re PR debug/46258 (gcc.dg/tree-ssa/pr23820.c: -fcompare-debug failure with -O3 -ffloat-store)

PR debug/46258
* tree-cfg.c (replace_uses_by): Don't mark BBs as altered on
debug stmts.

From-SVN: r167162

gcc/ChangeLog

 2010-11-26  Alexandre Oliva  <aoliva@redhat.com>
 
+	PR debug/46258
+	* tree-cfg.c (replace_uses_by): Don't mark BBs as altered on
+	debug stmts.
+
+2010-11-26  Alexandre Oliva  <aoliva@redhat.com>
+
 	* toplev.c (finalize): Add no_backend parameter.  Don't finish
 	passes when preprocessing only.  Adjust...
 	(do_compile): ... caller.

gcc/tree-cfg.c

@@ -1570,7 +1570,7 @@ replace_uses_by (tree name, tree val)
 	  size_t i;
 
 	  fold_stmt_inplace (stmt);
-	  if (cfgcleanup_altered_bbs)
+	  if (cfgcleanup_altered_bbs && !is_gimple_debug (stmt))
 	    bitmap_set_bit (cfgcleanup_altered_bbs, gimple_bb (stmt)->index);
 
 	  /* FIXME.  This should go in update_stmt.  */