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InstSimplify: Optimize away pointless comparisons

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(X & INT_MIN) ? X & INT_MAX : X  into  X & INT_MAX
(X & INT_MIN) ? X : X & INT_MAX  into  X
(X & INT_MIN) ? X | INT_MIN : X  into  X
(X & INT_MIN) ? X : X | INT_MIN  into  X | INT_MIN

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224669 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-12-20 03:04:38 +00:00
parent 93e03df3cf
commit 9cd99a0724
3 changed files with 121 additions and 2 deletions
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lib/Analysis/InstructionSimplify.cpp
+38 -2
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@@ -3155,10 +3155,10 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
if (const auto *ICI = dyn_cast<ICmpInst>(CondVal)) {
Value *X;
const APInt *Y;
if (ICI->isEquality() &&
ICmpInst::Predicate Pred = ICI->getPredicate();
if (ICmpInst::isEquality(Pred) &&
match(ICI->getOperand(0), m_And(m_Value(X), m_APInt(Y))) &&
match(ICI->getOperand(1), m_Zero())) {
ICmpInst::Predicate Pred = ICI->getPredicate();
const APInt *C;
// (X & Y) == 0 ? X & ~Y : X --> X
// (X & Y) != 0 ? X & ~Y : X --> X & ~Y
@@ -3184,6 +3184,42 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
return Pred == ICmpInst::ICMP_EQ ? TrueVal : FalseVal;
}
}
if (Pred == ICmpInst::ICMP_SLT && match(ICI->getOperand(1), m_Zero())) {
// (X < 0) ? X : X | SignBit --> X | SignBit
if (TrueVal == ICI->getOperand(0) &&
match(FalseVal, m_Or(m_Specific(TrueVal), m_SignBit())))
return FalseVal;
// (X < 0) ? X | SignBit : X --> X
if (FalseVal == ICI->getOperand(0) &&
match(TrueVal, m_Or(m_Specific(FalseVal), m_SignBit())))
return FalseVal;
// (X < 0) ? X & INT_MAX : X --> X & INT_MAX
if (FalseVal == ICI->getOperand(0) &&
match(TrueVal, m_And(m_Specific(FalseVal), m_MaxSignedValue())))
return TrueVal;
// (X < 0) ? X : X & INT_MAX --> X
if (TrueVal == ICI->getOperand(0) &&
match(FalseVal, m_And(m_Specific(TrueVal), m_MaxSignedValue())))
return TrueVal;
}
if (Pred == ICmpInst::ICMP_SGT && match(ICI->getOperand(1), m_AllOnes())) {
// (X > -1) ? X : X | SignBit --> X
if (TrueVal == ICI->getOperand(0) &&
match(FalseVal, m_Or(m_Specific(TrueVal), m_SignBit())))
return TrueVal;
// (X > -1) ? X | SignBit : X --> X | SignBit
if (FalseVal == ICI->getOperand(0) &&
match(TrueVal, m_Or(m_Specific(FalseVal), m_SignBit())))
return TrueVal;
// (X > -1) ? X & INT_MAX : X --> X
if (FalseVal == ICI->getOperand(0) &&
match(TrueVal, m_And(m_Specific(FalseVal), m_MaxSignedValue())))
return FalseVal;
// (X > -1) ? X : X & INT_MAX --> X & INT_MAX
if (TrueVal == ICI->getOperand(0) &&
match(FalseVal, m_And(m_Specific(TrueVal), m_MaxSignedValue())))
return FalseVal;
}
}
return nullptr;