Hi,
I was a little surprised to find out that dbr can silently drop the alignment
information for labels computed when the CFG is valid (in compute_alignments).
The pessimization can be significant for loops when the top label needs to be
overaligned, as seen on a private port. Hence the attached patch.
Tested on SPARC/Solaris and SPARC64/Solaris, any objections?
2013-07-10 Eric Botcazou <ebotca...@adacore.com>
* rtl.h (update_alignments): Declare.
* final.c (grow_label_align): New function extracted from...
(shorten_branches): ...here. Call it.
(update_alignments): New function.
* reorg.c (sibling_labels): New variable.
(get_label_before): Add SIBLING parameter. If it is non-zero, push
the new label along with it onto the sibling_labels vector.
(fill_simple_delay_slots): Adjust call to get_label_before.
(fill_slots_from_thread): Likewise.
(relax_delay_slots): Likewise.
(make_return_insns): Likewise.
(dbr_schedule): Invoke update_alignment on the sibling_labels vector.
--
Eric BotcazouIndex: rtl.h
===================================================================
--- rtl.h (revision 200780)
+++ rtl.h (working copy)
@@ -2749,6 +2749,7 @@ extern void simplify_using_condition (rt
/* In final.c */
extern unsigned int compute_alignments (void);
+extern void update_alignments (vec<rtx> &);
extern int asm_str_count (const char *templ);
struct rtl_hooks
Index: final.c
===================================================================
--- final.c (revision 200780)
+++ final.c (working copy)
@@ -814,7 +814,53 @@ struct rtl_opt_pass pass_compute_alignme
TODO_verify_rtl_sharing /* todo_flags_finish */
}
};
+
+/* Grow the LABEL_ALIGN array after new labels are created. */
+
+static void
+grow_label_align (void)
+{
+ int old = max_labelno;
+ int n_labels;
+ int n_old_labels;
+
+ max_labelno = max_label_num ();
+
+ n_labels = max_labelno - min_labelno + 1;
+ n_old_labels = old - min_labelno + 1;
+ label_align = XRESIZEVEC (struct label_alignment, label_align, n_labels);
+
+ /* Range of labels grows monotonically in the function. Failing here
+ means that the initialization of array got lost. */
+ gcc_assert (n_old_labels <= n_labels);
+
+ memset (label_align + n_old_labels, 0,
+ (n_labels - n_old_labels) * sizeof (struct label_alignment));
+}
+
+/* Update the already computed alignment information. LABEL_PAIRS is a vector
+ made up of pairs of labels for which the alignment information of the first
+ element will be copied from that of the second element. */
+
+void
+update_alignments (vec<rtx> &label_pairs)
+{
+ unsigned int i = 0;
+ rtx iter, label;
+
+ if (max_labelno != max_label_num ())
+ grow_label_align ();
+
+ FOR_EACH_VEC_ELT (label_pairs, i, iter)
+ if (i & 1)
+ {
+ LABEL_TO_ALIGNMENT (label) = LABEL_TO_ALIGNMENT (iter);
+ LABEL_TO_MAX_SKIP (label) = LABEL_TO_MAX_SKIP (iter);
+ }
+ else
+ label = iter;
+}
/* Make a pass over all insns and compute their actual lengths by shortening
any branches of variable length if possible. */
@@ -852,25 +898,7 @@ shorten_branches (rtx first)
uid_shuid = XNEWVEC (int, max_uid);
if (max_labelno != max_label_num ())
- {
- int old = max_labelno;
- int n_labels;
- int n_old_labels;
-
- max_labelno = max_label_num ();
-
- n_labels = max_labelno - min_labelno + 1;
- n_old_labels = old - min_labelno + 1;
-
- label_align = XRESIZEVEC (struct label_alignment, label_align, n_labels);
-
- /* Range of labels grows monotonically in the function. Failing here
- means that the initialization of array got lost. */
- gcc_assert (n_old_labels <= n_labels);
-
- memset (label_align + n_old_labels, 0,
- (n_labels - n_old_labels) * sizeof (struct label_alignment));
- }
+ grow_label_align ();
/* Initialize label_align and set up uid_shuid to be strictly
monotonically rising with insn order. */
Index: reorg.c
===================================================================
--- reorg.c (revision 200780)
+++ reorg.c (working copy)
@@ -1856,10 +1856,15 @@ update_reg_unused_notes (rtx insn, rtx r
}
}
-/* Return the label before INSN, or put a new label there. */
+static vec <rtx> sibling_labels;
+
+/* Return the label before INSN, or put a new label there. If SIBLING is
+ non-zero, it is another label associated with the new label (if any),
+ typically the former target of the jump that will be redirected to
+ the new label. */
static rtx
-get_label_before (rtx insn)
+get_label_before (rtx insn, rtx sibling)
{
rtx label;
@@ -1874,6 +1879,11 @@ get_label_before (rtx insn)
label = gen_label_rtx ();
emit_label_after (label, prev);
LABEL_NUSES (label) = 0;
+ if (sibling)
+ {
+ sibling_labels.safe_push (label);
+ sibling_labels.safe_push (sibling);
+ }
}
return label;
}
@@ -2219,7 +2229,7 @@ fill_simple_delay_slots (int non_jumps_p
rtx new_label = next_real_insn (next_trial);
if (new_label != 0)
- new_label = get_label_before (new_label);
+ new_label = get_label_before (new_label, JUMP_LABEL (trial));
else
new_label = find_end_label (simple_return_rtx);
@@ -2770,7 +2780,7 @@ fill_slots_from_thread (rtx insn, rtx co
else if (LABEL_P (new_thread))
label = new_thread;
else
- label = get_label_before (new_thread);
+ label = get_label_before (new_thread, JUMP_LABEL (insn));
if (label)
{
@@ -3321,7 +3331,7 @@ relax_delay_slots (rtx first)
/* Now emit a label before the special USE insn, and
redirect our jump to the new label. */
- target_label = get_label_before (PREV_INSN (tmp));
+ target_label = get_label_before (PREV_INSN (tmp), target_label);
reorg_redirect_jump (delay_insn, target_label);
next = insn;
continue;
@@ -3495,7 +3505,7 @@ make_return_insns (rtx first)
for (insn = first; insn; insn = NEXT_INSN (insn))
if (JUMP_P (insn) && ANY_RETURN_P (PATTERN (insn)))
{
- rtx t = get_label_before (insn);
+ rtx t = get_label_before (insn, NULL_RTX);
if (PATTERN (insn) == ret_rtx)
real_return_label = t;
else
@@ -3825,6 +3835,12 @@ dbr_schedule (rtx first)
fprintf (dump_file, "\n");
}
+ if (!sibling_labels.is_empty ())
+ {
+ update_alignments (sibling_labels);
+ sibling_labels.release ();
+ }
+
free_resource_info ();
free (uid_to_ruid);
crtl->dbr_scheduled_p = true;
