mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173781 91177308-0d34-0410-b5e6-96231b3b80d8
2670 lines
94 KiB
C++
2670 lines
94 KiB
C++
//===- ObjCARCOpts.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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/// \file
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/// This file defines ObjC ARC optimizations. ARC stands for Automatic
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/// Reference Counting and is a system for managing reference counts for objects
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/// 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-opts"
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#include "ObjCARC.h"
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#include "DependencyAnalysis.h"
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#include "ObjCARCAliasAnalysis.h"
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#include "ProvenanceAnalysis.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace llvm::objcarc;
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/// \defgroup MiscUtils Miscellaneous utilities that are not ARC specific.
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/// @{
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namespace {
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/// \brief An associative container with fast insertion-order (deterministic)
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/// iteration over its elements. Plus the special blot operation.
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template<class KeyT, class ValueT>
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class MapVector {
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/// 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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typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
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/// Keys and values.
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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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/// This is similar to erase, but instead of removing the element from the
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/// vector, it just zeros out the key in the vector. This leaves iterators
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/// intact, but clients must be prepared for zeroed-out keys when 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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///
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/// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
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/// @{
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/// \brief This is similar to StripPointerCastsAndObjCCalls but it stops as soon
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/// as it finds a value with multiple uses.
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static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
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if (Arg->hasOneUse()) {
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if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
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return FindSingleUseIdentifiedObject(BC->getOperand(0));
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if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
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if (GEP->hasAllZeroIndices())
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return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
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if (IsForwarding(GetBasicInstructionClass(Arg)))
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return FindSingleUseIdentifiedObject(
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cast<CallInst>(Arg)->getArgOperand(0));
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if (!IsObjCIdentifiedObject(Arg))
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return 0;
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return Arg;
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}
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// If we found an identifiable object but it has multiple uses, but they are
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// trivial uses, we can still consider this to be a single-use value.
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if (IsObjCIdentifiedObject(Arg)) {
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for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
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UI != UE; ++UI) {
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const User *U = *UI;
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if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
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return 0;
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}
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return Arg;
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}
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return 0;
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}
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/// \brief Test whether the given pointer, which is an Objective C block
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/// pointer, does not "escape".
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///
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/// This differs from regular escape analysis in that a use as an
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/// argument to a call is not considered an escape.
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///
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static bool DoesObjCBlockEscape(const Value *BlockPtr) {
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DEBUG(dbgs() << "DoesObjCBlockEscape: Target: " << *BlockPtr << "\n");
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// Walk the def-use chains.
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SmallVector<const Value *, 4> Worklist;
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Worklist.push_back(BlockPtr);
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// Ensure we do not visit any value twice.
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SmallPtrSet<const Value *, 4> VisitedSet;
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do {
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const Value *V = Worklist.pop_back_val();
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DEBUG(dbgs() << "DoesObjCBlockEscape: Visiting: " << *V << "\n");
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for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
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UI != UE; ++UI) {
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const User *UUser = *UI;
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DEBUG(dbgs() << "DoesObjCBlockEscape: User: " << *UUser << "\n");
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// Special - Use by a call (callee or argument) is not considered
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// to be an escape.
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switch (GetBasicInstructionClass(UUser)) {
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case IC_StoreWeak:
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case IC_InitWeak:
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case IC_StoreStrong:
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case IC_Autorelease:
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case IC_AutoreleaseRV: {
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DEBUG(dbgs() << "DoesObjCBlockEscape: User copies pointer arguments. "
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"Block Escapes!\n");
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// These special functions make copies of their pointer arguments.
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return true;
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}
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case IC_User:
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case IC_None:
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// Use by an instruction which copies the value is an escape if the
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// result is an escape.
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if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
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isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
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if (!VisitedSet.insert(UUser)) {
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DEBUG(dbgs() << "DoesObjCBlockEscape: User copies value. Escapes "
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"if result escapes. Adding to list.\n");
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Worklist.push_back(UUser);
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} else {
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DEBUG(dbgs() << "DoesObjCBlockEscape: Already visited node.\n");
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}
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continue;
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}
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// Use by a load is not an escape.
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if (isa<LoadInst>(UUser))
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continue;
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// Use by a store is not an escape if the use is the address.
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if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
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if (V != SI->getValueOperand())
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continue;
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break;
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default:
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// Regular calls and other stuff are not considered escapes.
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continue;
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}
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// Otherwise, conservatively assume an escape.
