diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index 8cc7901cbac7..86a39cf2ee93 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -3201,7 +3201,8 @@ Instruction *InstCombinerImpl::foldSelectOfBools(SelectInst &SI) { // pattern. static bool isSafeToRemoveBitCeilSelect(ICmpInst::Predicate Pred, Value *Cond0, const APInt *Cond1, Value *CtlzOp, - unsigned BitWidth) { + unsigned BitWidth, + bool &ShouldDropNUW) { // The challenge in recognizing std::bit_ceil(X) is that the operand is used // for the CTLZ proper and select condition, each possibly with some // operation like add and sub. @@ -3224,6 +3225,8 @@ static bool isSafeToRemoveBitCeilSelect(ICmpInst::Predicate Pred, Value *Cond0, ConstantRange CR = ConstantRange::makeExactICmpRegion( CmpInst::getInversePredicate(Pred), *Cond1); + ShouldDropNUW = false; + // Match the operation that's used to compute CtlzOp from CommonAncestor. If // CtlzOp == CommonAncestor, return true as no operation is needed. If a // match is found, execute the operation on CR, update CR, and return true. @@ -3237,6 +3240,7 @@ static bool isSafeToRemoveBitCeilSelect(ICmpInst::Predicate Pred, Value *Cond0, return true; } if (match(CtlzOp, m_Sub(m_APInt(C), m_Specific(CommonAncestor)))) { + ShouldDropNUW = true; CR = ConstantRange(*C).sub(CR); return true; } @@ -3306,14 +3310,20 @@ static Instruction *foldBitCeil(SelectInst &SI, IRBuilderBase &Builder) { Pred = CmpInst::getInversePredicate(Pred); } + bool ShouldDropNUW; + if (!match(FalseVal, m_One()) || !match(TrueVal, m_OneUse(m_Shl(m_One(), m_OneUse(m_Sub(m_SpecificInt(BitWidth), m_Value(Ctlz)))))) || !match(Ctlz, m_Intrinsic<Intrinsic::ctlz>(m_Value(CtlzOp), m_Zero())) || - !isSafeToRemoveBitCeilSelect(Pred, Cond0, Cond1, CtlzOp, BitWidth)) + !isSafeToRemoveBitCeilSelect(Pred, Cond0, Cond1, CtlzOp, BitWidth, + ShouldDropNUW)) return nullptr; + if (ShouldDropNUW) + cast<Instruction>(CtlzOp)->setHasNoUnsignedWrap(false); + // Build 1 << (-CTLZ & (BitWidth-1)). The negation likely corresponds to a // single hardware instruction as opposed to BitWidth - CTLZ, where BitWidth // is an integer constant. Masking with BitWidth-1 comes free on some |