[gcc r14-301] Unloop loops that no longer loops in tree-ssa-loop-ch

[gcc r14-301] Unloop loops that no longer loops in tree-ssa-loop-ch

[Jan Hubicka]

https://gcc.gnu.org/g:f2d6beb7a4ddf18dd95fdcc336181a8702a9f55f

commit r14-301-gf2d6beb7a4ddf18dd95fdcc336181a8702a9f55f
Author: Jan Hubicka <jh@suse.cz>
Date:   Thu Apr 27 15:49:37 2023 +0200

    Unloop loops that no longer loops in tree-ssa-loop-ch
    
    I noticed this after adding sanity check that the upper bound on number
    of iterations never drop to -1.  It seems to be relatively common case
    (happening few hundred times in testsuite and also during bootstrap)
    that loop-ch duplicates enough so the loop itself no longer loops.
    
    This is later detected in loop unrolling but since we test the number
    of iterations anyway it seems better to do that earlier.
    
            * cfgloopmanip.h (unloop_loops): Export.
            * tree-ssa-loop-ch.cc (ch_base::copy_headers): Unloop loops
            that no longer loop.
            * tree-ssa-loop-ivcanon.cc (unloop_loops): Export; do not free
            vectors of loops to unloop.
            (canonicalize_induction_variables): Free vectors here.
            (tree_unroll_loops_completely): Free vectors here.

Diff:
---
 gcc/cfgloopmanip.h           |  4 ++++
 gcc/tree-ssa-loop-ch.cc      | 33 +++++++++++++++++++++++++--------
 gcc/tree-ssa-loop-ivcanon.cc | 20 ++++++++++++++------
 3 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/gcc/cfgloopmanip.h b/gcc/cfgloopmanip.h
index c40cfeae0e3..75b2a5e9b75 100644
--- a/gcc/cfgloopmanip.h
+++ b/gcc/cfgloopmanip.h
@@ -43,6 +43,10 @@ extern edge create_empty_if_region_on_edge (edge, tree);
 extern class loop *create_empty_loop_on_edge (edge, tree, tree, tree, tree,
 					       tree *, tree *, class loop *);
 extern void unloop (class loop *, bool *, bitmap);
+extern void unloop_loops (vec<class loop *> &loops_to_unloop,
+			  vec<int> &loops_to_unloop_nunroll,
+			  bitmap loop_closed_ssa_invalidated,
+			  bool *irred_invalidated);
 extern void copy_loop_info (class loop *loop, class loop *target);
 extern class loop * duplicate_loop (class loop *, class loop *,
 				     class loop * = NULL);
diff --git a/gcc/tree-ssa-loop-ch.cc b/gcc/tree-ssa-loop-ch.cc
index 73b24c9a6f2..83c2c1c6792 100644
--- a/gcc/tree-ssa-loop-ch.cc
+++ b/gcc/tree-ssa-loop-ch.cc
@@ -396,6 +396,8 @@ ch_base::copy_headers (function *fun)
 
   auto_vec<loop_p> candidates;
   auto_vec<std::pair<edge, loop_p> > copied;
+  auto_vec<class loop *> loops_to_unloop;
+  auto_vec<int> loops_to_unloop_nunroll;
 
   mark_dfs_back_edges ();
   gimple_ranger *ranger = new gimple_ranger;
@@ -408,6 +410,14 @@ ch_base::copy_headers (function *fun)
 		 "Analyzing loop %i\n", loop->num);
 
       header = loop->header;
+      if (!get_max_loop_iterations_int (loop))
+	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "Loop %d never loops.\n", loop->num);
+	  loops_to_unloop.safe_push (loop);
+	  loops_to_unloop_nunroll.safe_push (0);
+	  continue;
+	}
 
