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7962dbdc65
definition below all of the header #include lines, lib/Transforms/... edition. This one is tricky for two reasons. We again have a couple of passes that define something else before the includes as well. I've sunk their name macros with the DEBUG_TYPE. Also, InstCombine contains headers that need DEBUG_TYPE, so now those headers #define and #undef DEBUG_TYPE around their code, leaving them well formed modular headers. Fixing these headers was a large motivation for all of these changes, as "leaky" macros of this form are hard on the modules implementation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206844 91177308-0d34-0410-b5e6-96231b3b80d8
3129 lines
113 KiB
C++
3129 lines
113 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, and numerous minor simplifications.
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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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#include "ObjCARC.h"
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#include "ARCRuntimeEntryPoints.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/DenseSet.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/CFG.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/LLVMContext.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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#define DEBUG_TYPE "objc-arc-opts"
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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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iterator find(const KeyT &Key) {
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typename MapTy::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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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 (const User *U : Arg->users())
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if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
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return 0;
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return Arg;
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}
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return 0;
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}
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/// This is a wrapper around getUnderlyingObjCPtr along the lines of
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/// GetUnderlyingObjects except that it returns early when it sees the first
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/// alloca.
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static inline bool AreAnyUnderlyingObjectsAnAlloca(const Value *V) {
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SmallPtrSet<const Value *, 4> Visited;
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SmallVector<const Value *, 4> Worklist;
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Worklist.push_back(V);
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do {
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const Value *P = Worklist.pop_back_val();
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P = GetUnderlyingObjCPtr(P);
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if (isa<AllocaInst>(P))
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return true;
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if (!Visited.insert(P))
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continue;
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if (const SelectInst *SI = dyn_cast<const SelectInst>(P)) {
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Worklist.push_back(SI->getTrueValue());
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Worklist.push_back(SI->getFalseValue());
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continue;
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}
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if (const PHINode *PN = dyn_cast<const PHINode>(P)) {
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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Worklist.push_back(PN->getIncomingValue(i));
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continue;
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}
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} while (!Worklist.empty());
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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+autoreleases 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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#ifndef NDEBUG
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STATISTIC(NumRetainsBeforeOpt,
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"Number of retains before optimization");
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STATISTIC(NumReleasesBeforeOpt,
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"Number of releases before optimization");
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STATISTIC(NumRetainsAfterOpt,
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"Number of retains after optimization");
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STATISTIC(NumReleasesAfterOpt,
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"Number of releases after optimization");
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#endif
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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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raw_ostream &operator<<(raw_ostream &OS, const Sequence S)
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LLVM_ATTRIBUTE_UNUSED;
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raw_ostream &operator<<(raw_ostream &OS, const Sequence S) {
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switch (S) {
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case S_None:
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return OS << "S_None";
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case S_Retain:
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return OS << "S_Retain";
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case S_CanRelease:
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return OS << "S_CanRelease";
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case S_Use:
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return OS << "S_Use";
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case S_Release:
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return OS << "S_Release";
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case S_MovableRelease:
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return OS << "S_MovableRelease";
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case S_Stop:
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return OS << "S_Stop";
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}
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llvm_unreachable("Unknown sequence type.");
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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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/// reverse 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 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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/// If this is true, we cannot perform code motion but can still remove
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/// retain/release pairs.
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bool CFGHazardAfflicted;
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RRInfo() :
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KnownSafe(false), IsTailCallRelease(false), ReleaseMetadata(0),
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CFGHazardAfflicted(false) {}
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void clear();
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/// Conservatively merge the two RRInfo. Returns true if a partial merge has
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/// occurred, false otherwise.
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bool Merge(const RRInfo &Other);
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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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IsTailCallRelease = false;
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ReleaseMetadata = 0;
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Calls.clear();
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ReverseInsertPts.clear();
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CFGHazardAfflicted = false;
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}
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bool RRInfo::Merge(const RRInfo &Other) {
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// Conservatively merge the ReleaseMetadata information.
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if (ReleaseMetadata != Other.ReleaseMetadata)
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ReleaseMetadata = 0;
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// Conservatively merge the boolean state.
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KnownSafe &= Other.KnownSafe;
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IsTailCallRelease &= Other.IsTailCallRelease;
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CFGHazardAfflicted |= Other.CFGHazardAfflicted;
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// Merge the call sets.
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Calls.insert(Other.Calls.begin(), Other.Calls.end());
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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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bool Partial = ReverseInsertPts.size() != Other.ReverseInsertPts.size();
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for (SmallPtrSet<Instruction *, 2>::const_iterator
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I = Other.ReverseInsertPts.begin(),
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E = Other.ReverseInsertPts.end(); I != E; ++I)
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Partial |= ReverseInsertPts.insert(*I);
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return Partial;
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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 if 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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unsigned char Seq : 8;
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/// Unidirectional information about the current sequence.
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RRInfo RRI;
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public:
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PtrState() : KnownPositiveRefCount(false), Partial(false),
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Seq(S_None) {}
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bool IsKnownSafe() const {
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return RRI.KnownSafe;
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}
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void SetKnownSafe(const bool NewValue) {
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RRI.KnownSafe = NewValue;
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}
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bool IsTailCallRelease() const {
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return RRI.IsTailCallRelease;
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}
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void SetTailCallRelease(const bool NewValue) {
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RRI.IsTailCallRelease = NewValue;
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}
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bool IsTrackingImpreciseReleases() const {
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return RRI.ReleaseMetadata != 0;
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}
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const MDNode *GetReleaseMetadata() const {
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return RRI.ReleaseMetadata;
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}
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void SetReleaseMetadata(MDNode *NewValue) {
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RRI.ReleaseMetadata = NewValue;
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}
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bool IsCFGHazardAfflicted() const {
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return RRI.CFGHazardAfflicted;
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}
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void SetCFGHazardAfflicted(const bool NewValue) {
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RRI.CFGHazardAfflicted = NewValue;
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}
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|
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void SetKnownPositiveRefCount() {
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DEBUG(dbgs() << "Setting Known Positive.\n");
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KnownPositiveRefCount = true;
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}
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|
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void ClearKnownPositiveRefCount() {
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DEBUG(dbgs() << "Clearing Known Positive.\n");
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KnownPositiveRefCount = false;
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}
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bool HasKnownPositiveRefCount() const {
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return KnownPositiveRefCount;
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}
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|
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void SetSeq(Sequence NewSeq) {
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DEBUG(dbgs() << "Old: " << Seq << "; New: " << NewSeq << "\n");
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Seq = NewSeq;
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|
}
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|
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Sequence GetSeq() const {
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return static_cast<Sequence>(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) {
|
|
DEBUG(dbgs() << "Resetting sequence progress.\n");
|
|
SetSeq(NewSeq);
|
|
Partial = false;
|
|
RRI.clear();
|
|
}
|
|
|
|
void Merge(const PtrState &Other, bool TopDown);
|
|
|
|
void InsertCall(Instruction *I) {
|
|
RRI.Calls.insert(I);
|
|
}
|
|
|
|
void InsertReverseInsertPt(Instruction *I) {
|
|
RRI.ReverseInsertPts.insert(I);
|
|
}
|
|
|
|
void ClearReverseInsertPts() {
|
|
RRI.ReverseInsertPts.clear();
|
|
}
|
|
|
|
bool HasReverseInsertPts() const {
|
|
return !RRI.ReverseInsertPts.empty();
|
|
}
|
|
|
|
const RRInfo &GetRRInfo() const {
|
|
return RRI;
|
|
}
|
|
};
|
|
}
|
|
|
|
void
|
|
PtrState::Merge(const PtrState &Other, bool TopDown) {
|
|
Seq = MergeSeqs(GetSeq(), Other.GetSeq(), TopDown);
|
|
KnownPositiveRefCount &= Other.KnownPositiveRefCount;
|
|
|
|
// If we're not in a sequence (anymore), drop all associated state.
