[llvm] r289882 - Don't combine splats with other shuffles.

Eli Friedman via llvm-commits llvm-commits at lists.llvm.org
Thu Dec 15 14:41:40 PST 2016 

Author: efriedma
Date: Thu Dec 15 16:41:40 2016
New Revision: 289882

URL: http://llvm.org/viewvc/llvm-project?rev=289882&view=rev
Log:
Don't combine splats with other shuffles.

We sometimes end up creating shuffles which are worse than the obvious
translation of the IR.

Fixes https://llvm.org/bugs/show_bug.cgi?id=31301 .

Differential Revision: https://reviews.llvm.org/D27793


Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/ARM/vzip.ll
    llvm/trunk/test/CodeGen/X86/vector-shuffle-128-v16.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=289882&r1=289881&r2=289882&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Dec 15 16:41:40 2016
@@ -14377,6 +14377,11 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE
       Level < AfterLegalizeDAG && TLI.isTypeLegal(VT)) {
     ShuffleVectorSDNode *OtherSV = cast<ShuffleVectorSDNode>(N0);
 
+    // Don't try to fold splats; they're likely to simplify somehow, or they
+    // might be free.
+    if (OtherSV->isSplat())
+      return SDValue();
+
     // The incoming shuffle must be of the same type as the result of the
     // current shuffle.
     assert(OtherSV->getOperand(0).getValueType() == VT &&

Modified: llvm/trunk/test/CodeGen/ARM/vzip.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/vzip.ll?rev=289882&r1=289881&r2=289882&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/vzip.ll (original)
+++ llvm/trunk/test/CodeGen/ARM/vzip.ll Thu Dec 15 16:41:40 2016
@@ -320,13 +320,10 @@ entry:
 define <8 x i8> @vdup_zip(i8* nocapture readonly %x, i8* nocapture readonly %y)  {
 entry:
   ; CHECK-LABEL: vdup_zip:
-  ; CHECK: ldrb
-  ; CHECK-NEXT: ldrb
-  ; CHECK-NEXT: vmov.i16 d{{.*}}, #0x800
-  ; CHECK-NEXT: vmov.8
-  ; CHECK-NEXT: vmov.8
-  ; CHECK-NEXT: vtbl.8
-  ; CHECK-NEXT: vmov    r0, r1
+  ; CHECK: vld1.8
+  ; CHECK-NEXT: vld1.8
+  ; CHECK-NEXT: vzip.8
+  ; CHECK-NEXT: vmov r0, r1
   %0 = load i8, i8* %x, align 1
   %1 = insertelement <8 x i8> undef, i8 %0, i32 0
   %lane = shufflevector <8 x i8> %1, <8 x i8> undef, <8 x i32> <i32 0, i32 0, i32 0, i32 0, i32 undef, i32 undef, i32 undef, i32 undef>

Modified: llvm/trunk/test/CodeGen/X86/vector-shuffle-128-v16.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/vector-shuffle-128-v16.ll?rev=289882&r1=289881&r2=289882&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/vector-shuffle-128-v16.ll (original)
+++ llvm/trunk/test/CodeGen/X86/vector-shuffle-128-v16.ll Thu Dec 15 16:41:40 2016
@@ -1799,60 +1799,58 @@ define <16 x i8> @PR31301(i8* nocapture
 ; SSE2:       # BB#0: # %entry
 ; SSE2-NEXT:    movzbl (%rdi), %eax
 ; SSE2-NEXT:    movd %eax, %xmm0
+; SSE2-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
+; SSE2-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
+; SSE2-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
 ; SSE2-NEXT:    movzbl (%rsi), %eax
 ; SSE2-NEXT:    movd %eax, %xmm1
-; SSE2-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm2 = xmm0[0,0,1,1]
-; SSE2-NEXT:    movdqa {{.*#+}} xmm0 = [255,0,255,0,255,0,255,0,255,0,255,0,255,0,255,0]
-; SSE2-NEXT:    pand %xmm0, %xmm2
 ; SSE2-NEXT:    punpcklbw {{.*#+}} xmm1 = xmm1[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
 ; SSE2-NEXT:    pshuflw {{.*#+}} xmm1 = xmm1[0,0,0,0,4,5,6,7]
 ; SSE2-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[0,0,1,1]
-; SSE2-NEXT:    pandn %xmm1, %xmm0
-; SSE2-NEXT:    por %xmm2, %xmm0
+; SSE2-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
 ; SSE2-NEXT:    retq
 ;
 ; SSSE3-LABEL: PR31301:
 ; SSSE3:       # BB#0: # %entry
 ; SSSE3-NEXT:    movzbl (%rdi), %eax
 ; SSSE3-NEXT:    movd %eax, %xmm0
+; SSSE3-NEXT:    pxor %xmm1, %xmm1
+; SSSE3-NEXT:    pshufb %xmm1, %xmm0
 ; SSSE3-NEXT:    movzbl (%rsi), %eax
-; SSSE3-NEXT:    movd %eax, %xmm1
-; SSSE3-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
-; SSSE3-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; SSSE3-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; SSSE3-NEXT:    movd %eax, %xmm2
+; SSSE3-NEXT:    pshufb %xmm1, %xmm2
+; SSSE3-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm2[0],xmm0[1],xmm2[1],xmm0[2],xmm2[2],xmm0[3],xmm2[3],xmm0[4],xmm2[4],xmm0[5],xmm2[5],xmm0[6],xmm2[6],xmm0[7],xmm2[7]
 ; SSSE3-NEXT:    retq
 ;
 ; SSE41-LABEL: PR31301:
 ; SSE41:       # BB#0: # %entry
 ; SSE41-NEXT:    movzbl (%rdi), %eax
 ; SSE41-NEXT:    movd %eax, %xmm0
+; SSE41-NEXT:    pxor %xmm1, %xmm1
+; SSE41-NEXT:    pshufb %xmm1, %xmm0
 ; SSE41-NEXT:    movzbl (%rsi), %eax
-; SSE41-NEXT:    movd %eax, %xmm1
-; SSE41-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
-; SSE41-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; SSE41-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; SSE41-NEXT:    movd %eax, %xmm2
+; SSE41-NEXT:    pshufb %xmm1, %xmm2
+; SSE41-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0],xmm2[0],xmm0[1],xmm2[1],xmm0[2],xmm2[2],xmm0[3],xmm2[3],xmm0[4],xmm2[4],xmm0[5],xmm2[5],xmm0[6],xmm2[6],xmm0[7],xmm2[7]
 ; SSE41-NEXT:    retq
 ;
 ; AVX1-LABEL: PR31301:
 ; AVX1:       # BB#0: # %entry
 ; AVX1-NEXT:    movzbl (%rdi), %eax
 ; AVX1-NEXT:    vmovd %eax, %xmm0
+; AVX1-NEXT:    vpxor %xmm1, %xmm1, %xmm1
+; AVX1-NEXT:    vpshufb %xmm1, %xmm0, %xmm0
 ; AVX1-NEXT:    movzbl (%rsi), %eax
-; AVX1-NEXT:    vmovd %eax, %xmm1
+; AVX1-NEXT:    vmovd %eax, %xmm2
+; AVX1-NEXT:    vpshufb %xmm1, %xmm2, %xmm1
 ; AVX1-NEXT:    vpunpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
-; AVX1-NEXT:    vpshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
 ; AVX1-NEXT:    retq
 ;
 ; AVX2OR512VL-LABEL: PR31301:
 ; AVX2OR512VL:       # BB#0: # %entry
-; AVX2OR512VL-NEXT:    movzbl (%rdi), %eax
-; AVX2OR512VL-NEXT:    vmovd %eax, %xmm0
-; AVX2OR512VL-NEXT:    movzbl (%rsi), %eax
-; AVX2OR512VL-NEXT:    vmovd %eax, %xmm1
+; AVX2OR512VL-NEXT:    vpbroadcastb (%rdi), %xmm0
+; AVX2OR512VL-NEXT:    vpbroadcastb (%rsi), %xmm1
 ; AVX2OR512VL-NEXT:    vpunpcklbw {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
-; AVX2OR512VL-NEXT:    vpbroadcastw %xmm0, %xmm0
 ; AVX2OR512VL-NEXT:    retq
 entry:
   %0 = load i8, i8* %x, align 1

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