/* Branch prediction routines for the GNU compiler.
Copyright (C) 2000, 2001 Free Software Foundation, Inc.
- This file is part of GNU CC.
+ This file is part of GCC.
- GNU CC is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
+ 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.
- GNU CC 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.
+ 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 GNU CC; see the file COPYING. If not, write to
- the Free Software Foundation, 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ 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. */
/* References:
static void combine_predictions_for_insn PARAMS ((rtx, basic_block));
static void dump_prediction PARAMS ((enum br_predictor, int,
- basic_block));
+ basic_block, int));
static void estimate_loops_at_level PARAMS ((struct loop *loop));
static void propagate_freq PARAMS ((basic_block));
static void estimate_bb_frequencies PARAMS ((struct loops *));
Filled using information from predict.def. */
struct predictor_info
{
- const char *name; /* Name used in the debugging dumps. */
- int hitrate; /* Expected hitrate used by
- predict_insn_def call. */
- int flags;
+ const char *const name; /* Name used in the debugging dumps. */
+ const int hitrate; /* Expected hitrate used by
+ predict_insn_def call. */
+ const int flags;
};
/* Use given predictor without Dempster-Shaffer theory if it matches
#define HITRATE(VAL) ((int)((VAL) * REG_BR_PROB_BASE + 50) / 100)
#define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) {NAME, HITRATE, FLAGS},
-struct predictor_info predictor_info[] = {
+static const struct predictor_info predictor_info[] = {
#include "predict.def"
- /* Upper bound on predictors. */
+ /* Upper bound on predictors. */
{NULL, 0, 0}
};
#undef DEF_PREDICTOR
/* Dump information about the branch prediction to the output file. */
static void
-dump_prediction (predictor, probability, bb)
+dump_prediction (predictor, probability, bb, used)
enum br_predictor predictor;
int probability;
basic_block bb;
+ int used;
{
edge e = bb->succ;
while (e->flags & EDGE_FALLTHRU)
e = e->succ_next;
- fprintf (rtl_dump_file, " %s heuristics: %.1f%%",
+ fprintf (rtl_dump_file, " %s heuristics%s: %.1f%%",
predictor_info[predictor].name,
+ used ? "" : " (ignored)",
probability * 100.0 / REG_BR_PROB_BASE);
if (bb->count)
{
rtx prob_note = find_reg_note (insn, REG_BR_PROB, 0);
rtx *pnote = ®_NOTES (insn);
+ rtx note = REG_NOTES (insn);
int best_probability = PROB_EVEN;
int best_predictor = END_PREDICTORS;
int combined_probability = REG_BR_PROB_BASE / 2;
int d;
+ bool first_match = false;
+ bool found = false;
if (rtl_dump_file)
fprintf (rtl_dump_file, "Predictions for insn %i bb %i\n", INSN_UID (insn),
/* We implement "first match" heuristics and use probability guessed
by predictor with smallest index. In the future we will use better
probability combination techniques. */
- while (*pnote)
+ while (note)
{
- if (REG_NOTE_KIND (*pnote) == REG_BR_PRED)
+ if (REG_NOTE_KIND (note) == REG_BR_PRED)
{
- int predictor = INTVAL (XEXP (XEXP (*pnote, 0), 0));
- int probability = INTVAL (XEXP (XEXP (*pnote, 0), 1));
+ int predictor = INTVAL (XEXP (XEXP (note, 0), 0));
+ int probability = INTVAL (XEXP (XEXP (note, 0), 1));
- dump_prediction (predictor, probability, bb);
+ found = true;
if (best_predictor > predictor)