|
|
if (Seq == S_None) {
|
|
Partial = false;
|
|
RRI.clear();
|
|
} else if (Partial || Other.Partial) {
|
|
// If we're doing a merge on a path that's previously seen a partial
|
|
// merge, conservatively drop the sequence, to avoid doing partial
|
|
// RR elimination. If the branch predicates for the two merge differ,
|
|
// mixing them is unsafe.
|
|
ClearSequenceProgress();
|
|
} else {
|
|
// Otherwise merge the other PtrState's RRInfo into our RRInfo. At this
|
|
// point, we know that currently we are not partial. Stash whether or not
|
|
// the merge operation caused us to undergo a partial merging of reverse
|
|
// insertion points.
|
|
Partial = RRI.Merge(Other.RRI);
|
|
}
|
|
}
|
|
|
|
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:
|
|
static const unsigned OverflowOccurredValue;
|
|
|
|
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; }
|
|
|
|
/// Attempt to find the PtrState object describing the top down state for
|
|
/// pointer Arg. Return a new initialized PtrState describing the top down
|
|
/// state for Arg if we do not find one.
|
|
PtrState &getPtrTopDownState(const Value *Arg) {
|
|
return PerPtrTopDown[Arg];
|
|
}
|
|
|
|
/// Attempt to find the PtrState object describing the bottom up state for
|
|
/// pointer Arg. Return a new initialized PtrState describing the bottom up
|
|
/// state for Arg if we do not find one.
|
|
PtrState &getPtrBottomUpState(const Value *Arg) {
|
|
return PerPtrBottomUp[Arg];
|
|
}
|
|
|
|
/// Attempt to find the PtrState object describing the bottom up state for
|
|
/// pointer Arg.
|
|
ptr_iterator findPtrBottomUpState(const Value *Arg) {
|
|
return PerPtrBottomUp.find(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);
|
|
|
|
/// Compute 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.
|
|
///
|
|
/// Returns true if overflow occurred. Returns false if overflow did not
|
|
/// occur.
|
|
bool GetAllPathCountWithOverflow(unsigned &PathCount) const {
|
|
if (TopDownPathCount == OverflowOccurredValue ||
|
|
BottomUpPathCount == OverflowOccurredValue)
|
|
return true;
|
|
unsigned long long Product =
|
|
(unsigned long long)TopDownPathCount*BottomUpPathCount;
|
|
// Overflow occurred if any of the upper bits of Product are set or if all
|
|
// the lower bits of Product are all set.
|
|
return (Product >> 32) ||
|
|
((PathCount = Product) == OverflowOccurredValue);
|
|
}
|
|
|
|
// Specialized CFG utilities.
|
|
typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
|
|
edge_iterator pred_begin() const { return Preds.begin(); }
|
|
edge_iterator pred_end() const { return Preds.end(); }
|
|
edge_iterator succ_begin() const { return Succs.begin(); }
|
|
edge_iterator succ_end() const { 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(); }
|
|
};
|
|
|
|
const unsigned BBState::OverflowOccurredValue = 0xffffffff;
|
|
}
|
|
|
|
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) {
|
|
if (TopDownPathCount == OverflowOccurredValue)
|
|
return;
|
|
|
|
// Other.TopDownPathCount can be 0, in which case it is either dead or a
|
|
// loop backedge. Loop backedges are special.
|
|
TopDownPathCount += Other.TopDownPathCount;
|
|
|
|
// In order to be consistent, we clear the top down pointers when by adding
|
|
// TopDownPathCount becomes OverflowOccurredValue even though "true" overflow
|
|
// has not occurred.
|
|
if (TopDownPathCount == OverflowOccurredValue) {
|
|
clearTopDownPointers();
|
|
return;
|
|
}
|
|
|
|
// Check for overflow. If we have overflow, fall back to conservative
|
|
// behavior.
|
|
if (TopDownPathCount < Other.TopDownPathCount) {
|
|
TopDownPathCount = OverflowOccurredValue;
|
|
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) {
|
|
if (BottomUpPathCount == OverflowOccurredValue)
|
|
return;
|
|
|
|
// Other.BottomUpPathCount can be 0, in which case it is either dead or a
|
|
// loop backedge. Loop backedges are special.
|
|
BottomUpPathCount += Other.BottomUpPathCount;
|
|
|
|
// In order to be consistent, we clear the top down pointers when by adding
|
|
// BottomUpPathCount becomes OverflowOccurredValue even though "true" overflow
|
|
// has not occurred.
|
|
if (BottomUpPathCount == OverflowOccurredValue) {
|
|
clearBottomUpPointers();
|
|
return;
|
|
}
|
|
|
|
// Check for overflow. If we have overflow, fall back to conservative
|
|
// behavior.
|
|
if (BottomUpPathCount < Other.BottomUpPathCount) {
|
|
BottomUpPathCount = OverflowOccurredValue;
|
|
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);
|
|
}
|
|
|
|
// Only enable ARC Annotations if we are building a debug version of
|
|
// libObjCARCOpts.
|
|
#ifndef NDEBUG
|
|
#define ARC_ANNOTATIONS
|
|
#endif
|
|
|
|
// Define some macros along the lines of DEBUG and some helper functions to make
|
|
// it cleaner to create annotations in the source code and to no-op when not
|
|
// building in debug mode.
|
|
#ifdef ARC_ANNOTATIONS
|
|
|
|
#include "llvm/Support/CommandLine.h"
|
|
|
|
/// Enable/disable ARC sequence annotations.
|
|
static cl::opt<bool>
|
|
EnableARCAnnotations("enable-objc-arc-annotations", cl::init(false),
|
|
cl::desc("Enable emission of arc data flow analysis "
|
|
"annotations"));
|
|
static cl::opt<bool>
|
|
DisableCheckForCFGHazards("disable-objc-arc-checkforcfghazards", cl::init(false),
|
|
cl::desc("Disable check for cfg hazards when "
|
|
"annotating"));
|
|
static cl::opt<std::string>
|
|
ARCAnnotationTargetIdentifier("objc-arc-annotation-target-identifier",
|
|
cl::init(""),
|
|
cl::desc("filter out all data flow annotations "
|
|
"but those that apply to the given "
|
|
"target llvm identifier."));
|
|
|
|
/// This function appends a unique ARCAnnotationProvenanceSourceMDKind id to an
|
|
/// instruction so that we can track backwards when post processing via the llvm
|
|
/// arc annotation processor tool. If the function is an
|
|
static MDString *AppendMDNodeToSourcePtr(unsigned NodeId,
|
|
Value *Ptr) {
|
|
MDString *Hash = 0;
|
|
|
|
// If pointer is a result of an instruction and it does not have a source
|
|
// MDNode it, attach a new MDNode onto it. If pointer is a result of
|
|
// an instruction and does have a source MDNode attached to it, return a
|
|
// reference to said Node. Otherwise just return 0.
|
|
if (Instruction *Inst = dyn_cast<Instruction>(Ptr)) {
|
|
MDNode *Node;
|
|
if (!(Node = Inst->getMetadata(NodeId))) {
|
|
// We do not have any node. Generate and attatch the hash MDString to the
|
|
// instruction.
|
|
|
|
// We just use an MDString to ensure that this metadata gets written out
|
|
// of line at the module level and to provide a very simple format
|
|
// encoding the information herein. Both of these makes it simpler to
|
|
// parse the annotations by a simple external program.
|
|
std::string Str;
|
|
raw_string_ostream os(Str);
|
|
os << "(" << Inst->getParent()->getParent()->getName() << ",%"
|
|
<< Inst->getName() << ")";
|
|
|
|
Hash = MDString::get(Inst->getContext(), os.str());
|
|
Inst->setMetadata(NodeId, MDNode::get(Inst->getContext(),Hash));
|
|
} else {
|
|
// We have a node. Grab its hash and return it.
