[PATCH] Don't reapply loops flags if unnecessary in loop_optimizer_init

[Tom de Vries]

[ was: Re: [PATCH, 10/16] Add pass_oacc_kernels pass group in passes.def ]
On 20/11/15 11:37, Richard Biener wrote:
I'd rather make loop_optimizer_init do nothing
if requested flags are already set and no fixup is needed and
call the above unconditionally.  Thus sth like

Index: gcc/loop-init.c
===================================================================
--- gcc/loop-init.c     (revision 230649)
+++ gcc/loop-init.c     (working copy)
@@ -103,7 +103,11 @@ loop_optimizer_init (unsigned flags)
        calculate_dominance_info (CDI_DOMINATORS);

        if (!needs_fixup)
-       checking_verify_loop_structure ();
+       {
+         checking_verify_loop_structure ();
+         if (loops_state_satisfies_p (flags))
+           goto out;
+       }

        /* Clear all flags.  */
        if (recorded_exits)
@@ -122,11 +126,12 @@ loop_optimizer_init (unsigned flags)
    /* Apply flags to loops.  */
    apply_loop_flags (flags);

+  checking_verify_loop_structure ();
+
+out:
    /* Dump loops.  */
    flow_loops_dump (dump_file, NULL, 1);

-  checking_verify_loop_structure ();
-
    timevar_pop (TV_LOOP_INIT);
  }

This patch implements that approach, but the patch is slightly more 
complicated because of the need to handle 
LOOPS_MAY_HAVE_MULTIPLE_LATCHES differently than the rest of the flags.

Bootstrapped and reg-tested on x86_64.

OK for stage3 trunk?

Thanks,
- Tom

Don't reapply loops flags if unnecessary in loop_optimizer_init

2015-11-22  Tom de Vries  <t...@codesourcery.com>

	* loop-init.c (loop_optimizer_init): Don't reapply loops flags if
	unnecessary.

---
 gcc/loop-init.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/gcc/loop-init.c b/gcc/loop-init.c
index e32c94a..4b72cab 100644
--- a/gcc/loop-init.c
+++ b/gcc/loop-init.c
@@ -85,6 +85,8 @@ loop_optimizer_init (unsigned flags)
 {
   timevar_push (TV_LOOP_INIT);
 
+  gcc_checking_assert ((flags & (LOOP_CLOSED_SSA | LOOPS_NEED_FIXUP)) == 0);
+
   if (!current_loops)
     {
       gcc_assert (!(cfun->curr_properties & PROP_loops));
@@ -103,7 +105,17 @@ loop_optimizer_init (unsigned flags)
       calculate_dominance_info (CDI_DOMINATORS);
 
       if (!needs_fixup)
-	checking_verify_loop_structure ();
+	{
+	  checking_verify_loop_structure ();
+
+	  bool need_reapply
+	    = (!loops_state_satisfies_p (flags
+					 & (~LOOPS_MAY_HAVE_MULTIPLE_LATCHES))
+	       || (loops_state_satisfies_p (LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
+		   && ((flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES) == 0)));
+	  if (!need_reapply)
+	    goto out;
+	}
 
       /* Clear all flags.  */
       if (recorded_exits)
@@ -122,11 +134,12 @@ loop_optimizer_init (unsigned flags)
   /* Apply flags to loops.  */
   apply_loop_flags (flags);
 
+  checking_verify_loop_structure ();
+
+ out:
   /* Dump loops.  */
   flow_loops_dump (dump_file, NULL, 1);
 
-  checking_verify_loop_structure ();
-
   timevar_pop (TV_LOOP_INIT);
 }