Re: RFA: Fix PR rtl-optimization/38449 (patch updated)

[Eric Botcazou <ebotcazou at adacore dot com>]

> Bootstrapped in revision 191429 on i686-pc-linux-gnu.

Bootstrap on x86 for a reorg.c patch doesn't say much though. :-)

> The arc.c context can be seen here:
> 
> http://gcc.gnu.org/viewcvs/branches/arc-4_4-20090909-branch/gcc/config/arc/a
> rc.c?content-type=text%2Fplain&view=co

OK, modulo the following changes:

-/* 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 *cp to (one of) the note(s), otherwise set it to NULL_RTX.  */
 
 static rtx
-follow_jumps (rtx label)
+follow_jumps (rtx label, rtx jump, rtx *cp)

You're using `cp' as a boolean named `crossing' throughout, so change 
follow_jumps accordingly:

   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, rtx jump, bool *crossing)



@@ -1350,6 +1350,16 @@ HOOK_VECTOR_END (vectorize)
  bool, (void),
  hook_bool_void_false)
 
+/* True if FOLLOWER may be modified to follow FOLLOWEE.  */
+DEFHOOK
+(can_follow_jump,
+ "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)

Explicitly mention that both FOLLOWER and FOLLOWEE are JUMP_INSN instructions.

-- 
Eric Botcazou