|
|
assert(Node->getNumOperands() == 1 &&
|
|
"An ARCAnnotationProvenanceSourceMDKind can only have 1 operand.");
|
|
Hash = cast<MDString>(Node->getOperand(0));
|
|
}
|
|
} else if (Argument *Arg = dyn_cast<Argument>(Ptr)) {
|
|
std::string str;
|
|
raw_string_ostream os(str);
|
|
os << "(" << Arg->getParent()->getName() << ",%" << Arg->getName()
|
|
<< ")";
|
|
Hash = MDString::get(Arg->getContext(), os.str());
|
|
}
|
|
|
|
return Hash;
|
|
}
|
|
|
|
static std::string SequenceToString(Sequence A) {
|
|
std::string str;
|
|
raw_string_ostream os(str);
|
|
os << A;
|
|
return os.str();
|
|
}
|
|
|
|
/// Helper function to change a Sequence into a String object using our overload
|
|
/// for raw_ostream so we only have printing code in one location.
|
|
static MDString *SequenceToMDString(LLVMContext &Context,
|
|
Sequence A) {
|
|
return MDString::get(Context, SequenceToString(A));
|
|
}
|
|
|
|
/// A simple function to generate a MDNode which describes the change in state
|
|
/// for Value *Ptr caused by Instruction *Inst.
|
|
static void AppendMDNodeToInstForPtr(unsigned NodeId,
|
|
Instruction *Inst,
|
|
Value *Ptr,
|
|
MDString *PtrSourceMDNodeID,
|
|
Sequence OldSeq,
|
|
Sequence NewSeq) {
|
|
MDNode *Node = 0;
|
|
Value *tmp[3] = {PtrSourceMDNodeID,
|
|
SequenceToMDString(Inst->getContext(),
|
|
OldSeq),
|
|
SequenceToMDString(Inst->getContext(),
|
|
NewSeq)};
|
|
Node = MDNode::get(Inst->getContext(),
|
|
ArrayRef<Value*>(tmp, 3));
|
|
|
|
Inst->setMetadata(NodeId, Node);
|
|
}
|
|
|
|
/// Add to the beginning of the basic block llvm.ptr.annotations which show the
|
|
/// state of a pointer at the entrance to a basic block.
|
|
static void GenerateARCBBEntranceAnnotation(const char *Name, BasicBlock *BB,
|
|
Value *Ptr, Sequence Seq) {
|
|
// If we have a target identifier, make sure that we match it before
|
|
// continuing.
|
|
if(!ARCAnnotationTargetIdentifier.empty() &&
|
|
!Ptr->getName().equals(ARCAnnotationTargetIdentifier))
|
|
return;
|
|
|
|
Module *M = BB->getParent()->getParent();
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *I8XX = PointerType::getUnqual(I8X);
|
|
Type *Params[] = {I8XX, I8XX};
|
|
FunctionType *FTy = FunctionType::get(Type::getVoidTy(C),
|
|
ArrayRef<Type*>(Params, 2),
|
|
/*isVarArg=*/false);
|
|
Constant *Callee = M->getOrInsertFunction(Name, FTy);
|
|
|
|
IRBuilder<> Builder(BB, BB->getFirstInsertionPt());
|
|
|
|
Value *PtrName;
|
|
StringRef Tmp = Ptr->getName();
|
|
if (0 == (PtrName = M->getGlobalVariable(Tmp, true))) {
|
|
Value *ActualPtrName = Builder.CreateGlobalStringPtr(Tmp,
|
|
Tmp + "_STR");
|
|
PtrName = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
|
|
cast<Constant>(ActualPtrName), Tmp);
|
|
}
|
|
|
|
Value *S;
|
|
std::string SeqStr = SequenceToString(Seq);
|
|
if (0 == (S = M->getGlobalVariable(SeqStr, true))) {
|
|
Value *ActualPtrName = Builder.CreateGlobalStringPtr(SeqStr,
|
|
SeqStr + "_STR");
|
|
S = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
|
|
cast<Constant>(ActualPtrName), SeqStr);
|
|
}
|
|
|
|
Builder.CreateCall2(Callee, PtrName, S);
|
|
}
|
|
|
|
/// Add to the end of the basic block llvm.ptr.annotations which show the state
|
|
/// of the pointer at the bottom of the basic block.
|
|
static void GenerateARCBBTerminatorAnnotation(const char *Name, BasicBlock *BB,
|
|
Value *Ptr, Sequence Seq) {
|
|
// If we have a target identifier, make sure that we match it before emitting
|
|
// an annotation.
|
|
if(!ARCAnnotationTargetIdentifier.empty() &&
|
|
!Ptr->getName().equals(ARCAnnotationTargetIdentifier))
|
|
return;
|
|
|
|
Module *M = BB->getParent()->getParent();
|
|
LLVMContext &C = M->getContext();
|
|
Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
|
|
Type *I8XX = PointerType::getUnqual(I8X);
|
|
Type *Params[] = {I8XX, I8XX};
|
|
FunctionType *FTy = FunctionType::get(Type::getVoidTy(C),
|
|
ArrayRef<Type*>(Params, 2),
|
|
/*isVarArg=*/false);
|
|
Constant *Callee = M->getOrInsertFunction(Name, FTy);
|
|
|
|
IRBuilder<> Builder(BB, std::prev(BB->end()));
|
|
|
|
Value *PtrName;
|
|
StringRef Tmp = Ptr->getName();
|
|
if (0 == (PtrName = M->getGlobalVariable(Tmp, true))) {
|
|
Value *ActualPtrName = Builder.CreateGlobalStringPtr(Tmp,
|
|
Tmp + "_STR");
|
|
PtrName = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
|
|
cast<Constant>(ActualPtrName), Tmp);
|
|
}
|
|
|
|
Value *S;
|
|
std::string SeqStr = SequenceToString(Seq);
|
|
if (0 == (S = M->getGlobalVariable(SeqStr, true))) {
|
|
Value *ActualPtrName = Builder.CreateGlobalStringPtr(SeqStr,
|
|
SeqStr + "_STR");
|
|
S = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
|
|
cast<Constant>(ActualPtrName), SeqStr);
|
|
}
|
|
Builder.CreateCall2(Callee, PtrName, S);
|
|
}
|
|
|
|
/// Adds a source annotation to pointer and a state change annotation to Inst
|
|
/// referencing the source annotation and the old/new state of pointer.
|
|
static void GenerateARCAnnotation(unsigned InstMDId,
|
|
unsigned PtrMDId,
|
|
Instruction *Inst,
|
|
Value *Ptr,
|
|
Sequence OldSeq,
|
|
Sequence NewSeq) {
|
|
if (EnableARCAnnotations) {
|
|
// If we have a target identifier, make sure that we match it before
|
|
// emitting an annotation.
|
|
if(!ARCAnnotationTargetIdentifier.empty() &&
|
|
!Ptr->getName().equals(ARCAnnotationTargetIdentifier))
|
|
return;
|
|
|
|
// First generate the source annotation on our pointer. This will return an
|
|
// MDString* if Ptr actually comes from an instruction implying we can put
|
|
// in a source annotation. If AppendMDNodeToSourcePtr returns 0 (i.e. NULL),
|
|
// then we know that our pointer is from an Argument so we put a reference
|
|
// to the argument number.
|
|
//
|
|
// The point of this is to make it easy for the
|
|
// llvm-arc-annotation-processor tool to cross reference where the source
|
|
// pointer is in the LLVM IR since the LLVM IR parser does not submit such
|
|
// information via debug info for backends to use (since why would anyone
|
|
// need such a thing from LLVM IR besides in non-standard cases
|
|
// [i.e. this]).
