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clean up handling of 'free', detangling it from everything else.

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It can be seriously improved, but at least now it isn't intertwined
with the other logic.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120377 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-11-30 01:28:33 +00:00
parent feea8fb6b4
commit 1ab4285b72
2 changed files with 26 additions and 22 deletions
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4
include/llvm/Analysis/MemoryBuiltins.h
View File

@ -74,6 +74,10 @@ Value *getMallocArraySize(CallInst *CI, const TargetData *TD,
/// isFreeCall - Returns non-null if the value is a call to the builtin free()
const CallInst *isFreeCall(const Value *I);
static inline CallInst *isFreeCall(Value *I) {
return const_cast<CallInst*>(isFreeCall((const Value*)I));
}
} // End llvm namespace

44
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -58,9 +58,7 @@ namespace {
}
bool runOnBasicBlock(BasicBlock &BB);
bool handleFreeWithNonTrivialDependency(const CallInst *F,
Instruction *Inst,
MemDepResult Dep);
bool HandleFree(CallInst *F);
bool handleEndBlock(BasicBlock &BB);
bool RemoveUndeadPointers(Value *Ptr, uint64_t killPointerSize,
BasicBlock::iterator &BBI,
@ -124,7 +122,7 @@ static bool isElidable(Instruction *I) {
return true;
}
/// getPointerOperand - Return the pointer that is being clobbered.
/// getPointerOperand - Return the pointer that is being written to.
static Value *getPointerOperand(Instruction *I) {
assert(doesClobberMemory(I));
if (StoreInst *SI = dyn_cast<StoreInst>(I))
@ -202,8 +200,14 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
for (BasicBlock::iterator BBI = BB.begin(), BBE = BB.end(); BBI != BBE; ) {
Instruction *Inst = BBI++;
// If we find a store or a free, get its memory dependence.
if (!doesClobberMemory(Inst) && !isFreeCall(Inst))
// Handle 'free' calls specially.
if (CallInst *F = isFreeCall(Inst)) {
MadeChange |= HandleFree(F);
continue;
}
// If we find a store, get its memory dependence.
if (!doesClobberMemory(Inst))
continue;
MemDepResult InstDep = MD.getDependency(Inst);
@ -211,13 +215,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
// Ignore non-local store liveness.
// FIXME: cross-block DSE would be fun. :)
if (InstDep.isNonLocal()) continue;
// Handle frees whose dependencies are non-trivial.
if (const CallInst *F = isFreeCall(Inst)) {
MadeChange |= handleFreeWithNonTrivialDependency(F, Inst, InstDep);
continue;
}
// If we're storing the same value back to a pointer that we just
// loaded from, then the store can be removed.
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
@ -292,24 +290,25 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
return MadeChange;
}
/// handleFreeWithNonTrivialDependency - Handle frees of entire structures whose
/// dependency is a store to a field of that structure.
bool DSE::handleFreeWithNonTrivialDependency(const CallInst *F,
Instruction *Inst,
MemDepResult Dep) {
/// HandleFree - Handle frees of entire structures whose dependency is a store
/// to a field of that structure.
bool DSE::HandleFree(CallInst *F) {
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
MemDepResult Dep = MD.getDependency(F);
do {
if (Dep.isNonLocal()) return false;
Instruction *Dependency = Dep.getInst();
if (!Dependency || !doesClobberMemory(Dependency) || !isElidable(Dependency))
if (!doesClobberMemory(Dependency) || !isElidable(Dependency))
return false;
Value *DepPointer = getPointerOperand(Dependency)->getUnderlyingObject();
// Check for aliasing.
if (AA.alias(F->getArgOperand(0), 1, DepPointer, 1) !=
AliasAnalysis::MustAlias)
AliasAnalysis::MustAlias)
return false;
// DCE instructions only used to calculate that store
@ -321,8 +320,9 @@ bool DSE::handleFreeWithNonTrivialDependency(const CallInst *F,
// s[0] = 0;
// s[1] = 0; // This has just been deleted.
// free(s);
Dep = MD.getDependency(Inst);
Dep = MD.getDependency(F);
} while (!Dep.isNonLocal());
return true;
}