Codegen: [X86] preservere memory refs for folded umul_lohi

Memory references were not being propagated for this folded load. This
prevented optimizations like LICM from hoisting the load.

Added test to verify that this allows LICM to proceed.

llvm-svn: 273617

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 7d3b7e98232..cb3b59438a8 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2223,24 +2223,32 @@ void X86DAGToDAGISel::Select(SDNode *Node) {
 
     if (foldedLoad) {
       SDValue Chain;
+      MachineSDNode *CNode = nullptr;
       SDValue Ops[] = { Tmp0, Tmp1, Tmp2, Tmp3, Tmp4, N1.getOperand(0),
                         InFlag };
       if (MOpc == X86::MULX32rm || MOpc == X86::MULX64rm) {
         SDVTList VTs = CurDAG->getVTList(NVT, NVT, MVT::Other, MVT::Glue);
-        SDNode *CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
+        CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
         ResHi = SDValue(CNode, 0);
         ResLo = SDValue(CNode, 1);
         Chain = SDValue(CNode, 2);
         InFlag = SDValue(CNode, 3);
       } else {
         SDVTList VTs = CurDAG->getVTList(MVT::Other, MVT::Glue);
-        SDNode *CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
+        CNode = CurDAG->getMachineNode(MOpc, dl, VTs, Ops);
         Chain = SDValue(CNode, 0);
         InFlag = SDValue(CNode, 1);
       }
 
       // Update the chain.
       ReplaceUses(N1.getValue(1), Chain);
+      // Record the mem-refs
+      LoadSDNode *LoadNode = cast<LoadSDNode>(N1);
+      if (LoadNode) {
+        MachineSDNode::mmo_iterator MemOp = MF->allocateMemRefsArray(1);
+        MemOp[0] = LoadNode->getMemOperand();
+        CNode->setMemRefs(MemOp, MemOp + 1);
+      }
     } else {
       SDValue Ops[] = { N1, InFlag };
       if (Opc == X86::MULX32rr || Opc == X86::MULX64rr) {