From 837c16097e99d7b648fb983213485974d25fcf9c Mon Sep 17 00:00:00 2001 From: Dinesh Dwivedi Date: Thu, 15 May 2014 06:01:33 +0000 Subject: Added inst combine transforms for single bit tests from Chris's note 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 Z3 Verifications code for above transform http://rise4fun.com/Z3/Pmsh Differential Revision: http://reviews.llvm.org/D3717 llvm-svn: 208848 --- .../Transforms/InstCombine/InstCombineSelect.cpp | 42 +++++++++++++++++++--- 1 file changed, 37 insertions(+), 5 deletions(-) (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index 795e645840c..50b5b3740f1 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -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(SI.getCondition()); @@ -384,10 +392,34 @@ static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal, return nullptr; const APInt *C2; - bool OrOnTrueVal = false; - bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2))); - if (!OrOnFalseVal) - OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2))); + + // if ((x & C) != 0) x ^= C becomes x &= ~C + if (match(FalseVal, m_Xor(m_Specific(TrueVal), m_APInt(C2))) && C1 == C2) { + return Builder->CreateAnd(TrueVal, ~(*C1)); + } + + // if ((x & C) == 0) x ^= C becomes x |= C + if (match(TrueVal, m_Xor(m_Specific(FalseVal), m_APInt(C2))) && C1 == C2) { + return Builder->CreateOr(FalseVal, *C1); + } + + // if ((x & C) != 0) x &= ~C becomes x &= ~C + // if ((x & C) == 0) x &= ~C becomes nothing + if ((match(FalseVal, m_And(m_Specific(TrueVal), m_APInt(C2))) || + match(TrueVal, m_And(m_Specific(FalseVal), m_APInt(C2)))) && + *C1 == ~(*C2)) { + return FalseVal; + } + + bool OrOnFalseVal = false; + bool OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2))); + + // if ((x & C) == 0) x |= C becomes x |= C + if (OrOnTrueVal && C1 == C2) + return TrueVal; + + if (!OrOnTrueVal) + OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2))); if (!OrOnFalseVal && !OrOnTrueVal) return nullptr; -- cgit v1.2.3