[Bug middle-end/118801] Excessive compile time with -g -O2 -fpeel-loops -fno-var-tracking

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118801

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
With the following we're down to 215 DEBUG BEGIN_STMT in the testcase

diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index be21a2d0b50..064e47cbf23 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -1508,6 +1508,7 @@ eliminate_unnecessary_stmts (bool aggressive)

       /* Remove dead statements.  */
       auto_bitmap debug_seen;
+      bool debug_begin_seen = false;
       for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi = psi)
        {
          stmt = gsi_stmt (gsi);
@@ -1670,6 +1671,16 @@ eliminate_unnecessary_stmts (bool aggressive)
                remove_dead_stmt (&gsi, bb, to_remove_edges);
              continue;
            }
+         else if (gimple_debug_begin_stmt_p (stmt))
+           {
+             /* We are only keeping the last debug-begin in a series of
+                debug-begin stmts.  */
+             if (debug_begin_seen)
+               remove_dead_stmt (&gsi, bb, to_remove_edges);
+             debug_begin_seen = true;
+             continue;
+           }
+         debug_begin_seen = false;
          bitmap_clear (debug_seen);
        }