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

Summary:
Add a simplification:
shuffle (splat-shuffle), undef, M --> splat-shuffle

Fixes pr32449

Patch by Sanjay Patel

Reviewers: eli.friedman, RKSimon, spatel

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31426

llvm-svn: 299047
This commit is contained in:
Zvi Rackover 2017-03-30 01:42:57 +00:00
parent d7d1d517ee
commit 7569436f81
2 changed files with 12 additions and 10 deletions
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6
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -14643,6 +14643,12 @@ 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
llvm/test/CodeGen/X86/shuffle-of-splat-multiuses.ll
View File

@ -5,9 +5,8 @@
define <2 x double> @foo2(<2 x double> %v, <2 x double> *%p) nounwind {
; AVX2-LABEL: foo2:
; AVX2: # BB#0:
; AVX2-NEXT: vpermilpd {{.*#+}} xmm1 = xmm0[1,1]
; AVX2-NEXT: vpermilpd {{.*#+}} xmm0 = xmm1[1,0]
; AVX2-NEXT: vmovapd %xmm1, (%rdi)
; AVX2-NEXT: vpermilpd {{.*#+}} xmm0 = xmm0[1,1]
; AVX2-NEXT: vmovapd %xmm0, (%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>
@ -18,9 +17,8 @@ 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 {{.*#+}} ymm1 = ymm0[2,2,2,2]
; AVX2-NEXT: vpermpd {{.*#+}} ymm0 = ymm1[2,0,2,3]
; AVX2-NEXT: vmovapd %ymm1, (%rdi)
; AVX2-NEXT: vpermpd {{.*#+}} ymm0 = ymm0[2,2,2,2]
; AVX2-NEXT: vmovapd %ymm0, (%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>
@ -32,10 +30,8 @@ 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 {{.*#+}} 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: vpermpd {{.*#+}} ymm0 = ymm0[2,2,2,2]
; AVX2-NEXT: vmovapd %ymm0, (%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>