[PATCH] Do not leak SSA names in PRE

[PATCH] Do not leak SSA names in PRE

[Richard Biener]

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When PRE creates representatives for expressions during PHI translation it never
releases the SSA names again.  The following patch arranges for SCCVN to release
them.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

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2012-12-13  Richard Biener  <rguenther@suse.de>

	* tree-ssa-pre.c (get_representative_for): Adjust dumping.
	Mark created SSA names for release.
	(eliminate_bb): Insert only when expr is not NULL.

Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c	(revision 194444)
--- gcc/tree-ssa-pre.c	(working copy)
*************** get_representative_for (const pre_expr e
*** 1395,1425 ****
  	    pre_expr rep = expression_for_id (i);
  	    if (rep->kind == NAME)
  	      return PRE_EXPR_NAME (rep);
  	  }
        }
        break;
      }
    /* If we reached here we couldn't find an SSA_NAME.  This can
       happen when we've discovered a value that has never appeared in
!      the program as set to an SSA_NAME, most likely as the result of
!      phi translation.  */
!   if (dump_file)
!     {
!       fprintf (dump_file,
! 	       "Could not find SSA_NAME representative for expression:");
!       print_pre_expr (dump_file, e);
!       fprintf (dump_file, "\n");
!     }
! 
!   /* Build and insert the assignment of the end result to the temporary
!      that we will return.  */
    name = make_temp_ssa_name (get_expr_type (e), gimple_build_nop (), "pretmp");
    VN_INFO_GET (name)->value_id = value_id;
!   VN_INFO (name)->valnum = sccvn_valnum_from_value_id (value_id);
!   if (VN_INFO (name)->valnum == NULL_TREE)
!     VN_INFO (name)->valnum = name;
    add_to_value (value_id, get_or_alloc_expr_for_name (name));
!   if (dump_file)
      {
        fprintf (dump_file, "Created SSA_NAME representative ");
        print_generic_expr (dump_file, name, 0);
--- 1395,1420 ----
  	    pre_expr rep = expression_for_id (i);
  	    if (rep->kind == NAME)
  	      return PRE_EXPR_NAME (rep);
+ 	    else if (rep->kind == CONSTANT)
+ 	      return PRE_EXPR_CONSTANT (rep);
  	  }
        }
        break;
      }
+ 
    /* If we reached here we couldn't find an SSA_NAME.  This can
       happen when we've discovered a value that has never appeared in
!      the program as set to an SSA_NAME, as the result of phi translation.
!      Create one here.
!      ???  We should be able to re-use this when we insert the statement
!      to compute it.  */
    name = make_temp_ssa_name (get_expr_type (e), gimple_build_nop (), "pretmp");
    VN_INFO_GET (name)->value_id = value_id;
!   VN_INFO (name)->valnum = name;
!   /* ???  For now mark this SSA name for release by SCCVN.  */
!   VN_INFO (name)->needs_insertion = true;
    add_to_value (value_id, get_or_alloc_expr_for_name (name));
!   if (dump_file && (dump_flags & TDF_DETAILS))
      {
        fprintf (dump_file, "Created SSA_NAME representative ");
        print_generic_expr (dump_file, name, 0);
*************** eliminate_bb (dom_walk_data *, basic_blo
*** 4170,4175 ****
--- 4165,4171 ----
  	      if (val != VN_TOP
  		  && TREE_CODE (val) == SSA_NAME
  		  && VN_INFO (val)->needs_insertion
+ 		  && VN_INFO (val)->expr != NULL_TREE
  		  && (sprime = eliminate_insert (&gsi, val)) != NULL_TREE)
  		eliminate_push_avail (sprime);
  	    }