From b5cb48c6ae16d6ffc54c7d7281160bcc4acdc4cb Mon Sep 17 00:00:00 2001 From: Nirav Dave Date: Tue, 1 Aug 2017 13:45:35 +0000 Subject: [DAG] Extend visitSCALAR_TO_VECTOR optimization to truncated vector. Summary: Allow SCALAR_TO_VECTOR of EXTRACT_VECTOR_ELT to reduce to EXTRACT_SUBVECTOR of vector shuffle when output is smaller. Marginally improves vector shuffle computations. Reviewers: efriedma, RKSimon, spatel Subscribers: javed.absar, llvm-commits Differential Revision: https://reviews.llvm.org/D35566 llvm-svn: 309680 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 37 +++++++++++++++++++-------- 1 file changed, 26 insertions(+), 11 deletions(-) (limited to 'llvm/lib/CodeGen/SelectionDAG') diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 85055862917..5c9db976a42 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -15710,23 +15710,38 @@ SDValue DAGCombiner::visitSCALAR_TO_VECTOR(SDNode *N) { EVT VT = N->getValueType(0); // Replace a SCALAR_TO_VECTOR(EXTRACT_VECTOR_ELT(V,C0)) pattern - // with a VECTOR_SHUFFLE. + // with a VECTOR_SHUFFLE and possible truncate. if (InVal.getOpcode() == ISD::EXTRACT_VECTOR_ELT) { SDValue InVec = InVal->getOperand(0); SDValue EltNo = InVal->getOperand(1); - - // FIXME: We could support implicit truncation if the shuffle can be - // scaled to a smaller vector scalar type. + auto InVecT = InVec.getValueType(); ConstantSDNode *C0 = dyn_cast(EltNo); - if (C0 && VT == InVec.getValueType() && - VT.getScalarType() == InVal.getValueType()) { - SmallVector NewMask(VT.getVectorNumElements(), -1); + + if (C0) { + SmallVector NewMask(InVecT.getVectorNumElements(), -1); int Elt = C0->getZExtValue(); NewMask[0] = Elt; - - if (TLI.isShuffleMaskLegal(NewMask, VT)) - return DAG.getVectorShuffle(VT, SDLoc(N), InVec, DAG.getUNDEF(VT), - NewMask); + SDValue Val; + if (VT.getVectorNumElements() <= InVecT.getVectorNumElements() && + TLI.isShuffleMaskLegal(NewMask, VT)) { + Val = DAG.getVectorShuffle(InVecT, SDLoc(N), InVec, + DAG.getUNDEF(InVecT), NewMask); + // If the initial vector is the correct size this shuffle is a + // valid result. + if (VT == InVecT) + return Val; + // If not we must truncate the vector. + if (VT.getVectorNumElements() != InVecT.getVectorNumElements()) { + MVT IdxTy = TLI.getVectorIdxTy(DAG.getDataLayout()); + SDValue ZeroIdx = DAG.getConstant(0, SDLoc(N), IdxTy); + EVT SubVT = + EVT::getVectorVT(*DAG.getContext(), InVecT.getVectorElementType(), + VT.getVectorNumElements()); + Val = DAG.getNode(ISD::EXTRACT_SUBVECTOR, SDLoc(N), SubVT, Val, + ZeroIdx); + return Val; + } + } } } -- cgit v1.2.3