mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-29 12:03:03 +00:00
383 lines
10 KiB
C
383 lines
10 KiB
C
/* The tracer pass for the GNU compiler.
|
|
Contributed by Jan Hubicka, SuSE Labs.
|
|
Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
|
|
|
|
This file is part of GCC.
|
|
|
|
GCC is free software; you can redistribute it and/or modify it
|
|
under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GCC is distributed in the hope that it will be useful, but WITHOUT
|
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
|
|
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
|
|
License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GCC; see the file COPYING. If not, write to the Free
|
|
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
|
|
02111-1307, USA. */
|
|
|
|
/* This pass performs the tail duplication needed for superblock formation.
|
|
For more information see:
|
|
|
|
Design and Analysis of Profile-Based Optimization in Compaq's
|
|
Compilation Tools for Alpha; Journal of Instruction-Level
|
|
Parallelism 3 (2000) 1-25
|
|
|
|
Unlike Compaq's implementation we don't do the loop peeling as most
|
|
probably a better job can be done by a special pass and we don't
|
|
need to worry too much about the code size implications as the tail
|
|
duplicates are crossjumped again if optimizations are not
|
|
performed. */
|
|
|
|
|
|
#include "config.h"
|
|
#include "system.h"
|
|
#include "coretypes.h"
|
|
#include "tm.h"
|
|
#include "tree.h"
|
|
#include "rtl.h"
|
|
#include "hard-reg-set.h"
|
|
#include "basic-block.h"
|
|
#include "output.h"
|
|
#include "cfglayout.h"
|
|
#include "fibheap.h"
|
|
#include "flags.h"
|
|
#include "timevar.h"
|
|
#include "params.h"
|
|
#include "coverage.h"
|
|
|
|
static int count_insns (basic_block);
|
|
static bool ignore_bb_p (basic_block);
|
|
static bool better_p (edge, edge);
|
|
static edge find_best_successor (basic_block);
|
|
static edge find_best_predecessor (basic_block);
|
|
static int find_trace (basic_block, basic_block *);
|
|
static void tail_duplicate (void);
|
|
static void layout_superblocks (void);
|
|
|
|
/* Minimal outgoing edge probability considered for superblock formation. */
|
|
static int probability_cutoff;
|
|
static int branch_ratio_cutoff;
|
|
|
|
/* Return true if BB has been seen - it is connected to some trace
|
|
already. */
|
|
|
|
#define seen(bb) (bb->rbi->visited || bb->rbi->next)
|
|
|
|
/* Return true if we should ignore the basic block for purposes of tracing. */
|
|
static bool
|
|
ignore_bb_p (basic_block bb)
|
|
{
|
|
if (bb->index < 0)
|
|
return true;
|
|
if (!maybe_hot_bb_p (bb))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/* Return number of instructions in the block. */
|
|
|
|
static int
|
|
count_insns (basic_block bb)
|
|
{
|
|
rtx insn;
|
|
int n = 0;
|
|
|
|
for (insn = BB_HEAD (bb);
|
|
insn != NEXT_INSN (BB_END (bb));
|
|
insn = NEXT_INSN (insn))
|
|
if (active_insn_p (insn))
|
|
n++;
|
|
return n;
|
|
}
|
|
|
|
/* Return true if E1 is more frequent than E2. */
|
|
static bool
|
|
better_p (edge e1, edge e2)
|
|
{
|
|
if (e1->count != e2->count)
|
|
return e1->count > e2->count;
|
|
if (e1->src->frequency * e1->probability !=
|
|
e2->src->frequency * e2->probability)
|
|
return (e1->src->frequency * e1->probability
|
|
> e2->src->frequency * e2->probability);
|
|
/* This is needed to avoid changes in the decision after
|
|
CFG is modified. */
|
|
if (e1->src != e2->src)
|
|
return e1->src->index > e2->src->index;
|
|
return e1->dest->index > e2->dest->index;
|
|
}
|
|
|
|
/* Return most frequent successor of basic block BB. */
|
|
|
|
static edge
|
|
find_best_successor (basic_block bb)
|
|
{
|
|
edge e;
|
|
edge best = NULL;
|
|
|
|
for (e = bb->succ; e; e = e->succ_next)
|
|
if (!best || better_p (e, best))
|
|
best = e;
|
|
if (!best || ignore_bb_p (best->dest))
|
|
return NULL;
|
|
if (best->probability <= probability_cutoff)
|
|
return NULL;
|
|
return best;
|
|
}
|
|
|
|
/* Return most frequent predecessor of basic block BB. */
|
|
|
|
static edge
|
|
find_best_predecessor (basic_block bb)
|
|
{
|
|
edge e;
|
|
edge best = NULL;
|
|
|
|
for (e = bb->pred; e; e = e->pred_next)
|
|
if (!best || better_p (e, best))
|
|
best = e;
|
|
if (!best || ignore_bb_p (best->src))
|
|
return NULL;
|
|
if (EDGE_FREQUENCY (best) * REG_BR_PROB_BASE
|
|
< bb->frequency * branch_ratio_cutoff)
|
|
return NULL;
|
|
return best;
|
|
}
|
|
|
|
/* Find the trace using bb and record it in the TRACE array.