best_probability = probability, best_predictor = predictor;
- *pnote = XEXP (*pnote, 1);
d = (combined_probability * probability
+ (REG_BR_PROB_BASE - combined_probability)
combined_probability = (((double)combined_probability) * probability
* REG_BR_PROB_BASE / d + 0.5);
}
- else
- pnote = &XEXP (*pnote, 1);
+ note = XEXP (note, 1);
}
+
+ /* Decide heuristic to use. In case we didn't match anything, use
+ no_prediction heuristic, in case we did match, use either
+ first match or Dempster-Shaffer theory depending on the flags. */
+
if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH)
+ first_match = true;
+
+ if (!found)
+ dump_prediction (PRED_NO_PREDICTION, combined_probability, bb, true);
+ else
+ {
+ dump_prediction (PRED_DS_THEORY, combined_probability, bb,
+ !first_match);
+ dump_prediction (PRED_FIRST_MATCH, best_probability, bb, first_match);
+ }
+
+ if (first_match)
combined_probability = best_probability;
- dump_prediction (PRED_FIRST_MATCH, best_probability, bb);
- dump_prediction (PRED_COMBINED, combined_probability, bb);
+ dump_prediction (PRED_COMBINED, combined_probability, bb, true);
+
+ while (*pnote)
+ {
+ if (REG_NOTE_KIND (*pnote) == REG_BR_PRED)
+ {
+ int predictor = INTVAL (XEXP (XEXP (*pnote, 0), 0));
+ int probability = INTVAL (XEXP (XEXP (*pnote, 0), 1));
+
+ dump_prediction (predictor, probability, bb,
+ !first_match || best_predictor == predictor);
+ *pnote = XEXP (*pnote, 1);
+ }
+ else
+ pnote = &XEXP (*pnote, 1);
+ }
if (!prob_note)
{
REG_NOTES (insn)
rtx cond, earliest;
edge e;
- /* If block has no sucessor, predict all possible paths to
+ /* If block has no successor, predict all possible paths to
it as improbable, as the block contains a call to a noreturn
function and thus can be executed only once. */
if (bb->succ == NULL && !found_noreturn)
{
ev = NOTE_EXPECTED_VALUE (insn);
ev_reg = XEXP (ev, 0);
+ delete_insn (insn);
}
continue;
continue;
case JUMP_INSN:
- /* Look for simple conditional branches. If we havn't got an
+ /* Look for simple conditional branches. If we haven't got an
expected value yet, no point going further. */
if (GET_CODE (insn) != JUMP_INSN || ev == NULL_RTX)
continue;
as canonicalize_condition will render this to us as
(lt r70, r71)
Could use cselib to try and reduce this further. */
- cond = XEXP (SET_SRC (PATTERN (insn)), 0);
+ cond = XEXP (SET_SRC (pc_set (insn)), 0);
cond = canonicalize_condition (insn, cond, 0, NULL, ev_reg);
if (! cond
|| XEXP (cond, 0) != ev_reg
typedef struct block_info_def
{
/* Estimated frequency of execution of basic_block. */
- double frequency;
+ volatile double frequency;
/* To keep queue of basic blocks to process. */
basic_block next;
- /* True if block already converted. */
- int visited:1;
+ /* True if block needs to be visited in prop_freqency. */
+ int tovisit:1;
- /* Number of block proceeded before adding basic block to the queue. Used
- to recognize irregular regions. */
- int nvisited;
+ /* Number of predecessors we need to visit first. */
+ int npredecessors;
} *block_info;
/* Similar information for edges. */
{
/* In case edge is an loopback edge, the probability edge will be reached
in case header is. Estimated number of iterations of the loop can be
- then computed as 1 / (1 - back_edge_prob). */
- double back_edge_prob;
+ then computed as 1 / (1 - back_edge_prob).
