From d5391478340c6e63b28d03c29ea9fde580b38e93 Mon Sep 17 00:00:00 2001
From: Michael Kuperstein <michael.m.kuperstein@intel.com>
Date: Sun, 23 Nov 2014 13:09:06 +0000
Subject: [PATCH] [X86] Fixes bug in build_vector v4x32 lowering

r222375 made some improvements to build_vector lowering of v4x32 and v4xf32 into an insertps, but it missed a case where:

1. A single extracted element is used twice.
2. The lower of the two non-zero indexes should be preserved, and the higher should be used for the dest mask.

This caused a crash, since the source value for the insertps ends-up uninitialized.

Differential Revision: http://reviews.llvm.org/D6377

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222635 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp |  9 ++++++---
 test/CodeGen/X86/sse41.ll          | 17 +++++++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 90e88171dcc..0347a517444 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5771,7 +5771,8 @@ static SDValue LowerBuildVectorv4x32(SDValue Op, SelectionDAG &DAG,
   // We only know how to deal with build_vector nodes where elements are either
   // zeroable or extract_vector_elt with constant index.
   SDValue FirstNonZero;
-  for (int i=0; i < 4; ++i) {
+  unsigned FirstNonZeroIdx;
+  for (unsigned i=0; i < 4; ++i) {
     if (Zeroable[i])
       continue;
     SDValue Elt = Op->getOperand(i);
@@ -5782,8 +5783,10 @@ static SDValue LowerBuildVectorv4x32(SDValue Op, SelectionDAG &DAG,
     MVT VT = Elt.getOperand(0).getSimpleValueType();
     if (!VT.is128BitVector())
       return SDValue();
-    if (!FirstNonZero.getNode())
+    if (!FirstNonZero.getNode()) {
       FirstNonZero = Elt;
+      FirstNonZeroIdx = i;
+    }
   }
 
   assert(FirstNonZero.getNode() && "Unexpected build vector of all zeros!");
@@ -5822,7 +5825,7 @@ static SDValue LowerBuildVectorv4x32(SDValue Op, SelectionDAG &DAG,
     return SDValue();
 
   SDValue V2 = Elt.getOperand(0);
-  if (Elt == FirstNonZero)
+  if (Elt == FirstNonZero && EltIdx == FirstNonZeroIdx)
     V1 = SDValue();
 
   bool CanFold = true;
diff --git a/test/CodeGen/X86/sse41.ll b/test/CodeGen/X86/sse41.ll
index 2bdfafe8374..71c1c9ed33c 100644
--- a/test/CodeGen/X86/sse41.ll
+++ b/test/CodeGen/X86/sse41.ll
@@ -1145,6 +1145,23 @@ entry:
   ret <4 x float> %vecinit3
 }
 
+define <4 x float> @insertps_10(<4 x float> %A)
+{
+; X32-LABEL: insertps_10:
+; X32:       ## BB#0:
+; X32-NEXT:    insertps {{.*#+}} xmm0 = xmm0[0],zero,xmm0[0],zero
+; X32-NEXT:    retl
+;
+; X64-LABEL: insertps_10:
+; X64:       ## BB#0:
+; X64-NEXT:    insertps {{.*#+}} xmm0 = xmm0[0],zero,xmm0[0],zero
+; X64-NEXT:    retq
+  %vecext = extractelement <4 x float> %A, i32 0
+  %vecbuild1 = insertelement <4 x float> <float 0.000000e+00, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00>, float %vecext, i32 0
+  %vecbuild2 = insertelement <4 x float> %vecbuild1, float %vecext, i32 2
+  ret <4 x float> %vecbuild2
+}
+
 define <4 x float> @build_vector_to_shuffle_1(<4 x float> %A) {
 ; X32-LABEL: build_vector_to_shuffle_1:
 ; X32:       ## BB#0:
-- 
2.34.1