diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 24 |
1 files changed, 8 insertions, 16 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 7a8c762d494..1201ac196ec 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -492,7 +492,7 @@ static Instruction *foldVecTruncToExtElt(TruncInst &Trunc, InstCombiner &IC) { } /// Rotate left/right may occur in a wider type than necessary because of type -/// promotion rules. Try to narrow all of the component instructions. +/// promotion rules. Try to narrow the inputs and convert to funnel shift. Instruction *InstCombiner::narrowRotate(TruncInst &Trunc) { assert((isa<VectorType>(Trunc.getSrcTy()) || shouldChangeType(Trunc.getSrcTy(), Trunc.getType())) && @@ -563,23 +563,15 @@ Instruction *InstCombiner::narrowRotate(TruncInst &Trunc) { // We have an unnecessarily wide rotate! // trunc (or (lshr ShVal, ShAmt), (shl ShVal, BitWidth - ShAmt)) - // Narrow it down to eliminate the zext/trunc: - // or (lshr trunc(ShVal), ShAmt0'), (shl trunc(ShVal), ShAmt1') + // Narrow the inputs and convert to funnel shift intrinsic: + // llvm.fshl.i8(trunc(ShVal), trunc(ShVal), trunc(ShAmt)) Value *NarrowShAmt = Builder.CreateTrunc(ShAmt, DestTy); - Value *NegShAmt = Builder.CreateNeg(NarrowShAmt); - - // Mask both shift amounts to ensure there's no UB from oversized shifts. - Constant *MaskC = ConstantInt::get(DestTy, NarrowWidth - 1); - Value *MaskedShAmt = Builder.CreateAnd(NarrowShAmt, MaskC); - Value *MaskedNegShAmt = Builder.CreateAnd(NegShAmt, MaskC); - - // Truncate the original value and use narrow ops. Value *X = Builder.CreateTrunc(ShVal, DestTy); - Value *NarrowShAmt0 = SubIsOnLHS ? MaskedNegShAmt : MaskedShAmt; - Value *NarrowShAmt1 = SubIsOnLHS ? MaskedShAmt : MaskedNegShAmt; - Value *NarrowSh0 = Builder.CreateBinOp(ShiftOpcode0, X, NarrowShAmt0); - Value *NarrowSh1 = Builder.CreateBinOp(ShiftOpcode1, X, NarrowShAmt1); - return BinaryOperator::CreateOr(NarrowSh0, NarrowSh1); + bool IsFshl = (!SubIsOnLHS && ShiftOpcode0 == BinaryOperator::Shl) || + (SubIsOnLHS && ShiftOpcode1 == BinaryOperator::Shl); + Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr; + Function *F = Intrinsic::getDeclaration(Trunc.getModule(), IID, DestTy); + return IntrinsicInst::Create(F, { X, X, NarrowShAmt }); } /// Try to narrow the width of math or bitwise logic instructions by pulling a |
