[SelectionDAG] Simplify extract_subvector( insert_subvector ( Vec, In, Idx ), Idx...

If we are extracting a subvector that has just been inserted then we should just use the original inserted subvector.

This has come up in certain several x86 shuffle lowering cases where we are crossing 128-bit lanes.

Differential Revision: https://reviews.llvm.org/D24254

llvm-svn: 280715

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 6cefa820c204270726aca217e28443d3149bfede..9ac600bad72607b4300fe98aeb51f69986ff54a1 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3750,6 +3750,12 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
       // Trivial extraction.
       if (VT.getSimpleVT() == N1.getSimpleValueType())
         return N1;
+
+      // EXTRACT_SUBVECTOR of INSERT_SUBVECTOR is often created
+      // during shuffle legalization.
+      if (N1.getOpcode() == ISD::INSERT_SUBVECTOR && N2 == N1.getOperand(2) &&
+          VT == N1.getOperand(1).getValueType())
+        return N1.getOperand(1);
     }
     break;
   }

diff --git a/llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll b/llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
index 29715e07a8168e3815647611cfeceb5d34838d38..cea1fb9098d79fba7bb8d10c2fbb501fb8efc44a 100644 (file)
--- a/llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
+++ b/llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
@@ -3500,8 +3500,7 @@ define <16 x i16> @insert_dup_mem_v16i16_i32(i32* %ptr) {
 ; AVX1-LABEL: insert_dup_mem_v16i16_i32:
 ; AVX1:       # BB#0:
 ; AVX1-NEXT:    vmovd {{.*#+}} xmm0 = mem[0],zero,zero,zero
-; AVX1-NEXT:    vpshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; AVX1-NEXT:    vpshufb {{.*#+}} xmm0 = xmm0[0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1]
 ; AVX1-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
 ; AVX1-NEXT:    retq
 ;
@@ -3521,8 +3520,7 @@ define <16 x i16> @insert_dup_mem_v16i16_sext_i16(i16* %ptr) {
 ; AVX1:       # BB#0:
 ; AVX1-NEXT:    movswl (%rdi), %eax
 ; AVX1-NEXT:    vmovd %eax, %xmm0
-; AVX1-NEXT:    vpshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; AVX1-NEXT:    vpshufb {{.*#+}} xmm0 = xmm0[0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1]
 ; AVX1-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
 ; AVX1-NEXT:    retq
 ;
@@ -3544,8 +3542,7 @@ define <16 x i16> @insert_dup_elt1_mem_v16i16_i32(i32* %ptr) #0 {
 ; AVX1-LABEL: insert_dup_elt1_mem_v16i16_i32:
 ; AVX1:       # BB#0:
 ; AVX1-NEXT:    vmovd {{.*#+}} xmm0 = mem[0],zero,zero,zero
-; AVX1-NEXT:    vpshuflw {{.*#+}} xmm0 = xmm0[1,1,1,1,4,5,6,7]
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; AVX1-NEXT:    vpshufb {{.*#+}} xmm0 = xmm0[2,3,2,3,2,3,2,3,2,3,2,3,2,3,2,3]
 ; AVX1-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
 ; AVX1-NEXT:    retq
 ;
@@ -3564,9 +3561,7 @@ define <16 x i16> @insert_dup_elt3_mem_v16i16_i32(i32* %ptr) #0 {
 ; AVX1-LABEL: insert_dup_elt3_mem_v16i16_i32:
 ; AVX1:       # BB#0:
 ; AVX1-NEXT:    vmovd {{.*#+}} xmm0 = mem[0],zero,zero,zero
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[1,0,1,1]
-; AVX1-NEXT:    vpshuflw {{.*#+}} xmm0 = xmm0[3,3,3,3,4,5,6,7]
-; AVX1-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,1,1]
+; AVX1-NEXT:    vpshufb {{.*#+}} xmm0 = xmm0[2,3,2,3,2,3,2,3,2,3,2,3,2,3,2,3]
 ; AVX1-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
 ; AVX1-NEXT:    retq
 ;