dag-combine: Transfer debug information when folding (zext (truncate x))

  -> (zext (truncate x))

This patch adds debug info support to the dagcombine rule (zext
(truncate x)) -> (zext (truncate x)).

Differential Revision: https://reviews.llvm.org/D41924

llvm-svn: 322304

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4ae22d69eaf..093a20057c6 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7800,7 +7800,10 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
         SDValue Op = N0.getOperand(0);
         Op = DAG.getZeroExtendInReg(Op, SDLoc(N), MinVT.getScalarType());
         AddToWorklist(Op.getNode());
-        return DAG.getZExtOrTrunc(Op, SDLoc(N), VT);
+        SDValue ZExtOrTrunc = DAG.getZExtOrTrunc(Op, SDLoc(N), VT);
+        // Transfer the debug info; the new node is equivalent to N0.
+        DAG.transferDbgValues(N0, ZExtOrTrunc);
+        return ZExtOrTrunc;
       }
     }