+
+ Volatile is needed to avoid differences in the optimized and unoptimized
+ builds on machines where FP registers are wider than double. */
+ volatile double back_edge_prob;
/* True if the edge is an loopback edge in the natural loop. */
int back_edge:1;
} *edge_info;
basic_block last = bb;
edge e;
basic_block nextbb;
- int nvisited = 0;
+ int n;
+
+ /* For each basic block we need to visit count number of his predecessors
+ we need to visit first. */
+ for (n = 0; n < n_basic_blocks; n++)
+ {
+ basic_block bb = BASIC_BLOCK (n);
+ if (BLOCK_INFO (bb)->tovisit)
+ {
+ int count = 0;
+ for (e = bb->pred; e; e = e->pred_next)
+ if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
+ count++;
+ else if (BLOCK_INFO (e->src)->tovisit
+ && rtl_dump_file && !EDGE_INFO (e)->back_edge)
+ fprintf (rtl_dump_file,
+ "Irreducible region hit, ignoring edge to %i->%i\n",
+ e->src->index, bb->index);
+ BLOCK_INFO (bb)->npredecessors = count;
+ }
+ }
BLOCK_INFO (head)->frequency = 1;
for (; bb; bb = nextbb)
{
- double cyclic_probability = 0, frequency = 0;
+ volatile double cyclic_probability = 0, frequency = 0;
nextbb = BLOCK_INFO (bb)->next;
BLOCK_INFO (bb)->next = NULL;
/* Compute frequency of basic block. */
if (bb != head)
{
+#ifdef ENABLE_CHECKING
for (e = bb->pred; e; e = e->pred_next)
- if (!BLOCK_INFO (e->src)->visited && !EDGE_INFO (e)->back_edge)
- break;
-
- /* We haven't proceeded all predecessors of edge e yet.
- These may be waiting in the queue or we may hit an
- irreducible region.
-
- To avoid infinite looping on irrecudible regions, count
- the number of blocks proceeded at the time the basic
- block has been queued. In the case the number doesn't
- change, we've hit an irreducible region and we can forget
- the backward edge. This can increase the time complexity
- by the number of irreducible blocks, but in the same way
- the standard the loop does, so it should not result in a
- noticeable slowdown.
-
- Alternatively we may distinguish backward and cross edges
- in the DFS tree by the preprocessing pass and ignore the
- existence of non-loop backward edges. */
- if (e && BLOCK_INFO (bb)->nvisited != nvisited)
- {
- if (!nextbb)
- nextbb = e->dest;
- else
- BLOCK_INFO (last)->next = e->dest;
- BLOCK_INFO (last)->nvisited = nvisited;
- last = e->dest;
- continue;
- }
- else if (e && rtl_dump_file)
- fprintf (rtl_dump_file, "Irreducible region hit, ignoring edge to bb %i\n",
- bb->index);
+ if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
+ abort ();
+#endif
for (e = bb->pred; e; e = e->pred_next)
if (EDGE_INFO (e)->back_edge)
cyclic_probability += EDGE_INFO (e)->back_edge_prob;
- else if (BLOCK_INFO (e->src)->visited)
+ else if (!(e->flags & EDGE_DFS_BACK))
frequency += (e->probability
* BLOCK_INFO (e->src)->frequency /
REG_BR_PROB_BASE);
BLOCK_INFO (bb)->frequency = frequency / (1 - cyclic_probability);
}
- BLOCK_INFO (bb)->visited = 1;
+ BLOCK_INFO (bb)->tovisit = 0;
/* Compute back edge frequencies. */
for (e = bb->succ; e; e = e->succ_next)
/* Propagate to successor blocks. */
for (e = bb->succ; e; e = e->succ_next)
- if (!EDGE_INFO (e)->back_edge
- && !BLOCK_INFO (e->dest)->visited
- && !BLOCK_INFO (e->dest)->next && e->dest != last)
+ if (!(e->flags & EDGE_DFS_BACK)
+ && BLOCK_INFO (e->dest)->npredecessors)
{
- if (!nextbb)
- nextbb = e->dest;
- else
- BLOCK_INFO (last)->next = e->dest;
- BLOCK_INFO (last)->nvisited = nvisited;
- last = e->dest;
- }
- nvisited ++;
+ BLOCK_INFO (e->dest)->npredecessors--;
