On Tue, Jan 27, 2015 at 12:52 AM, Kaz Kojima wrote:
> This patch is to fix 2 issues found in dbr_schedule when trying to
> fix PR target/64761. The first is relax_delay_slots removes
> the jump insn in the insns like below:
>
> (jump_insn/j 74 58 59 (set (pc) (label_ref:SI 29)) ...)
> (barrier 59 74 105)
> (note 105 59 29 NOTE_INSN_SWITCH_TEXT_SECTIONS)
> (code_label 29 105 30 31 "" [5 uses])
> (insn 31 30 32 (set (reg ...
>
> i.e. relax_delay_slot tries to delete the jump insn pointing to
> the next active insn of that jump insn as a trivial jump even when
> there is a NOTE_INSN_SWITCH_TEXT_SECTIONS note between that jump
> and its next active insn.
> The second issue is that relax_delay_slots does a variant of
> follow jump optimization without checking targetm.can_follow_jump.
>
> --
> PR target/64761
> * reorg.c (switch_text_sections_between_p): New function.
> (relax_delay_slots): Call it when testing if the jump insn
> is removable. Use targetm.can_follow_jump when testing if
> the conditional branch can follow an unconditional jump.
This patch merely papers over another issue, probably a missing
CROSSING_JUMP_P test.
Ciao!
Steven
> diff --git a/reorg.c b/reorg.c
> index 326fa53..2387910 100644
> --- a/reorg.c
> +++ b/reorg.c
> @@ -3211,6 +3211,19 @@ label_before_next_insn (rtx x, rtx scan_limit)
> return insn;
> }
>
> +/* Return TRUE if there is a NOTE_INSN_SWITCH_TEXT_SECTIONS note in between
> + BEG and END. */
> +
> +static bool
> +switch_text_sections_between_p (const rtx_insn *beg, const rtx_insn *end)
> +{
> + const rtx_insn *p;
> + for (p = beg; p != end; p = NEXT_INSN (p))
> + if (NOTE_P (p) && NOTE_KIND (p) == NOTE_INSN_SWITCH_TEXT_SECTIONS)
> + return true;
> + return false;
> +}
> +
>
> /* Once we have tried two ways to fill a delay slot, make a pass over the
> code to try to improve the results and to do such things as more jump
> @@ -3247,7 +3260,8 @@ relax_delay_slots (rtx_insn *first)
> target_label = find_end_label (target_label);
>
> if (target_label && next_active_insn (target_label) == next
> - && ! condjump_in_parallel_p (insn))
> + && ! condjump_in_parallel_p (insn)
> + && ! (next && switch_text_sections_between_p (insn, next)))
> {
> delete_jump (insn);
> continue;
> @@ -3262,12 +3276,13 @@ relax_delay_slots (rtx_insn *first)
>
> /* See if this jump conditionally branches around an unconditional
> jump. If so, invert this jump and point it to the target of the
> - second jump. */
> + second jump. Check if it's possible on the target. */
> if (next && simplejump_or_return_p (next)
> && any_condjump_p (insn)
> && target_label
> && next_active_insn (target_label) == next_active_insn (next)
> - && no_labels_between_p (insn, next))
> + && no_labels_between_p (insn, next)
> + && targetm.can_follow_jump (insn, next))
> {
> rtx label = JUMP_LABEL (next);
>
