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it isn't safe to speculative load from a malloc, it might have
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
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@ -374,37 +374,6 @@ bool Instruction::isCommutative(unsigned op) {
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}
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}
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// Code here matches isMalloc from MemoryBuiltins, which is not in VMCore.
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static bool isMalloc(const Value* I) {
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const CallInst *CI = dyn_cast<CallInst>(I);
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if (!CI) {
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const BitCastInst *BCI = dyn_cast<BitCastInst>(I);
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if (!BCI) return false;
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CI = dyn_cast<CallInst>(BCI->getOperand(0));
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}
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if (!CI)
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return false;
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Function *Callee = CI->getCalledFunction();
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if (Callee == 0 || !Callee->isDeclaration() || Callee->getName() != "malloc")
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return false;
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// Check malloc prototype.
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// FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
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// attribute will exist.
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const FunctionType *FTy = Callee->getFunctionType();
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if (FTy->getNumParams() != 1)
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return false;
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if (IntegerType *ITy = dyn_cast<IntegerType>(FTy->param_begin()->get())) {
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if (ITy->getBitWidth() != 32 && ITy->getBitWidth() != 64)
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return false;
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return true;
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}
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return false;
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}
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bool Instruction::isSafeToSpeculativelyExecute() const {
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for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
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if (Constant *C = dyn_cast<Constant>(getOperand(i)))
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@ -430,7 +399,7 @@ bool Instruction::isSafeToSpeculativelyExecute() const {
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case Load: {
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if (cast<LoadInst>(this)->isVolatile())
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return false;
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if (isa<AllocaInst>(getOperand(0)) || isMalloc(getOperand(0)))
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if (isa<AllocaInst>(getOperand(0)))
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return true;
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0)))
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return !GV->hasExternalWeakLinkage();
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