Remove unused locals in copyrename/forwprop

[Jan Hubicka <jh at suse dot cz>]

Hi,
while looking at dumps of some C++ testcase I noticed that both
tree-ssa-copyrename.c and tree-ssa-forwprop.c tends to render many
variables unused but keeps them in the lists.  Since we never run
remove_unused_locals unconditionally before IPA, we end up with those being
referenced and consuming noticeable memory.

I've tested that the patch saves about 23MB out of tramp3d footprint
and don't seem to produce noticeable slowdown.

Honza

:ADDPATCH tree-optimization:
bootstrapped/regtested i686-linux. OK

	* tree-ssa-copyrename.c (copy_rename_partition_coalesce): Return
	true when something was changed.
	(rename_ssa_copies): When something was changed, do
	TODO_remove_unused_locals.
	* tree-ssa-forwprop.c (tree_ssa_forward_propagate_single_use_value):
	add TODO_remove_unused_locals when instruction was removed.
Index: tree-ssa-copyrename.c
===================================================================
--- tree-ssa-copyrename.c	(revision 121280)
+++ tree-ssa-copyrename.c	(working copy)
@@ -109,7 +109,7 @@ Boston, MA 02110-1301, USA.  */
 /* Coalesce the partitions in MAP representing VAR1 and VAR2 if it is valid.
    Choose a representative for the partition, and send debug info to DEBUG.  */
 
-static void
+static bool
 copy_rename_partition_coalesce (var_map map, tree var1, tree var2, FILE *debug)
 {
   int p1, p2, p3;
@@ -151,7 +151,7 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
 	fprintf (debug, " : Already coalesced.\n");
-      return;
+      return false;
     }
 
   /* Don't coalesce if one of the variables occurs in an abnormal PHI.  */
@@ -161,7 +161,7 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
 	fprintf (debug, " : Abnormal PHI barrier.  No coalesce.\n");
-      return;
+      return false;
     }
 
   /* Partitions already have the same root, simply merge them.  */
@@ -170,7 +170,7 @@ copy_rename_partition_coalesce (var_map 
       p1 = partition_union (map->var_partition, p1, p2);
       if (debug)
 	fprintf (debug, " : Same root, coalesced --> P%d.\n", p1);
-      return;
+      return false;
     }
 
   /* Never attempt to coalesce 2 difference parameters.  */
@@ -178,14 +178,14 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
         fprintf (debug, " : 2 different PARM_DECLS. No coalesce.\n");
-      return;
+      return false;
     }
 
   if ((TREE_CODE (root1) == RESULT_DECL) != (TREE_CODE (root2) == RESULT_DECL))
     {
       if (debug)
         fprintf (debug, " : One root a RESULT_DECL. No coalesce.\n");
-      return;
+      return false;
     }
 
   ign1 = TREE_CODE (root1) == VAR_DECL && DECL_IGNORED_P (root1);
@@ -203,7 +203,7 @@ copy_rename_partition_coalesce (var_map 
 	{
 	  if (debug)
 	    fprintf (debug, " : 2 different USER vars. No coalesce.\n");
-	  return;
+	  return false;
 	}
     }
 
@@ -214,7 +214,7 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
 	fprintf (debug, " : 2 memory tags. No coalesce.\n");
-      return;
+      return false;
     }
 
   /* If both values have default defs, we can't coalesce.  If only one has a 
@@ -225,7 +225,7 @@ copy_rename_partition_coalesce (var_map 
 	{
 	  if (debug)
 	    fprintf (debug, " : 2 default defs. No coalesce.\n");
-	  return;
+	  return false;
 	}
       else
         {
@@ -244,7 +244,7 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
 	fprintf (debug, " : Incompatible types.  No coalesce.\n");
-      return;
+      return false;
     }
 
   /* Don't coalesce if the aliasing sets of the types are different.  */
@@ -255,7 +255,7 @@ copy_rename_partition_coalesce (var_map 
     {
       if (debug)
 	fprintf (debug, " : 2 different aliasing sets. No coalesce.\n");
-      return;
+      return false;
     }
 
 
@@ -283,6 +283,7 @@ copy_rename_partition_coalesce (var_map 
 			  TDF_SLIM);
       fprintf (debug, "\n");
     }
+  return true;
 }
 
 
@@ -301,6 +302,7 @@ rename_ssa_copies (void)
   tree phi, stmt, var, part_var;
   unsigned x;
   FILE *debug;
+  bool updated = false;
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     debug = dump_file;
@@ -321,7 +323,7 @@ rename_ssa_copies (void)
 	      tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
 
               if (TREE_CODE (lhs) == SSA_NAME && TREE_CODE (rhs) == SSA_NAME)
-		copy_rename_partition_coalesce (map, lhs, rhs, debug);
+		updated |= copy_rename_partition_coalesce (map, lhs, rhs, debug);
 	    }
 	}
     }
@@ -342,7 +344,7 @@ rename_ssa_copies (void)
             {
               tree arg = PHI_ARG_DEF (phi, i);
               if (TREE_CODE (arg) == SSA_NAME)
-		copy_rename_partition_coalesce (map, res, arg, debug);
+		updated |= copy_rename_partition_coalesce (map, res, arg, debug);
             }
         }
     }
@@ -374,7 +376,7 @@ rename_ssa_copies (void)
     }
 
   delete_var_map (map);
-  return 0;
+  return updated ? TODO_remove_unused_locals : 0;
 }
 
 /* Return true if copy rename is to be performed.  */
Index: tree-ssa-forwprop.c
===================================================================
--- tree-ssa-forwprop.c	(revision 121554)
+++ tree-ssa-forwprop.c	(working copy)
@@ -1003,6 +1003,7 @@ tree_ssa_forward_propagate_single_use_va
 		  if (forward_propagate_addr_expr (stmt, &some))
 		    {
 		      release_defs (stmt);
+		      todoflags |= TODO_remove_unused_locals;
 		      bsi_remove (&bsi, true);
 		    }
 		  else