[llvm] r229285 - [x86] Fix PR22377, a regression with the new vector shuffle legality

[Chandler Carruth]

Author: chandlerc
Date: Sun Feb 15 01:01:10 2015
New Revision: 229285

URL: http://llvm.org/viewvc/llvm-project?rev=229285&view=rev
Log:
[x86] Fix PR22377, a regression with the new vector shuffle legality
test.

This was just a matter of the DAG combine for vector shuffles being too
aggressive. This is a bit of a grey area, but I think generally if we
can re-use intermediate shuffles, we should. Certainly, given the test
cases I have available, this seems like the right call.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/X86/vector-shuffle-combining.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=229285&r1=229284&r2=229285&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Sun Feb 15 01:01:10 2015
@@ -11770,8 +11770,9 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE
   //   shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, C, M2)
   //   shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, C, M2)
   // Don't try to fold shuffles with illegal type.
-  if (N0.getOpcode() == ISD::VECTOR_SHUFFLE && Level < AfterLegalizeDAG &&
-      TLI.isTypeLegal(VT)) {
+  // Only fold if this shuffle is the only user of the other shuffle.
+  if (N0.getOpcode() == ISD::VECTOR_SHUFFLE && N->isOnlyUserOf(N0.getNode()) &&
+      Level < AfterLegalizeDAG && TLI.isTypeLegal(VT)) {
     ShuffleVectorSDNode *OtherSV = cast<ShuffleVectorSDNode>(N0);
 
     // The incoming shuffle must be of the same type as the result of the

Modified: llvm/trunk/test/CodeGen/X86/vector-shuffle-combining.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/vector-shuffle-combining.ll?rev=229285&r1=229284&r2=229285&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/vector-shuffle-combining.ll (original)
+++ llvm/trunk/test/CodeGen/X86/vector-shuffle-combining.ll Sun Feb 15 01:01:10 2015
@@ -2537,3 +2537,28 @@ define <4 x float> @combine_insertps4(<4
   %d = shufflevector <4 x float> %a, <4 x float> %c, <4 x i32><i32 4, i32 1, i32 6, i32 5>
   ret <4 x float> %d
 }
+
+define <4 x float> @PR22377(<4 x float> %a, <4 x float> %b) #0 {
+; SSE-LABEL: PR22377:
+; SSE:       # BB#0: # %entry
+; SSE-NEXT:    movaps %xmm0, %xmm1
+; SSE-NEXT:    shufps {{.*#+}} xmm1 = xmm1[1,3,1,3]
+; SSE-NEXT:    shufps {{.*#+}} xmm0 = xmm0[0,2,0,2]
+; SSE-NEXT:    addps %xmm0, %xmm1
+; SSE-NEXT:    unpcklps {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: PR22377:
+; AVX:       # BB#0: # %entry
+; AVX-NEXT:    vpermilps {{.*#+}} xmm1 = xmm0[1,3,1,3]
+; AVX-NEXT:    vpermilps {{.*#+}} xmm0 = xmm0[0,2,0,2]
+; AVX-NEXT:    vaddps %xmm0, %xmm1, %xmm1
+; AVX-NEXT:    vunpcklps {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]
+; AVX-NEXT:    retq
+entry:
+  %s1 = shufflevector <4 x float> %a, <4 x float> undef, <4 x i32> <i32 1, i32 3, i32 1, i32 3>
+  %s2 = shufflevector <4 x float> %a, <4 x float> undef, <4 x i32> <i32 0, i32 2, i32 0, i32 2>
+  %r2 = fadd <4 x float> %s1, %s2
+  %s3 = shufflevector <4 x float> %s2, <4 x float> %r2, <4 x i32> <i32 0, i32 4, i32 1, i32 5>
+  ret <4 x float> %s3
+}