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[X86][SSE] Lower directly to SSE shifts in the BLEND(SHIFT, SHIFT) combine. NFCI. 

We don't gain anything from forcing another round of generic shift lowering - we know these are legal constant splat shifts.

llvm-svn: 340300
This commit is contained in:
Simon Pilgrim 2018-08-21 16:46:48 +00:00
parent 63072abbb9
commit dbe4e9e3ff
1 changed files with 13 additions and 9 deletions
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20
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -23581,6 +23581,7 @@ static SDValue LowerShift(SDValue Op, const X86Subtarget &Subtarget,
SDValue R = Op.getOperand(0);
SDValue Amt = Op.getOperand(1);
unsigned Opc = Op.getOpcode();
unsigned EltSizeInBits = VT.getScalarSizeInBits();
bool ConstantAmt = ISD::isBuildVectorOfConstantSDNodes(Amt.getNode());
assert(VT.isVector() && "Custom lowering only for vector shifts!");
@ -23669,20 +23670,23 @@ static SDValue LowerShift(SDValue Op, const X86Subtarget &Subtarget,
// Only perform this blend if we can perform it without loading a mask.
if (ShuffleMask.size() == NumElts && Amt1 && Amt2 &&
isa<ConstantSDNode>(Amt1) && isa<ConstantSDNode>(Amt2) &&
(VT != MVT::v16i16 ||
is128BitLaneRepeatedShuffleMask(VT, ShuffleMask)) &&
(VT == MVT::v4i32 || Subtarget.hasSSE41() || Opc != ISD::SHL ||
canWidenShuffleElements(ShuffleMask))) {
SDValue Splat1 =
DAG.getConstant(cast<ConstantSDNode>(Amt1)->getAPIntValue(), dl, VT);
SDValue Shift1 = DAG.getNode(Op->getOpcode(), dl, VT, R, Splat1);
SDValue Splat2 =
DAG.getConstant(cast<ConstantSDNode>(Amt2)->getAPIntValue(), dl, VT);
SDValue Shift2 = DAG.getNode(Op->getOpcode(), dl, VT, R, Splat2);
auto *Cst1 = dyn_cast<ConstantSDNode>(Amt1);
auto *Cst2 = dyn_cast<ConstantSDNode>(Amt2);
if (Cst1 && Cst2 && Cst1->getAPIntValue().ult(EltSizeInBits) &&
Cst2->getAPIntValue().ult(EltSizeInBits)) {
unsigned X86Opc = getTargetVShiftUniformOpcode(Opc, false);
SDValue Shift1 = getTargetVShiftByConstNode(X86Opc, dl, VT, R,
Cst1->getZExtValue(), DAG);
SDValue Shift2 = getTargetVShiftByConstNode(X86Opc, dl, VT, R,
Cst2->getZExtValue(), DAG);
return DAG.getVectorShuffle(VT, dl, Shift1, Shift2, ShuffleMask);
}
}
}
// If possible, lower this packed shift into a vector multiply instead of
// expanding it into a sequence of scalar shifts.
@ -23697,7 +23701,7 @@ static SDValue LowerShift(SDValue Op, const X86Subtarget &Subtarget,
((Subtarget.hasSSE41() && VT == MVT::v8i16) ||
DAG.isKnownNeverZero(Amt)) &&
(VT == MVT::v8i16 || (VT == MVT::v16i16 && Subtarget.hasInt256()))) {
SDValue EltBits = DAG.getConstant(VT.getScalarSizeInBits(), dl, VT);
SDValue EltBits = DAG.getConstant(EltSizeInBits, dl, VT);
SDValue RAmt = DAG.getNode(ISD::SUB, dl, VT, EltBits, Amt);
if (SDValue Scale = convertShiftLeftToScale(RAmt, dl, Subtarget, DAG)) {
SDValue Zero = DAG.getConstant(0, dl, VT);