change DF to use the proper CFG order for DF_FORWARD problems

This changes DF to use RPO on the forward graph for DF_FORWARD
problems.  While that naturally maps to pre_and_rev_postorder_compute
we use the existing (wrong) CFG order for DF_BACKWARD problems
computed by post_order_compute since that provides the required
side-effect of deleting unreachable blocks.

The change requires turning the inconsistent vec<int> vs int * back
to consistent int *.  A followup patch will change the
inverted_post_order_compute API and change the DF_BACKWARD problem
to use the correct RPO on the backward graph together with statistics
I produced last year for the combined effect.

	* df.h (df_d::postorder_inverted): Change back to int *,
	clarify comments.
	* df-core.cc (rest_of_handle_df_finish): Adjust.
	(df_analyze_1): Likewise.
	(df_analyze): For DF_FORWARD problems use RPO on the forward
	graph.  Adjust.
	(loop_inverted_post_order_compute): Adjust API.
	(df_analyze_loop): Adjust.
	(df_get_n_blocks): Likewise.
	(df_get_postorder): Likewise.

1 files changed, 4 insertions, 4 deletions

diff --git a/gcc/df.h b/gcc/df.h
index aec2223..402657a 100644
--- a/gcc/df.h
+++ b/gcc/df.h
@@ -581,10 +581,10 @@ public:
   bitmap_head insns_to_delete;
   bitmap_head insns_to_rescan;
   bitmap_head insns_to_notes_rescan;
-  int *postorder;                /* The current set of basic blocks
-                                    in reverse postorder.  */
-  vec<int> postorder_inverted;       /* The current set of basic blocks
-                                    in reverse postorder of inverted CFG.  */
+  int *postorder;                /* The current set of basic blocks in reverse
+				    postorder for DF_BACKWARD problems.  */
+  int *postorder_inverted;       /* The current set of basic blocks in reverse
+				    postorder for DF_FORWARD problems. */
   int n_blocks;                  /* The number of blocks in reverse postorder.  */
 
   /* An array [FIRST_PSEUDO_REGISTER], indexed by regno, of the number