tree-optimization/45178 - DCE of dead control flow in infinite loop

[thirdparty/gcc.git] / gcc / tree-ssa-dce.c

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 0778eb9704a6753df6f8bbf8d948c7c39de16f6f..c4907af923cb5c21991d6fbcf64577ad3bc2be2c 100644 (file)
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -414,7 +414,9 @@ find_obviously_necessary_stmts (bool aggressive)
   if ((flags & (ECF_CONST|ECF_PURE)) && !(flags & ECF_LOOPING_CONST_OR_PURE))
     return;
 
-  /* Prevent the empty possibly infinite loops from being removed.  */
+  /* Prevent the empty possibly infinite loops from being removed.  This is
+     needed to make the logic in remove_dead_stmt work to identify the
+     correct edge to keep when removing a controlling condition.  */
   if (aggressive)
     {
       if (mark_irreducible_loops ())
@@ -426,17 +428,19 @@ find_obviously_necessary_stmts (bool aggressive)
                  && (e->flags & EDGE_IRREDUCIBLE_LOOP))
                {
                  if (dump_file)
-                   fprintf (dump_file, "Marking back edge of irreducible loop %i->%i\n",
-                            e->src->index, e->dest->index);
+                   fprintf (dump_file, "Marking back edge of irreducible "
+                            "loop %i->%i\n", e->src->index, e->dest->index);
                  mark_control_dependent_edges_necessary (e->dest, false);
                }
          }
 
       for (auto loop : loops_list (cfun, 0))
-       if (!finite_loop_p (loop))
+       /* For loops without an exit do not mark any condition.  */
+       if (loop->exits->next && !finite_loop_p (loop))
          {
            if (dump_file)
-             fprintf (dump_file, "cannot prove finiteness of loop %i\n", loop->num);
+             fprintf (dump_file, "cannot prove finiteness of loop %i\n",
+                      loop->num);
            mark_control_dependent_edges_necessary (loop->latch, false);
          }
     }