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Fix a thinko pointed out by Frits van Bommel: looking through global variables in isBytewiseValue is not safe.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122550 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2010-12-24 22:23:59 +00:00
parent fea753b397
commit 49c7e3e290
1 changed files with 19 additions and 22 deletions
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41
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -40,13 +40,6 @@ STATISTIC(NumCpyToSet, "Number of memcpys converted to memset");
/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated
/// byte store (e.g. i16 0x1234), return null.
static Value *isBytewiseValue(Value *V) {
// Look through constant globals.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
if (GV->mayBeOverridden() || !GV->isConstant() || !GV->hasInitializer())
return 0;
V = GV->getInitializer();
}
// All byte-wide stores are splatable, even of arbitrary variables.
if (V->getType()->isIntegerTy(8)) return V;
@ -793,21 +786,25 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
}
// If copying from a constant, try to turn the memcpy into a memset.
if (Value *ByteVal = isBytewiseValue(M->getSource())) {
Value *Ops[] = {
M->getRawDest(), ByteVal, // Start, value
CopySize, // Size
M->getAlignmentCst(), // Alignment
ConstantInt::getFalse(M->getContext()), // volatile
};
const Type *Tys[] = { Ops[0]->getType(), Ops[2]->getType() };
Module *Mod = M->getParent()->getParent()->getParent();
Function *MemSetF = Intrinsic::getDeclaration(Mod, Intrinsic::memset, Tys, 2);
CallInst::Create(MemSetF, Ops, Ops+5, "", M);
M->eraseFromParent();
++NumCpyToSet;
return true;
}
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
if (!GV->mayBeOverridden() && GV->isConstant() && GV->hasInitializer())
if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
Value *Ops[] = {
M->getRawDest(), ByteVal, // Start, value
CopySize, // Size
M->getAlignmentCst(), // Alignment
ConstantInt::getFalse(M->getContext()), // volatile
};
const Type *Tys[] = { Ops[0]->getType(), Ops[2]->getType() };
Module *Mod = M->getParent()->getParent()->getParent();
Function *MemSetF = Intrinsic::getDeclaration(Mod, Intrinsic::memset,
Tys, 2);
CallInst::Create(MemSetF, Ops, Ops+5, "", M);
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
return true;
}
// The are two possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.