitcast in the predecessor block.
|
|
unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
|
|
BasicBlock *BB = PHI->getIncomingBlock(ValNo);
|
|
if (Replacement->getType() != UseTy)
|
|
Replacement = new BitCastInst(Replacement, UseTy, "",
|
|
&BB->back());
|
|
// While we're here, rewrite all edges for this PHI, rather
|
|
// than just one use at a time, to minimize the number of
|
|
// bitcasts we emit.
|
|
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
|
|
if (PHI->getIncomingBlock(i) == BB) {
|
|
// Keep the UI iterator valid.
|
|
if (&PHI->getOperandUse(
|
|
PHINode::getOperandNumForIncomingValue(i)) ==
|
|
&UI.getUse())
|
|
++UI;
|
|
PHI->setIncomingValue(i, Replacement);
|
|
}
|
|
} else {
|
|
if (Replacement->getType() != UseTy)
|
|
Replacement = new BitCastInst(Replacement, UseTy, "",
|
|
cast<Instruction>(U.getUser()));
|
|
U.set(Replacement);
|
|
}
|
|
}
|
|
}
|
|
|
|
// If Arg is a no-op casted pointer, strip one level of casts and iterate.
|
|
if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
|
|
Arg = BI->getOperand(0);
|
|
else if (isa<GEPOperator>(Arg) &&
|
|
cast<GEPOperator>(Arg)->hasAllZeroIndices())
|
|
Arg = cast<GEPOperator>(Arg)->getPointerOperand();
|
|
else if (isa<GlobalAlias>(Arg) &&
|
|
!cast<GlobalAlias>(Arg)->mayBeOverridden())
|
|
Arg = cast<GlobalAlias>(Arg)->getAliasee();
|
|
else
|
|
break;
|
|
}
|
|
}
|
|
|
|
// If this function has no escaping allocas or suspicious vararg usage,
|
|
// objc_storeStrong calls can be marked with the "tail" keyword.
|
|
if (TailOkForStoreStrongs)
|
|
for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
|
|
E = StoreStrongCalls.end(); I != E; ++I)
|
|
(*I)->setTailCall();
|
|
StoreStrongCalls.clear();
|
|
|
|
return Changed;
|
|
}
|