re PR rtl-optimization/38449 (delay branch scheduling follows REG_CROSSING_JUMP…

re PR rtl-optimization/38449 (delay branch scheduling follows REG_CROSSING_JUMP jumps indiscriminately)

        PR rtl-optimization/38449:
        * hooks.c (hook_bool_const_rtx_const_rtx_true): New function.
        * hooks.h (hook_bool_const_rtx_const_rtx_true): Declare.
        * target.def: Merge in definitions and documentation for
        TARGET_CAN_FOLLOW_JUMP.
        * doc/tm.texi.in: Add documentation locations for the above.
        * doc/tm.texi: Regenerate.
        * reorg.c (follow_jumps): New parameters jump and crossing.
        Changed all callers.

From-SVN: r191878

gcc/ChangeLog

+2012-09-30  Joern Rennecke  <joern.rennecke@embecosm.com>
+
+	PR rtl-optimization/38449:
+	* hooks.c (hook_bool_const_rtx_const_rtx_true): New function.
+	* hooks.h (hook_bool_const_rtx_const_rtx_true): Declare.
+	* target.def: Merge in definitions and documentation for
+	TARGET_CAN_FOLLOW_JUMP.
+	* doc/tm.texi.in: Add documentation locations for the above.
+	* doc/tm.texi: Regenerate.
+	* reorg.c (follow_jumps): New parameters jump and crossing.
+	Changed all callers.
+
 2012-09-30  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* reorg.c (relax_delay_slots): Use delay_insn consistently.

gcc/doc/tm.texi

@@ -10958,6 +10958,10 @@ filling of delay slots can result in branches being redirected, and this
 may in turn cause a branch offset to overflow.
 @end defmac
 
+@deftypefn {Target Hook} bool TARGET_CAN_FOLLOW_JUMP (const_rtx @var{follower}, const_rtx @var{followee})
+FOLLOWER and FOLLOWEE are JUMP_INSN instructions;  return true if FOLLOWER may be modified to follow FOLLOWEE;  false, if it can't.  For example, on some targets, certain kinds of branches can't be made to  follow through a hot/cold partitioning.
+@end deftypefn
+
 @deftypefn {Target Hook} bool TARGET_COMMUTATIVE_P (const_rtx @var{x}, int @var{outer_code})
 This target hook returns @code{true} if @var{x} is considered to be commutative.
 Usually, this is just COMMUTATIVE_P (@var{x}), but the HP PA doesn't consider

gcc/doc/tm.texi.in

@@ -10814,6 +10814,8 @@ filling of delay slots can result in branches being redirected, and this
 may in turn cause a branch offset to overflow.
 @end defmac
 
+@hook TARGET_CAN_FOLLOW_JUMP
+
 @hook TARGET_COMMUTATIVE_P
 This target hook returns @code{true} if @var{x} is considered to be commutative.
 Usually, this is just COMMUTATIVE_P (@var{x}), but the HP PA doesn't consider

gcc/hooks.c

@@ -117,6 +117,14 @@ hook_bool_mode_rtx_true (enum machine_mode mode ATTRIBUTE_UNUSED,
   return true;
 }
 
+/* Generic hook that takes (rtx, rtx) and returns true.  */
+bool
+hook_bool_const_rtx_const_rtx_true (const_rtx follower ATTRIBUTE_UNUSED,
+				    const_rtx followee ATTRIBUTE_UNUSED)
+{
+  return true;
+}
+
 /* Generic hook that takes (enum machine_mode, unsigned HOST_WIDE_INT)
    and returns false.  */
 bool

gcc/hooks.h

@@ -36,6 +36,7 @@ extern bool hook_bool_mode_const_rtx_false (enum machine_mode, const_rtx);
 extern bool hook_bool_mode_const_rtx_true (enum machine_mode, const_rtx);
 extern bool hook_bool_mode_rtx_false (enum machine_mode, rtx);
 extern bool hook_bool_mode_rtx_true (enum machine_mode, rtx);
+extern bool hook_bool_const_rtx_const_rtx_true (const_rtx, const_rtx);
 extern bool hook_bool_mode_uhwi_false (enum machine_mode,
 				       unsigned HOST_WIDE_INT);
 extern bool hook_bool_tree_false (tree);

gcc/reorg.c

@@ -2494,22 +2494,25 @@ fill_simple_delay_slots (int non_jumps_p)
 #endif
 }
 
-/* Follow any unconditional jump at LABEL;
+/* Follow any unconditional jump at LABEL, for the purpose of redirecting JUMP;
    return the ultimate label reached by any such chain of jumps.
    Return a suitable return rtx if the chain ultimately leads to a
    return instruction.
    If LABEL is not followed by a jump, return LABEL.
    If the chain loops or we can't find end, return LABEL,
-   since that tells caller to avoid changing the insn.  */
+   since that tells caller to avoid changing the insn.
+   If the returned label is obtained by following a REG_CROSSING_JUMP
+   jump, set *CROSSING to true, otherwise set it to false.  */
 
 static rtx
-follow_jumps (rtx label)
+follow_jumps (rtx label, rtx jump, bool *crossing)
 {
   rtx insn;
   rtx next;
   rtx value = label;
   int depth;
 
