From 32510207382720a97c682e098d45cb1371c48639 Mon Sep 17 00:00:00 2001
From: Elena Demikhovsky <elena.demikhovsky@intel.com>
Date: Tue, 4 Sep 2012 12:49:02 +0000
Subject: [PATCH] This patch optimizes shuffle instruction - generates 2
 instructions instead of 4. Since this specific shuffle is widely used in many
 workloads we have ~10% performance on them.

shufflevector <8 x float> %A, <8 x float> %B, <8 x i32> <i32 0, i32 8, i32 2, i32 10, i32 4, i32 12, i32 6, i32 14>

vmovaps (%rdx), %ymm0
vshufps $8, %ymm0, %ymm0, %ymm0
vmovaps (%rcx), %ymm1
vshufps $8, %ymm0, %ymm1, %ymm1
vunpcklps       %ymm0, %ymm1, %ymm0

vmovaps (%rcx), %ymm0
vmovsldup       (%rdx), %ymm1
vblendps        $85, %ymm0, %ymm1, %ymm0


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163134 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 31 +++++++++++++++---------------
 test/CodeGen/X86/avx-shuffle.ll    | 10 ++++------
 2 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index ce5e61f0f3f..9f487a6b0f2 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -3506,25 +3506,26 @@ SDValue Compact8x32ShuffleNode(ShuffleVectorSDNode *SVOp,
     if (!isUndefOrEqual(Mask[i], MaskToOptimizeOdd[i]))
       MatchOddMask = false;
   }
-  static const int CompactionMaskEven[] = {0, 2, -1, -1, 4, 6, -1, -1};
-  static const int CompactionMaskOdd [] = {1, 3, -1, -1, 5, 7, -1, -1};
 
-  const int *CompactionMask;
-  if (MatchEvenMask)
-    CompactionMask = CompactionMaskEven;
-  else if (MatchOddMask)
-    CompactionMask = CompactionMaskOdd;
-  else
+  if (!MatchEvenMask && !MatchOddMask)
     return SDValue();
-
+  
   SDValue UndefNode = DAG.getNode(ISD::UNDEF, dl, VT);
 
-  SDValue Op0 = DAG.getVectorShuffle(VT, dl, SVOp->getOperand(0),
-                                     UndefNode, CompactionMask);
-  SDValue Op1 = DAG.getVectorShuffle(VT, dl, SVOp->getOperand(1),
-                                     UndefNode, CompactionMask);
-  static const int UnpackMask[] = {0, 8, 1, 9, 4, 12, 5, 13};
-  return DAG.getVectorShuffle(VT, dl, Op0, Op1, UnpackMask);
+  SDValue Op0 = SVOp->getOperand(0);
+  SDValue Op1 = SVOp->getOperand(1);
+
+  if (MatchEvenMask) {
+    // Shift the second operand right to 32 bits.
+    static const int ShiftRightMask[] = {-1, 0, -1, 2, -1, 4, -1, 6 };
+    Op1 = DAG.getVectorShuffle(VT, dl, Op1, UndefNode, ShiftRightMask);
+  } else {
+    // Shift the first operand left to 32 bits.
+    static const int ShiftLeftMask[] = {1, -1, 3, -1, 5, -1, 7, -1 };
+    Op0 = DAG.getVectorShuffle(VT, dl, Op0, UndefNode, ShiftLeftMask);
+  }
+  static const int BlendMask[] = {0, 9, 2, 11, 4, 13, 6, 15};
+  return DAG.getVectorShuffle(VT, dl, Op0, Op1, BlendMask);
 }
 
 /// isUNPCKLMask - Return true if the specified VECTOR_SHUFFLE operand
diff --git a/test/CodeGen/X86/avx-shuffle.ll b/test/CodeGen/X86/avx-shuffle.ll
index 9b41709a3b1..ec11654b355 100644
--- a/test/CodeGen/X86/avx-shuffle.ll
+++ b/test/CodeGen/X86/avx-shuffle.ll
@@ -229,9 +229,8 @@ define   <8 x float> @test17(<4 x float> %y) {
 }
 
 ; CHECK: test18
-; CHECK: vshufps
-; CHECK: vshufps
-; CHECK: vunpcklps
+; CHECK: vmovshdup
+; CHECK: vblendps
 ; CHECK: ret
 define <8 x float> @test18(<8 x float> %A, <8 x float>%B) nounwind {
   %S = shufflevector <8 x float> %A, <8 x float> %B, <8 x i32> <i32 1, i32 9, i32 3, i32 11, i32 5, i32 13, i32 7, i32 15>
@@ -239,9 +238,8 @@ define <8 x float> @test18(<8 x float> %A, <8 x float>%B) nounwind {
 }
 
 ; CHECK: test19
-; CHECK: vshufps
-; CHECK: vshufps
-; CHECK: vunpcklps
+; CHECK: vmovsldup
+; CHECK: vblendps
 ; CHECK: ret
 define <8 x float> @test19(<8 x float> %A, <8 x float>%B) nounwind {
   %S = shufflevector <8 x float> %A, <8 x float> %B, <8 x i32> <i32 0, i32 8, i32 2, i32 10, i32 4, i32 12, i32 6, i32 14>