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DEBUG(dbgs() << "DoesObjCBlockEscape: Assuming block escapes.\n");
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return true;
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}
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} while (!Worklist.empty());
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// No escapes found.
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DEBUG(dbgs() << "DoesObjCBlockEscape: Block does not escape.\n");
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return false;
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}
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/// @}
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///
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/// \defgroup ARCOpt ARC Optimization.
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/// @{
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// TODO: On code like this:
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//
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// objc_retain(%x)
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// stuff_that_cannot_release()
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// objc_autorelease(%x)
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// stuff_that_cannot_release()
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// objc_retain(%x)
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// stuff_that_cannot_release()
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// objc_autorelease(%x)
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//
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// The second retain and autorelease can be deleted.
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// TODO: It should be possible to delete
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// objc_autoreleasePoolPush and objc_autoreleasePoolPop
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// pairs if nothing is actually autoreleased between them. Also, autorelease
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// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
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// after inlining) can be turned into plain release calls.
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// TODO: Critical-edge splitting. If the optimial insertion point is
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// a critical edge, the current algorithm has to fail, because it doesn't
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// know how to split edges. It should be possible to make the optimizer
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// think in terms of edges, rather than blocks, and then split critical
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// edges on demand.
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// TODO: OptimizeSequences could generalized to be Interprocedural.
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// TODO: Recognize that a bunch of other objc runtime calls have
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// non-escaping arguments and non-releasing arguments, and may be
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// non-autoreleasing.
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// TODO: Sink autorelease calls as far as possible. Unfortunately we
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// usually can't sink them past other calls, which would be the main
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// case where it would be useful.
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// TODO: The pointer returned from objc_loadWeakRetained is retained.
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// TODO: Delete release+retain pairs (rare).
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STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
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STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
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STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
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STATISTIC(NumRets, "Number of return value forwarding "
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"retain+autoreleaes eliminated");
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STATISTIC(NumRRs, "Number of retain+release paths eliminated");
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STATISTIC(NumPeeps, "Number of calls peephole-optimized");
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namespace {
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/// \enum Sequence
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///
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/// \brief A sequence of states that a pointer may go through in which an
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/// objc_retain and objc_release are actually needed.
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enum Sequence {
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S_None,
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S_Retain, ///< objc_retain(x)
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S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
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S_Use, ///< any use of x
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S_Stop, ///< like S_Release, but code motion is stopped
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S_Release, ///< objc_release(x)
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S_MovableRelease ///< objc_release(x), !clang.imprecise_release
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};
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}
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static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
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// The easy cases.
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if (A == B)
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return A;
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if (A == S_None || B == S_None)
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return S_None;
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if (A > B) std::swap(A, B);
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if (TopDown) {
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// Choose the side which is further along in the sequence.
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if ((A == S_Retain || A == S_CanRelease) &&
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(B == S_CanRelease || B == S_Use))
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return B;
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} else {
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// Choose the side which is further along in the sequence.
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if ((A == S_Use || A == S_CanRelease) &&
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(B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
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return A;
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// If both sides are releases, choose the more conservative one.
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if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
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return A;
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if (A == S_Release && B == S_MovableRelease)
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return A;
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}
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return S_None;
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}
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namespace {
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/// \brief Unidirectional information about either a
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/// retain-decrement-use-release sequence or release-use-decrement-retain
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/// reverese sequence.
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struct RRInfo {
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/// After an objc_retain, the reference count of the referenced
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/// object is known to be positive. Similarly, before an objc_release, the
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/// reference count of the referenced object is known to be positive. If
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/// there are retain-release pairs in code regions where the retain count
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/// is known to be positive, they can be eliminated, regardless of any side
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/// effects between them.
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///
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/// Also, a retain+release pair nested within another retain+release
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/// pair all on the known same pointer value can be eliminated, regardless
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/// of any intervening side effects.
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///
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/// KnownSafe is true when either of these conditions is satisfied.
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bool KnownSafe;
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/// True if the Calls are objc_retainBlock calls (as opposed to objc_retain
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/// calls).
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bool IsRetainBlock;
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/// True of the objc_release calls are all marked with the "tail" keyword.
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bool IsTailCallRelease;
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/// If the Calls are objc_release calls and they all have a
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/// clang.imprecise_release tag, this is the metadata tag.
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MDNode *ReleaseMetadata;
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/// For a top-down sequence, the set of objc_retains or
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/// objc_retainBlocks. For bottom-up, the set of objc_releases.
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SmallPtrSet<Instruction *, 2> Calls;
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/// The set of optimal insert positions for moving calls in the opposite
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/// sequence.
