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InstCombine: Defensively avoid undefined shifts by limiting the amount to the bit width.

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No test case, undefined shifts get folded early, but can occur when other
transforms generate a constant. Thanks to Duncan for bringing this up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162755 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2012-08-28 13:59:23 +00:00
parent aac7c650a6
commit 37dca6331d
1 changed files with 2 additions and 2 deletions
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4
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
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@ -467,7 +467,7 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
Value *X;
ConstantInt *C1;
if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) {
APInt NC = C2->getValue().shl(C1->getZExtValue());
APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1));
return BinaryOperator::CreateUDiv(X, Builder->getInt(NC));
}
}
@ -548,7 +548,7 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
Value *X;
ConstantInt *C1;
if (match(Op0, m_AShr(m_Value(X), m_ConstantInt(C1)))) {
APInt NC = C2->getValue().shl(C1->getZExtValue());
APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1));
return BinaryOperator::CreateSDiv(X, Builder->getInt(NC));
}
}