loop-init.c (loop_optimizer_init, [...]): Do not destroy dominance information.

	* loop-init.c (loop_optimizer_init, loop_optimizer_finalize): Do not
	destroy dominance information.
	* passes.c (rest_of_handle_loop2):  Free dominance information.
	* tree-cfg.c (cleanup_tree_cfg): Remove unreachable blocks before
	jump threading.
	(thread_jumps): Update dominance information and remove unreachable
	blocks.
	* tree-ssa-phiopt.c (replace_phi_with_stmt):  Update dominance
	information and remove the unreachable block.

From-SVN: r84873

gcc/ChangeLog

+2004-07-17  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+	* loop-init.c (loop_optimizer_init, loop_optimizer_finalize): Do not
+	destroy dominance information.
+	* passes.c (rest_of_handle_loop2):  Free dominance information.
+	* tree-cfg.c (cleanup_tree_cfg): Remove unreachable blocks before
+	jump threading.
+	(thread_jumps): Update dominance information and remove unreachable
+	blocks.
+	* tree-ssa-phiopt.c (replace_phi_with_stmt):  Update dominance
+	information and remove the unreachable block.
+
 2004-07-17  Graham Stott  <graham.stott@btinternet.com>
 
 	* emit-rtl.c (reorder_insns): Don't set BB for a BARRIER insn.

gcc/loop-init.c

@@ -55,7 +55,6 @@ loop_optimizer_init (FILE *dumpfile)
     {
       /* No loops.  */
       flow_loops_free (loops);
-      free_dominance_info (CDI_DOMINATORS);
       free (loops);
 
       return NULL;
@@ -105,7 +104,6 @@ loop_optimizer_finalize (struct loops *loops, FILE *dumpfile)
 
   /* Clean up.  */
   flow_loops_free (loops);
-  free_dominance_info (CDI_DOMINATORS);
   free (loops);
 
   /* Checking.  */

gcc/passes.c

@@ -1380,6 +1380,8 @@ rest_of_handle_loop2 (void)
       loop_optimizer_finalize (loops, dump_file);
     }
 
+  free_dominance_info (CDI_DOMINATORS);
+
   /* Finalize layout changes.  */
   FOR_EACH_BB (bb)
     if (bb->next_bb != EXIT_BLOCK_PTR)

gcc/tree-cfg.c

@@ -733,8 +733,8 @@ cleanup_tree_cfg (void)
   while (something_changed)
     {
       something_changed = cleanup_control_flow ();
-      something_changed |= thread_jumps ();
       something_changed |= delete_unreachable_blocks ();
+      something_changed |= thread_jumps ();
     }
 
   /* Merging the blocks creates no new opportunities for the other
@@ -3904,7 +3904,7 @@ static bool
 thread_jumps (void)
 {
   edge e, next, last, old;
-  basic_block bb, dest, tmp;
+  basic_block bb, dest, tmp, old_dest, dom;
   tree phi;
   int arg;
   bool retval = false;
@@ -3991,11 +3991,9 @@ thread_jumps (void)
 
 	  /* Perform the redirection.  */
 	  retval = true;
+	  old_dest = e->dest;
 	  e = redirect_edge_and_branch (e, dest);
 
-	  /* TODO -- updating dominators in this case is simple.  */
-	  free_dominance_info (CDI_DOMINATORS);
-
 	  if (!old)
 	    {
 	      /* Update PHI nodes.   We know that the new argument should
@@ -4009,6 +4007,49 @@ thread_jumps (void)
 		  add_phi_arg (&phi, PHI_ARG_DEF (phi, arg), e);
 		}
 	    }
+
+	  /* Update the dominators.  */
+	  if (dom_computed[CDI_DOMINATORS] >= DOM_CONS_OK)
+	    {
+	      /* Remove the unreachable blocks (observe that if all blocks
+		 were reachable before, only those in the path we threaded
+		 over and did not have any predecessor outside of the path
+		 become unreachable).  */
+	      for (; old_dest != dest; old_dest = tmp)
+		{
+		  tmp = old_dest->succ->dest;
+
+		  if (old_dest->pred)
+		    break;
+
+		  delete_basic_block (old_dest);
+		}
+	      /* If the dominator of the destination was in the path, set its
+		 dominator to the start of the redirected edge.  */
+	      if (get_immediate_dominator (CDI_DOMINATORS, old_dest) == NULL)
+		set_immediate_dominator (CDI_DOMINATORS, old_dest, bb);
+
+	      /* Now proceed like if we forwarded just over one edge at a time.
+		 Algorithm for forwarding over edge A --> B then is
+
+		 if (idom (B) == A)
+		   idom (B) = idom (A);
+		 recount_idom (A);  */
+
+	      for (; old_dest != dest; old_dest = tmp)
+		{
+		  tmp = old_dest->succ->dest;
+
+		  if (get_immediate_dominator (CDI_DOMINATORS, tmp) == old_dest)
+		    {
+		      dom = get_immediate_dominator (CDI_DOMINATORS, old_dest);
+  		      set_immediate_dominator (CDI_DOMINATORS, tmp, dom);
+		    }
+
+		  dom = recount_dominator (CDI_DOMINATORS, old_dest);
+		  set_immediate_dominator (CDI_DOMINATORS, old_dest, dom);
+		}
+	    }
 	}
 
       /* Reset the forwardable bit on our block since it's no longer in

gcc/tree-ssa-phiopt.c

@@ -236,6 +236,8 @@ static void
 replace_phi_with_stmt (block_stmt_iterator bsi, basic_block bb,
 		       basic_block cond_block, tree phi, tree new)
 {
+  basic_block block_to_remove;
+
   /* Insert our new statement at the head of our block.  */
   bsi_insert_after (&bsi, new, BSI_NEW_STMT);
   
@@ -250,21 +252,23 @@ replace_phi_with_stmt (block_stmt_iterator bsi, basic_block bb,
   release_phi_node (phi);
   bb_ann (bb)->phi_nodes = NULL;
   
-  /* Disconnect the edge leading into the empty block.  That will
-     make the empty block unreachable and it will be removed later.  */
+  /* Remove the empty basic block.  */
   if (cond_block->succ->dest == bb)
     {
       cond_block->succ->flags |= EDGE_FALLTHRU;
       cond_block->succ->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
-      ssa_remove_edge (cond_block->succ->succ_next);
+
+      block_to_remove = cond_block->succ->succ_next->dest;
     }
   else
     {
       cond_block->succ->succ_next->flags |= EDGE_FALLTHRU;
       cond_block->succ->succ_next->flags
 	&= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
-      ssa_remove_edge (cond_block->succ);
+
+      block_to_remove = cond_block->succ->dest;
     }
+  delete_basic_block (block_to_remove);
   
   /* Eliminate the COND_EXPR at the end of COND_BLOCK.  */
   bsi = bsi_last (cond_block);