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SmallPtrSet<Instruction *, 2> ReverseInsertPts;
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RRInfo() :
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KnownSafe(false), IsRetainBlock(false),
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IsTailCallRelease(false),
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ReleaseMetadata(0) {}
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void clear();
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};
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}
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void RRInfo::clear() {
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KnownSafe = false;
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IsRetainBlock = false;
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IsTailCallRelease = false;
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ReleaseMetadata = 0;
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Calls.clear();
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ReverseInsertPts.clear();
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}
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namespace {
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/// \brief This class summarizes several per-pointer runtime properties which
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/// are propogated through the flow graph.
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class PtrState {
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/// True if the reference count is known to be incremented.
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bool KnownPositiveRefCount;
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/// True of we've seen an opportunity for partial RR elimination, such as
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/// pushing calls into a CFG triangle or into one side of a CFG diamond.
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bool Partial;
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/// The current position in the sequence.
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Sequence Seq : 8;
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public:
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/// Unidirectional information about the current sequence.
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///
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/// TODO: Encapsulate this better.
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RRInfo RRI;
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PtrState() : KnownPositiveRefCount(false), Partial(false),
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Seq(S_None) {}
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void SetKnownPositiveRefCount() {
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KnownPositiveRefCount = true;
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}
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void ClearRefCount() {
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KnownPositiveRefCount = false;
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}
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bool IsKnownIncremented() const {
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return KnownPositiveRefCount;
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}
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void SetSeq(Sequence NewSeq) {
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Seq = NewSeq;
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}
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Sequence GetSeq() const {
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return Seq;
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}
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|
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void ClearSequenceProgress() {
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ResetSequenceProgress(S_None);
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}
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void ResetSequenceProgress(Sequence NewSeq) {
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Seq = NewSeq;
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Partial = false;
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RRI.clear();
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}
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void Merge(const PtrState &Other, bool TopDown);
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};
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}
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void
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PtrState::Merge(const PtrState &Other, bool TopDown) {
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Seq = MergeSeqs(Seq, Other.Seq, TopDown);
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KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
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// We can't merge a plain objc_retain with an objc_retainBlock.
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if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
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Seq = S_None;
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// If we're not in a sequence (anymore), drop all associated state.
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if (Seq == S_None) {
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Partial = false;
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RRI.clear();
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} else if (Partial || Other.Partial) {
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// If we're doing a merge on a path that's previously seen a partial
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// merge, conservatively drop the sequence, to avoid doing partial
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// RR elimination. If the branch predicates for the two merge differ,
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// mixing them is unsafe.
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ClearSequenceProgress();
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} else {
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// Conservatively merge the ReleaseMetadata information.
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if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
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RRI.ReleaseMetadata = 0;
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RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
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RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
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Other.RRI.IsTailCallRelease;
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RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
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|
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// Merge the insert point sets. If there are any differences,
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// that makes this a partial merge.
|
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Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
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for (SmallPtrSet<Instruction *, 2>::const_iterator
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I = Other.RRI.ReverseInsertPts.begin(),
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E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
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Partial |= RRI.ReverseInsertPts.insert(*I);
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}
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}
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namespace {
|
|
/// \brief Per-BasicBlock state.
|
|
class BBState {
|
|
/// The number of unique control paths from the entry which can reach this
|
|
/// block.
|
|
unsigned TopDownPathCount;
|
|
|
|
/// The number of unique control paths to exits from this block.
|
|
unsigned BottomUpPathCount;
|
|
|
|
/// A type for PerPtrTopDown and PerPtrBottomUp.
|
|
typedef MapVector<const Value *, PtrState> MapTy;
|
|
|
|
/// The top-down traversal uses this to record information known about a
|
|
/// pointer at the bottom of each block.
|
|
MapTy PerPtrTopDown;
|
|
|
|
/// The bottom-up traversal uses this to record information known about a
|
|
/// pointer at the top of each block.
|
|
MapTy PerPtrBottomUp;
|
|
|
|
/// Effective predecessors of the current block ignoring ignorable edges and
|
|
/// ignored backedges.
|
|
SmallVector<BasicBlock *, 2> Preds;
|
|
/// Effective successors of the current block ignoring ignorable edges and
|
|
/// ignored backedges.
|
|
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();
|
|
}
|
|
|
|
/// Mark this block as being an entry block, which has one path from the
|
|
/// entry by definition.
