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
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 601d9b4..036f0d3 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -30,6 +30,14 @@
}
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 @@
// 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);