Fix PR20087 by using the source index when changing the vector load

llvm-svn: 211472

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -7805,12 +7805,13 @@ static SDValue getINSERTPS(ShuffleVectorSDNode *SVOp, SDLoc &dl,
         std::find_if(Mask.begin(), Mask.end(), FromV2Predicate) - Mask.begin();
   }
 
+  unsigned SrcIndex = Mask[DestIndex] % 4;
   if (MayFoldLoad(From)) {
     // Trivial case, when From comes from a load and is only used by the
     // shuffle. Make it use insertps from the vector that we need from that
     // load.
     SDValue NewLoad =
-        NarrowVectorLoadToElement(cast<LoadSDNode>(From), DestIndex, DAG);
+        NarrowVectorLoadToElement(cast<LoadSDNode>(From), SrcIndex, DAG);
     if (!NewLoad.getNode())
       return SDValue();
 
@@ -7831,7 +7832,6 @@ static SDValue getINSERTPS(ShuffleVectorSDNode *SVOp, SDLoc &dl,
   }
 
   // Vector-element-to-vector
-  unsigned SrcIndex = Mask[DestIndex] % 4;
   SDValue InsertpsMask = DAG.getIntPtrConstant(DestIndex << 4 | SrcIndex << 6);
   return DAG.getNode(X86ISD::INSERTPS, dl, VT, To, From, InsertpsMask);
 }

llvm/test/CodeGen/X86/sse41.ll

@@ -703,3 +703,14 @@ define <4 x float> @insertps_with_undefs(<4 x float> %a, float* %b) {
   %result = shufflevector <4 x float> %a, <4 x float> %2, <4 x i32> <i32 4, i32 undef, i32 0, i32 7>
   ret <4 x float> %result
 }
+
+; Test for a bug in X86ISelLowering.cpp:getINSERTPS where we were using
+; the destination index to change the load, instead of the source index.
+define <4 x float> @pr20087(<4 x float> %a, <4 x float> *%ptr) {
+; CHECK-LABEL: pr20087:
+; CHECK: insertps  $48
+; CHECK: ret
+  %load = load <4 x float> *%ptr
+  %ret = shufflevector <4 x float> %load, <4 x float> %a, <4 x i32> <i32 4, i32 undef, i32 6, i32 2>
+  ret <4 x float> %ret
+}