|
|
void SetAsEntry() { TopDownPathCount = 1; }
|
|
|
|
/// 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);
|
|
|
|
/// 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;
|
|
}
|
|
|
|
/// 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);
|
|
}
|
|
|
|
/// 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 {
|
|
/// \brief The main ARC optimization pass.
|
|
class ObjCARCOpt : public FunctionPass {
|
|
bool Changed;
|
|
ProvenanceAnalysis PA;
|
|
|
|
/// A flag indicating whether this optimization pass should run.
|
|
bool Run;
|
|
|
|
/// 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.
|
|
|
|
/// Declaration for ObjC runtime function
|
|
/// objc_retainAutoreleasedReturnValue.
|
|
Constant *RetainRVCallee;
|
|
/// Declaration for ObjC runtime function objc_autoreleaseReturnValue.
|
|
Constant *AutoreleaseRVCallee;
|
|
/// Declaration for ObjC runtime function objc_release.
|
|
Constant *ReleaseCallee;
|
|
/// Declaration for ObjC runtime function objc_retain.
|
|
Constant *RetainCallee;
|
|
/// Declaration for ObjC runtime function objc_retainBlock.
|
|
Constant *RetainBlockCallee;
|
|
/// Declaration for ObjC runtime function objc_autorelease.
|
|
Constant *AutoreleaseCallee;
|
|
|
|
/// Flags which determine whether each of the interesting runtine functions
|
|
/// is in fact used in the current function.
|
|
unsigned UsedInThisFunction;
|
|
|
|
/// The Metadata Kind for clang.imprecise_release metadata.
|
|
unsigned ImpreciseReleaseMDKind;
|
|
|
|
/// The Metadata Kind for clang.arc.copy_on_escape metadata.
|
|
unsigned CopyOnEscapeMDKind;
|
|
|
|
/// 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,
|
|
InstructionClass &Class);
|
|
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 ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState> &BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
Module *M,
|
|
SmallVector<Instruction *, 4> &NewRetains,
|
|
SmallVector<Instruction *, 4> &NewReleases,
|
|
SmallVector<Instruction *, 8> &DeadInsts,
|
|
RRInfo &RetainsToMove,
|
|
RRInfo &ReleasesToMove,
|
|
Value *Arg,
|
|
bool KnownSafe,
|
|
bool &AnyPairsCompletelyEliminated);
|
|
|
|
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);
|
|
AttributeSet Attribute =
|
|
AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
|
|
Attribute::NoUnwind);
|
|
RetainRVCallee =
|
|
M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
|
|
Attribute);
|
|
}
|
|
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);
|
|
AttributeSet Attribute =
|
|
AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
|
|
Attribute::NoUnwind);
|
|
AutoreleaseRVCallee =
|
|
M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
|
|
Attribute);
|
|
}
|
|
return AutoreleaseRVCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
|
|
if (!ReleaseCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttributeSet Attribute =
|
|
AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
|
|
Attribute::NoUnwind);
|
|
ReleaseCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_release",
|
|
FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
|
|
Attribute);
|
|
}
|
|
return ReleaseCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getRetainCallee(Module *M) {
|
|
if (!RetainCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttributeSet Attribute =
|
|
AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
|
|
Attribute::NoUnwind);
|
|
RetainCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_retain",
|
|
FunctionType::get(Params[0], Params, /*isVarArg=*/false),
|
|
Attribute);
|
|
}
|
|
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),
|
|
AttributeSet());
|
|
}
|
|
return RetainBlockCallee;
|
|
}
|
|
|
|
Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
|
|
if (!AutoreleaseCallee) {
|
|
LLVMContext &C = M->getContext();
|
|
Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
|
|
AttributeSet Attribute =
|
|
AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
|
|
Attribute::NoUnwind);
|
|
AutoreleaseCallee =
|
|
M->getOrInsertFunction(
|
|
"objc_autorelease",
|
|
FunctionType::get(Params[0], Params, /*isVarArg=*/false),
|
|
Attribute);
|
|
}
|
|
return AutoreleaseCallee;
|
|
}
|
|
|
|
/// 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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainCall: Transforming "
|
|
"objc_retain => objc_retainAutoreleasedReturnValue"
|
|
" since the operand is a return value.\n"
|
|
" Old: "
|
|
<< *Retain << "\n");
|
|
|
|
cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
|
|
|
|
DEBUG(dbgs() << " New: "
|
|
<< *Retain << "\n");
|
|
}
|
|
|
|
/// 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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
|
|
<< " Erasing " << *RetainRV
|
|
<< "\n");
|
|
|
|
EraseInstruction(I);
|
|
EraseInstruction(RetainRV);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Turn it to a plain objc_retain.
