Implement salavageDebugInfo functionality for SelectionDAG.

Similar to how llvm::salvagDebugInfo hooks into InstCombine, this adds
a hook that can be invoked before an SDNode that is associated with an
SDDbgValue is erased to capture the effect of the deleted node in a
DIExpression.

The motivating example is an SDDebugValue attached to an ADD operation
that gets folded into a LOAD+OFFSET operation.

rdar://problem/32121503

llvm-svn: 316525

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 5311ef437e9..4c4d196427e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -3550,6 +3550,7 @@ void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
                "NodeToMatch was removed partway through selection");
         SelectionDAG::DAGNodeDeletedListener NDL(*CurDAG, [&](SDNode *N,
                                                               SDNode *E) {
+          CurDAG->salvageDebugInfo(*N);
           auto &Chain = ChainNodesMatched;
           assert((!E || !is_contained(Chain, N)) &&
                  "Chain node replaced during MorphNode");