|
|
MDString *SourcePtrMDNode =
|
|
AppendMDNodeToSourcePtr(PtrMDId, Ptr);
|
|
AppendMDNodeToInstForPtr(InstMDId, Inst, Ptr, SourcePtrMDNode, OldSeq,
|
|
NewSeq);
|
|
}
|
|
}
|
|
|
|
// The actual interface for accessing the above functionality is defined via
|
|
// some simple macros which are defined below. We do this so that the user does
|
|
// not need to pass in what metadata id is needed resulting in cleaner code and
|
|
// additionally since it provides an easy way to conditionally no-op all
|
|
// annotation support in a non-debug build.
|
|
|
|
/// Use this macro to annotate a sequence state change when processing
|
|
/// instructions bottom up,
|
|
#define ANNOTATE_BOTTOMUP(inst, ptr, old, new) \
|
|
GenerateARCAnnotation(ARCAnnotationBottomUpMDKind, \
|
|
ARCAnnotationProvenanceSourceMDKind, (inst), \
|
|
const_cast<Value*>(ptr), (old), (new))
|
|
/// Use this macro to annotate a sequence state change when processing
|
|
/// instructions top down.
|
|
#define ANNOTATE_TOPDOWN(inst, ptr, old, new) \
|
|
GenerateARCAnnotation(ARCAnnotationTopDownMDKind, \
|
|
ARCAnnotationProvenanceSourceMDKind, (inst), \
|
|
const_cast<Value*>(ptr), (old), (new))
|
|
|
|
#define ANNOTATE_BB(_states, _bb, _name, _type, _direction) \
|
|
do { \
|
|
if (EnableARCAnnotations) { \
|
|
for(BBState::ptr_const_iterator I = (_states)._direction##_ptr_begin(), \
|
|
E = (_states)._direction##_ptr_end(); I != E; ++I) { \
|
|
Value *Ptr = const_cast<Value*>(I->first); \
|
|
Sequence Seq = I->second.GetSeq(); \
|
|
GenerateARCBB ## _type ## Annotation(_name, (_bb), Ptr, Seq); \
|
|
} \
|
|
} \
|
|
} while (0)
|
|
|
|
#define ANNOTATE_BOTTOMUP_BBSTART(_states, _basicblock) \
|
|
ANNOTATE_BB(_states, _basicblock, "llvm.arc.annotation.bottomup.bbstart", \
|
|
Entrance, bottom_up)
|
|
#define ANNOTATE_BOTTOMUP_BBEND(_states, _basicblock) \
|
|
ANNOTATE_BB(_states, _basicblock, "llvm.arc.annotation.bottomup.bbend", \
|
|
Terminator, bottom_up)
|
|
#define ANNOTATE_TOPDOWN_BBSTART(_states, _basicblock) \
|
|
ANNOTATE_BB(_states, _basicblock, "llvm.arc.annotation.topdown.bbstart", \
|
|
Entrance, top_down)
|
|
#define ANNOTATE_TOPDOWN_BBEND(_states, _basicblock) \
|
|
ANNOTATE_BB(_states, _basicblock, "llvm.arc.annotation.topdown.bbend", \
|
|
Terminator, top_down)
|
|
|
|
#else // !ARC_ANNOTATION
|
|
// If annotations are off, noop.
|
|
#define ANNOTATE_BOTTOMUP(inst, ptr, old, new)
|
|
#define ANNOTATE_TOPDOWN(inst, ptr, old, new)
|
|
#define ANNOTATE_BOTTOMUP_BBSTART(states, basicblock)
|
|
#define ANNOTATE_BOTTOMUP_BBEND(states, basicblock)
|
|
#define ANNOTATE_TOPDOWN_BBSTART(states, basicblock)
|
|
#define ANNOTATE_TOPDOWN_BBEND(states, basicblock)
|
|
#endif // !ARC_ANNOTATION
|
|
|
|
namespace {
|
|
/// \brief The main ARC optimization pass.
|
|
class ObjCARCOpt : public FunctionPass {
|
|
bool Changed;
|
|
ProvenanceAnalysis PA;
|
|
ARCRuntimeEntryPoints EP;
|
|
|
|
// This is used to track if a pointer is stored into an alloca.
|
|
DenseSet<const Value *> MultiOwnersSet;
|
|
|
|
/// A flag indicating whether this optimization pass should run.
|
|
bool Run;
|
|
|
|
/// 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;
|
|
|
|
#ifdef ARC_ANNOTATIONS
|
|
/// The Metadata Kind for llvm.arc.annotation.bottomup metadata.
|
|
unsigned ARCAnnotationBottomUpMDKind;
|
|
/// The Metadata Kind for llvm.arc.annotation.topdown metadata.
|
|
unsigned ARCAnnotationTopDownMDKind;
|
|
/// The Metadata Kind for llvm.arc.annotation.provenancesource metadata.
|
|
unsigned ARCAnnotationProvenanceSourceMDKind;
|
|
#endif // ARC_ANNOATIONS
|
|
|
|
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,
|
|
SmallVectorImpl<Instruction *> &NewRetains,
|
|
SmallVectorImpl<Instruction *> &NewReleases,
|
|
SmallVectorImpl<Instruction *> &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);
|
|
|
|
#ifndef NDEBUG
|
|
void GatherStatistics(Function &F, bool AfterOptimization = false);
|
|
#endif
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override;
|
|
bool doInitialization(Module &M) override;
|
|
bool runOnFunction(Function &F) override;
|
|
void releaseMemory() override;
|
|
|
|
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();
|
|
}
|
|
|
|
/// 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() << "Erasing autoreleaseRV,retainRV pair: " << *I << "\n"
|
|
<< "Erasing " << *RetainRV << "\n");
|
|
|
|
EraseInstruction(I);
|
|
EraseInstruction(RetainRV);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Turn it to a plain objc_retain.
|
|
Changed = true;
|
|
++NumPeeps;
|
|
|
|
DEBUG(dbgs() << "Transforming objc_retainAutoreleasedReturnValue => "
|
|
"objc_retain since the operand is not a return value.\n"
|
|
"Old = " << *RetainRV << "\n");
|
|
|
|
Constant *NewDecl = EP.get(ARCRuntimeEntryPoints::EPT_Retain);
|
|
cast<CallInst>(RetainRV)->setCalledFunction(NewDecl);
|
|
|
|
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 (const User *U : Ptr->users()) {
|
|
if (isa<ReturnInst>(U) || GetBasicInstructionClass(U) == IC_RetainRV)
|
|
return;
|
|
if (isa<BitCastInst>(U))
|
|
Users.push_back(U);
|
|
}
|
|
} while (!Users.empty());
|
|
|
|
Changed = true;
|
|
++NumPeeps;
|
|
|
|
DEBUG(dbgs() << "Transforming objc_autoreleaseReturnValue => "
|
|
"objc_autorelease since its operand is not used as a return "
|
|
"value.\n"
|
|
"Old = " << *AutoreleaseRV << "\n");
|
|
|
|
CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
|
|
Constant *NewDecl = EP.get(ARCRuntimeEntryPoints::EPT_Autorelease);
|
|
AutoreleaseRVCI->setCalledFunction(NewDecl);
|
|
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) {
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeIndividualCalls ==\n");
|
|
// 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() << "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() << "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() << "A null pointer-to-weak-pointer is undefined behavior."
|
|
"\nOld = " << *CI << "\nNew = " << *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() << "A null pointer-to-weak-pointer is undefined behavior."
