merge consecutive stores of extracted vector elements

Add a path to DAGCombiner::MergeConsecutiveStores() 
to combine multiple scalar stores when the store operands
are extracted vector elements. This is a partial fix for
PR21711 ( http://llvm.org/bugs/show_bug.cgi?id=21711 ).

For the new test case, codegen improves from:

   vmovss  %xmm0, (%rdi)
   vextractps      $1, %xmm0, 4(%rdi)
   vextractps      $2, %xmm0, 8(%rdi)
   vextractps      $3, %xmm0, 12(%rdi)
   vextractf128    $1, %ymm0, %xmm0
   vmovss  %xmm0, 16(%rdi)
   vextractps      $1, %xmm0, 20(%rdi)
   vextractps      $2, %xmm0, 24(%rdi)
   vextractps      $3, %xmm0, 28(%rdi)
   vzeroupper
   retq

To:

   vmovups	%ymm0, (%rdi)
   vzeroupper
   retq

Patch reviewed by Nadav Rotem.

Differential Revision: http://reviews.llvm.org/D6698

llvm-svn: 224611

1 files changed, 33 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/MergeConsecutiveStores.ll b/llvm/test/CodeGen/X86/MergeConsecutiveStores.ll
index dfdaea523fd..cf984a4f3a9 100644
--- a/llvm/test/CodeGen/X86/MergeConsecutiveStores.ll
+++ b/llvm/test/CodeGen/X86/MergeConsecutiveStores.ll
@@ -434,3 +434,36 @@ define void @loadStoreBaseIndexOffsetSextNoSex(i8* %a, i8* %b, i8* %c, i32 %n) {
 ; <label>:14
   ret void
 }
+
+define void @merge_vec_element_store(<8 x float> %v, float* %ptr) {
+  %vecext0 = extractelement <8 x float> %v, i32 0
+  %vecext1 = extractelement <8 x float> %v, i32 1
+  %vecext2 = extractelement <8 x float> %v, i32 2
+  %vecext3 = extractelement <8 x float> %v, i32 3
+  %vecext4 = extractelement <8 x float> %v, i32 4
+  %vecext5 = extractelement <8 x float> %v, i32 5
+  %vecext6 = extractelement <8 x float> %v, i32 6
+  %vecext7 = extractelement <8 x float> %v, i32 7
+  %arrayidx1 = getelementptr inbounds float* %ptr, i64 1
+  %arrayidx2 = getelementptr inbounds float* %ptr, i64 2
+  %arrayidx3 = getelementptr inbounds float* %ptr, i64 3
+  %arrayidx4 = getelementptr inbounds float* %ptr, i64 4
+  %arrayidx5 = getelementptr inbounds float* %ptr, i64 5
+  %arrayidx6 = getelementptr inbounds float* %ptr, i64 6
+  %arrayidx7 = getelementptr inbounds float* %ptr, i64 7
+  store float %vecext0, float* %ptr, align 4
+  store float %vecext1, float* %arrayidx1, align 4
+  store float %vecext2, float* %arrayidx2, align 4
+  store float %vecext3, float* %arrayidx3, align 4
+  store float %vecext4, float* %arrayidx4, align 4
+  store float %vecext5, float* %arrayidx5, align 4
+  store float %vecext6, float* %arrayidx6, align 4
+  store float %vecext7, float* %arrayidx7, align 4
+  ret void
+
+; CHECK-LABEL: merge_vec_element_store
+; CHECK: vmovups
+; CHECK-NEXT: vzeroupper
+; CHECK-NEXT: retq
+}
+