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enhance memcpy opt to turn memmoves into memcpy when the src/dest

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don't alias.  Remove an old and poorly reduced testcase that fails
with this transform for reasons unrelated to the original test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80693 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-09-01 17:56:32 +00:00
parent c517cb0065
commit f41eaacee4
3 changed files with 78 additions and 113 deletions
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47
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -317,6 +317,7 @@ namespace {
// Helper fuctions
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M);
bool processMemMove(MemMoveInst *M);
bool performCallSlotOptzn(MemCpyInst *cpy, CallInst *C);
bool iterateOnFunction(Function &F);
};
@ -431,9 +432,8 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
BasicBlock::iterator InsertPt = BI;
if (MemSetF == 0) {
const Type *Tys[] = {Type::getInt64Ty(SI->getContext())};
MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset,
Tys, 1);
const Type *Ty = Type::getInt64Ty(SI->getContext());
MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset, &Ty, 1);
}
// Get the starting pointer of the block.
@ -679,11 +679,10 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
return false;
// If all checks passed, then we can transform these memcpy's
const Type *Tys[1];
Tys[0] = M->getLength()->getType();
const Type *Ty = M->getLength()->getType();
Function *MemCpyFun = Intrinsic::getDeclaration(
M->getParent()->getParent()->getParent(),
M->getIntrinsicID(), Tys, 1);
M->getIntrinsicID(), &Ty, 1);
Value *Args[4] = {
M->getRawDest(), MDep->getRawSource(), M->getLength(), M->getAlignmentCst()
@ -708,6 +707,36 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
return false;
}
/// processMemMove - Transforms memmove calls to memcpy calls when the src/dst
/// are guaranteed not to alias.
bool MemCpyOpt::processMemMove(MemMoveInst *M) {
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// If the memmove is a constant size, use it for the alias query, this allows
// us to optimize things like: memmove(P, P+64, 64);
uint64_t MemMoveSize = ~0ULL;
if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength()))
MemMoveSize = Len->getZExtValue();
// See if the pointers alias.
if (AA.alias(M->getRawDest(), MemMoveSize, M->getRawSource(), MemMoveSize) !=
AliasAnalysis::NoAlias)
return false;
DEBUG(errs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n");
// If not, then we know we can transform this.
Module *Mod = M->getParent()->getParent()->getParent();
const Type *Ty = M->getLength()->getType();
M->setOperand(0, Intrinsic::getDeclaration(Mod, Intrinsic::memcpy, &Ty, 1));
// MemDep may have over conservative information about this instruction, just
// conservatively flush it from the cache.
getAnalysis<MemoryDependenceAnalysis>().removeInstruction(M);
return true;
}
// MemCpyOpt::iterateOnFunction - Executes one iteration of GVN.
bool MemCpyOpt::iterateOnFunction(Function &F) {
bool MadeChange = false;
@ -723,6 +752,12 @@ bool MemCpyOpt::iterateOnFunction(Function &F) {
MadeChange |= processStore(SI, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
MadeChange |= processMemCpy(M);
else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I)) {
if (processMemMove(M)) {
--BI; // Reprocess the new memcpy.
MadeChange = true;
}
}
}
}