|
|
"\nOld = " << *CI << "\nNew = " << *NewValue << "\n");
|
|
|
|
CI->replaceAllUsesWith(NewValue);
|
|
CI->eraseFromParent();
|
|
continue;
|
|
}
|
|
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();
|
|
|
|
Constant *Decl = EP.get(ARCRuntimeEntryPoints::EPT_Release);
|
|
CallInst *NewCall = CallInst::Create(Decl, Call->getArgOperand(0), "",
|
|
Call);
|
|
NewCall->setMetadata(ImpreciseReleaseMDKind, MDNode::get(C, None));
|
|
|
|
DEBUG(dbgs() << "Replacing autorelease{,RV}(x) with objc_release(x) "
|
|
"since x is otherwise unused.\nOld: " << *Call << "\nNew: "
|
|
<< *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() << "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() << "Removing tail keyword from function: " << *Inst <<
|
|
"\n");
|
|
cast<CallInst>(Inst)->setTailCall(false);
|
|
}
|
|
|
|
// Set nounwind as needed.
|
|
if (IsNoThrow(Class)) {
|
|
Changed = true;
|
|
DEBUG(dbgs() << "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() << "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() << "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());
|
|
}
|
|
}
|
|
|
|
/// If we have a top down pointer in the S_Use state, make sure that there are
|
|
/// no CFG hazards by checking the states of various bottom up pointers.
|
|
static void CheckForUseCFGHazard(const Sequence SuccSSeq,
|
|
const bool SuccSRRIKnownSafe,
|
|
PtrState &S,
|
|
bool &SomeSuccHasSame,
|
|
bool &AllSuccsHaveSame,
|
|
bool &NotAllSeqEqualButKnownSafe,
|
|
bool &ShouldContinue) {
|
|
switch (SuccSSeq) {
|
|
case S_CanRelease: {
|
|
if (!S.IsKnownSafe() && !SuccSRRIKnownSafe) {
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
}
|
|
S.SetCFGHazardAfflicted(true);
|
|
ShouldContinue = true;
|
|
break;
|
|
}
|
|
case S_Use:
|
|
SomeSuccHasSame = true;
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
if (!S.IsKnownSafe() && !SuccSRRIKnownSafe)
|
|
AllSuccsHaveSame = false;
|
|
else
|
|
NotAllSeqEqualButKnownSafe = true;
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
case S_None:
|
|
llvm_unreachable("This should have been handled earlier.");
|
|
}
|
|
}
|
|
|
|
/// If we have a Top Down pointer in the S_CanRelease state, make sure that
|
|
/// there are no CFG hazards by checking the states of various bottom up
|
|
/// pointers.
|
|
static void CheckForCanReleaseCFGHazard(const Sequence SuccSSeq,
|
|
const bool SuccSRRIKnownSafe,
|
|
PtrState &S,
|
|
bool &SomeSuccHasSame,
|
|
bool &AllSuccsHaveSame,
|
|
bool &NotAllSeqEqualButKnownSafe) {
|
|
switch (SuccSSeq) {
|
|
case S_CanRelease:
|
|
SomeSuccHasSame = true;
|
|
break;
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
case S_Use:
|
|
if (!S.IsKnownSafe() && !SuccSRRIKnownSafe)
|
|
AllSuccsHaveSame = false;
|
|
else
|
|
NotAllSeqEqualButKnownSafe = true;
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
case S_None:
|
|
llvm_unreachable("This should have been handled earlier.");
|
|
}
|
|
}
|
|
|
|
/// 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) {
|
|
PtrState &S = I->second;
|
|
const Sequence Seq = I->second.GetSeq();
|
|
|
|
// We only care about S_Retain, S_CanRelease, and S_Use.
|
|
if (Seq == S_None)
|
|
continue;
|
|
|
|
// Make sure that if extra top down states are added in the future that this
|
|
// code is updated to handle it.
|
|
assert((Seq == S_Retain || Seq == S_CanRelease || Seq == S_Use) &&
|
|
"Unknown top down sequence state.");
|
|
|
|
const Value *Arg = I->first;
|
|
const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
|
|
bool SomeSuccHasSame = false;
|
|
bool AllSuccsHaveSame = true;
|
|
bool NotAllSeqEqualButKnownSafe = false;
|
|
|
|
succ_const_iterator SI(TI), SE(TI, false);
|
|
|
|
for (; SI != SE; ++SI) {
|
|
// If VisitBottomUp has pointer information for this successor, take
|
|
// what we know about it.
|
|
const DenseMap<const BasicBlock *, BBState>::iterator BBI =
|
|
BBStates.find(*SI);
|
|
assert(BBI != BBStates.end());
|
|
const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
|
|
const Sequence SuccSSeq = SuccS.GetSeq();
|
|
|
|
// If bottom up, the pointer is in an S_None state, clear the sequence
|
|
// progress since the sequence in the bottom up state finished
|
|
// suggesting a mismatch in between retains/releases. This is true for
|
|
// all three cases that we are handling here: S_Retain, S_Use, and
|
|
// S_CanRelease.
|
|
if (SuccSSeq == S_None) {
|
|
S.ClearSequenceProgress();
|
|
continue;
|
|
}
|
|
|
|
// If we have S_Use or S_CanRelease, perform our check for cfg hazard
|
|
// checks.
|
|
const bool SuccSRRIKnownSafe = SuccS.IsKnownSafe();
|
|
|
|
// *NOTE* We do not use Seq from above here since we are allowing for
|
|
// S.GetSeq() to change while we are visiting basic blocks.
|
|
switch(S.GetSeq()) {
|
|
case S_Use: {
|
|
bool ShouldContinue = false;
|
|
CheckForUseCFGHazard(SuccSSeq, SuccSRRIKnownSafe, S, SomeSuccHasSame,
|
|
AllSuccsHaveSame, NotAllSeqEqualButKnownSafe,
|
|
ShouldContinue);
|
|
if (ShouldContinue)
|
|
continue;
|
|
break;
|
|
}
|
|
case S_CanRelease: {
|
|
CheckForCanReleaseCFGHazard(SuccSSeq, SuccSRRIKnownSafe, S,
|
|
SomeSuccHasSame, AllSuccsHaveSame,
|
|
NotAllSeqEqualButKnownSafe);
|
|
break;
|
|
}
|
|
case S_Retain:
|
|
case S_None:
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
break;
|
|
}
|
|
}
|
|
|
|
// 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();
|
|
} else if (NotAllSeqEqualButKnownSafe) {
|
|
// If we would have cleared the state foregoing the fact that we are known
|
|
// safe, stop code motion. This is because whether or not it is safe to
|
|
// remove RR pairs via KnownSafe is an orthogonal concept to whether we
|
|
// are allowed to perform code motion.
|
|
S.SetCFGHazardAfflicted(true);
|
|
}
|
|
}
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
|
|
BasicBlock *BB,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
BBState &MyStates) {
|
|
bool NestingDetected = false;
|
|
InstructionClass Class = GetInstructionClass(Inst);
|
|
const Value *Arg = 0;
|
|
|
|
DEBUG(dbgs() << "Class: " << Class << "\n");
|
|
|
|
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() << "Found nested releases (i.e. a release pair)\n");
|
|
NestingDetected = true;
|
|
}
|
|
|
|
MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
|
|
Sequence NewSeq = ReleaseMetadata ? S_MovableRelease : S_Release;
|
|
ANNOTATE_BOTTOMUP(Inst, Arg, S.GetSeq(), NewSeq);
|
|
S.ResetSequenceProgress(NewSeq);
|
|
S.SetReleaseMetadata(ReleaseMetadata);
|
|
S.SetKnownSafe(S.HasKnownPositiveRefCount());
|
|
S.SetTailCallRelease(cast<CallInst>(Inst)->isTailCall());
|
|
S.InsertCall(Inst);
|
|
S.SetKnownPositiveRefCount();
|
|
break;
|
|
}
|
|
case IC_RetainBlock:
|
|
// In OptimizeIndividualCalls, we have strength reduced all optimizable
|
|
// objc_retainBlocks to objc_retains. Thus at this point any
|
|
// objc_retainBlocks that we see are not optimizable.