|
|
Changed = true;
|
|
++NumPeeps;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Transforming "
|
|
"objc_retainAutoreleasedReturnValue => "
|
|
"objc_retain since the operand is not a return value.\n"
|
|
" Old: "
|
|
<< *RetainRV << "\n");
|
|
|
|
cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
|
|
|
|
DEBUG(dbgs() << " New: "
|
|
<< *RetainRV << "\n");
|
|
|
|
return false;
|
|
}
|
|
|
|
/// Turn objc_autoreleaseReturnValue into objc_autorelease if the result is not
|
|
/// used as a return value.
|
|
void
|
|
ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
|
|
InstructionClass &Class) {
|
|
// 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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeAutoreleaseRVCall: Transforming "
|
|
"objc_autoreleaseReturnValue => "
|
|
"objc_autorelease since its operand is not used as a return "
|
|
"value.\n"
|
|
" Old: "
|
|
<< *AutoreleaseRV << "\n");
|
|
|
|
CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
|
|
AutoreleaseRVCI->
|
|
setCalledFunction(getAutoreleaseCallee(F.getParent()));
|
|
AutoreleaseRVCI->setTailCall(false); // Never tail call objc_autorelease.
|
|
Class = IC_Autorelease;
|
|
|
|
DEBUG(dbgs() << " New: "
|
|
<< *AutoreleaseRV << "\n");
|
|
|
|
}
|
|
|
|
/// 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);
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Visiting: Class: "
|
|
<< Class << "; " << *Inst << "\n");
|
|
|
|
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;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Erasing no-op cast:"
|
|
" " << *Inst << "\n");
|
|
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);
|
|
llvm::Value *NewValue = UndefValue::get(CI->getType());
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
|
|
"pointer-to-weak-pointer is undefined behavior.\n"
|
|
" Old = " << *CI <<
|
|
"\n New = " <<
|
|
*NewValue << "\n");
|
|
CI->replaceAllUsesWith(NewValue);
|
|
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);
|
|
|
|
llvm::Value *NewValue = UndefValue::get(CI->getType());
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
|
|
"pointer-to-weak-pointer is undefined behavior.\n"
|
|
" Old = " << *CI <<
|
|
"\n New = " <<
|
|
*NewValue << "\n");
|
|
|
|
CI->replaceAllUsesWith(NewValue);
|
|
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, Class);
|
|
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 *>()));
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Replacing "
|
|
"objc_autorelease(x) with objc_release(x) since x is "
|
|
"otherwise unused.\n"
|
|
" Old: " << *Call <<
|
|
"\n New: " <<
|
|
*NewCall << "\n");
|
|
|
|
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;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Adding tail keyword"
|
|
" to function since it can never be passed stack args: " << *Inst <<
|
|
"\n");
|
|
cast<CallInst>(Inst)->setTailCall();
|
|
}
|
|
|
|
// Ensure that functions that can never have a "tail" keyword due to the
|
|
// semantics of ARC truly do not do so.
|
|
if (IsNeverTail(Class)) {
|
|
Changed = true;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Removing tail "
|
|
"keyword from function: " << *Inst <<
|
|
"\n");
|
|
cast<CallInst>(Inst)->setTailCall(false);
|
|
}
|
|
|
|
// Set nounwind as needed.
|
|
if (IsNoThrow(Class)) {
|
|
Changed = true;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Found no throw"
|
|
" class. Setting nounwind on: " << *Inst << "\n");
|
|
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;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: ARC calls with "
|
|
" null are no-ops. Erasing: " << *Inst << "\n");
|
|
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);
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Cloning "
|
|
<< *CInst << "\n"
|
|
" And inserting "
|
|
"clone at " << *InsertPos << "\n");
|
|
Worklist.push_back(std::make_pair(Clone, Incoming));
|
|
}
|
|
}
|
|
// Erase the original call.
