/* Branch prediction routines for the GNU compiler.
- Copyright (C) 2000-2017 Free Software Foundation, Inc.
+ Copyright (C) 2000-2019 Free Software Foundation, Inc.
This file is part of GCC.
enum predictor_reason, edge);
static void predict_paths_leading_to (basic_block, enum br_predictor,
enum prediction,
- struct loop *in_loop = NULL);
+ class loop *in_loop = NULL);
static void predict_paths_leading_to_edge (edge, enum br_predictor,
enum prediction,
- struct loop *in_loop = NULL);
+ class loop *in_loop = NULL);
static bool can_predict_insn_p (const rtx_insn *);
+static HOST_WIDE_INT get_predictor_value (br_predictor, HOST_WIDE_INT);
+static void determine_unlikely_bbs ();
/* Information we hold about each branch predictor.
Filled using information from predict.def. */
gcov_type
get_hot_bb_threshold ()
{
- gcov_working_set_t *ws;
if (min_count == -1)
{
- ws = find_working_set (PARAM_VALUE (HOT_BB_COUNT_WS_PERMILLE));
- gcc_assert (ws);
- min_count = ws->min_counter;
+ const int hot_frac = PARAM_VALUE (HOT_BB_COUNT_FRACTION);
+ const gcov_type min_hot_count
+ = hot_frac
+ ? profile_info->sum_max / hot_frac
+ : (gcov_type)profile_count::max_count;
+ set_hot_bb_threshold (min_hot_count);
+ if (dump_file)
+ fprintf (dump_file, "Setting hotness threshold to %" PRId64 ".\n",
+ min_hot_count);
}
return min_count;
}
min_count = min;
}
-/* Return TRUE if frequency FREQ is considered to be hot. */
+/* Return TRUE if COUNT is considered to be hot in function FUN. */
bool
maybe_hot_count_p (struct function *fun, profile_count count)
if (node->frequency == NODE_FREQUENCY_EXECUTED_ONCE
&& count < (ENTRY_BLOCK_PTR_FOR_FN (fun)->count.apply_scale (2, 3)))
return false;
- if (PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION) == 0)
- return false;
if (count.apply_scale (PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION), 1)
< ENTRY_BLOCK_PTR_FOR_FN (fun)->count)
return false;
return (count.to_gcov_type () >= get_hot_bb_threshold ());
}
-/* Return true in case BB can be CPU intensive and should be optimized
- for maximal performance. */
+/* Return true if basic block BB of function FUN can be CPU intensive
+ and should thus be optimized for maximum performance. */
bool
maybe_hot_bb_p (struct function *fun, const_basic_block bb)
return maybe_hot_count_p (fun, bb->count);
}
-/* Return true in case BB can be CPU intensive and should be optimized
- for maximal performance. */
+/* Return true if edge E can be CPU intensive and should thus be optimized
+ for maximum performance. */
bool
maybe_hot_edge_p (edge e)
return maybe_hot_count_p (cfun, e->count ());
}
-/* Return true if profile COUNT and FREQUENCY, or function FUN static
- node frequency reflects never being executed. */
+/* Return true if COUNT is considered to be never executed in function FUN
+ or if function FUN is considered so in the static profile. */
static bool
-probably_never_executed (struct function *fun,
- profile_count count)
+probably_never_executed (struct function *fun, profile_count count)
{
gcc_checking_assert (fun);
- if (count == profile_count::zero ())
+ if (count.ipa () == profile_count::zero ())
return true;
- if (count.initialized_p () && profile_status_for_fn (fun) == PROFILE_READ)
+ /* Do not trust adjusted counts. This will make us to drop int cold section
+ code with low execution count as a result of inlining. These low counts
+ are not safe even with read profile and may lead us to dropping
+ code which actually gets executed into cold section of binary that is not
+ desirable. */
+ if (count.precise_p () && profile_status_for_fn (fun) == PROFILE_READ)
{
- int unlikely_count_fraction = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
- if (count.apply_scale (unlikely_count_fraction, 1) >= profile_info->runs)
+ const int unlikely_frac = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
+ if (count.apply_scale (unlikely_frac, 1) >= profile_info->runs)
return false;
return true;
}
return false;
}
-
-/* Return true in case BB is probably never executed. */
+/* Return true if basic block BB of function FUN is probably never executed. */
bool
probably_never_executed_bb_p (struct function *fun, const_basic_block bb)
return probably_never_executed (fun, bb->count);
