From 68651f86d5082f9ac35045c106af4d54191a9321 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Wed, 29 Mar 2017 13:00:00 +0000
Subject: [PATCH] [X86][AVX2] Prevent unary interleaving patterns from calling
 lowerVectorShuffleAsSplitOrBlend (PR32453)

llvm-svn: 298993
---
 lib/Target/X86/X86ISelLowering.cpp        |  7 ++++---
 test/CodeGen/X86/vector-shuffle-256-v8.ll | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index fbb78e3eafc..7f0c285043e 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -12838,9 +12838,10 @@ static SDValue lowerV8I32VectorShuffle(const SDLoc &DL, ArrayRef<int> Mask,
   // For non-AVX512 if the Mask is of 16bit elements in lane then try to split
   // since after split we get a more efficient code than vblend by using
   // vpunpcklwd and vpunpckhwd instrs.
-  if (isUnpackWdShuffleMask(Mask, MVT::v8i32) && !Subtarget.hasAVX512())
-    if (SDValue V = lowerVectorShuffleAsSplitOrBlend(DL, MVT::v8i32, V1, V2,
-                                                     Mask, DAG))
+  if (isUnpackWdShuffleMask(Mask, MVT::v8i32) && !V2.isUndef() &&
+      !Subtarget.hasAVX512())
+    if (SDValue V =
+            lowerVectorShuffleAsSplitOrBlend(DL, MVT::v8i32, V1, V2, Mask, DAG))
       return V;
 
   if (SDValue Blend = lowerVectorShuffleAsBlend(DL, MVT::v8i32, V1, V2, Mask,
diff --git a/test/CodeGen/X86/vector-shuffle-256-v8.ll b/test/CodeGen/X86/vector-shuffle-256-v8.ll
index 0928a3c66b3..8d49321a6af 100644
--- a/test/CodeGen/X86/vector-shuffle-256-v8.ll
+++ b/test/CodeGen/X86/vector-shuffle-256-v8.ll
@@ -2072,6 +2072,21 @@ define <8 x i32> @shuffle_v8i32_5555uuuu(<8 x i32> %a, <8 x i32> %b) {
   ret <8 x i32> %shuffle
 }
 
+; PR32453
+define <8 x i32> @shuffle_v8i32_uuuuuu7u(<8 x i32> %a, <8 x i32> %b) nounwind {
+; AVX1-LABEL: shuffle_v8i32_uuuuuu7u:
+; AVX1:       # BB#0:
+; AVX1-NEXT:    vmovshdup {{.*#+}} ymm0 = ymm0[1,1,3,3,5,5,7,7]
+; AVX1-NEXT:    retq
+;
+; AVX2OR512VL-LABEL: shuffle_v8i32_uuuuuu7u:
+; AVX2OR512VL:       # BB#0:
+; AVX2OR512VL-NEXT:    vpshufd {{.*#+}} ymm0 = ymm0[0,1,3,3,4,5,7,7]
+; AVX2OR512VL-NEXT:    retq
+  %shuffle = shufflevector <8 x i32> %a, <8 x i32> %b, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 7, i32 undef>
+  ret <8 x i32> %shuffle
+}
+
 define <8 x float> @splat_mem_v8f32_2(float* %p) {
 ; ALL-LABEL: splat_mem_v8f32_2:
 ; ALL:       # BB#0: