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 --git a/gcc/omp-expand.cc b/gcc/omp-expand.cc
index 936adff7f45ff85f3c2277fa5b4c866e92b71f3d..64e6308fc7b83a14c2dd7580071a0b020e9f4211 100644 (file)
--- 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.  */