}
-
-/* Return true if E is unlikely executed for obvious reasons. */
+/* Return true if edge E is unlikely executed for obvious reasons. */
static bool
unlikely_executed_edge_p (edge e)
|| (e->flags & (EDGE_EH | EDGE_FAKE));
}
-/* Return true in case edge E is probably never executed. */
+/* Return true if edge E of function FUN is probably never executed. */
bool
probably_never_executed_edge_p (struct function *fun, edge e)
return probably_never_executed (fun, e->count ());
}
-/* Return true when current function should always be optimized for size. */
+/* Return true if function FUN should always be optimized for size. */
bool
optimize_function_for_size_p (struct function *fun)
return n && n->optimize_for_size_p ();
}
-/* Return true when current function should always be optimized for speed. */
+/* Return true if function FUN should always be optimized for speed. */
bool
optimize_function_for_speed_p (struct function *fun)
return !optimize_function_for_size_p (fun);
}
-/* Return the optimization type that should be used for the function FUN. */
+/* Return the optimization type that should be used for function FUN. */
optimization_type
function_optimization_type (struct function *fun)
: OPTIMIZE_FOR_SIZE);
}
-/* Return TRUE when BB should be optimized for size. */
+/* Return TRUE if basic block BB should be optimized for size. */
bool
optimize_bb_for_size_p (const_basic_block bb)
|| (bb && !maybe_hot_bb_p (cfun, bb)));
}
-/* Return TRUE when BB should be optimized for speed. */
+/* Return TRUE if basic block BB should be optimized for speed. */
bool
optimize_bb_for_speed_p (const_basic_block bb)
return !optimize_bb_for_size_p (bb);
}
-/* Return the optimization type that should be used for block BB. */
+/* Return the optimization type that should be used for basic block BB. */
optimization_type
bb_optimization_type (const_basic_block bb)
: OPTIMIZE_FOR_SIZE);
}
-/* Return TRUE when BB should be optimized for size. */
+/* Return TRUE if edge E should be optimized for size. */
bool
optimize_edge_for_size_p (edge e)
return optimize_function_for_size_p (cfun) || !maybe_hot_edge_p (e);
}
-/* Return TRUE when BB should be optimized for speed. */
+/* Return TRUE if edge E should be optimized for speed. */
bool
optimize_edge_for_speed_p (edge e)
return !optimize_edge_for_size_p (e);
}
-/* Return TRUE when BB should be optimized for size. */
+/* Return TRUE if the current function is optimized for size. */
bool
optimize_insn_for_size_p (void)
return optimize_function_for_size_p (cfun) || !crtl->maybe_hot_insn_p;
}
-/* Return TRUE when BB should be optimized for speed. */
+/* Return TRUE if the current function is optimized for speed. */
bool
optimize_insn_for_speed_p (void)
return !optimize_insn_for_size_p ();
}
-/* Return TRUE when LOOP should be optimized for size. */
+/* Return TRUE if LOOP should be optimized for size. */
bool
-optimize_loop_for_size_p (struct loop *loop)
+optimize_loop_for_size_p (class loop *loop)
{
return optimize_bb_for_size_p (loop->header);
}
-/* Return TRUE when LOOP should be optimized for speed. */
+/* Return TRUE if LOOP should be optimized for speed. */
bool
-optimize_loop_for_speed_p (struct loop *loop)
+optimize_loop_for_speed_p (class loop *loop)
{
return optimize_bb_for_speed_p (loop->header);
}
-/* Return TRUE when LOOP nest should be optimized for speed. */
+/* Return TRUE if nest rooted at LOOP should be optimized for speed. */
bool
-optimize_loop_nest_for_speed_p (struct loop *loop)
+optimize_loop_nest_for_speed_p (class loop *loop)
{
- struct loop *l = loop;
+ class loop *l = loop;
if (optimize_loop_for_speed_p (loop))
return true;
l = loop->inner;
return false;
}
-/* Return TRUE when LOOP nest should be optimized for size. */
+/* Return TRUE if nest rooted at LOOP should be optimized for size. */
bool
-optimize_loop_nest_for_size_p (struct loop *loop)
+optimize_loop_nest_for_size_p (class loop *loop)
{
return !optimize_loop_nest_for_speed_p (loop);
}
-/* Return true when edge E is likely to be well predictable by branch
+/* Return true if edge E is likely to be well predictable by branch
predictor. */
bool
enum prediction taken)
{
int probability = predictor_info[(int) predictor].hitrate;
