gcse.c (bypass_block, [...]): Do not create irreducible loops.

	* gcse.c (bypass_block, bypass_conditional_jumps): Do not create
	irreducible loops.

	* loop-unroll.c (unroll_loop_runtime_iterations): Update irreducible
	loops info correctly.

From-SVN: r63980

gcc/ChangeLog

+2003-03-08  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
+
+	* gcse.c (bypass_block, bypass_conditional_jumps): Do not create
+	irreducible loops.
+
+	* loop-unroll.c (unroll_loop_runtime_iterations): Update irreducible
+	loops info correctly.
+
 2003-03-08  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	PR middle-end/7796

gcc/gcse.c

@@ -4759,6 +4759,7 @@ bypass_block (bb, setcc, jump)
   rtx insn, note;
   edge e, enext;
   int i, change;
+  int may_be_loop_header;
 
   insn = (setcc != NULL) ? setcc : jump;
 
@@ -4769,6 +4770,14 @@ bypass_block (bb, setcc, jump)
   if (note)
     find_used_regs (&XEXP (note, 0), NULL);
 
+  may_be_loop_header = false;
+  for (e = bb->pred; e; e = e->pred_next)
+    if (e->flags & EDGE_DFS_BACK)
+      {
+	may_be_loop_header = true;
+	break;
+      }
+
   change = 0;
   for (e = bb->pred; e; e = enext)
     {
@@ -4780,6 +4789,13 @@ bypass_block (bb, setcc, jump)
       if (e->src->index >= bypass_last_basic_block)
 	continue;
 
+      /* The irreducible loops created by redirecting of edges entering the
+	 loop from outside would decrease effectivity of some of the following
+	 optimalizations, so prevent this.  */
+      if (may_be_loop_header
+	  && !(e->flags & EDGE_DFS_BACK))
+	continue;
+
       for (i = 0; i < reg_use_count; i++)
 	{
 	  struct reg_use *reg_used = &reg_use_table[i];
@@ -4866,6 +4882,7 @@ bypass_conditional_jumps ()
     return 0;
 
   bypass_last_basic_block = last_basic_block;
+  mark_dfs_back_edges ();
 
   changed = 0;
   FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb,

gcc/loop-unroll.c

@@ -895,7 +895,8 @@ unroll_loop_runtime_iterations (loops, loop)
 	  swtch = loop_split_edge_with (swtch->pred, branch_code, loops);
 	  set_immediate_dominator (loops->cfg.dom, preheader, swtch);
 	  swtch->succ->probability = REG_BR_PROB_BASE - p;
-	  e = make_edge (swtch, preheader, 0);
+	  e = make_edge (swtch, preheader,
+			 swtch->succ->flags & EDGE_IRREDUCIBLE_LOOP);
 	  e->probability = p;
 	}
     }
@@ -925,7 +926,8 @@ unroll_loop_runtime_iterations (loops, loop)
       swtch = loop_split_edge_with (swtch->succ, branch_code, loops);
       set_immediate_dominator (loops->cfg.dom, preheader, swtch);
       swtch->succ->probability = REG_BR_PROB_BASE - p;
-      e = make_edge (swtch, preheader, 0);
+      e = make_edge (swtch, preheader,
+		     swtch->succ->flags & EDGE_IRREDUCIBLE_LOOP);
       e->probability = p;
     }