[gcc r12-4969] Cleanup back_threader::find_path_to_names.

[gcc r12-4969] Cleanup back_threader::find_path_to_names.

[Aldy Hernandez]

https://gcc.gnu.org/g:98b212c19a7b8822a93407af548df45c15917695

commit r12-4969-g98b212c19a7b8822a93407af548df45c15917695
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Thu Nov 4 19:44:15 2021 +0100

    Cleanup back_threader::find_path_to_names.
    
    The main path discovery function was due for a cleanup.  First,
    there's a nagging goto and second, my bitmap use was sloppy.  Hopefully
    this makes the code easier for others to read.
    
    Regstrapped on x86-64 Linux.  I also made sure there were no difference
    in the number of threads with this patch.
    
    No functional changes.
    
    gcc/ChangeLog:
    
            * tree-ssa-threadbackward.c (back_threader::find_paths_to_names):
            Remove gotos and other cleanups.

Diff:
---
 gcc/tree-ssa-threadbackward.c | 65 ++++++++++++++++---------------------------
 1 file changed, 24 insertions(+), 41 deletions(-)

diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index b7eaff94567..0085ad01cdc 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -89,7 +89,7 @@ private:
   void find_paths (basic_block bb, tree name);
   bool debug_counter ();
   edge maybe_register_path ();
-  bool find_paths_to_names (basic_block bb, bitmap imports);
+  void find_paths_to_names (basic_block bb, bitmap imports);
   bool resolve_def (tree name, bitmap interesting, vec<tree> &worklist);
   void resolve_phi (gphi *phi, bitmap imports);
   edge find_taken_edge (const vec<basic_block> &path);
@@ -388,40 +388,28 @@ back_threader::resolve_def (tree name, bitmap interesting, vec<tree> &worklist)
 // Find jump threading paths to any of the SSA names in the
 // INTERESTING bitmap, and register any such paths.
 //
-// Return TRUE if no further processing past this block is necessary.
-// This is because we've either registered a path, or because there is
-// nothing of interesting beyond this block.
-//
 // BB is the current path being processed.
 
-bool
+void
 back_threader::find_paths_to_names (basic_block bb, bitmap interesting)
 {
   if (m_visited_bbs.add (bb))
-    return true;
+    return;
 
   m_path.safe_push (bb);
 
-  if (m_path.length () > 1
-      && !m_profit.profitable_path_p (m_path, m_name, NULL))
-    {
-      m_path.pop ();
-      m_visited_bbs.remove (bb);
-      return false;
-    }
-
   // Try to resolve the path without looking back.
-  if (m_path.length () > 1 && maybe_register_path ())
+  if (m_path.length () > 1
+      && (!m_profit.profitable_path_p (m_path, m_name, NULL)
+	  || maybe_register_path ()))
     {
       m_path.pop ();
       m_visited_bbs.remove (bb);
-      return true;
+      return;
     }
 
   auto_bitmap processed;
-  unsigned i;
   bool done = false;
-
   // We use a worklist instead of iterating through the bitmap,
   // because we may add new items in-flight.
   auto_vec<tree> worklist (bitmap_count_bits (interesting));
@@ -433,37 +421,32 @@ back_threader::find_paths_to_names (basic_block bb, bitmap interesting)
       basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (name));
 
       // Process any names defined in this block.
-      if (def_bb == bb)
+      if (def_bb == bb
+	  && bitmap_set_bit (processed, i)
+	  && resolve_def (name, interesting, worklist))
 	{
-	  bitmap_set_bit (processed, i);
-
-	  if (resolve_def (name, interesting, worklist))
-	    {
-	      done = true;
-	      goto leave_bb;
-	    }
+	  done = true;
+	  break;
 	}
     }
-
   // If there are interesting names not yet processed, keep looking.
-  bitmap_and_compl_into (interesting, processed);
-  if (!bitmap_empty_p (interesting))
+  if (!done)
     {
-      edge_iterator iter;
-      edge e;
-      FOR_EACH_EDGE (e, iter, bb->preds)
-	if ((e->flags & EDGE_ABNORMAL) == 0)
-	  done |= find_paths_to_names (e->src, interesting);
+      bitmap_and_compl_into (interesting, processed);
+      if (!bitmap_empty_p (interesting))
+	{
+	  edge_iterator iter;
+	  edge e;
+	  FOR_EACH_EDGE (e, iter, bb->preds)
+	    if ((e->flags & EDGE_ABNORMAL) == 0)
+	      find_paths_to_names (e->src, interesting);
+	}
     }
 
- leave_bb:
-  bitmap_iterator bi;
-  EXECUTE_IF_SET_IN_BITMAP (processed, 0, i, bi)
-    bitmap_set_bit (interesting, i);
-
+  // Reset things to their original state.
+  bitmap_ior_into (interesting, processed);
   m_path.pop ();
   m_visited_bbs.remove (bb);
-  return done;
 }
 
 // Search backwards from BB looking for paths where the final