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Reapply a fixed version of r133285.

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This tightens up checking for overflow in alloca sizes, based on feedback
from Duncan and John about the change in r132926.

llvm-svn: 134749
This commit is contained in:
Bob Wilson 2011-07-08 22:09:33 +00:00
parent 2b8103505a
commit d5c5f63f43
1 changed files with 8 additions and 5 deletions
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13
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -30,6 +30,14 @@ static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
}
if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
// Cannot look past anything that might overflow.
OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
if (OBI && !OBI->hasNoUnsignedWrap()) {
Scale = 1;
Offset = 0;
return Val;
}
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
@ -71,11 +79,6 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
// This requires TargetData to get the alloca alignment and size information.
if (!TD) return 0;
// Insist that the amount-to-allocate not overflow.
OverflowingBinaryOperator *OBI =
dyn_cast<OverflowingBinaryOperator>(AI.getOperand(0));
if (OBI && !(OBI->hasNoSignedWrap() || OBI->hasNoUnsignedWrap())) return 0;
const PointerType *PTy = cast<PointerType>(CI.getType());
BuilderTy AllocaBuilder(*Builder);