[X86] Fix assertion in subreg extraction

This assert fires when attempting to extract a subregister from the
global PIC base register. This virtual register SD node is not in the
VRBaseMap, so we shouldn't call getVR to look it up there. If this is a
RegisterSDNode, we should be able to use the virtual register directly.

Fixes PR38385

llvm-svn: 339056

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp b/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
index d6171f3177d..238ea878510 100644
--- a/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
@@ -524,7 +524,7 @@ void InstrEmitter::EmitSubregNode(SDNode *Node,
       Reg = R->getReg();
       DefMI = nullptr;
     } else {
-      Reg = getVR(Node->getOperand(0), VRBaseMap);
+      Reg = R ? R->getReg() : getVR(Node->getOperand(0), VRBaseMap);
       DefMI = MRI->getVRegDef(Reg);
     }