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it isn't safe to speculative load from a malloc, it might have

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returned null, and may not have been big enough in any case.  
Thanks to Jay Foad for pointing this out!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92452 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-01-03 18:14:24 +00:00
parent 2ef90d782e
commit fa5dd977e4
1 changed files with 1 additions and 32 deletions
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33
lib/VMCore/Instruction.cpp
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@ -374,37 +374,6 @@ bool Instruction::isCommutative(unsigned op) {
} }
} }
// Code here matches isMalloc from MemoryBuiltins, which is not in VMCore.
static bool isMalloc(const Value* I) {
const CallInst *CI = dyn_cast<CallInst>(I);
if (!CI) {
const BitCastInst *BCI = dyn_cast<BitCastInst>(I);
if (!BCI) return false;
CI = dyn_cast<CallInst>(BCI->getOperand(0));
}
if (!CI)
return false;
Function *Callee = CI->getCalledFunction();
if (Callee == 0 || !Callee->isDeclaration() || Callee->getName() != "malloc")
return false;
// Check malloc prototype.
// FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
// attribute will exist.
const FunctionType *FTy = Callee->getFunctionType();
if (FTy->getNumParams() != 1)
return false;
if (IntegerType *ITy = dyn_cast<IntegerType>(FTy->param_begin()->get())) {
if (ITy->getBitWidth() != 32 && ITy->getBitWidth() != 64)
return false;
return true;
}
return false;
}
bool Instruction::isSafeToSpeculativelyExecute() const { bool Instruction::isSafeToSpeculativelyExecute() const {
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
if (Constant *C = dyn_cast<Constant>(getOperand(i))) if (Constant *C = dyn_cast<Constant>(getOperand(i)))
@ -430,7 +399,7 @@ bool Instruction::isSafeToSpeculativelyExecute() const {
case Load: { case Load: {
if (cast<LoadInst>(this)->isVolatile()) if (cast<LoadInst>(this)->isVolatile())
return false; return false;
if (isa<AllocaInst>(getOperand(0)) || isMalloc(getOperand(0))) if (isa<AllocaInst>(getOperand(0)))
return true; return true;
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0))) if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0)))
return !GV->hasExternalWeakLinkage(); return !GV->hasExternalWeakLinkage();