+ gcc_assert (probability != PROB_UNINITIALIZED);
if (taken != TAKEN)
probability = REG_BR_PROB_BASE - probability;
else
edge_info_str[0] = '\0';
- fprintf (file, " %s heuristics%s%s: %.1f%%",
+ fprintf (file, " %s heuristics%s%s: %.2f%%",
predictor_info[predictor].name,
edge_info_str, reason_messages[reason],
probability * 100.0 / REG_BR_PROB_BASE);
}
fprintf (file, "\n");
+
+ /* Print output that be easily read by analyze_brprob.py script. We are
+ interested only in counts that are read from GCDA files. */
+ if (dump_file && (dump_flags & TDF_DETAILS)
+ && bb->count.precise_p ()
+ && reason == REASON_NONE)
+ {
+ gcc_assert (e->count ().precise_p ());
+ fprintf (file, ";;heuristics;%s;%" PRId64 ";%" PRId64 ";%.1f;\n",
+ predictor_info[predictor].name,
+ bb->count.to_gcov_type (), e->count ().to_gcov_type (),
+ probability * 100.0 / REG_BR_PROB_BASE);
+ }
}
/* Return true if STMT is known to be unlikely executed. */
return false;
}
-/* We can not predict the probabilities of outgoing edges of bb. Set them
+/* We cannot predict the probabilities of outgoing edges of bb. Set them
evenly and hope for the best. If UNLIKELY_EDGES is not null, distribute
even probability for all edges not mentioned in the set. These edges
- are given PROB_VERY_UNLIKELY probability. */
+ are given PROB_VERY_UNLIKELY probability. Similarly for LIKELY_EDGES,
+ if we have exactly one likely edge, make the other edges predicted
+ as not probable. */
static void
set_even_probabilities (basic_block bb,
- hash_set<edge> *unlikely_edges = NULL)
+ hash_set<edge> *unlikely_edges = NULL,
+ hash_set<edge_prediction *> *likely_edges = NULL)
{
unsigned nedges = 0, unlikely_count = 0;
edge e = NULL;
all -= e->probability;
else if (!unlikely_executed_edge_p (e))
{
- nedges ++;
+ nedges++;
if (unlikely_edges != NULL && unlikely_edges->contains (e))
{
all -= profile_probability::very_unlikely ();
}
/* Make the distribution even if all edges are unlikely. */
+ unsigned likely_count = likely_edges ? likely_edges->elements () : 0;
if (unlikely_count == nedges)
{
unlikely_edges = NULL;
unlikely_count = 0;
}
- unsigned c = nedges - unlikely_count;
+ /* If we have one likely edge, then use its probability and distribute
+ remaining probabilities as even. */
+ if (likely_count == 1)
+ {
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->probability.initialized_p ())
+ ;
+ else if (!unlikely_executed_edge_p (e))
+ {
+ edge_prediction *prediction = *likely_edges->begin ();
+ int p = prediction->ep_probability;
+ profile_probability prob
+ = profile_probability::from_reg_br_prob_base (p);
+
+ if (prediction->ep_edge == e)
+ e->probability = prob;
+ else if (unlikely_edges != NULL && unlikely_edges->contains (e))
+ e->probability = profile_probability::very_unlikely ();
+ else
+ {
+ profile_probability remainder = prob.invert ();
+ remainder -= profile_probability::very_unlikely ()
+ .apply_scale (unlikely_count, 1);
+ int count = nedges - unlikely_count - 1;
+ gcc_assert (count >= 0);
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->probability.initialized_p ())
- ;
- else if (!unlikely_executed_edge_p (e))
- {
- if (unlikely_edges != NULL && unlikely_edges->contains (e))
- e->probability = profile_probability::very_unlikely ();
+ e->probability = remainder.apply_scale (1, count);
+ }
+ }
else
- e->probability = all.apply_scale (1, c).guessed ();
- }
- else
- e->probability = profile_probability::never ();
+ e->probability = profile_probability::never ();
+ }
+ else
+ {
+ /* Make all unlikely edges unlikely and the rest will have even
+ probability. */
+ unsigned scale = nedges - unlikely_count;
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->probability.initialized_p ())
+ ;
+ else if (!unlikely_executed_edge_p (e))
+ {
+ if (unlikely_edges != NULL && unlikely_edges->contains (e))
+ e->probability = profile_probability::very_unlikely ();
+ else
+ e->probability = all.apply_scale (1, scale);
+ }
+ else
+ e->probability = profile_probability::never ();
+ }
}
/* Add REG_BR_PROB note to JUMP with PROB. */
if (nedges != 2)
{
hash_set<edge> unlikely_edges (4);
+ hash_set<edge_prediction *> likely_edges (4);
/* Identify all edges that have a probability close to very unlikely.
Doing the approach for very unlikely doesn't worth for doing as
edge_prediction **preds = bb_predictions->get (bb);
if (preds)
for (pred = *preds; pred; pred = pred->ep_next)
- if (pred->ep_probability <= PROB_VERY_UNLIKELY)
- unlikely_edges.add (pred->ep_edge);
+ {
+ if (pred->ep_probability <= PROB_VERY_UNLIKELY
+ || pred->ep_predictor == PRED_COLD_LABEL)
+ unlikely_edges.add (pred->ep_edge);
+ else if (pred->ep_probability >= PROB_VERY_LIKELY
+ || pred->ep_predictor == PRED_BUILTIN_EXPECT
+ || pred->ep_predictor == PRED_HOT_LABEL)
+ likely_edges.add (pred);
+ }
+
+ /* It can happen that an edge is both in likely_edges and unlikely_edges.
+ Clear both sets in that situation. */
+ for (hash_set<edge_prediction *>::iterator it = likely_edges.begin ();
+ it != likely_edges.end (); ++it)
+ if (unlikely_edges.contains ((*it)->ep_edge))
+ {
+ likely_edges.empty ();
+ unlikely_edges.empty ();
+ break;
+ }
if (!dry_run)
- set_even_probabilities (bb, &unlikely_edges);
+ set_even_probabilities (bb, &unlikely_edges, &likely_edges);
clear_bb_predictions (bb);
if (dump_file)
{
fprintf (dump_file, "Predictions for bb %i\n", bb->index);
- if (unlikely_edges.elements () == 0)
+ if (unlikely_edges.is_empty ())
fprintf (dump_file,
"%i edges in bb %i predicted to even probabilities\n",
nedges, bb->index);
Otherwise return false and set LOOP_INVAIANT to NULL. */
static bool
-is_comparison_with_loop_invariant_p (gcond *stmt, struct loop *loop,
+is_comparison_with_loop_invariant_p (gcond *stmt, class loop *loop,
tree *loop_invariant,
enum tree_code *compare_code,
tree *loop_step,
In this loop, we will predict the branch inside the loop to be taken. */
static void
-predict_iv_comparison (struct loop *loop, basic_block bb,
+predict_iv_comparison (class loop *loop, basic_block bb,
tree loop_bound_var,
tree loop_iv_base_var,
enum tree_code loop_bound_code,
&& tree_fits_shwi_p (compare_base))
{
int probability;
- bool overflow, overall_overflow = false;
+ wi::overflow_type overflow;
+ bool overall_overflow = false;
widest_int compare_count, tem;
/* (loop_bound - base) / compare_step */
static void
predict_loops (void)
{
- struct loop *loop;
+ class loop *loop;
basic_block bb;
- hash_set <struct loop *> with_recursion(10);
+ hash_set <class loop *> with_recursion(10);
FOR_EACH_BB_FN (bb, cfun)
{
basic_block bb, *bbs;
unsigned j, n_exits = 0;
vec<edge> exits;
- struct tree_niter_desc niter_desc;
+ class tree_niter_desc niter_desc;
edge ex;
- struct nb_iter_bound *nb_iter;
+ class nb_iter_bound *nb_iter;
enum tree_code loop_bound_code = ERROR_MARK;
tree loop_bound_step = NULL;
tree loop_bound_var = NULL;
combine_predictions_for_insn (BB_END (bb), bb);
}
\f
-static tree expr_expected_value (tree, bitmap, enum br_predictor *predictor);
+static tree expr_expected_value (tree, bitmap, enum br_predictor *predictor,
+ HOST_WIDE_INT *probability);
/* Helper function for expr_expected_value. */
static tree
expr_expected_value_1 (tree type, tree op0, enum tree_code code,
- tree op1, bitmap visited, enum br_predictor *predictor)
+ tree op1, bitmap visited, enum br_predictor *predictor,
+ HOST_WIDE_INT *probability)
{
gimple *def;
- if (predictor)
- *predictor = PRED_UNCONDITIONAL;
+ /* Reset returned probability value. */
+ *probability = -1;
