diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index e60687fa7ad..a1ac64dda35 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -463,6 +463,23 @@ Instruction *InstCombiner::shrinkBitwiseLogic(TruncInst &Trunc) { return BinaryOperator::Create(LogicOp->getOpcode(), NarrowOp0, NarrowC); } +/// Try to narrow the width of a splat shuffle. This could be generalized to any +/// shuffle with a constant operand, but we limit the transform to avoid +/// creating a shuffle type that targets may not be able to lower effectively. +static Instruction *shrinkSplatShuffle(TruncInst &Trunc, + InstCombiner::BuilderTy &Builder) { + auto *Shuf = dyn_cast<ShuffleVectorInst>(Trunc.getOperand(0)); + if (Shuf && Shuf->hasOneUse() && isa<UndefValue>(Shuf->getOperand(1)) && + Shuf->getMask()->getSplatValue()) { + // trunc (shuf X, Undef, SplatMask) --> shuf (trunc X), Undef, SplatMask + Constant *NarrowUndef = UndefValue::get(Trunc.getType()); + Value *NarrowOp = Builder.CreateTrunc(Shuf->getOperand(0), Trunc.getType()); + return new ShuffleVectorInst(NarrowOp, NarrowUndef, Shuf->getMask()); + } + + return nullptr; +} + Instruction *InstCombiner::visitTrunc(TruncInst &CI) { if (Instruction *Result = commonCastTransforms(CI)) return Result; @@ -554,6 +571,9 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) { if (Instruction *I = shrinkBitwiseLogic(CI)) return I; + if (Instruction *I = shrinkSplatShuffle(CI, *Builder)) + return I; + if (Src->hasOneUse() && isa<IntegerType>(SrcTy) && shouldChangeType(SrcTy, DestTy)) { // Transform "trunc (shl X, cst)" -> "shl (trunc X), cst" so long as the |
