haifa-sched.c (recompute_todo_spec): Simplify and correct the code checking for…

haifa-sched.c (recompute_todo_spec): Simplify and correct the code checking for a clobber of a condition register...

	* haifa-sched.c (recompute_todo_spec): Simplify and correct the
	code checking for a clobber of a condition register when deciding
	whether to predicate.

From-SVN: r181806

gcc/ChangeLog

+2011-11-29  Bernd Schmidt  <bernds@codesourcery.com>
+
+	* haifa-sched.c (recompute_todo_spec): Simplify and correct the
+	code checking for a clobber of a condition register when deciding
+	whether to predicate.
+
 2011-11-29   Diego Novillo  <dnovillo@google.com>
 
 	* gimple.c (gimple_call_set_cannot_inline): Move from gimple.h.

gcc/haifa-sched.c

@@ -1178,33 +1178,20 @@ recompute_todo_spec (rtx next)
       regno = REGNO (XEXP (cond, 0));
 
       /* Find the last scheduled insn that modifies the condition register.
-	 If we have a true dependency on it, it sets it to the correct value,
-	 otherwise it must be a later insn scheduled in-between that clobbers
-	 the condition.  */
-      FOR_EACH_VEC_ELT_REVERSE (rtx, scheduled_insns, i, prev)
-	{
-	  sd_iterator_def sd_it;
-	  dep_t dep;
-	  HARD_REG_SET t;
-	  bool found;
-
-	  find_all_hard_reg_sets (prev, &t);
-	  if (!TEST_HARD_REG_BIT (t, regno))
-	    continue;
+	 We can stop looking once we find the insn we depend on through the
+	 REG_DEP_CONTROL; if the condition register isn't modified after it,
+	 we know that it still has the right value.  */
+      if (QUEUE_INDEX (pro) == QUEUE_SCHEDULED)
+	FOR_EACH_VEC_ELT_REVERSE (rtx, scheduled_insns, i, prev)
+	  {
+	    HARD_REG_SET t;
 
-	  found = false;
-	  FOR_EACH_DEP (next, SD_LIST_RES_BACK, sd_it, dep)
-	    {
-	      if (DEP_PRO (dep) == prev && DEP_TYPE (dep) == REG_DEP_TRUE)
-		{
-		  found = true;
-		  break;
-		}
-	    }
-	  if (!found)
-	    return HARD_DEP;
-	  break;
-	}
+	    find_all_hard_reg_sets (prev, &t);
+	    if (TEST_HARD_REG_BIT (t, regno))
+	      return HARD_DEP;
+	    if (prev == pro)
+	      break;
+	  }
       if (ORIG_PAT (next) == NULL_RTX)
 	{
 	  ORIG_PAT (next) = PATTERN (next);