+ *predictor = PRED_UNCONDITIONAL;
if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
{
{
/* Assume that any given atomic operation has low contention,
and thus the compare-and-swap operation succeeds. */
- if (predictor)
- *predictor = PRED_COMPARE_AND_SWAP;
+ *predictor = PRED_COMPARE_AND_SWAP;
return build_one_cst (TREE_TYPE (op0));
}
}
if (arg == PHI_RESULT (def))
continue;
- new_val = expr_expected_value (arg, visited, &predictor2);
+ HOST_WIDE_INT probability2;
+ new_val = expr_expected_value (arg, visited, &predictor2,
+ &probability2);
/* It is difficult to combine value predictors. Simply assume
that later predictor is weaker and take its prediction. */
- if (predictor && *predictor < predictor2)
- *predictor = predictor2;
+ if (*predictor < predictor2)
+ {
+ *predictor = predictor2;
+ *probability = probability2;
+ }
if (!new_val)
return NULL;
if (!val)
gimple_assign_rhs1 (def),
gimple_assign_rhs_code (def),
gimple_assign_rhs2 (def),
- visited, predictor);
+ visited, predictor, probability);
}
if (is_gimple_call (def))
tree val = gimple_call_arg (def, 0);
if (TREE_CONSTANT (val))
return val;
- if (predictor)
- {
- tree val2 = gimple_call_arg (def, 2);
- gcc_assert (TREE_CODE (val2) == INTEGER_CST
- && tree_fits_uhwi_p (val2)
- && tree_to_uhwi (val2) < END_PREDICTORS);
- *predictor = (enum br_predictor) tree_to_uhwi (val2);
- }
+ tree val2 = gimple_call_arg (def, 2);
+ gcc_assert (TREE_CODE (val2) == INTEGER_CST
+ && tree_fits_uhwi_p (val2)
+ && tree_to_uhwi (val2) < END_PREDICTORS);
+ *predictor = (enum br_predictor) tree_to_uhwi (val2);
+ if (*predictor == PRED_BUILTIN_EXPECT)
+ *probability
+ = HITRATE (PARAM_VALUE (BUILTIN_EXPECT_PROBABILITY));
return gimple_call_arg (def, 1);
}
return NULL;
}
+
+ if (DECL_IS_MALLOC (decl) || DECL_IS_OPERATOR_NEW_P (decl))
+ {
+ if (predictor)
+ *predictor = PRED_MALLOC_NONNULL;
+ return boolean_true_node;
+ }
+
if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL)
switch (DECL_FUNCTION_CODE (decl))
{
val = gimple_call_arg (def, 0);
if (TREE_CONSTANT (val))
return val;
- if (predictor)
- *predictor = PRED_BUILTIN_EXPECT;
+ *predictor = PRED_BUILTIN_EXPECT;
+ *probability
+ = HITRATE (PARAM_VALUE (BUILTIN_EXPECT_PROBABILITY));
+ return gimple_call_arg (def, 1);
+ }
+ case BUILT_IN_EXPECT_WITH_PROBABILITY:
+ {
+ tree val;
+ if (gimple_call_num_args (def) != 3)
+ return NULL;
+ val = gimple_call_arg (def, 0);
+ if (TREE_CONSTANT (val))
+ return val;
+ /* Compute final probability as:
+ probability * REG_BR_PROB_BASE. */
+ tree prob = gimple_call_arg (def, 2);
+ tree t = TREE_TYPE (prob);
+ tree base = build_int_cst (integer_type_node,
+ REG_BR_PROB_BASE);
+ base = build_real_from_int_cst (t, base);
+ tree r = fold_build2_initializer_loc (UNKNOWN_LOCATION,
+ MULT_EXPR, t, prob, base);
+ if (TREE_CODE (r) != REAL_CST)
+ {
+ error_at (gimple_location (def),
+ "probability %qE must be "
+ "constant floating-point expression", prob);
+ return NULL;
+ }
+ HOST_WIDE_INT probi
+ = real_to_integer (TREE_REAL_CST_PTR (r));
+ if (probi >= 0 && probi <= REG_BR_PROB_BASE)
+ {
+ *predictor = PRED_BUILTIN_EXPECT_WITH_PROBABILITY;
+ *probability = probi;
+ }
+ else
+ error_at (gimple_location (def),
+ "probability %qE is outside "
+ "the range [0.0, 1.0]", prob);
+
return gimple_call_arg (def, 1);
