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Revert "[DAGCombine] A shuffle of a splat is always the splat itself"

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This reverts commit r299047 which is incorrect because the
simplification may result in incorrect propogation of undefs to users of
the folded shuffle.

Thanks to Andrea Di Biagio for pointing this out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299368 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Zvi Rackover 2017-04-03 17:41:19 +00:00
parent ab1bde3393
commit f60f35be0a
2 changed files with 10 additions and 12 deletions
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6
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -14633,12 +14633,6 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
return DAG.getVectorShuffle(VT, SDLoc(N), N0, N1, NewMask);
}
// A shuffle of a splat is always the splat itself:
// shuffle (splat-shuffle), undef, M --> splat-shuffle
if (auto *N0Shuf = dyn_cast<ShuffleVectorSDNode>(N0))
if (N1.isUndef() && N0Shuf->isSplat())
return N0;
// If it is a splat, check if the argument vector is another splat or a
// build_vector.
if (SVN->isSplat() && SVN->getSplatIndex() < (int)NumElts) {

16
test/CodeGen/X86/shuffle-of-splat-multiuses.ll
View File

@ -5,8 +5,9 @@
define <2 x double> @foo2(<2 x double> %v, <2 x double> *%p) nounwind {
; AVX2-LABEL: foo2:
; AVX2: # BB#0:
; AVX2-NEXT: vpermilpd {{.*#+}} xmm0 = xmm0[1,1]
; AVX2-NEXT: vmovapd %xmm0, (%rdi)
; AVX2-NEXT: vpermilpd {{.*#+}} xmm1 = xmm0[1,1]
; AVX2-NEXT: vpermilpd {{.*#+}} xmm0 = xmm1[1,0]
; AVX2-NEXT: vmovapd %xmm1, (%rdi)
; AVX2-NEXT: retq
%res = shufflevector <2 x double> %v, <2 x double> undef, <2 x i32> <i32 1, i32 1>
%res1 = shufflevector<2 x double> %res, <2 x double> undef, <2 x i32> <i32 1, i32 undef>
@ -17,8 +18,9 @@ define <2 x double> @foo2(<2 x double> %v, <2 x double> *%p) nounwind {
define <4 x double> @foo4(<4 x double> %v, <4 x double> *%p) nounwind {
; AVX2-LABEL: foo4:
; AVX2: # BB#0:
; AVX2-NEXT: vpermpd {{.*#+}} ymm0 = ymm0[2,2,2,2]
; AVX2-NEXT: vmovapd %ymm0, (%rdi)
; AVX2-NEXT: vpermpd {{.*#+}} ymm1 = ymm0[2,2,2,2]
; AVX2-NEXT: vpermpd {{.*#+}} ymm0 = ymm1[2,0,2,3]
; AVX2-NEXT: vmovapd %ymm1, (%rdi)
; AVX2-NEXT: retq
%res = shufflevector <4 x double> %v, <4 x double> undef, <4 x i32> <i32 2, i32 2, i32 2, i32 2>
%res1 = shufflevector<4 x double> %res, <4 x double> undef, <4 x i32> <i32 2, i32 0, i32 undef, i32 undef>
@ -30,8 +32,10 @@ define <8 x float> @foo8(<8 x float> %v, <8 x float> *%p) nounwind {
; AVX2-LABEL: foo8:
; AVX2: # BB#0:
; AVX2-NEXT: vmovshdup {{.*#+}} ymm0 = ymm0[1,1,3,3,5,5,7,7]
; AVX2-NEXT: vpermpd {{.*#+}} ymm0 = ymm0[2,2,2,2]
; AVX2-NEXT: vmovapd %ymm0, (%rdi)
; AVX2-NEXT: vpermpd {{.*#+}} ymm1 = ymm0[2,2,2,2]
; AVX2-NEXT: vmovaps {{.*#+}} ymm0 = <2,0,u,u,5,1,3,7>
; AVX2-NEXT: vpermps %ymm1, %ymm0, %ymm0
; AVX2-NEXT: vmovapd %ymm1, (%rdi)
; AVX2-NEXT: retq
%res = shufflevector <8 x float> %v, <8 x float> undef, <8 x i32> <i32 5, i32 5, i32 5, i32 5, i32 5, i32 5, i32 5, i32 5>
%res1 = shufflevector<8 x float> %res, <8 x float> undef, <8 x i32> <i32 2, i32 0, i32 undef, i32 undef, i32 5, i32 1, i32 3, i32 7>