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Reapply a fixed version of r133285.
This tightens up checking for overflow in alloca sizes, based on feedback from Duncan and John about the change in r132926. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134749 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -30,6 +30,14 @@ static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
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}
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if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
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// Cannot look past anything that might overflow.
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OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
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if (OBI && !OBI->hasNoUnsignedWrap()) {
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Scale = 1;
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Offset = 0;
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return Val;
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}
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
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if (I->getOpcode() == Instruction::Shl) {
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// This is a value scaled by '1 << the shift amt'.
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@ -71,11 +79,6 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
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// This requires TargetData to get the alloca alignment and size information.
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if (!TD) return 0;
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// Insist that the amount-to-allocate not overflow.
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OverflowingBinaryOperator *OBI =
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dyn_cast<OverflowingBinaryOperator>(AI.getOperand(0));
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if (OBI && !(OBI->hasNoSignedWrap() || OBI->hasNoUnsignedWrap())) return 0;
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const PointerType *PTy = cast<PointerType>(CI.getType());
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BuilderTy AllocaBuilder(*Builder);
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