+  *crossing = false;
   if (ANY_RETURN_P (label))
     return label;
   for (depth = 0;
@@ -2537,6 +2540,11 @@ follow_jumps (rtx label)
 	      || GET_CODE (PATTERN (tem)) == ADDR_DIFF_VEC))
 	break;
 
+      if (!targetm.can_follow_jump (jump, insn))
+	break;
+      if (!*crossing)
+	*crossing
+	  = find_reg_note (insn, REG_CROSSING_JUMP, NULL_RTX) != NULL_RTX;
       value = this_label;
     }
   if (depth == 10)
@@ -2984,6 +2992,7 @@ fill_slots_from_thread (rtx insn, rtx condition, rtx thread,
   if (new_thread != thread)
     {
       rtx label;
+      bool crossing = false;
 
       gcc_assert (thread_if_true);
 
@@ -2991,7 +3000,7 @@ fill_slots_from_thread (rtx insn, rtx condition, rtx thread,
 	  && redirect_with_delay_list_safe_p (insn,
 					      JUMP_LABEL (new_thread),
 					      delay_list))
-	new_thread = follow_jumps (JUMP_LABEL (new_thread));
+	new_thread = follow_jumps (JUMP_LABEL (new_thread), insn, &crossing);
 
       if (ANY_RETURN_P (new_thread))
 	label = find_end_label (new_thread);
@@ -3001,7 +3010,11 @@ fill_slots_from_thread (rtx insn, rtx condition, rtx thread,
 	label = get_label_before (new_thread);
 
       if (label)
-	reorg_redirect_jump (insn, label);
+	{
+	  reorg_redirect_jump (insn, label);
+	  if (crossing)
+	    set_unique_reg_note (insn, REG_CROSSING_JUMP, NULL_RTX);
+	}
     }
 
   return delay_list;
@@ -3347,6 +3360,7 @@ relax_delay_slots (rtx first)
   for (insn = first; insn; insn = next)
     {
       rtx other;
+      bool crossing;
 
       next = next_active_insn (insn);
 
@@ -3357,7 +3371,9 @@ relax_delay_slots (rtx first)
 	  && (condjump_p (insn) || condjump_in_parallel_p (insn))
 	  && !ANY_RETURN_P (target_label = JUMP_LABEL (insn)))
 	{
-	  target_label = skip_consecutive_labels (follow_jumps (target_label));
+	  target_label
+	    = skip_consecutive_labels (follow_jumps (target_label, insn,
+						     &crossing));
 	  if (ANY_RETURN_P (target_label))
 	    target_label = find_end_label (target_label);
 
@@ -3369,7 +3385,11 @@ relax_delay_slots (rtx first)
 	    }
 
 	  if (target_label && target_label != JUMP_LABEL (insn))
-	    reorg_redirect_jump (insn, target_label);
+	    {
+	      reorg_redirect_jump (insn, target_label);
+	      if (crossing)
+		set_unique_reg_note (insn, REG_CROSSING_JUMP, NULL_RTX);
+	    }
 
 	  /* See if this jump conditionally branches around an unconditional
 	     jump.  If so, invert this jump and point it to the target of the
@@ -3503,7 +3523,8 @@ relax_delay_slots (rtx first)
 
       /* If this jump goes to another unconditional jump, thread it, but
 	 don't convert a jump into a RETURN here.  */
-      trial = skip_consecutive_labels (follow_jumps (target_label));
+      trial = skip_consecutive_labels (follow_jumps (target_label, delay_insn,
+						     &crossing));
       if (ANY_RETURN_P (trial))
 	trial = find_end_label (trial);
 
@@ -3512,6 +3533,8 @@ relax_delay_slots (rtx first)
 	{
 	  reorg_redirect_jump (delay_insn, trial);
 	  target_label = trial;
+	  if (crossing)
+	    set_unique_reg_note (insn, REG_CROSSING_JUMP, NULL_RTX);
 	}
 
       /* If the first insn at TARGET_LABEL is redundant with a previous

gcc/target.def

@@ -1350,6 +1350,17 @@ DEFHOOK
  bool, (void),
  hook_bool_void_false)
 
+/* True if FOLLOWER may be modified to follow FOLLOWEE.  */
+DEFHOOK
+(can_follow_jump,
+ "FOLLOWER and FOLLOWEE are JUMP_INSN instructions;\
+  return true if FOLLOWER may be modified to follow FOLLOWEE;\
+  false, if it can't.\
+  For example, on some targets, certain kinds of branches can't be made to\
+  follow through a hot/cold partitioning.",
+ bool, (const_rtx follower, const_rtx followee),
+ hook_bool_const_rtx_const_rtx_true)
+
 /* Return a register class for which branch target register
    optimizations should be applied.  */
 DEFHOOK