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[x86] Stop shuffling zero vectors. =] 

I was somewhat surprised this pattern really came up, but it does. It
seems better to just directly handle it than try to special case every
place where we end up forming a shuffle that devolves to a shuffle of
a zero vector.

llvm-svn: 229301
This commit is contained in:
Chandler Carruth 2015-02-15 10:34:52 +00:00
parent 3d272daaed
commit 56e0ceda0d
3 changed files with 13 additions and 8 deletions
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7
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -11285,6 +11285,13 @@ static SDValue lowerVectorShuffle(SDValue Op, const X86Subtarget *Subtarget,
return DAG.getVectorShuffle(VT, dl, V1, V2, NewMask);
}
// We actually see shuffles that are entirely re-arrangements of a set of
// zero inputs. This mostly happens while decomposing complex shuffles into
// simple ones. Directly lower these as a buildvector of zeros.
SmallBitVector Zeroable = computeZeroableShuffleElements(Mask, V1, V2);
if (Zeroable.all())
return getZeroVector(VT, Subtarget, DAG, dl);
// Try to collapse shuffles into using a vector type with fewer elements but
// wider element types. We cap this to not form integers or floating point
// elements wider than 64 bits, but it might be interesting to form i128

7
llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
View File

@ -1457,10 +1457,9 @@ define <16 x i16> @shuffle_v16i16_16_zz_zz_zz_17_zz_zz_zz_18_zz_zz_zz_19_zz_zz_z
define <16 x i16> @shuffle_v16i16_16_zz_17_zz_18_zz_19_zz_20_zz_21_zz_22_zz_22_zz(<16 x i16> %a) {
; AVX1-LABEL: shuffle_v16i16_16_zz_17_zz_18_zz_19_zz_20_zz_21_zz_22_zz_22_zz:
; AVX1: # BB#0:
; AVX1-NEXT: vpxor %xmm1, %xmm1, %xmm1
; AVX1-NEXT: vpmovzxwq {{.*#+}} xmm1 = xmm1[0],zero,zero,zero,xmm1[1],zero,zero,zero
; AVX1-NEXT: vpshufd {{.*#+}} xmm2 = xmm0[2,3,0,1]
; AVX1-NEXT: vpunpcklwd {{.*#+}} xmm1 = xmm2[0],xmm1[0],xmm2[1],xmm1[1],xmm2[2],xmm1[2],xmm2[3],xmm1[3]
; AVX1-NEXT: vpshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
; AVX1-NEXT: vpxor %xmm2, %xmm2, %xmm2
; AVX1-NEXT: vpunpcklwd {{.*#+}} xmm1 = xmm1[0],xmm2[0],xmm1[1],xmm2[1],xmm1[2],xmm2[2],xmm1[3],xmm2[3]
; AVX1-NEXT: vpmovzxwd {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero
; AVX1-NEXT: vinsertf128 $1, %xmm1, %ymm0, %ymm0
; AVX1-NEXT: retq

7
llvm/test/CodeGen/X86/vector-shuffle-256-v32.ll
View File

@ -1802,10 +1802,9 @@ define <32 x i8> @shuffle_v32i8_32_zz_zz_zz_33_zz_zz_zz_34_zz_zz_zz_35_zz_zz_zz_
define <32 x i8> @shuffle_v32i8_32_zz_33_zz_34_zz_35_zz_36_zz_37_zz_38_zz_39_zz_40_zz_41_zz_42_zz_43_zz_44_zz_45_zz_46_zz_47_zz(<32 x i8> %a) {
; AVX1-LABEL: shuffle_v32i8_32_zz_33_zz_34_zz_35_zz_36_zz_37_zz_38_zz_39_zz_40_zz_41_zz_42_zz_43_zz_44_zz_45_zz_46_zz_47_zz:
; AVX1: # BB#0:
; AVX1-NEXT: vpxor %xmm1, %xmm1, %xmm1
; AVX1-NEXT: vpsllq $56, %xmm1, %xmm1
; AVX1-NEXT: vpshufd {{.*#+}} xmm2 = xmm0[2,3,0,1]
; AVX1-NEXT: vpunpcklbw {{.*#+}} xmm1 = xmm2[0],xmm1[0],xmm2[1],xmm1[1],xmm2[2],xmm1[2],xmm2[3],xmm1[3],xmm2[4],xmm1[4],xmm2[5],xmm1[5],xmm2[6],xmm1[6],xmm2[7],xmm1[7]
; AVX1-NEXT: vpshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
; AVX1-NEXT: vpxor %xmm2, %xmm2, %xmm2
; AVX1-NEXT: vpunpcklbw {{.*#+}} xmm1 = xmm1[0],xmm2[0],xmm1[1],xmm2[1],xmm1[2],xmm2[2],xmm1[3],xmm2[3],xmm1[4],xmm2[4],xmm1[5],xmm2[5],xmm1[6],xmm2[6],xmm1[7],xmm2[7]
; AVX1-NEXT: vpmovzxbw {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero,xmm0[2],zero,xmm0[3],zero,xmm0[4],zero,xmm0[5],zero,xmm0[6],zero,xmm0[7],zero
; AVX1-NEXT: vinsertf128 $1, %xmm1, %ymm0, %ymm0
; AVX1-NEXT: retq