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Re: Bug fix for optimize_mode_switching / NORMAL_MODE
Richard Henderson wrote:
> Well, hmm. This is pre-reload, thus return insns can't exist yet.
> Therefore there are only two ways to have an edge to the exit block:
> the last block fallthru and sibcalls. But sibcalls are calls, and
> so we must return to normal mode before the call, so there is only
> one exit predecessor to concern ourselves with -- the fallthru block.
>
> At which point the problem seems much reduced, since we can simply
> split that one edge.
>
> > At the end, you'd have to remove the edge between exit block and fake block,
> > redirect the fake block predecessors back to the exit block, and deallocate.
>
> Actually, you wouldn't have to do anything of the sort. One, it would
> seem that it's possible that code might have been dropped into the block
> to return to normal mode. Two, if the block is really empty, then a
> subsequent call to cleanup_cfg should remove the block.
I have attached a patch that fixes the discussed problems by useing split_edge
to split the edge from the entry block and the fallthrough edge to the exit
block.
--
--------------------------
SuperH
2430 Aztec West / Almondsbury / BRISTOL / BS32 4AQ
T:+44 1454 462330
Thu May 30 11:58:48 2002 J"orn Rennecke <joern.rennecke@superh.com>
* lcm.c (output.h): #include.
(compute_earliest): Remove hack to treat renumbered EXIT_BLOCK
as an ordinary block.
(optimize_mode_switching): Don't pretend that the exit block is
an ordinary block, or handle sucessors of entry block specially.
Instead, split edges from entry block and to exit block, and
put a computing definition on the thus gained post-entry-block,
and a need on the pre-exit-block.
Index: lcm.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/lcm.c,v
retrieving revision 1.46
diff -p -u -r1.46 lcm.c
--- lcm.c 28 May 2002 12:53:44 -0000 1.46
+++ lcm.c 29 May 2002 23:27:45 -0000
@@ -59,6 +59,7 @@ Software Foundation, 59 Temple Place - S
#include "insn-config.h"
#include "recog.h"
#include "basic-block.h"
+#include "output.h"
#include "tm_p.h"
/* We want target macros for the mode switching code to be able to refer
@@ -207,11 +208,7 @@ compute_earliest (edge_list, n_exprs, an
sbitmap_copy (earliest[x], antin[succ->index]);
else
{
- /* We refer to the EXIT_BLOCK index, instead of testing for
- EXIT_BLOCK_PTR, so that EXIT_BLOCK_PTR's index can be
- changed so as to pretend it's a regular block, so that
- its antin can be taken into account. */
- if (succ->index == EXIT_BLOCK)
+ if (succ == EXIT_BLOCK_PTR)
sbitmap_zero (earliest[x]);
else
{
@@ -1027,43 +1024,54 @@ optimize_mode_switching (file)
int n_entities;
int max_num_modes = 0;
bool emited = false;
+ basic_block post_entry, pre_exit ATTRIBUTE_UNUSED;
clear_bb_flags ();
-#ifdef NORMAL_MODE
- /* Increment last_basic_block before allocating bb_info. */
- last_basic_block++;
-#endif
for (e = N_ENTITIES - 1, n_entities = 0; e >= 0; e--)
if (OPTIMIZE_MODE_SWITCHING (e))
{
- /* Create the list of segments within each basic block. */
+ int entry_exit_extra = 0;
+
+ /* Create the list of segments within each basic block.
+ If NORMAL_MODE is defined, allow for two extra
+ blocks split from the entry and exit block. */
+#ifdef NORMAL_MODE
+ entry_exit_extra = 2;
+#endif
bb_info[n_entities]
- = (struct bb_info *) xcalloc (last_basic_block, sizeof **bb_info);
+ = (struct bb_info *) xcalloc (last_basic_block + entry_exit_extra,
+ sizeof **bb_info);
entity_map[n_entities++] = e;
if (num_modes[e] > max_num_modes)
max_num_modes = num_modes[e];
}
-#ifdef NORMAL_MODE
- /* Decrement it back in case we return below. */
- last_basic_block--;
-#endif
-
if (! n_entities)
return 0;
#ifdef NORMAL_MODE
- /* We're going to pretend the EXIT_BLOCK is a regular basic block,
- so that switching back to normal mode when entering the
- EXIT_BLOCK isn't optimized away. We do this by incrementing the
- basic block count, growing the VARRAY of basic_block_info and
- appending the EXIT_BLOCK_PTR to it. */
- last_basic_block++;
- if (VARRAY_SIZE (basic_block_info) < last_basic_block)
- VARRAY_GROW (basic_block_info, last_basic_block);
- BASIC_BLOCK (last_basic_block - 1) = EXIT_BLOCK_PTR;
- EXIT_BLOCK_PTR->index = last_basic_block - 1;
+ {
