From f3ff7c32f78f9fafe72a182837f42e14a12cff70 Mon Sep 17 00:00:00 2001
From: Cameron McInally <cameron.mcinally@nyu.edu>
Date: Wed, 5 Mar 2014 19:41:16 +0000
Subject: [PATCH] Lower AVX v4i64->v4i32 truncate to one shuffle.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202996 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 14 ++------------
 test/CodeGen/X86/avx-trunc.ll      |  8 +++++---
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 5058fb9b7a5..951d3ded99d 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9134,24 +9134,14 @@ SDValue X86TargetLowering::LowerTRUNCATE(SDValue Op, SelectionDAG &DAG) const {
                          DAG.getIntPtrConstant(0));
     }
 
-    // On AVX, v4i64 -> v4i32 becomes a sequence that uses PSHUFD and MOVLHPS.
     SDValue OpLo = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, MVT::v2i64, In,
                                DAG.getIntPtrConstant(0));
     SDValue OpHi = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, MVT::v2i64, In,
                                DAG.getIntPtrConstant(2));
-
     OpLo = DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, OpLo);
     OpHi = DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, OpHi);
-
-    // The PSHUFD mask:
-    static const int ShufMask1[] = {0, 2, 0, 0};
-    SDValue Undef = DAG.getUNDEF(VT);
-    OpLo = DAG.getVectorShuffle(VT, DL, OpLo, Undef, ShufMask1);
-    OpHi = DAG.getVectorShuffle(VT, DL, OpHi, Undef, ShufMask1);
-
-    // The MOVLHPS mask:
-    static const int ShufMask2[] = {0, 1, 4, 5};
-    return DAG.getVectorShuffle(VT, DL, OpLo, OpHi, ShufMask2);
+    static const int ShufMask[] = {0, 2, 4, 6};
+    return DAG.getVectorShuffle(VT, DL, OpLo, OpHi, ShufMask);
   }
 
   if ((VT == MVT::v8i16) && (InVT == MVT::v8i32)) {
diff --git a/test/CodeGen/X86/avx-trunc.ll b/test/CodeGen/X86/avx-trunc.ll
index 58d0a356909..bf8d9a7f1a4 100644
--- a/test/CodeGen/X86/avx-trunc.ll
+++ b/test/CodeGen/X86/avx-trunc.ll
@@ -1,13 +1,15 @@
 ; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=corei7-avx -mattr=+avx | FileCheck %s
 
 define <4 x i32> @trunc_64_32(<4 x i64> %A) nounwind uwtable readnone ssp{
-; CHECK: trunc_64_32
-; CHECK: pshufd
+; CHECK-LABEL: trunc_64_32
+; CHECK: shufps
+; CHECK-NOT: pshufd
+; CHECK-NOT: movlhps 
   %B = trunc <4 x i64> %A to <4 x i32>
   ret <4 x i32>%B
 }
 define <8 x i16> @trunc_32_16(<8 x i32> %A) nounwind uwtable readnone ssp{
-; CHECK: trunc_32_16
+; CHECK-LABEL: trunc_32_16
 ; CHECK: pshufb
   %B = trunc <8 x i32> %A to <8 x i16>
   ret <8 x i16>%B