[gcc r13-1926] tree-optimization/106498 - reduce SSA updates in autopar

[gcc r13-1926] tree-optimization/106498 - reduce SSA updates in autopar

[Richard Biener]

https://gcc.gnu.org/g:c30bbd4d169c98b7535a30384c6a971ee875fa44

commit r13-1926-gc30bbd4d169c98b7535a30384c6a971ee875fa44
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Aug 2 08:37:16 2022 +0200

    tree-optimization/106498 - reduce SSA updates in autopar
    
    The following reduces the number of SSA updates done during autopar
    OMP expansion, specifically avoiding the cases that just add virtual
    operands (where maybe none have been before) in dead regions of the CFG.
    
    Instead virtual SSA update is delayed until after the pass.  There's
    much more TLC needed here, but test coverage makes it really difficult.
    
            PR tree-optimization/106498
            * omp-expand.cc (expand_omp_taskreg): Do not perform virtual
            SSA update here.
            (expand_omp_for): Or here.
            (execute_expand_omp): Instead schedule it here together
            with CFG cleanup via TODO.

Diff:
---
 gcc/omp-expand.cc | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/gcc/omp-expand.cc b/gcc/omp-expand.cc
index 936adff7f45..64e6308fc7b 100644
--- a/gcc/omp-expand.cc
+++ b/gcc/omp-expand.cc
@@ -1530,8 +1530,6 @@ expand_omp_taskreg (struct omp_region *region)
     expand_teams_call (new_bb, as_a <gomp_teams *> (entry_stmt));
   else
     expand_task_call (region, new_bb, as_a <gomp_task *> (entry_stmt));
-  if (gimple_in_ssa_p (cfun))
-    update_ssa (TODO_update_ssa_only_virtuals);
 }
 
 /* Information about members of an OpenACC collapsed loop nest.  */
@@ -8191,9 +8189,6 @@ expand_omp_for (struct omp_region *region, gimple *inner_stmt)
 			      (enum built_in_function) next_ix, sched_arg,
 			      inner_stmt);
     }
-
-  if (gimple_in_ssa_p (cfun))
-    update_ssa (TODO_update_ssa_only_virtuals);
 }
 
 /* Expand code for an OpenMP sections directive.  In pseudo code, we generate
@@ -10591,13 +10586,10 @@ execute_expand_omp (void)
 
   expand_omp (root_omp_region);
 
-  if (flag_checking && !loops_state_satisfies_p (LOOPS_NEED_FIXUP))
-    verify_loop_structure ();
-  cleanup_tree_cfg ();
-
   omp_free_regions ();
 
-  return 0;
+  return (TODO_cleanup_cfg
+	  | (gimple_in_ssa_p (cfun) ? TODO_update_ssa_only_virtuals : 0));
 }
 
 /* OMP expansion -- the default pass, run before creation of SSA form.  */