|
|
break;
|
|
case IC_Retain:
|
|
case IC_RetainRV: {
|
|
Arg = GetObjCArg(Inst);
|
|
|
|
PtrState &S = MyStates.getPtrBottomUpState(Arg);
|
|
S.SetKnownPositiveRefCount();
|
|
|
|
Sequence OldSeq = S.GetSeq();
|
|
switch (OldSeq) {
|
|
case S_Stop:
|
|
case S_Release:
|
|
case S_MovableRelease:
|
|
case S_Use:
|
|
// If OldSeq is not S_Use or OldSeq is S_Use and we are tracking an
|
|
// imprecise release, clear our reverse insertion points.
|
|
if (OldSeq != S_Use || S.IsTrackingImpreciseReleases())
|
|
S.ClearReverseInsertPts();
|
|
// 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)
|
|
Retains[Inst] = S.GetRRInfo();
|
|
S.ClearSequenceProgress();
|
|
break;
|
|
case S_None:
|
|
break;
|
|
case S_Retain:
|
|
llvm_unreachable("bottom-up pointer in retain state!");
|
|
}
|
|
ANNOTATE_BOTTOMUP(Inst, Arg, OldSeq, S.GetSeq());
|
|
// A retain moving bottom up can be a use.
|
|
break;
|
|
}
|
|
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;
|
|
case IC_User:
|
|
// If we have a store into an alloca of a pointer we are tracking, the
|
|
// pointer has multiple owners implying that we must be more conservative.
|
|
//
|
|
// This comes up in the context of a pointer being ``KnownSafe''. In the
|
|
// presence of a block being initialized, the frontend will emit the
|
|
// objc_retain on the original pointer and the release on the pointer loaded
|
|
// from the alloca. The optimizer will through the provenance analysis
|
|
// realize that the two are related, but since we only require KnownSafe in
|
|
// one direction, will match the inner retain on the original pointer with
|
|
// the guard release on the original pointer. This is fixed by ensuring that
|
|
// in the presence of allocas we only unconditionally remove pointers if
|
|
// both our retain and our release are KnownSafe.
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
if (AreAnyUnderlyingObjectsAnAlloca(SI->getPointerOperand())) {
|
|
BBState::ptr_iterator I = MyStates.findPtrBottomUpState(
|
|
StripPointerCastsAndObjCCalls(SI->getValueOperand()));
|
|
if (I != MyStates.bottom_up_ptr_end())
|
|
MultiOwnersSet.insert(I->first);
|
|
}
|
|
}
|
|
break;
|
|
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)) {
|
|
DEBUG(dbgs() << "CanAlterRefCount: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
S.ClearKnownPositiveRefCount();
|
|
switch (Seq) {
|
|
case S_Use:
|
|
S.SetSeq(S_CanRelease);
|
|
ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, S.GetSeq());
|
|
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)) {
|
|
DEBUG(dbgs() << "CanUse: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
assert(!S.HasReverseInsertPts());
|
|
// 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.InsertReverseInsertPt(BB->getFirstInsertionPt());
|
|
else
|
|
S.InsertReverseInsertPt(std::next(BasicBlock::iterator(Inst)));
|
|
S.SetSeq(S_Use);
|
|
ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, S_Use);
|
|
} else if (Seq == S_Release && IsUser(Class)) {
|
|
DEBUG(dbgs() << "PreciseReleaseUse: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
// Non-movable releases depend on any possible objc pointer use.
|
|
S.SetSeq(S_Stop);
|
|
ANNOTATE_BOTTOMUP(Inst, Ptr, S_Release, S_Stop);
|
|
assert(!S.HasReverseInsertPts());
|
|
// As above; handle invoke specially.
|
|
if (isa<InvokeInst>(Inst))
|
|
S.InsertReverseInsertPt(BB->getFirstInsertionPt());
|
|
else
|
|
S.InsertReverseInsertPt(std::next(BasicBlock::iterator(Inst)));
|
|
}
|
|
break;
|
|
case S_Stop:
|
|
if (CanUse(Inst, Ptr, PA, Class)) {
|
|
DEBUG(dbgs() << "PreciseStopUse: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
S.SetSeq(S_Use);
|
|
ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, 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) {
|
|
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::VisitBottomUp ==\n");
|
|
|
|
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);
|
|
}
|
|
}
|
|
|
|
// If ARC Annotations are enabled, output the current state of pointers at the
|
|
// bottom of the basic block.
|
|
ANNOTATE_BOTTOMUP_BBEND(MyStates, BB);
|
|
|
|
// Visit all the instructions, bottom-up.
|
|
for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
|
|
Instruction *Inst = std::prev(I);
|
|
|
|
// Invoke instructions are visited as part of their successors (below).
|
|
if (isa<InvokeInst>(Inst))
|
|
continue;
|
|
|
|
DEBUG(dbgs() << "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);
|
|
}
|
|
|
|
// If ARC Annotations are enabled, output the current state of pointers at the
|
|
// top of the basic block.
|
|
ANNOTATE_BOTTOMUP_BBSTART(MyStates, BB);
|
|
|
|
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:
|
|
// In OptimizeIndividualCalls, we have strength reduced all optimizable
|
|
// objc_retainBlocks to objc_retains. Thus at this point any
|
|
// objc_retainBlocks that we see are not optimizable.
|
|
break;
|
|
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;
|
|
|
|
ANNOTATE_TOPDOWN(Inst, Arg, S.GetSeq(), S_Retain);
|
|
S.ResetSequenceProgress(S_Retain);
|
|
S.SetKnownSafe(S.HasKnownPositiveRefCount());
|
|
S.InsertCall(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.ClearKnownPositiveRefCount();
|
|
|
|
Sequence OldSeq = S.GetSeq();
|
|
|
|
MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
|
|
|
|
switch (OldSeq) {
|
|
case S_Retain:
|
|
case S_CanRelease:
|
|
if (OldSeq == S_Retain || ReleaseMetadata != 0)
|
|
S.ClearReverseInsertPts();
|
|
// FALL THROUGH
|
|
case S_Use:
|
|
S.SetReleaseMetadata(ReleaseMetadata);
|
|
S.SetTailCallRelease(cast<CallInst>(Inst)->isTailCall());
|
|
Releases[Inst] = S.GetRRInfo();
|
|
ANNOTATE_TOPDOWN(Inst, Arg, S.GetSeq(), S_None);
|
|
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)) {
|
|
DEBUG(dbgs() << "CanAlterRefCount: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
S.ClearKnownPositiveRefCount();
|
|
switch (Seq) {
|
|
case S_Retain:
|
|
S.SetSeq(S_CanRelease);
|
|
ANNOTATE_TOPDOWN(Inst, Ptr, Seq, S_CanRelease);
|
|
assert(!S.HasReverseInsertPts());
|
|
S.InsertReverseInsertPt(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)) {
|
|
DEBUG(dbgs() << "CanUse: Seq: " << Seq << "; " << *Ptr
|
|
<< "\n");
|
|
S.SetSeq(S_Use);
|
|
ANNOTATE_TOPDOWN(Inst, Ptr, Seq, 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) {
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::VisitTopDown ==\n");
|
|
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);
|
|
}
|
|
}
|
|
|
|
// If ARC Annotations are enabled, output the current state of pointers at the
|
|
// top of the basic block.
|
|
ANNOTATE_TOPDOWN_BBSTART(MyStates, BB);
|
|
|
|
// Visit all the instructions, top-down.
