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Add trivial support for the invariance intrinsics to memdep. This logic is

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purely local for now.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85378 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2009-10-28 06:18:42 +00:00
parent 50b136dae9
commit 4bc737c5ef
2 changed files with 56 additions and 1 deletions
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36
lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -171,13 +171,42 @@ getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
/// location depends. If isLoad is true, this routine ignore may-aliases with
/// read-only operations.
MemDepResult MemoryDependenceAnalysis::
getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
BasicBlock::iterator ScanIt, BasicBlock *BB) {
Value* invariantTag = 0;
// Walk backwards through the basic block, looking for dependencies.
while (ScanIt != BB->begin()) {
Instruction *Inst = --ScanIt;
// If we're in an invariant region, no dependencies can be found before
// we pass an invariant-begin marker.
if (invariantTag == Inst) {
invariantTag = 0;
continue;
// If we pass an invariant-end marker, then we've just entered an invariant
// region and can start ignoring dependencies.
} else if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst)) {
if (II->getIntrinsicID() == Intrinsic::invariant_end) {
uint64_t invariantSize = ~0ULL;
if (ConstantInt* CI = dyn_cast<ConstantInt>(II->getOperand(2)))
invariantSize = CI->getZExtValue();
AliasAnalysis::AliasResult R =
AA->alias(II->getOperand(3), invariantSize, MemPtr, MemSize);
if (R == AliasAnalysis::MustAlias) {
invariantTag = II->getOperand(1);
continue;
}
}
}
// If we're querying on a load and we're in an invariant region, we're done
// at this point. Nothing a load depends on can live in an invariant region.
if (isLoad && invariantTag) continue;
// Debug intrinsics don't cause dependences.
if (isa<DbgInfoIntrinsic>(Inst)) continue;
@ -201,6 +230,11 @@ getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
return MemDepResult::getDef(Inst);
}
// If we're querying on a store and we're in an invariant region, we're done
// at this point. The only things that stores depend on that could exist in
// an invariant region are loads, which we've already checked.
if (invariantTag) continue;
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// If alias analysis can tell that this store is guaranteed to not modify
// the query pointer, ignore it. Use getModRefInfo to handle cases where