[Bug tree-optimization/34265] Missed optimizations

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #17 from rguenth at gcc dot gnu dot org  2007-11-29 10:11 -------
Doh, not only I missed to diff the chunk mentioned in comment #6, but I also
added the original unrolling pass, not the one only supposed to unroll inner
loops #)

So, change the passes.c hunk to

Index: gcc/passes.c
===================================================================
--- gcc/passes.c        (revision 130511)
+++ gcc/passes.c        (working copy)
@@ -570,6 +570,9 @@ init_optimization_passes (void)
       NEXT_PASS (pass_merge_phi);
       NEXT_PASS (pass_vrp);
       NEXT_PASS (pass_dce);
+      NEXT_PASS (pass_tree_loop_init);
+      NEXT_PASS (pass_complete_unrolli);
+      NEXT_PASS (pass_tree_loop_done);
       NEXT_PASS (pass_cselim);
       NEXT_PASS (pass_dominator);
       /* The only const/copy propagation opportunities left after


that should fix some of the testsuite failures.  Some thing also to experiment
with (to maybe fix some of the compile-time problems) is in the
tree-lssa-loop-ivcanon.c hunk change the condition to

           if (!unroll_outer
               && loop->inner)
             continue;

to only unroll innermost loops, not all-but-outermost loops.

As of pass placement another thing to look at is if it works as part of
early optimizations around

          NEXT_PASS (pass_early_inline);
          NEXT_PASS (pass_cleanup_cfg);
          NEXT_PASS (pass_rename_ssa_copies);
.... here
          NEXT_PASS (pass_ccp);
          NEXT_PASS (pass_forwprop);
          NEXT_PASS (pass_update_address_taken);
.... or here
          NEXT_PASS (pass_simple_dse);
          NEXT_PASS (pass_sra_early);

because this may enable SRA of variables in the loop body.

Most of the compile-time impact is actually from doing loop discovery, but
as we preserve loops now maybe we do not need pass_tree_loop_done after
the early unrolling and as well not pass_tree_loop_init before the rest
of loop optimizations anymore?  Zdenek, can you confirm this?


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rakdver at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34265