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[X86, AVX] recognize shufflevector with zero input as a vperm2 (PR22984) 

vperm2x128 instructions have the special ability (aka free hardware capability)
to shuffle zero values into a vector.

This patch recognizes that type of shuffle and generates the appropriate
control byte.

https://llvm.org/bugs/show_bug.cgi?id=22984

Differential Revision: http://reviews.llvm.org/D8563

llvm-svn: 233100
This commit is contained in:
Sanjay Patel 2015-03-24 19:19:07 +00:00
parent a98fac28aa
commit 99d246d7d7
2 changed files with 147 additions and 20 deletions
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56
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -9055,33 +9055,48 @@ static SDValue lowerV2X128VectorShuffle(SDLoc DL, MVT VT, SDValue V1,
SDValue V2, ArrayRef<int> Mask,
const X86Subtarget *Subtarget,
SelectionDAG &DAG) {
// TODO: If minimizing size and one of the inputs is a zero vector and the
// the zero vector has only one use, we could use a VPERM2X128 to save the
// instruction bytes needed to explicitly generate the zero vector.
// Blends are faster and handle all the non-lane-crossing cases.
if (SDValue Blend = lowerVectorShuffleAsBlend(DL, VT, V1, V2, Mask,
Subtarget, DAG))
return Blend;
MVT SubVT = MVT::getVectorVT(VT.getVectorElementType(),
VT.getVectorNumElements() / 2);
bool IsV1Zero = ISD::isBuildVectorAllZeros(V1.getNode());
bool IsV2Zero = ISD::isBuildVectorAllZeros(V2.getNode());
// 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) {
// 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});
if (OnlyUsesV1 || isShuffleEquivalent(V1, V2, Mask, {0, 1, 4, 5})) {
MVT SubVT = MVT::getVectorVT(VT.getVectorElementType(),
VT.getVectorNumElements() / 2);
SDValue LoV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V1,
DAG.getIntPtrConstant(0));
SDValue HiV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT,
OnlyUsesV1 ? V1 : V2, DAG.getIntPtrConstant(0));
return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, LoV, HiV);
}
if (isShuffleEquivalent(V1, V2, Mask, {0, 1, 6, 7})) {
SDValue LoV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V1,
DAG.getIntPtrConstant(0));
SDValue HiV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V2,
DAG.getIntPtrConstant(2));
return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, LoV, HiV);
}
// Otherwise form a 128-bit permutation.
// FIXME: Detect zero-vector inputs and use the VPERM2X128 to zero that half.
// Otherwise form a 128-bit permutation. After accounting for undefs,
// convert the 64-bit shuffle mask selection values into 128-bit
// selection bits by dividing the indexes by 2 and shifting into positions
// defined by a vperm2*128 instruction's immediate control byte.
// The immediate permute control byte looks like this:
// [1:0] - select 128 bits from sources for low half of destination
// [2] - ignore
// [3] - zero low half of destination
// [5:4] - select 128 bits from sources for high half of destination
// [6] - ignore
// [7] - zero high half of destination
int MaskLO = Mask[0];
if (MaskLO == SM_SentinelUndef)
MaskLO = Mask[1] == SM_SentinelUndef ? 0 : Mask[1];
@ -9091,6 +9106,27 @@ static SDValue lowerV2X128VectorShuffle(SDLoc DL, MVT VT, SDValue V1,
MaskHI = Mask[3] == SM_SentinelUndef ? 0 : Mask[3];
unsigned PermMask = MaskLO / 2 | (MaskHI / 2) << 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) {
V1 = DAG.getUNDEF(VT);
if (MaskLO < 4)
PermMask = (PermMask & 0xf0) | 0x08;
if (MaskHI < 4)
PermMask = (PermMask & 0x0f) | 0x80;
}
if (IsV2Zero) {
V2 = DAG.getUNDEF(VT);
if (MaskLO >= 4)
PermMask = (PermMask & 0xf0) | 0x08;
if (MaskHI >= 4)
PermMask = (PermMask & 0x0f) | 0x80;
}
return DAG.getNode(X86ISD::VPERM2X128, DL, VT, V1, V2,
DAG.getConstant(PermMask, MVT::i8));
}

91
llvm/test/CodeGen/X86/avx-vperm2x128.ll
View File

@ -261,3 +261,94 @@ entry:
%shuffle = shufflevector <8 x float> %a, <8 x float> %b, <8 x i32> <i32 undef, i32 undef, i32 6, i32 7, i32 undef, i32 12, i32 undef, i32 15>
ret <8 x float> %shuffle
}
;; Test zero mask generation.
;; PR22984: https://llvm.org/bugs/show_bug.cgi?id=22984
;; Prefer xor+vblendpd over vperm2f128 because that has better performance.
define <4 x double> @vperm2z_0x08(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x08:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $40, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> %a, <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x i32> <i32 4, i32 5, i32 0, i32 1>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x18(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x18:
; ALL: # BB#0:
; ALL-NEXT: vxorpd %ymm1, %ymm1, %ymm1
; ALL-NEXT: vblendpd $12, %ymm0, %ymm1, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> %a, <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x28(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x28:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $40, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x double> %a, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x38(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x38:
; ALL: # BB#0:
; ALL-NEXT: vxorpd %ymm1, %ymm1, %ymm1
; ALL-NEXT: vblendpd $12, %ymm0, %ymm1, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x double> %a, <4 x i32> <i32 0, i32 1, i32 6, i32 7>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x80(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x80:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $128, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> %a, <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x81(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x81:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $129, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> %a, <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x i32> <i32 2, i32 3, i32 4, i32 5>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x82(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x82:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $128, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x double> %a, <4 x i32> <i32 4, i32 5, i32 0, i32 1>
ret <4 x double> %s
}
define <4 x double> @vperm2z_0x83(<4 x double> %a) {
; ALL-LABEL: vperm2z_0x83:
; ALL: # BB#0:
; ALL-NEXT: vperm2f128 $129, %ymm0, %ymm0, %ymm0
; ALL-NEXT: retq
%s = shufflevector <4 x double> <double 0.0, double 0.0, double undef, double undef>, <4 x double> %a, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
ret <4 x double> %s
}
;; With AVX2 select the integer version of the instruction. Use an add to force the domain selection.
define <4 x i64> @vperm2z_int_0x83(<4 x i64> %a, <4 x i64> %b) {
; ALL-LABEL: vperm2z_int_0x83:
; ALL: # BB#0:
; AVX1: vperm2f128 $129, %ymm0, %ymm0, %ymm0
; AVX2: vperm2i128 $129, %ymm0, %ymm0, %ymm0
%s = shufflevector <4 x i64> <i64 0, i64 0, i64 undef, i64 undef>, <4 x i64> %a, <4 x i32> <i32 6, i32 7, i32 0, i32 1>
%c = add <4 x i64> %b, %s
ret <4 x i64> %c
}