gcc/ChangeLog:

PR debug/46240
* tree-into-ssa.c (maybe_register_def): Do not attempt to add
debug bind stmt on merge edges.
gcc/testsuite/ChangeLog:
PR debug/46240
* g++.dg/debug/pr46240.cc: New.

git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@169035 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 21 insertions, 5 deletions

diff --git a/gcc/tree-into-ssa.c b/gcc/tree-into-ssa.c
index 8d31fe7607e..c425586a156 100644
--- a/gcc/tree-into-ssa.c
+++ b/gcc/tree-into-ssa.c
@@ -1869,11 +1869,27 @@ maybe_register_def (def_operand_p def_p, gimple stmt,
 			gcc_assert (!ef);
 			ef = e;
 		      }
-		  gcc_assert (ef
-			      && single_pred_p (ef->dest)
-			      && !phi_nodes (ef->dest)
-			      && ef->dest != EXIT_BLOCK_PTR);
-		  gsi_insert_on_edge_immediate (ef, note);
+		  /* If there are other predecessors to ef->dest, then
+		     there must be PHI nodes for the modified
+		     variable, and therefore there will be debug bind
+		     stmts after the PHI nodes.  The debug bind notes
+		     we'd insert would force the creation of a new
+		     block (diverging codegen) and be redundant with
+		     the post-PHI bind stmts, so don't add them.
+
+		     As for the exit edge, there wouldn't be redundant
+		     bind stmts, but there wouldn't be a PC to bind
+		     them to either, so avoid diverging the CFG.  */
+		  if (ef && single_pred_p (ef->dest)
+		      && ef->dest != EXIT_BLOCK_PTR)
+		    {
+		      /* If there were PHI nodes in the node, we'd
+			 have to make sure the value we're binding
+			 doesn't need rewriting.  But there shouldn't
+			 be PHI nodes in a single-predecessor block,
+			 so we just add the note.  */
+		      gsi_insert_on_edge_immediate (ef, note);
+		    }
 		}
 	      else
 		gsi_insert_after (&gsi, note, GSI_SAME_STMT);