gcse store-motion problem and ACATS test c95072a

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

We've been back and forth with this a number of times, but I think this is
the most direct way to fix the problem, which fundamentally is that you can't
move a store to a block where there wasn't a store previously due to having
an abnormal edge.  Every way that both you and I tried to do it by affecting
the computation of stores didn't work, but this does, though it is somewhat
in the kludge category.

Tested on x86_64-linux-gnu.

Does this seem reasonable?

2004-09-01  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>

	* gcse.c (pre_edge_insert): Minor cleanup.
	(insert_store): Abort if asked to insert on abnormal edge.
	(store_motion): If any edges that we'd have to put a store on
	are abnormal, don't move the store.

*** gcse.c	18 Aug 2004 20:53:59 -0000	1.310
--- gcse.c	29 Aug 2004 21:32:54 -0000
*************** pre_edge_insert (struct edge_list *edge_
*** 4200,4204 ****
  			   now.  */
  
! 			if ((eg->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
  			  insert_insn_end_bb (index_map[j], bb, 0);
  			else
--- 4200,4204 ----
  			   now.  */
  
! 			if (eg->flags & EDGE_ABNORMAL)
  			  insert_insn_end_bb (index_map[j], bb, 0);
  			else
*************** insert_store (struct ls_expr * expr, edg
*** 6224,6234 ****
      }
  
!   /* We can't insert on this edge, so we'll insert at the head of the
!      successors block.  See Morgan, sec 10.5.  */
!   if ((e->flags & EDGE_ABNORMAL) == EDGE_ABNORMAL)
!     {
!       insert_insn_start_bb (insn, bb);
!       return 0;
!     }
  
    insert_insn_on_edge (insn, e);
--- 6237,6244 ----
      }
  
!   /* We can't put stores in the front of blocks pointed to by abnormal
!      edges since that may put a store where one didn't used to be.  */
!   if (e->flags & EDGE_ABNORMAL)
!     abort ();
  
    insert_insn_on_edge (insn, e);
*************** store_motion (void)
*** 6462,6465 ****
--- 6472,6494 ----
    for (ptr = first_ls_expr (); ptr != NULL; ptr = next_ls_expr (ptr))
      {
+       /* If any of the edges we have above are abnormal, we can't move this
+ 	 store.  */
+       for (x = NUM_EDGES (edge_list) - 1; x >= 0; x--)
+ 	if (TEST_BIT (pre_insert_map[x], ptr->index)
+ 	    && (INDEX_EDGE (edge_list, x)->flags & EDGE_ABNORMAL))
+ 	  break;
+ 
+       if (x >= 0)
+ 	{
+ 	  if (gcse_file != NULL)
+ 	    fprintf (gcse_file,
+ 		     "Can't replace store %d: abnormal edge from %d to %d\n",
+ 		     ptr->index, INDEX_EDGE (edge_list, x)->src->index,
+ 		     INDEX_EDGE (edge_list, x)->dest->index);
+ 	  continue;
+ 	}
+ 		      
+       /* Now we want to insert the new stores which are going to be needed.  */
+ 
        FOR_EACH_BB (bb)
  	if (TEST_BIT (pre_delete_map[bb->index], ptr->index))