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
|
|
Instruction *Inst = I;
|
|
|
|
DEBUG(dbgs() << "Visiting " << *Inst << "\n");
|
|
|
|
NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
|
|
}
|
|
|
|
// If ARC Annotations are enabled, output the current state of pointers at the
|
|
// bottom of the basic block.
|
|
ANNOTATE_TOPDOWN_BBEND(MyStates, BB);
|
|
|
|
#ifdef ARC_ANNOTATIONS
|
|
if (!(EnableARCAnnotations && DisableCheckForCFGHazards))
|
|
#endif
|
|
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()));
|
|
|
|
DEBUG(dbgs() << "== ObjCARCOpt::MoveCalls ==\n");
|
|
|
|
// 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);
|
|
Constant *Decl = EP.get(ARCRuntimeEntryPoints::EPT_Retain);
|
|
CallInst *Call = CallInst::Create(Decl, MyArg, "", InsertPt);
|
|
Call->setDoesNotThrow();
|
|
Call->setTailCall();
|
|
|
|
DEBUG(dbgs() << "Inserting new Retain: " << *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);
|
|
Constant *Decl = EP.get(ARCRuntimeEntryPoints::EPT_Release);
|
|
CallInst *Call = CallInst::Create(Decl, 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() << "Inserting new Release: " << *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() << "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() << "Deleting release: " << *OrigRelease << "\n");
|
|
}
|
|
|
|
}
|
|
|
|
bool
|
|
ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
|
|
&BBStates,
|
|
MapVector<Value *, RRInfo> &Retains,
|
|
DenseMap<Value *, RRInfo> &Releases,
|
|
Module *M,
|
|
SmallVectorImpl<Instruction *> &NewRetains,
|
|
SmallVectorImpl<Instruction *> &NewReleases,
|
|
SmallVectorImpl<Instruction *> &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 unless
|
|
// we are dealing with a retainable object with multiple provenance sources.
|
|
bool KnownSafeTD = true, KnownSafeBU = true;
|
|
bool MultipleOwners = false;
|
|
bool CFGHazardAfflicted = false;
|
|
|
|
// 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;
|
|
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;
|
|
MultipleOwners =
|
|
MultipleOwners || MultiOwnersSet.count(GetObjCArg(NewRetain));
|
|
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;
|
|
|
|
// If the release does not have a reference to the retain as well,
|
|
// something happened which is unaccounted for. Do not do anything.
|
|
//
|
|
// This can happen if we catch an additive overflow during path count
|
|
// merging.
|
|
if (!NewRetainReleaseRRI.Calls.count(NewRetain))
|
|
return false;
|
|
|
|
if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
|
|
|
|
// If we overflow when we compute the path count, don't remove/move
|
|
// anything.
|
|
const BBState &NRRBBState = BBStates[NewRetainRelease->getParent()];
|
|
unsigned PathCount = BBState::OverflowOccurredValue;
|
|
if (NRRBBState.GetAllPathCountWithOverflow(PathCount))
|
|
return false;
|
|
assert(PathCount != BBState::OverflowOccurredValue &&
|
|
"PathCount at this point can not be "
|
|
"OverflowOccurredValue.");
|
|
OldDelta -= PathCount;
|
|
|
|
// 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)) {
|
|
// If we overflow when we compute the path count, don't
|
|
// remove/move anything.
|
|
const BBState &RIPBBState = BBStates[RIP->getParent()];
|
|
PathCount = BBState::OverflowOccurredValue;
|
|
if (RIPBBState.GetAllPathCountWithOverflow(PathCount))
|
|
return false;
|
|
assert(PathCount != BBState::OverflowOccurredValue &&
|
|
"PathCount at this point can not be "
|
|
"OverflowOccurredValue.");
|
|
NewDelta -= PathCount;
|
|
}
|
|
}
|
|
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;
|
|
CFGHazardAfflicted |= NewReleaseRRI.CFGHazardAfflicted;
|
|
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;
|
|
|
|
// If the retain does not have a reference to the release as well,
|
|
// something happened which is unaccounted for. Do not do anything.
|
|
//
|
|
// This can happen if we catch an additive overflow during path count
|
|
// merging.
|
|
if (!NewReleaseRetainRRI.Calls.count(NewRelease))
|
|
return false;
|
|
|
|
if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
|
|
// If we overflow when we compute the path count, don't remove/move
|
|
// anything.
|
|
const BBState &NRRBBState = BBStates[NewReleaseRetain->getParent()];
|
|
unsigned PathCount = BBState::OverflowOccurredValue;
|
|
if (NRRBBState.GetAllPathCountWithOverflow(PathCount))
|
|
return false;
|
|
assert(PathCount != BBState::OverflowOccurredValue &&
|
|
"PathCount at this point can not be "
|
|
"OverflowOccurredValue.");
|
|
OldDelta += PathCount;
|
|
OldCount += PathCount;
|
|
|
|
// 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)) {
|
|
// If we overflow when we compute the path count, don't
|
|
// remove/move anything.
|
|
const BBState &RIPBBState = BBStates[RIP->getParent()];
|
|
|
|
PathCount = BBState::OverflowOccurredValue;
|
|
if (RIPBBState.GetAllPathCountWithOverflow(PathCount))
|
|
return false;
|
|
assert(PathCount != BBState::OverflowOccurredValue &&
|
|
"PathCount at this point can not be "
|
|
"OverflowOccurredValue.");
|
|
NewDelta += PathCount;
|
|
NewCount += PathCount;
|
|
}
|
|
}
|
|
NewRetains.push_back(NewReleaseRetain);
|
|
}
|
|
}
|
|
}
|
|
NewReleases.clear();
|
|
if (NewRetains.empty()) break;
|
|
}
|
|
|
|
// If the pointer is known incremented in 1 direction and we do not have
|
|
// MultipleOwners, we can safely remove the retain/releases. Otherwise we need
|
|
// to be known safe in both directions.
|
|
bool UnconditionallySafe = (KnownSafeTD && KnownSafeBU) ||
|
|
((KnownSafeTD || KnownSafeBU) && !MultipleOwners);
|
|
if (UnconditionallySafe) {
|
|
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;
|
|
|
|
// At this point, we are not going to remove any RR pairs, but we still are
|
|
// able to move RR pairs. If one of our pointers is afflicted with
|
|
// CFGHazards, we cannot perform such code motion so exit early.
|
|
const bool WillPerformCodeMotion = RetainsToMove.ReverseInsertPts.size() ||
|
|
ReleasesToMove.ReverseInsertPts.size();
|
|
if (CFGHazardAfflicted && WillPerformCodeMotion)
|
|
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;
|
|
|
|
#ifdef ARC_ANNOTATIONS
|
|
// Do not move calls if ARC annotations are requested.
|
|
if (EnableARCAnnotations)
|
|
return false;
|
|
#endif // ARC_ANNOTATIONS
|
|
|
|
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) {
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::PerformCodePlacement ==\n");
|
|
|
|
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() << "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) {
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeWeakCalls ==\n");
|
|
|
|
// 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() << "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 = std::prev(I);
|
|
BasicBlock *CurrentBB = Current.getBasicBlockIterator();
|
|
for (BasicBlock::iterator B = CurrentBB->begin(),
|
|
J = Current.getInstructionIterator();
|
|
J != B; --J) {
|
|
Instruction *EarlierInst = &*std::prev(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) {
|
|
Constant *Decl = EP.get(ARCRuntimeEntryPoints::EPT_Retain);
|
|
CallInst *CI = CallInst::Create(Decl, 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) {
|
|
Constant *Decl = EP.get(ARCRuntimeEntryPoints::EPT_Retain);
|
|
CallInst *CI = CallInst::Create(Decl, 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_IntrinsicUser:
|
|
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 (User *U : Alloca->users()) {
|
|
const Instruction *UserInst = cast<Instruction>(U);
|
|
switch (GetBasicInstructionClass(UserInst)) {
|
|
case IC_InitWeak:
|
|
case IC_StoreWeak:
|
|
case IC_DestroyWeak:
|
|
continue;
|
|
default:
|
|
goto done;
|
|
}
|
|
}
|
|
Changed = true;
|
|
for (auto UI = Alloca->user_begin(), UE = Alloca->user_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:;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// 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.
