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Added inst combine transforms for single bit tests from Chris's note

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if ((x & C) == 0) x |= C becomes x |= C
if ((x & C) != 0) x ^= C becomes x &= ~C
if ((x & C) == 0) x ^= C becomes x |= C
if ((x & C) != 0) x &= ~C becomes x &= ~C
if ((x & C) == 0) x &= ~C becomes nothing

Differential Revision: http://reviews.llvm.org/D3777



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210006 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dinesh Dwivedi
2014-06-02 07:24:36 +00:00
parent 01fa655228
commit c469e543a0
2 changed files with 133 additions and 1 deletions
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29
lib/Transforms/InstCombine/InstCombineSelect.cpp
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@ -365,7 +365,15 @@ static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
/// 1. The icmp predicate is inverted
/// 2. The select operands are reversed
/// 3. The magnitude of C2 and C1 are flipped
static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
///
/// This also tries to turn
/// --- Single bit tests:
/// if ((x & C) == 0) x |= C to x |= C
/// if ((x & C) != 0) x ^= C to x &= ~C
/// if ((x & C) == 0) x ^= C to x |= C
/// if ((x & C) != 0) x &= ~C to x &= ~C
/// if ((x & C) == 0) x &= ~C to nothing
static Value *foldSelectICmpAndOr(SelectInst &SI, Value *TrueVal,
Value *FalseVal,
InstCombiner::BuilderTy *Builder) {
const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
@ -384,6 +392,25 @@ static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
return nullptr;
const APInt *C2;
if (match(TrueVal, m_Specific(X))) {
// if ((X & C) != 0) X ^= C becomes X &= ~C
if (match(FalseVal, m_Xor(m_Specific(X), m_APInt(C2))) && C1 == C2)
return Builder->CreateAnd(X, ~(*C1));
// if ((X & C) != 0) X &= ~C becomes X &= ~C
if (match(FalseVal, m_And(m_Specific(X), m_APInt(C2))) && *C1 == ~(*C2))
return FalseVal;
} else if (match(FalseVal, m_Specific(X))) {
// if ((X & C) == 0) X ^= C becomes X |= C
if (match(TrueVal, m_Xor(m_Specific(X), m_APInt(C2))) && C1 == C2)
return Builder->CreateOr(X, *C1);
// if ((X & C) == 0) X &= ~C becomes nothing
if (match(TrueVal, m_And(m_Specific(X), m_APInt(C2))) && *C1 == ~(*C2))
return X;
// if ((X & C) == 0) X |= C becomes X |= C
if (match(TrueVal, m_Or(m_Specific(X), m_APInt(C2))) && C1 == C2)
return TrueVal;
}
bool OrOnTrueVal = false;
bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
if (!OrOnFalseVal)