From 04340b6235ff5d6fab528723df36b09f340d2ced Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Sat, 24 Oct 2015 20:48:08 +0000
Subject: [PATCH] [X86][SSE] lowerVectorShuffleWithUNPCK - use equivalent
 shuffle mask test.

Use isShuffleEquivalent to match UNPCK shuffles - better support for build vector inputs.

llvm-svn: 251207
---
 lib/Target/X86/X86ISelLowering.cpp | 39 +++++++++++-------------------
 1 file changed, 14 insertions(+), 25 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 43c2b14d0b1..9fcff312e66 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -6785,43 +6785,32 @@ static SDValue lowerVectorShuffleWithUNPCK(SDLoc DL, MVT VT, ArrayRef<int> Mask,
                                            SDValue V1, SDValue V2,
                                            SelectionDAG &DAG) {
   int NumElts = VT.getVectorNumElements();
-  bool Unpckl = true;
-  bool Unpckh = true;
-  bool UnpcklSwapped = true;
-  bool UnpckhSwapped = true;
   int NumEltsInLane = 128 / VT.getScalarSizeInBits();
+  SmallVector<int, 8> Unpckl;
+  SmallVector<int, 8> Unpckh;
 
   for (int i = 0; i < NumElts; ++i) {
     unsigned LaneStart = (i / NumEltsInLane) * NumEltsInLane;
-
     int LoPos = (i % NumEltsInLane) / 2 + LaneStart + NumElts * (i % 2);
     int HiPos = LoPos + NumEltsInLane / 2;
-    int LoPosSwapped = (LoPos + NumElts) % (NumElts * 2);
-    int HiPosSwapped = (HiPos + NumElts) % (NumElts * 2);
-
-    if (Mask[i] == -1)
-      continue;
-    if (Mask[i] != LoPos)
-      Unpckl = false;
-    if (Mask[i] != HiPos)
-      Unpckh = false;
-    if (Mask[i] != LoPosSwapped)
-      UnpcklSwapped = false;
-    if (Mask[i] != HiPosSwapped)
-      UnpckhSwapped = false;
-    if (!Unpckl && !Unpckh && !UnpcklSwapped && !UnpckhSwapped)
-      return SDValue();
+    Unpckl.push_back(LoPos);
+    Unpckh.push_back(HiPos);
   }
-  if (Unpckl)
+
+  if (isShuffleEquivalent(V1, V2, Mask, Unpckl))
     return DAG.getNode(X86ISD::UNPCKL, DL, VT, V1, V2);
-  if (Unpckh)
+  if (isShuffleEquivalent(V1, V2, Mask, Unpckh))
     return DAG.getNode(X86ISD::UNPCKH, DL, VT, V1, V2);
-  if (UnpcklSwapped)
+
+  // Commute and try again.
+  ShuffleVectorSDNode::commuteMask(Unpckl);
+  if (isShuffleEquivalent(V1, V2, Mask, Unpckl))
     return DAG.getNode(X86ISD::UNPCKL, DL, VT, V2, V1);
-  if (UnpckhSwapped)
+
+  ShuffleVectorSDNode::commuteMask(Unpckh);
+  if (isShuffleEquivalent(V1, V2, Mask, Unpckh))
     return DAG.getNode(X86ISD::UNPCKH, DL, VT, V2, V1);
 
-  llvm_unreachable("Unexpected result of UNPCK mask analysis");
   return SDValue();
 }