+ /* Split the edge from the entry block and the fallthrough edge to the
+ exit block, so that we can note that there NORMAL_MODE is supplied /
+ required. */
+ edge eg;
+ post_entry = split_edge (ENTRY_BLOCK_PTR->succ);
+ /* The only non-call predecessor at this stage is a block with a
+ fallthrough edge; there can be at most one, but there could be
+ none at all, e.g. when exit is called. */
+ for (pre_exit = 0, eg = EXIT_BLOCK_PTR->pred; eg; eg = eg->pred_next)
+ if (eg->flags & EDGE_FALLTHRU)
+ {
+ regset live_at_end = eg->src->global_live_at_end;
+
+ if (pre_exit)
+ abort ();
+ pre_exit = split_edge (eg);
+ COPY_REG_SET (pre_exit->global_live_at_start, live_at_end);
+ COPY_REG_SET (pre_exit->global_live_at_end, live_at_end);
+ }
+ }
#endif
/* Create the bitmap vectors. */
@@ -1124,7 +1132,7 @@ optimize_mode_switching (file)
/* Check for blocks without ANY mode requirements. */
if (last_mode == no_mode)
{
- ptr = new_seginfo (no_mode, insn, bb->index, live_now);
+ ptr = new_seginfo (no_mode, bb->end, bb->index, live_now);
add_seginfo (info + bb->index, ptr);
}
}
@@ -1134,36 +1142,21 @@ optimize_mode_switching (file)
if (mode != no_mode)
{
- edge eg;
-
- for (eg = ENTRY_BLOCK_PTR->succ; eg; eg = eg->succ_next)
- {
- bb = eg->dest;
+ bb = post_entry;
- /* By always making this nontransparent, we save
- an extra check in make_preds_opaque. We also
- need this to avoid confusing pre_edge_lcm when
- antic is cleared but transp and comp are set. */
- RESET_BIT (transp[bb->index], j);
-
- /* If the block already has MODE, pretend it
- has none (because we don't need to set it),
- but retain whatever mode it computes. */
- if (info[bb->index].seginfo->mode == mode)
- info[bb->index].seginfo->mode = no_mode;
-
- /* Insert a fake computing definition of MODE into entry
- blocks which compute no mode. This represents the mode on
- entry. */
- else if (info[bb->index].computing == no_mode)
- {
- info[bb->index].computing = mode;
- info[bb->index].seginfo->mode = no_mode;
- }
- }
+ /* By always making this nontransparent, we save
+ an extra check in make_preds_opaque. We also
+ need this to avoid confusing pre_edge_lcm when
+ antic is cleared but transp and comp are set. */
+ RESET_BIT (transp[bb->index], j);
+
+ /* Insert a fake computing definition of MODE into entry
+ blocks which compute no mode. This represents the mode on
+ entry. */
+ info[bb->index].computing = mode;
- bb = EXIT_BLOCK_PTR;
- info[bb->index].seginfo->mode = mode;
+ if (pre_exit)
+ info[pre_exit->index].seginfo->mode = mode;
}
}
#endif /* NORMAL_MODE */
@@ -1288,63 +1281,11 @@ optimize_mode_switching (file)
free_edge_list (edge_list);
}
-#ifdef NORMAL_MODE
- /* Restore the special status of EXIT_BLOCK. */
- last_basic_block--;
- VARRAY_POP (basic_block_info);
- EXIT_BLOCK_PTR->index = EXIT_BLOCK;
-#endif
-
/* Now output the remaining mode sets in all the segments. */
for (j = n_entities - 1; j >= 0; j--)
{
int no_mode = num_modes[entity_map[j]];
-#ifdef NORMAL_MODE
- if (bb_info[j][last_basic_block].seginfo->mode != no_mode)
- {
- edge eg;
- struct seginfo *ptr = bb_info[j][last_basic_block].seginfo;
-
- for (eg = EXIT_BLOCK_PTR->pred; eg; eg = eg->pred_next)
- {
- rtx mode_set;
-
- if (bb_info[j][eg->src->index].computing == ptr->mode)
- continue;
-
- start_sequence ();
- EMIT_MODE_SET (entity_map[j], ptr->mode, ptr->regs_live);
- mode_set = gen_sequence ();
- end_sequence ();
-
- /* Do not bother to insert empty sequence. */
- if (GET_CODE (mode_set) == SEQUENCE
- && !XVECLEN (mode_set, 0))
- continue;
-
- /* If this is an abnormal edge, we'll insert at the end of the
- previous block. */
- if (eg->flags & EDGE_ABNORMAL)
- {
- emited = true;
- if (GET_CODE (eg->src->end) == JUMP_INSN)
- emit_insn_before (mode_set, eg->src->end);
- else if (GET_CODE (eg->src->end) == INSN)
- emit_insn_after (mode_set, eg->src->end);
- else
- abort ();
- }
- else
- {
- need_commit = 1;
- insert_insn_on_edge (mode_set, eg);
- }
- }
-
- }
-#endif
-
FOR_EACH_BB_REVERSE (bb)
{
struct seginfo *ptr, *next;
@@ -1393,8 +1334,12 @@ optimize_mode_switching (file)
if (need_commit)
commit_edge_insertions ();
+#ifdef NORMAL_MODE
+ cleanup_cfg (CLEANUP_NO_INSN_DEL);
+#else
if (!need_commit && !emited)
return 0;
+#endif
max_regno = max_reg_num ();
allocate_reg_info (max_regno, FALSE, FALSE);