[vta] handle debug stmts in loop parallelization

[Alexandre Oliva <aoliva at redhat dot com>]

Parallelizing loops needed special handling of debug stmts to avoid
introducing copies of decls that wouldn't be created in the absence of
debug stmts.

The patch is more complex than simply discarding the stmts to maximize
the amount of debug info preserved: if the decl is remapped
afterwards, we'll retain the debug bind stmt for it.

I'm installing this in the branch.

Index: gcc/ChangeLog.vta
from  Alexandre Oliva  <aoliva@redhat.com>

	* tree-parloops.c (eliminate_local_variables_stmt): Replace
	elements in the value portion of debug stmts.
	(separate_decls_in_region_debug_bind): New.
	(separate_decls_in_region): Call it for debug bind stmts.

Index: gcc/tree-parloops.c
===================================================================
--- gcc/tree-parloops.c.orig	2008-10-10 09:31:05.000000000 -0300
+++ gcc/tree-parloops.c	2008-11-18 02:30:38.000000000 -0200
@@ -658,7 +658,11 @@ eliminate_local_variables_stmt (edge ent
   dta.decl_address = decl_address;
   dta.changed = false;
 
-  walk_gimple_op (stmt, eliminate_local_variables_1, &dta.info);
+  if (IS_DEBUG_BIND (stmt))
+    walk_tree (gimple_debug_bind_get_value_ptr (stmt),
+	       eliminate_local_variables_1, &dta.info, NULL);
+  else
+    walk_gimple_op (stmt, eliminate_local_variables_1, &dta.info);
 
   if (dta.changed)
     update_stmt (stmt);
@@ -842,6 +846,53 @@ separate_decls_in_region_stmt (edge entr
   }
 }
 
+/* Finds the ssa names used in STMT that are defined outside the
+   region between ENTRY and EXIT and replaces such ssa names with
+   their duplicates.  The duplicates are stored to NAME_COPIES.  Base
+   decls of all ssa names used in STMT (including those defined in
+   LOOP) are replaced with the new temporary variables; the
+   replacement decls are stored in DECL_COPIES.  */
+
+static bool
+separate_decls_in_region_debug_bind (gimple stmt,
+				     htab_t name_copies, htab_t decl_copies)
+{
+  use_operand_p use;
+  ssa_op_iter oi;
+  tree var, name;
+  struct int_tree_map ielt;
+  struct name_to_copy_elt elt;
+  void **slot, **dslot;
+
+  var = gimple_debug_bind_get_var (stmt);
+  gcc_assert (DECL_P (var) && SSA_VAR_P (var));
+  ielt.uid = DECL_UID (var);
+  dslot = htab_find_slot_with_hash (decl_copies, &ielt, ielt.uid, NO_INSERT);
+  if (!dslot)
+    return true;
+  gimple_debug_bind_set_var (stmt, ((struct int_tree_map *) *dslot)->to);
+
+  FOR_EACH_PHI_OR_STMT_USE (use, stmt, oi, SSA_OP_USE)
+  {
+    name = USE_FROM_PTR (use);
+    if (TREE_CODE (name) != SSA_NAME)
+      continue;
+
+    elt.version = SSA_NAME_VERSION (name);
+    slot = htab_find_slot_with_hash (name_copies, &elt, elt.version, NO_INSERT);
+    if (!slot)
+      {
+	gimple_debug_bind_set_value (stmt, VAR_DEBUG_VALUE_NOVALUE);
+	update_stmt (stmt);
+	break;
+      }
+
+    SET_USE (use, ((struct name_to_copy_elt *) *slot)->new_name);
+  }
+
+  return false;
+}
+
 /* Callback for htab_traverse.  Adds a field corresponding to the reduction
    specified in SLOT. The type is passed in DATA.  */
 
@@ -1173,6 +1224,7 @@ separate_decls_in_region (edge entry, ed
   basic_block bb;
   basic_block entry_bb = bb1;
   basic_block exit_bb = exit->dest;
+  bool has_debug_stmt = false;
 
   entry = single_succ_edge (entry_bb);
   gather_blocks_in_sese_region (entry_bb, exit_bb, &body);
@@ -1186,11 +1238,43 @@ separate_decls_in_region (edge entry, ed
 					   name_copies, decl_copies);
 
 	  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
-	    separate_decls_in_region_stmt (entry, exit, gsi_stmt (gsi),
-					   name_copies, decl_copies);
+	    {
+	      gimple stmt = gsi_stmt (gsi);
+
+	      if (IS_DEBUG_STMT (stmt))
+		has_debug_stmt = true;
+	      else
+		separate_decls_in_region_stmt (entry, exit, stmt,
+					       name_copies, decl_copies);
+	    }
 	}
     }
 
+  if (has_debug_stmt)
+    for (i = 0; VEC_iterate (basic_block, body, i, bb); i++)
+      if (bb != entry_bb && bb != exit_bb) 
+	{
+	  for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
+	    {
+	      gimple stmt = gsi_stmt (gsi);
+
+	      if (IS_DEBUG_BIND (stmt))
+		{
+		  if (separate_decls_in_region_debug_bind (stmt,
+							   name_copies,
+							   decl_copies))
+		    {
+		      gsi_remove (&gsi, true);
+		      continue;
+		    }
+		}
+	      else
+		gcc_assert (!IS_DEBUG_STMT (stmt));
+
+	      gsi_next (&gsi);
+	    }
+	}
+
   VEC_free (basic_block, heap, body);
 
   if (htab_elements (name_copies) == 0)


-- 
Alexandre Oliva           http://www.lsd.ic.unicamp.br/~oliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer