* gcse.c (gcse_main): Avoid global optimizations if we have a

        large number of basic blocks and the ratio of edges to blocks
        is high.
        (delete_null_pointer_checks): Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@29882 138bc75d-0d04-0410-961f-82ee72b054a4

2 files changed, 37 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index da2340a6fea..340125313c9 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+Sat Oct  9 23:26:55 1999  Jeffrey A Law  (law@cygnus.com)
+
+        * gcse.c (gcse_main): Avoid global optimizations if we have a
+        large number of basic blocks and the ratio of edges to blocks
+        is high.
+        (delete_null_pointer_checks): Likewise.
+
 Sat Oct  9 23:16:01 1999  Ken Raeburn  <raeburn@mit.edu>
 
 	* c-common.c (check_format_info): Warn if format string isn't a
diff --git a/gcc/gcse.c b/gcc/gcse.c
index def34898cd7..cc9d2666dfb 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -672,6 +672,21 @@ gcse_main (f, file)
       return 0;
     }
 
+  /* Trying to perform global optimizations on flow graphs which have
+     a high connectivity will take a long time and is unlikely to be
+     particularly useful.
+
+     In normal circumstances a cfg should have about twice has many edges
+     as blocks.  But we do not want to punish small functions which have
+     a couple switch statements.  So we require a relatively large number
+     of basic blocks and the ratio of edges to blocks to be high.  */
+  if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
+    {
+      /* Free storage allocated by find_basic_blocks.  */
+      free_basic_block_vars (0);
+      return 0;
+    }
+
   /* See what modes support reg/reg copy operations.  */
   if (! can_copy_init_p)
     {
@@ -4908,6 +4923,21 @@ delete_null_pointer_checks (f)
       return;
     }
 
+  /* Trying to perform global optimizations on flow graphs which have
+     a high connectivity will take a long time and is unlikely to be
+     particularly useful.
+
+     In normal circumstances a cfg should have about twice has many edges
+     as blocks.  But we do not want to punish small functions which have
+     a couple switch statements.  So we require a relatively large number
+     of basic blocks and the ratio of edges to blocks to be high.  */
+  if (n_basic_blocks > 1000 && n_edges / n_basic_blocks >= 20)
+    {
+      /* Free storage allocated by find_basic_blocks.  */
+      free_basic_block_vars (0);
+      return 0;
+    }
+
   /* We need predecessor/successor lists as well as pred/succ counts for
      each basic block.  */
   s_preds = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));