On Tue, Oct 30, 2012 at 6:20 AM, Teresa Johnson wrote:
> Index: bb-reorder.c
> ===================================================================
> --- bb-reorder.c (revision 192692)
> +++ bb-reorder.c (working copy)
> @@ -2188,6 +2188,8 @@ insert_section_boundary_note (void)
> first_partition = BB_PARTITION (bb);
> if (BB_PARTITION (bb) != first_partition)
> {
> + /* There should be a barrier between text sections. */
> + emit_barrier_after (BB_END (bb->prev_bb));
So why isn't there one? There can't be a fall-through edge from one
section to the other, so cfgrtl.c:fixup_reorder_chain should have
added a barrier here already in the code under the comment:
/* Now add jumps and labels as needed to match the blocks new
outgoing edges. */
Why isn't it doing that for you?
BTW, something else I noted in cfgrtl.c:
NOTE_INSN_SWITCH_TEXT_SECTIONS shouldn't be copied in
duplicate_insn_chain, so the following is necessary for robustness:
Index: cfgrtl.c
===================================================================
--- cfgrtl.c (revision 191819)
+++ cfgrtl.c (working copy)
@@ -3615,7 +3615,6 @@
break;
case NOTE_INSN_EPILOGUE_BEG:
- case NOTE_INSN_SWITCH_TEXT_SECTIONS:
emit_note_copy (insn);
break;
There can be only one! One note to rule them all! etc.
> Index: cfgrtl.c
> ===================================================================
> --- cfgrtl.c (revision 192692)
> +++ cfgrtl.c (working copy)
> @@ -912,7 +912,8 @@ rtl_can_merge_blocks (basic_block a, basic_block b
> partition boundaries). See the comments at the top of
> bb-reorder.c:partition_hot_cold_basic_blocks for complete details. */
>
> - if (BB_PARTITION (a) != BB_PARTITION (b))
> + if (find_reg_note (BB_END (a), REG_CROSSING_JUMP, NULL_RTX)
> + || BB_PARTITION (a) != BB_PARTITION (b))
> return false;
My dislike for this whole scheme just continues to grow... How can
there be a REG_CROSSING_JUMP note if BB_PARTITION(a)==BB_PARTITION(b)?
That is a bug. We should not need the notes here.
As long as we have the CFG, BB_PARTITION(a)==BB_PARTITION(b) should be
the canonical way to check whether two blocks are in the same
partition, and the EDGE_CROSSING flag should be set iff an edge
crosses from one section to another. The REG_CROSSING_JUMP note should
only be used to see if a JUMP_INSN may jump to another section,
without having to check all successor edges.
Any place where we have to check the BB_PARTITION or
edge->flags&EDGE_CROSSING *and* REG_CROSSING_JUMP indicates a bug in
the partitioning updating.
Another BTW: sched-vis.c doesn't handle REG_CROSSING_JUMP notes so
that slim RTL dumping breaks. I need this patchlet to make things
work:
Index: sched-vis.c
===================================================================
--- sched-vis.c (revision 191819)
+++ sched-vis.c (working copy)
@@ -553,6 +553,11 @@
{
char t1[BUF_LEN], t2[BUF_LEN], t3[BUF_LEN];
+ if (! x)
+ {
+ sprintf (buf, "(nil)");
+ return;
+ }
switch (GET_CODE (x))
{
case SET:
Ciao!
Steven