|
|
bool AnyPairsCompletelyEliminated = PerformCodePlacement(BBStates, Retains,
|
|
Releases,
|
|
F.getParent());
|
|
|
|
// Cleanup.
|
|
MultiOwnersSet.clear();
|
|
|
|
return AnyPairsCompletelyEliminated && NestingDetected;
|
|
}
|
|
|
|
/// Check if there is a dependent call earlier that does not have anything in
|
|
/// between the Retain and the call that can affect the reference count of their
|
|
/// shared pointer argument. Note that Retain need not be in BB.
|
|
static bool
|
|
HasSafePathToPredecessorCall(const Value *Arg, Instruction *Retain,
|
|
SmallPtrSet<Instruction *, 4> &DepInsts,
|
|
SmallPtrSet<const BasicBlock *, 4> &Visited,
|
|
ProvenanceAnalysis &PA) {
|
|
FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
|
|
DepInsts, Visited, PA);
|
|
if (DepInsts.size() != 1)
|
|
return false;
|
|
|
|
CallInst *Call =
|
|
dyn_cast_or_null<CallInst>(*DepInsts.begin());
|
|
|
|
// Check that the pointer is the return value of the call.
|
|
if (!Call || Arg != Call)
|
|
return false;
|
|
|
|
// Check that the call is a regular call.
|
|
InstructionClass Class = GetBasicInstructionClass(Call);
|
|
if (Class != IC_CallOrUser && Class != IC_Call)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Find a dependent retain that precedes the given autorelease for which there
|
|
/// is nothing in between the two instructions that can affect the ref count of
|
|
/// Arg.
|
|
static CallInst *
|
|
FindPredecessorRetainWithSafePath(const Value *Arg, BasicBlock *BB,
|
|
Instruction *Autorelease,
|
|
SmallPtrSet<Instruction *, 4> &DepInsts,
|
|
SmallPtrSet<const BasicBlock *, 4> &Visited,
|
|
ProvenanceAnalysis &PA) {
|
|
FindDependencies(CanChangeRetainCount, Arg,
|
|
BB, Autorelease, DepInsts, Visited, PA);
|
|
if (DepInsts.size() != 1)
|
|
return 0;
|
|
|
|
CallInst *Retain =
|
|
dyn_cast_or_null<CallInst>(*DepInsts.begin());
|
|
|
|
// Check that we found a retain with the same argument.
|
|
if (!Retain ||
|
|
!IsRetain(GetBasicInstructionClass(Retain)) ||
|
|
GetObjCArg(Retain) != Arg) {
|
|
return 0;
|
|
}
|
|
|
|
return Retain;
|
|
}
|
|
|
|
/// Look for an ``autorelease'' instruction dependent on Arg such that there are
|
|
/// no instructions dependent on Arg that need a positive ref count in between
|
|
/// the autorelease and the ret.
|
|
static CallInst *
|
|
FindPredecessorAutoreleaseWithSafePath(const Value *Arg, BasicBlock *BB,
|
|
ReturnInst *Ret,
|
|
SmallPtrSet<Instruction *, 4> &DepInsts,
|
|
SmallPtrSet<const BasicBlock *, 4> &V,
|
|
ProvenanceAnalysis &PA) {
|
|
FindDependencies(NeedsPositiveRetainCount, Arg,
|
|
BB, Ret, DepInsts, V, PA);
|
|
if (DepInsts.size() != 1)
|
|
return 0;
|
|
|
|
CallInst *Autorelease =
|
|
dyn_cast_or_null<CallInst>(*DepInsts.begin());
|
|
if (!Autorelease)
|
|
return 0;
|
|
InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
|
|
if (!IsAutorelease(AutoreleaseClass))
|
|
return 0;
|
|
if (GetObjCArg(Autorelease) != Arg)
|
|
return 0;
|
|
|
|
return Autorelease;
|
|
}
|
|
|
|
/// 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.
|
|
void ObjCARCOpt::OptimizeReturns(Function &F) {
|
|
if (!F.getReturnType()->isPointerTy())
|
|
return;
|
|
|
|
DEBUG(dbgs() << "\n== ObjCARCOpt::OptimizeReturns ==\n");
|
|
|
|
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() << "Visiting: " << *Ret << "\n");
|
|
|
|
if (!Ret)
|
|
continue;
|
|
|
|
const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
|
|
|
|
// Look for an ``autorelease'' instruction that is a predecessor of Ret and
|
|
// dependent on Arg such that there are no instructions dependent on Arg
|
|
// that need a positive ref count in between the autorelease and Ret.
|
|
CallInst *Autorelease =
|
|
FindPredecessorAutoreleaseWithSafePath(Arg, BB, Ret,
|
|
DependingInstructions, Visited,
|
|
PA);
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
|
|
if (!Autorelease)
|
|
continue;
|
|
|
|
CallInst *Retain =
|
|
FindPredecessorRetainWithSafePath(Arg, BB, Autorelease,
|
|
DependingInstructions, Visited, PA);
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
|
|
if (!Retain)
|
|
continue;
|
|
|
|
// 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.
|
|
bool HasSafePathToCall = HasSafePathToPredecessorCall(Arg, Retain,
|
|
DependingInstructions,
|
|
Visited, PA);
|
|
DependingInstructions.clear();
|
|
Visited.clear();
|
|
|
|
if (!HasSafePathToCall)
|
|
continue;
|
|
|
|
// If so, we can zap the retain and autorelease.
|
|
Changed = true;
|
|
++NumRets;
|
|
DEBUG(dbgs() << "Erasing: " << *Retain << "\nErasing: "
|
|
<< *Autorelease << "\n");
|
|
EraseInstruction(Retain);
|
|
EraseInstruction(Autorelease);
|
|
}
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
void
|
|
ObjCARCOpt::GatherStatistics(Function &F, bool AfterOptimization) {
|
|
llvm::Statistic &NumRetains =
|
|
AfterOptimization? NumRetainsAfterOpt : NumRetainsBeforeOpt;
|
|
llvm::Statistic &NumReleases =
|
|
AfterOptimization? NumReleasesAfterOpt : NumReleasesBeforeOpt;
|
|
|
|
for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
|
|
Instruction *Inst = &*I++;
|
|
switch (GetBasicInstructionClass(Inst)) {
|
|
default:
|
|
break;
|
|
case IC_Retain:
|
|
++NumRetains;
|
|
break;
|
|
case IC_Release:
|
|
++NumReleases;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
|
|
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");
|
|
#ifdef ARC_ANNOTATIONS
|
|
ARCAnnotationBottomUpMDKind =
|
|
M.getContext().getMDKindID("llvm.arc.annotation.bottomup");
|
|
ARCAnnotationTopDownMDKind =
|
|
M.getContext().getMDKindID("llvm.arc.annotation.topdown");
|
|
ARCAnnotationProvenanceSourceMDKind =
|
|
M.getContext().getMDKindID("llvm.arc.annotation.provenancesource");
|
|
#endif // ARC_ANNOTATIONS
|
|
|
|
// 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.
|
|
|
|
// Initialize our runtime entry point cache.
|
|
EP.Initialize(&M);
|
|
|
|
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>());
|
|
|
|
#ifndef NDEBUG
|
|
if (AreStatisticsEnabled()) {
|
|
GatherStatistics(F, false);
|
|
}
|
|
#endif
|
|
|
|
// 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 computes 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);
|
|
|
|
// Gather statistics after optimization.
|
|
#ifndef NDEBUG
|
|
if (AreStatisticsEnabled()) {
|
|
GatherStatistics(F, true);
|
|
}
|
|
#endif
|
|
|
|
DEBUG(dbgs() << "\n");
|
|
|
|
return Changed;
|
|
}
|
|
|
|
void ObjCARCOpt::releaseMemory() {
|
|
PA.clear();
|
|
}
|
|
|
|
/// @}
|
|
///
|