       /* If the loop is already a do-while style one (either because it was
 	 written as such, or because jump threading transformed it into one),
@@ -593,13 +603,6 @@ ch_base::copy_headers (function *fun)
       /* We possibly decreased number of itrations by 1.  */
       auto_vec<edge> exits = get_loop_exit_edges (loop);
       bool precise = (nexits == (int) exits.length ());
-      if (!get_max_loop_iterations_int (loop))
-	{
-	  if (dump_file && (dump_flags & TDF_DETAILS))
-	    fprintf (dump_file, "Loop %d no longer loops.\n", loop->num);
-	  /* TODO: We can unloop like in tree-ssa-loop-ivcanon.  */
-	  precise = false;
-	}
       /* Check that loop may not terminate in other way than via
 	 basic blocks we duplicated.  */
       if (precise)
@@ -640,7 +643,15 @@ ch_base::copy_headers (function *fun)
 		 precise = false;
 	   }
 	}
-      if (precise)
+      if (precise
+	  && get_max_loop_iterations_int (loop) == 1)
+	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "Loop %d no longer loops.\n", loop->num);
+	  loops_to_unloop.safe_push (loop);
+	  loops_to_unloop_nunroll.safe_push (0);
+	}
+      else if (precise)
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
 	    fprintf (dump_file,
@@ -688,6 +699,12 @@ ch_base::copy_headers (function *fun)
 	  BITMAP_FREE (exit_bbs);
 	}
     }
+  if (!loops_to_unloop.is_empty ())
+    {
+      bool irred_invalidated;
+      unloop_loops (loops_to_unloop, loops_to_unloop_nunroll, NULL, &irred_invalidated);
+      changed = true;
+    }
   free (bbs);
   free (copied_bbs);
 
diff --git a/gcc/tree-ssa-loop-ivcanon.cc b/gcc/tree-ssa-loop-ivcanon.cc
index e965cf94eb7..e41ec73a52a 100644
--- a/gcc/tree-ssa-loop-ivcanon.cc
+++ b/gcc/tree-ssa-loop-ivcanon.cc
@@ -618,8 +618,10 @@ static bitmap peeled_loops;
    LOOP_CLOSED_SSA_INVALIDATED is used to bookkepp the case
    when we need to go into loop closed SSA form.  */
 
-static void
-unloop_loops (bitmap loop_closed_ssa_invalidated,
+void
+unloop_loops (vec<class loop *> &loops_to_unloop,
+	      vec<int> &loops_to_unloop_nunroll,
+	      bitmap loop_closed_ssa_invalidated,
 	      bool *irred_invalidated)
 {
   while (loops_to_unloop.length ())
@@ -653,8 +655,6 @@ unloop_loops (bitmap loop_closed_ssa_invalidated,
       gsi = gsi_start_bb (latch_edge->dest);
       gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
     }
-  loops_to_unloop.release ();
-  loops_to_unloop_nunroll.release ();
 
   /* Remove edges in peeled copies.  Given remove_path removes dominated
      regions we need to cope with removal of already removed paths.  */
@@ -1326,7 +1326,10 @@ canonicalize_induction_variables (void)
     }
   gcc_assert (!need_ssa_update_p (cfun));
 
-  unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated);
+  unloop_loops (loops_to_unloop, loops_to_unloop_nunroll,
+		loop_closed_ssa_invalidated, &irred_invalidated);
+  loops_to_unloop.release ();
+  loops_to_unloop_nunroll.release ();
   if (irred_invalidated
       && loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))
     mark_irreducible_loops ();
@@ -1473,7 +1476,12 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
 	{
 	  unsigned i;
 
-          unloop_loops (loop_closed_ssa_invalidated, &irred_invalidated);
+	  unloop_loops (loops_to_unloop,
+			loops_to_unloop_nunroll,
+			loop_closed_ssa_invalidated,
+			&irred_invalidated);
+	  loops_to_unloop.release ();
+	  loops_to_unloop_nunroll.release ();
 
 	  /* We cannot use TODO_update_ssa_no_phi because VOPS gets confused.  */
 	  if (loop_closed_ssa_invalidated