re PR rtl-optimization/19210 (not using do-loop for some loops)

gcc:
2005-07-21  Paolo Bonzini  <bonzini@gnu.org>
            Zdenek Dvorak  <dvorakz@suse.cz>

	PR tree-optimization/19210
	* common.opt (Wunsafe-loop-optimizations, funsafe-loop-optimizations):
	New.
	* Makefile.in (tree-ssa-loop-niter.o): Depend intl.o.
	* loop-iv.c (get_simple_loop_desc): If -funsafe-loop-optimizations,
	rely on unproven assumptions.
	* predict.c (predict_loops): Adjust call to number_of_iterations_exit.
	* tree-flow.h (number_of_iterations_exit): Add final parameter.
	* tree-scalar-evolution.c (number_of_iterations_in_loop): Adjust call
	to number_of_iterations_exit.
	* tree-ssa-loop-ivcanon.c (empty_loop_p): Likewise.
	* tree-ssa-loop-ivopts.c (niter_for_exit): Likewise.
	* tree-ssa-loop-niter.c (find_loop_niter,
	estimate_numbers_of_iterations_loop): Likewise.
	(number_of_iterations_exit): Honor the new options.
	* doc/invoke.texi (Wunsafe-loop-optimizations,
	funsafe-loop-optimizations): Document them.

gcc/testsuite:
2005-07-21  Paolo Bonzini  <bonzini@gnu.org>

        * gcc.dg/tree-ssa/pr19210-1.c: New.
        * gcc.dg/tree-ssa/pr19210-2.c: New.

Co-Authored-By: Zdenek Dvorak <dvorakz@suse.cz>

From-SVN: r102225

1 files changed, 37 insertions, 0 deletions

diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index 48bae0b..7c7a5de 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -57,7 +57,9 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
 #include "basic-block.h"
 #include "cfgloop.h"
 #include "expr.h"
+#include "intl.h"
 #include "output.h"
+#include "toplev.h"
 
 /* The insn information.  */
 
@@ -2692,6 +2694,41 @@ get_simple_loop_desc (struct loop *loop)
   find_simple_exit (loop, desc);
   loop->aux = desc;
 
+  if (desc->simple_p && (desc->assumptions || desc->infinite))
+    {
+      const char *wording; 
+
+      /* Assume that no overflow happens and that the loop is finite.  
+	 We already warned at the tree level if we ran optimizations there.  */
+      if (!flag_tree_loop_optimize && warn_unsafe_loop_optimizations)
+	{
+	  if (desc->infinite)
+	    {
+	      wording = 
+		flag_unsafe_loop_optimizations
+		? N_("assuming that the loop is not infinite")
+		: N_("cannot optimize possibly infinite loops");
+	      warning (OPT_Wunsafe_loop_optimizations, "%s",
+		       gettext (wording));
+	    }
+	  if (desc->assumptions)
+	    {
+	      wording = 
+		flag_unsafe_loop_optimizations
+		? N_("assuming that the loop counter does not overflow")
+		: N_("cannot optimize loop, the loop counter may overflow");
+	      warning (OPT_Wunsafe_loop_optimizations, "%s",
+		       gettext (wording));
+	    }
+	}
+
+      if (flag_unsafe_loop_optimizations)
+	{
+	  desc->assumptions = NULL_RTX;
+	  desc->infinite = NULL_RTX;
+	}
+    }
+
   return desc;
 }