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[X86] Combine vpmovdw+vpacksswb into vpmovdb. 

This is similar to the combine we already have for vpmovdw+vpackuswb.

llvm-svn: 348910
This commit is contained in:
Craig Topper 2018-12-12 05:56:01 +00:00
parent 5b69b5e20a
commit 1fe466689b
2 changed files with 10 additions and 12 deletions
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16
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -35455,6 +35455,8 @@ static SDValue combineVectorPack(SDNode *N, SelectionDAG &DAG,
N1.getScalarValueSizeInBits() == SrcBitsPerElt &&
"Unexpected PACKSS/PACKUS input type");
bool IsSigned = (X86ISD::PACKSS == Opcode);
// Constant Folding.
APInt UndefElts0, UndefElts1;
SmallVector<APInt, 32> EltBits0, EltBits1;
@ -35467,7 +35469,6 @@ static SDValue combineVectorPack(SDNode *N, SelectionDAG &DAG,
unsigned NumSrcElts = NumDstElts / 2;
unsigned NumDstEltsPerLane = NumDstElts / NumLanes;
unsigned NumSrcEltsPerLane = NumSrcElts / NumLanes;
bool IsSigned = (X86ISD::PACKSS == Opcode);
APInt Undefs(NumDstElts, 0);
SmallVector<APInt, 32> Bits(NumDstElts, APInt::getNullValue(DstBitsPerElt));
@ -35511,15 +35512,14 @@ static SDValue combineVectorPack(SDNode *N, SelectionDAG &DAG,
return getConstVector(Bits, Undefs, VT.getSimpleVT(), DAG, SDLoc(N));
}
// Try to combine a PACKUSWB implemented truncate with a regular truncate to
// create a larger truncate.
// TODO: Match PACKSSWB as well?
if (Subtarget.hasAVX512() && Opcode == X86ISD::PACKUS &&
// Try to combine a PACKUSWB/PACKSSWB implemented truncate with a regular
// truncate to create a larger truncate.
if (Subtarget.hasAVX512() &&
N0.getOpcode() == ISD::TRUNCATE && N1.isUndef() && VT == MVT::v16i8 &&
N0.getOperand(0).getValueType() == MVT::v8i32) {
APInt ZeroMask = APInt::getHighBitsSet(16, 8);
if (DAG.MaskedValueIsZero(N0, ZeroMask)) {
if ((IsSigned && DAG.ComputeNumSignBits(N0) > 8) ||
(!IsSigned &&
DAG.MaskedValueIsZero(N0, APInt::getHighBitsSet(16, 8)))) {
if (Subtarget.hasVLX())
return DAG.getNode(X86ISD::VTRUNC, SDLoc(N), VT, N0.getOperand(0));

6
llvm/test/CodeGen/X86/avx512-cvt-widen.ll
View File

@ -648,16 +648,14 @@ define <8 x i8> @f64to8sc(<8 x double> %f) {
; NOVL-LABEL: f64to8sc:
; NOVL: # %bb.0:
; NOVL-NEXT: vcvttpd2dq %zmm0, %ymm0
; NOVL-NEXT: vpmovdw %zmm0, %ymm0
; NOVL-NEXT: vpacksswb %xmm0, %xmm0, %xmm0
; NOVL-NEXT: vpmovdb %zmm0, %xmm0
; NOVL-NEXT: vzeroupper
; NOVL-NEXT: retq
;
; VL-LABEL: f64to8sc:
; VL: # %bb.0:
; VL-NEXT: vcvttpd2dq %zmm0, %ymm0
; VL-NEXT: vpmovdw %ymm0, %xmm0
; VL-NEXT: vpacksswb %xmm0, %xmm0, %xmm0
; VL-NEXT: vpmovdb %ymm0, %xmm0
; VL-NEXT: vzeroupper
; VL-NEXT: retq
%res = fptosi <8 x double> %f to <8 x i8>