+ if (!BLOCK_INFO (e->dest)->npredecessors)
+ {
+ if (!nextbb)
+ nextbb = e->dest;
+ else
+ BLOCK_INFO (last)->next = e->dest;
+ last = e->dest;
+ }
+ }
}
}
for (l = loop->shared ? first_loop : loop; l != loop->next; l = l->next)
if (loop->header == l->header)
EXECUTE_IF_SET_IN_SBITMAP (l->nodes, 0, n,
- BLOCK_INFO (BASIC_BLOCK (n))->visited =
- 0);
+ BLOCK_INFO (BASIC_BLOCK (n))->tovisit = 1
+ );
propagate_freq (loop->header);
}
}
}
}
+/* Return true if function is likely to be expensive, so there is no point
+ to optimizer performance of prologue, epilogue or do inlining at the
+ expense of code size growth. THRESHOLD is the limit of number
+ of isntructions function can execute at average to be still considered
+ not expensive. */
+bool
+expensive_function_p (threshold)
+ int threshold;
+{
+ unsigned int sum = 0;
+ int i;
+ unsigned int limit;
+
+ /* We can not compute accurately for large thresholds due to scaled
+ frequencies. */
+ if (threshold > BB_FREQ_MAX)
+ abort ();
+
+ /* Frequencies are out of range. This either means that function contains
+ internal loop executing more than BB_FREQ_MAX times or profile feedback
+ is available and function has not been executed at all. */
+ if (ENTRY_BLOCK_PTR->frequency == 0)
+ return true;
+
+ /* Maximally BB_FREQ_MAX^2 so overflow won't happen. */
+ limit = ENTRY_BLOCK_PTR->frequency * threshold;
+ for (i = 0; i < n_basic_blocks; i++)
+ {
+ basic_block bb = BASIC_BLOCK (i);
+ rtx insn;
+
+ for (insn = bb->head; insn != NEXT_INSN (bb->end);
+ insn = NEXT_INSN (insn))
+ {
+ if (active_insn_p (insn))
+ {
+ sum += bb->frequency;
+ if (sum > limit)
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
/* Estimate basic blocks frequency by given branch probabilities. */
static void
estimate_bb_frequencies (loops)
struct loops *loops;
{
- block_info bi;
- edge_info ei;
- int edgenum = 0;
int i;
double freq_max = 0;
+ mark_dfs_back_edges ();
if (flag_branch_probabilities)
{
counts_to_freqs ();
ENTRY_BLOCK_PTR->succ->probability = REG_BR_PROB_BASE;
/* Set up block info for each basic block. */
- bi = (block_info) xcalloc ((n_basic_blocks + 2), sizeof (*bi));
- ei = (edge_info) xcalloc ((n_edges), sizeof (*ei));
+ alloc_aux_for_blocks (sizeof (struct block_info_def));
+ alloc_aux_for_edges (sizeof (struct edge_info_def));
for (i = -2; i < n_basic_blocks; i++)
{
edge e;
bb = EXIT_BLOCK_PTR;
else
bb = BASIC_BLOCK (i);
- bb->aux = bi + i + 2;
- BLOCK_INFO (bb)->visited = 1;
+ BLOCK_INFO (bb)->tovisit = 0;
for (e = bb->succ; e; e = e->succ_next)
- {
- e->aux = ei + edgenum, edgenum++;
- EDGE_INFO (e)->back_edge_prob = ((double) e->probability
- / REG_BR_PROB_BASE);
- }
+ EDGE_INFO (e)->back_edge_prob = ((double) e->probability
+ / REG_BR_PROB_BASE);
}
/* First compute probabilities locally for each loop from innermost
to outermost to examine probabilities for back edges. */
/* Now fake loop around whole function to finalize probabilities. */
for (i = 0; i < n_basic_blocks; i++)
- BLOCK_INFO (BASIC_BLOCK (i))->visited = 0;
- BLOCK_INFO (ENTRY_BLOCK_PTR)->visited = 0;
- BLOCK_INFO (EXIT_BLOCK_PTR)->visited = 0;
+ BLOCK_INFO (BASIC_BLOCK (i))->tovisit = 1;
+ BLOCK_INFO (ENTRY_BLOCK_PTR)->tovisit = 1;
+ BLOCK_INFO (EXIT_BLOCK_PTR)->tovisit = 1;
propagate_freq (ENTRY_BLOCK_PTR);
for (i = 0; i < n_basic_blocks; i++)
+ 0.5);
}
- free (ei);
- free (bi);
+ free_aux_for_blocks ();
+ free_aux_for_edges ();
}
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