|
|
Return number of basic blocks recorded. */
|
|
|
|
static int
|
|
find_trace (basic_block bb, basic_block *trace)
|
|
{
|
|
int i = 0;
|
|
edge e;
|
|
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, "Trace seed %i [%i]", bb->index, bb->frequency);
|
|
|
|
while ((e = find_best_predecessor (bb)) != NULL)
|
|
{
|
|
basic_block bb2 = e->src;
|
|
if (seen (bb2) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
|
|
|| find_best_successor (bb2) != e)
|
|
break;
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, ",%i [%i]", bb->index, bb->frequency);
|
|
bb = bb2;
|
|
}
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, " forward %i [%i]", bb->index, bb->frequency);
|
|
trace[i++] = bb;
|
|
|
|
/* Follow the trace in forward direction. */
|
|
while ((e = find_best_successor (bb)) != NULL)
|
|
{
|
|
bb = e->dest;
|
|
if (seen (bb) || (e->flags & (EDGE_DFS_BACK | EDGE_COMPLEX))
|
|
|| find_best_predecessor (bb) != e)
|
|
break;
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, ",%i [%i]", bb->index, bb->frequency);
|
|
trace[i++] = bb;
|
|
}
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, "\n");
|
|
return i;
|
|
}
|
|
|
|
/* Look for basic blocks in frequency order, construct traces and tail duplicate
|
|
if profitable. */
|
|
|
|
static void
|
|
tail_duplicate (void)
|
|
{
|
|
fibnode_t *blocks = xcalloc (last_basic_block, sizeof (fibnode_t));
|
|
basic_block *trace = xmalloc (sizeof (basic_block) * n_basic_blocks);
|
|
int *counts = xmalloc (sizeof (int) * last_basic_block);
|
|
int ninsns = 0, nduplicated = 0;
|
|
gcov_type weighted_insns = 0, traced_insns = 0;
|
|
fibheap_t heap = fibheap_new ();
|
|
gcov_type cover_insns;
|
|
int max_dup_insns;
|
|
basic_block bb;
|
|
|
|
if (profile_info && flag_branch_probabilities)
|
|
probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY_FEEDBACK);
|
|
else
|
|
probability_cutoff = PARAM_VALUE (TRACER_MIN_BRANCH_PROBABILITY);
|
|
probability_cutoff = REG_BR_PROB_BASE / 100 * probability_cutoff;
|
|
|
|
branch_ratio_cutoff =
|
|
(REG_BR_PROB_BASE / 100 * PARAM_VALUE (TRACER_MIN_BRANCH_RATIO));
|
|
|
|
FOR_EACH_BB (bb)
|
|
{
|
|
int n = count_insns (bb);
|
|
if (!ignore_bb_p (bb))
|
|
blocks[bb->index] = fibheap_insert (heap, -bb->frequency,
|
|
bb);
|
|
|
|
counts [bb->index] = n;
|
|
ninsns += n;
|
|
weighted_insns += n * bb->frequency;
|
|
}
|
|
|
|
if (profile_info && flag_branch_probabilities)
|
|
cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE_FEEDBACK);
|
|
else
|
|
cover_insns = PARAM_VALUE (TRACER_DYNAMIC_COVERAGE);
|
|
cover_insns = (weighted_insns * cover_insns + 50) / 100;
|
|
max_dup_insns = (ninsns * PARAM_VALUE (TRACER_MAX_CODE_GROWTH) + 50) / 100;
|
|
|
|
while (traced_insns < cover_insns && nduplicated < max_dup_insns
|
|
&& !fibheap_empty (heap))
|
|
{
|
|
basic_block bb = fibheap_extract_min (heap);
|
|
int n, pos;
|
|
|
|
if (!bb)
|
|
break;
|
|
|
|
blocks[bb->index] = NULL;
|
|
|
|
if (ignore_bb_p (bb))
|
|
continue;
|
|
if (seen (bb))
|
|
abort ();
|
|
|
|
n = find_trace (bb, trace);
|
|
|
|
bb = trace[0];
|
|
traced_insns += bb->frequency * counts [bb->index];
|
|
if (blocks[bb->index])
|
|
{
|
|
fibheap_delete_node (heap, blocks[bb->index]);
|
|
blocks[bb->index] = NULL;
|
|
}
|
|
|
|
for (pos = 1; pos < n; pos++)
|
|
{
|
|
basic_block bb2 = trace[pos];
|
|
|
|
if (blocks[bb2->index])
|
|
{
|
|
fibheap_delete_node (heap, blocks[bb2->index]);
|
|
blocks[bb2->index] = NULL;
|
|
}
|
|
traced_insns += bb2->frequency * counts [bb2->index];
|
|
if (bb2->pred && bb2->pred->pred_next
|
|
&& cfg_layout_can_duplicate_bb_p (bb2))
|
|
{
|
|
edge e = bb2->pred;
|
|
basic_block old = bb2;
|
|
|
|
while (e->src != bb)
|
|
e = e->pred_next;
|
|
nduplicated += counts [bb2->index];
|
|
bb2 = cfg_layout_duplicate_bb (bb2, e);
|
|
|
|
/* Reconsider the original copy of block we've duplicated.
