diff options
Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp index 3f2ddcacce2b..8cec865c6422 100644 --- a/contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp +++ b/contrib/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp @@ -682,11 +682,11 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) { return BinaryOperator::CreateAnd(X, ConstantInt::get(Ty, Mask)); } - if (match(Op0, m_SExt(m_Value(X)))) { + if (match(Op0, m_SExt(m_Value(X))) && + (!Ty->isIntegerTy() || shouldChangeType(Ty, X->getType()))) { // Are we moving the sign bit to the low bit and widening with high zeros? unsigned SrcTyBitWidth = X->getType()->getScalarSizeInBits(); - if (ShAmt == BitWidth - 1 && - (!Ty->isIntegerTy() || shouldChangeType(Ty, X->getType()))) { + if (ShAmt == BitWidth - 1) { // lshr (sext i1 X to iN), N-1 --> zext X to iN if (SrcTyBitWidth == 1) return new ZExtInst(X, Ty); @@ -698,7 +698,13 @@ Instruction *InstCombiner::visitLShr(BinaryOperator &I) { } } - // TODO: Convert to ashr+zext if the shift equals the extension amount. + // lshr (sext iM X to iN), N-M --> zext (ashr X, min(N-M, M-1)) to iN + if (ShAmt == BitWidth - SrcTyBitWidth && Op0->hasOneUse()) { + // The new shift amount can't be more than the narrow source type. + unsigned NewShAmt = std::min(ShAmt, SrcTyBitWidth - 1); + Value *AShr = Builder->CreateAShr(X, NewShAmt); + return new ZExtInst(AShr, Ty); + } } if (match(Op0, m_LShr(m_Value(X), m_APInt(ShOp1)))) { |