|
|
DEBUG(dbgs() << "Erasing: " << *CInst << "\n");
|
|
EraseInstruction(CInst);
|
|
continue;
|
|
}
|
|
}
|
|
} while (!Worklist.empty());
|
|
}
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Finished List.\n");
|
|
}
|
|
|
|
/// 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);
|
|
|
|
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);
|
|
|
|
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) {
|
|
DEBUG(dbgs() << "ObjCARCOpt::VisitInstructionBottomUp: Found nested "
|
|
"releases (i.e. a release pair)\n");
|
|
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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::VisitButtonUp: Visiting " << *Inst << "\n");
|
|
|
|
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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::VisitTopDown: Visiting " << *Inst << "\n");
|
|
|
|
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) {
|
|
/// 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);
|
|
|
|
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 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;
|
|
}
|
|
|
|
/// 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();
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Release: " << *Call
|
|
<< "\n"
|
|
" At insertion point: " << *InsertPt
|
|
<< "\n");
|
|
}
|
|
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();
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Retain: " << *Call
|
|
<< "\n"
|
|
" At insertion point: " << *InsertPt
|
|
<< "\n");
|
|
}
|
|
|
|
// 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);
|
|
DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting retain: " << *OrigRetain <<
|
|
"\n");
|
|
}
|
|
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);
|
|
DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting release: " << *OrigRelease
|
|
<< "\n");
|
|
}
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
|
|
&BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
Module *M,
|
|
SmallVector<Instruction *, 4> &NewRetains,
|
|
SmallVector<Instruction *, 4> &NewReleases,
|
|
SmallVector<Instruction *, 8> &DeadInsts,
|
|
RRInfo &RetainsToMove,
|
|
RRInfo &ReleasesToMove,
|
|
Value *Arg,
|
|
bool KnownSafe,
|
|
bool &AnyPairsCompletelyEliminated) {
|
|
// 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;
|
|
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())
|
|
return false;
|
|
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())
|
|
return false;
|
|
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.
|
|
return false;
|
|
|
|
// 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)
|
|
return false;
|
|
}
|
|
|
|
// 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)
|
|
return false;
|
|
|
|
Changed = true;
|
|
assert(OldCount != 0 && "Unreachable code?");
|
|
NumRRs += OldCount - NewCount;
|
|
// Set to true if we completely removed any RR pairs.
|
|
AnyPairsCompletelyEliminated = NewCount == 0;
|
|
|
|
// We can move calls!
|
|
return true;
|
|
}
|
|
|
|
/// 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);
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::PerformCodePlacement: Visiting: " << *Retain
|
|
<< "\n");
|
|
|
|
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;
|
|
|
|
// Connect the dots between the top-down-collected RetainsToMove and
|
|
// bottom-up-collected ReleasesToMove to form sets of related calls.
|
|
NewRetains.push_back(Retain);
|
|
bool PerformMoveCalls =
|
|
ConnectTDBUTraversals(BBStates, Retains, Releases, M, NewRetains,
|
|
NewReleases, DeadInsts, RetainsToMove,
|
|
ReleasesToMove, Arg, KnownSafe,
|
|
AnyPairsCompletelyEliminated);
|
|
|
|
if (PerformMoveCalls) {
|
|
// Ok, everything checks out and we're all set. Let's move/delete some
|
|
// code!
|
|
MoveCalls(Arg, RetainsToMove, ReleasesToMove,
|
|
Retains, Releases, DeadInsts, M);
|
|
}
|
|
|
|
// Clean up state for 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;
|
|
}
|
|
|
|
/// 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++;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Visiting: " << *Inst <<
|
|
"\n");
|
|
|
|
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:;
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Finished List.\n\n");
|
|
|
|
}
|
|
|
|
/// 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;
|
|
|
|
/// 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;
|
|
}
|
|
|
|
/// 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());
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Visiting: " << *Ret << "\n");
|
|
|
|
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) {
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease "
|
|
"=> autoreleaseRV since it's returning a value.\n"
|
|
" In: " << *Autorelease
|
|
<< "\n");
|
|
Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
|
|
DEBUG(dbgs() << " Out: " << *Autorelease
|
|
<< "\n");
|
|
Autorelease->setTailCall(); // Always tail call autoreleaseRV.
|
|
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;
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Erasing: " << *Retain
|
|
<< "\n Erasing: "
|
|
<< *Autorelease << "\n");
|
|
EraseInstruction(Retain);
|
|
EraseInstruction(Autorelease);
|
|
}
|
|
}
|
|
}
|
|
|
|
next_block:
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
}
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Finished List.\n\n");
|
|
|
|
}
|
|
|
|
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;
|
|
|
|
DEBUG(dbgs() << "ObjCARCOpt: Visiting Function: " << F.getName() << "\n");
|
|
|
|
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);
|
|
|
|
DEBUG(dbgs() << "\n");
|
|
|
|
return Changed;
|
|
}
|
|
|
|
void ObjCARCOpt::releaseMemory() {
|
|
PA.clear();
|
|
}
|
|
|
|
/// @}
|
|
///
|