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[InstCombine] Replace an 'if' that should always be true with an assert.

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The bitwidth of the operation should always be wider than the result width of the truncate since we don't recurse through any width changing operations.

llvm-svn: 332055
This commit is contained in:
Craig Topper 2018-05-10 22:45:28 +00:00
parent a01ce37a7f
commit c50865580a
1 changed files with 6 additions and 7 deletions
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13
lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -364,13 +364,12 @@ static bool canEvaluateTruncated(Value *V, Type *Ty, InstCombiner &IC,
// UDiv and URem can be truncated if all the truncated bits are zero.
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (BitWidth < OrigBitWidth) {
APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
if (IC.MaskedValueIsZero(I->getOperand(0), Mask, 0, CxtI) &&
IC.MaskedValueIsZero(I->getOperand(1), Mask, 0, CxtI)) {
return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
}
assert(BitWidth < OrigBitWidth && "Unexpected bitwidths!");
APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
if (IC.MaskedValueIsZero(I->getOperand(0), Mask, 0, CxtI) &&
IC.MaskedValueIsZero(I->getOperand(1), Mask, 0, CxtI)) {
return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
}
break;
}