Make sure to replace the chain properly when DAGCombining a LOAD+EXTR…

…ACT_VECTOR_ELT into a single LOAD. Fixes PR10747/PR11393.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144863 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -6936,10 +6936,23 @@ SDValue DAGCombiner::visitEXTRACT_VECTOR_ELT(SDNode *N) {
                            DAG.getConstant(PtrOff, PtrType));
     }
 
-    return DAG.getLoad(LVT, N->getDebugLoc(), LN0->getChain(), NewPtr,
-                       LN0->getPointerInfo().getWithOffset(PtrOff),
-                       LN0->isVolatile(), LN0->isNonTemporal(), 
-                       LN0->isInvariant(), Align);
+    // The replacement we need to do here is a little tricky: we need to
+    // replace an extractelement of a load with a load.
+    // Use ReplaceAllUsesOfValuesWith to do the replacement.
+    SDValue Load = DAG.getLoad(LVT, N->getDebugLoc(), LN0->getChain(), NewPtr,
+                               LN0->getPointerInfo().getWithOffset(PtrOff),
+                               LN0->isVolatile(), LN0->isNonTemporal(), 
+                               LN0->isInvariant(), Align);
+    WorkListRemover DeadNodes(*this);
+    SDValue From[] = { SDValue(N, 0), SDValue(LN0,1) };
+    SDValue To[] = { Load.getValue(0), Load.getValue(1) };
+    DAG.ReplaceAllUsesOfValuesWith(From, To, 2, &DeadNodes);
+    // Since we're explcitly calling ReplaceAllUses, add the new node to the
+    // worklist explicitly as well.
+    AddToWorkList(Load.getNode());
+    // Make sure to revisit this node to clean it up; it will usually be dead.
+    AddToWorkList(N);
+    return SDValue(N, 0);
   }
 
   return SDValue();

test/CodeGen/X86/vec_extract-sse4.ll

@@ -2,7 +2,7 @@
 ; RUN: not grep extractps   %t
 ; RUN: not grep pextrd      %t
 ; RUN: not grep pshufd  %t
-; RUN: grep movss   %t | count 2
+; RUN: not grep movss   %t
 
 define void @t1(float* %R, <4 x float>* %P1) nounwind {
 	%X = load <4 x float>* %P1