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InstCombine: Don't turn -(x/INT_MIN) -> x/INT_MIN

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It is not safe to negate the smallest signed integer, doing so yields
the same number back.

This fixes PR20186.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212164 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-07-02 06:07:09 +00:00
parent 90fdedc064
commit 5f5939c14c
4 changed files with 47 additions and 3 deletions
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lib/IR/Constants.cpp
+22
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@@ -107,6 +107,28 @@ bool Constant::isAllOnesValue() const {
return false;
}
bool Constant::isMinSignedValue() const {
// Check for INT_MIN integers
if (const ConstantInt *CI = dyn_cast<ConstantInt>(this))
return CI->isMinValue(/*isSigned=*/true);
// Check for FP which are bitcasted from INT_MIN integers
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
return CFP->getValueAPF().bitcastToAPInt().isMinSignedValue();
// Check for constant vectors which are splats of INT_MIN values.
if (const ConstantVector *CV = dyn_cast<ConstantVector>(this))
if (Constant *Splat = CV->getSplatValue())
return Splat->isMinSignedValue();
// Check for constant vectors which are splats of INT_MIN values.
if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
if (Constant *Splat = CV->getSplatValue())
return Splat->isMinSignedValue();
return false;
}
// Constructor to create a '0' constant of arbitrary type...
Constant *Constant::getNullValue(Type *Ty) {
switch (Ty->getTypeID()) {