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[X86] Rewrite the zero vector checks in lowerV2X128VectorShuffle to use the Zeroable APInt

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We already have zeroable bits in an APInt. We might as well use that instead of checking for an all zero BUILD_VECTOR.

Differential Revision: https://reviews.llvm.org/D37950

llvm-svn: 314332
This commit is contained in:
Craig Topper 2017-09-27 18:56:20 +00:00
parent e5ee3608d5
commit 02740e488c
1 changed files with 10 additions and 23 deletions
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33
lib/Target/X86/X86ISelLowering.cpp
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@ -12085,12 +12085,12 @@ static SDValue lowerV2X128VectorShuffle(const SDLoc &DL, MVT VT, SDValue V1,
Zeroable, Subtarget, DAG))
return Blend;
bool IsV1Zero = ISD::isBuildVectorAllZeros(V1.getNode());
bool IsV2Zero = ISD::isBuildVectorAllZeros(V2.getNode());
bool IsLowZero = (Zeroable & 0x3) == 0x3;
bool IsHighZero = (Zeroable & 0xc) == 0xc;
// If either input operand is a zero vector, use VPERM2X128 because its mask
// allows us to replace the zero input with an implicit zero.
if (!IsV1Zero && !IsV2Zero) {
if (!IsLowZero && !IsHighZero) {
// Check for patterns which can be matched with a single insert of a 128-bit
// subvector.
bool OnlyUsesV1 = isShuffleEquivalent(V1, V2, Mask, {0, 1, 0, 1});
@ -12124,30 +12124,17 @@ static SDValue lowerV2X128VectorShuffle(const SDLoc &DL, MVT VT, SDValue V1,
// [6] - ignore
// [7] - zero high half of destination
int MaskLO = WidenedMask[0] < 0 ? 0 : WidenedMask[0];
int MaskHI = WidenedMask[1] < 0 ? 0 : WidenedMask[1];
assert(WidenedMask[0] >= 0 && WidenedMask[1] >= 0 && "Undef half?");
unsigned PermMask = MaskLO | (MaskHI << 4);
unsigned PermMask = 0;
PermMask |= IsLowZero ? 0x08 : (WidenedMask[0] << 0);
PermMask |= IsHighZero ? 0x80 : (WidenedMask[1] << 4);
// If either input is a zero vector, replace it with an undef input.
// Shuffle mask values < 4 are selecting elements of V1.
// Shuffle mask values >= 4 are selecting elements of V2.
// Adjust each half of the permute mask by clearing the half that was
// selecting the zero vector and setting the zero mask bit.
if (IsV1Zero) {
// Check the immediate mask and replace unused sources with undef.
if ((PermMask & 0x0a) != 0x00 && (PermMask & 0xa0) != 0x00)
V1 = DAG.getUNDEF(VT);
if (MaskLO < 2)
PermMask = (PermMask & 0xf0) | 0x08;
if (MaskHI < 2)
PermMask = (PermMask & 0x0f) | 0x80;
}
if (IsV2Zero) {
if ((PermMask & 0x0a) != 0x02 && (PermMask & 0xa0) != 0x20)
V2 = DAG.getUNDEF(VT);
if (MaskLO >= 2)
PermMask = (PermMask & 0xf0) | 0x08;
if (MaskHI >= 2)
PermMask = (PermMask & 0x0f) | 0x80;
}
return DAG.getNode(X86ISD::VPERM2X128, DL, VT, V1, V2,
DAG.getConstant(PermMask, DL, MVT::i8));