|
|
Removing the most common predecessor may make it to be
|
|
head. */
|
|
blocks[old->index] =
|
|
fibheap_insert (heap, -old->frequency, old);
|
|
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, "Duplicated %i as %i [%i]\n",
|
|
old->index, bb2->index, bb2->frequency);
|
|
}
|
|
bb->rbi->next = bb2;
|
|
bb2->rbi->visited = 1;
|
|
bb = bb2;
|
|
/* In case the trace became infrequent, stop duplicating. */
|
|
if (ignore_bb_p (bb))
|
|
break;
|
|
}
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, " covered now %.1f\n\n",
|
|
traced_insns * 100.0 / weighted_insns);
|
|
}
|
|
if (rtl_dump_file)
|
|
fprintf (rtl_dump_file, "Duplicated %i insns (%i%%)\n", nduplicated,
|
|
nduplicated * 100 / ninsns);
|
|
|
|
free (blocks);
|
|
free (trace);
|
|
free (counts);
|
|
fibheap_delete (heap);
|
|
}
|
|
|
|
/* Connect the superblocks into linear sequence. At the moment we attempt to keep
|
|
the original order as much as possible, but the algorithm may be made smarter
|
|
later if needed. BB reordering pass should void most of the benefits of such
|
|
change though. */
|
|
|
|
static void
|
|
layout_superblocks (void)
|
|
{
|
|
basic_block end = ENTRY_BLOCK_PTR->succ->dest;
|
|
basic_block bb = ENTRY_BLOCK_PTR->succ->dest->next_bb;
|
|
|
|
while (bb != EXIT_BLOCK_PTR)
|
|
{
|
|
edge e, best = NULL;
|
|
while (end->rbi->next)
|
|
end = end->rbi->next;
|
|
|
|
for (e = end->succ; e; e = e->succ_next)
|
|
if (e->dest != EXIT_BLOCK_PTR
|
|
&& e->dest != ENTRY_BLOCK_PTR->succ->dest
|
|
&& !e->dest->rbi->visited
|
|
&& (!best || EDGE_FREQUENCY (e) > EDGE_FREQUENCY (best)))
|
|
best = e;
|
|
|
|
if (best)
|
|
{
|
|
end->rbi->next = best->dest;
|
|
best->dest->rbi->visited = 1;
|
|
}
|
|
else
|
|
for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb)
|
|
{
|
|
if (!bb->rbi->visited)
|
|
{
|
|
end->rbi->next = bb;
|
|
bb->rbi->visited = 1;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Main entry point to this file. FLAGS is the set of flags to pass
|
|
to cfg_layout_initialize(). */
|
|
|
|
void
|
|
tracer (unsigned int flags)
|
|
{
|
|
if (n_basic_blocks <= 1)
|
|
return;
|
|
|
|
timevar_push (TV_TRACER);
|
|
|
|
cfg_layout_initialize (flags);
|
|
mark_dfs_back_edges ();
|
|
if (rtl_dump_file)
|
|
dump_flow_info (rtl_dump_file);
|
|
tail_duplicate ();
|
|
layout_superblocks ();
|
|
if (rtl_dump_file)
|
|
dump_flow_info (rtl_dump_file);
|
|
cfg_layout_finalize ();
|
|
|
|
/* Merge basic blocks in duplicated traces. */
|
|
cleanup_cfg (CLEANUP_EXPENSIVE);
|
|
|
|
timevar_pop (TV_TRACER);
|
|
}
|