}
case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_16:
/* Assume that any given atomic operation has low contention,
and thus the compare-and-swap operation succeeds. */
+ *predictor = PRED_COMPARE_AND_SWAP;
+ return boolean_true_node;
+ case BUILT_IN_REALLOC:
if (predictor)
- *predictor = PRED_COMPARE_AND_SWAP;
+ *predictor = PRED_MALLOC_NONNULL;
return boolean_true_node;
default:
break;
{
tree res;
enum br_predictor predictor2;
- op0 = expr_expected_value (op0, visited, predictor);
+ HOST_WIDE_INT probability2;
+ op0 = expr_expected_value (op0, visited, predictor, probability);
if (!op0)
return NULL;
- op1 = expr_expected_value (op1, visited, &predictor2);
- if (predictor && *predictor < predictor2)
- *predictor = predictor2;
+ op1 = expr_expected_value (op1, visited, &predictor2, &probability2);
if (!op1)
return NULL;
res = fold_build2 (code, type, op0, op1);
- if (TREE_CONSTANT (res))
- return res;
+ if (TREE_CODE (res) == INTEGER_CST
+ && TREE_CODE (op0) == INTEGER_CST
+ && TREE_CODE (op1) == INTEGER_CST)
+ {
+ /* Combine binary predictions. */
+ if (*probability != -1 || probability2 != -1)
+ {
+ HOST_WIDE_INT p1 = get_predictor_value (*predictor, *probability);
+ HOST_WIDE_INT p2 = get_predictor_value (predictor2, probability2);
+ *probability = RDIV (p1 * p2, REG_BR_PROB_BASE);
+ }
+
+ if (*predictor < predictor2)
+ *predictor = predictor2;
+
+ return res;
+ }
return NULL;
}
if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS)
{
tree res;
- op0 = expr_expected_value (op0, visited, predictor);
+ op0 = expr_expected_value (op0, visited, predictor, probability);
if (!op0)
return NULL;
res = fold_build1 (code, type, op0);
static tree
expr_expected_value (tree expr, bitmap visited,
- enum br_predictor *predictor)
+ enum br_predictor *predictor,
+ HOST_WIDE_INT *probability)
{
enum tree_code code;
tree op0, op1;
if (TREE_CONSTANT (expr))
{
- if (predictor)
- *predictor = PRED_UNCONDITIONAL;
+ *predictor = PRED_UNCONDITIONAL;
+ *probability = -1;
return expr;
}
extract_ops_from_tree (expr, &code, &op0, &op1);
return expr_expected_value_1 (TREE_TYPE (expr),
- op0, code, op1, visited, predictor);
+ op0, code, op1, visited, predictor,
+ probability);
}
\f
+
+/* Return probability of a PREDICTOR. If the predictor has variable
+ probability return passed PROBABILITY. */
+
+static HOST_WIDE_INT
+get_predictor_value (br_predictor predictor, HOST_WIDE_INT probability)
+{
+ switch (predictor)
+ {
+ case PRED_BUILTIN_EXPECT:
+ case PRED_BUILTIN_EXPECT_WITH_PROBABILITY:
+ gcc_assert (probability != -1);
+ return probability;
+ default:
+ gcc_assert (probability == -1);
+ return predictor_info[(int) predictor].hitrate;
+ }
+}
+
/* Predict using opcode of the last statement in basic block. */
static void
tree_predict_by_opcode (basic_block bb)
enum tree_code cmp;
edge_iterator ei;
enum br_predictor predictor;
+ HOST_WIDE_INT probability;
- if (!stmt || gimple_code (stmt) != GIMPLE_COND)
+ if (!stmt)
+ return;
+
+ if (gswitch *sw = dyn_cast <gswitch *> (stmt))
+ {
+ tree index = gimple_switch_index (sw);
+ tree val = expr_expected_value (index, auto_bitmap (),
+ &predictor, &probability);
+ if (val && TREE_CODE (val) == INTEGER_CST)
+ {
+ edge e = find_taken_edge_switch_expr (sw, val);
+ if (predictor == PRED_BUILTIN_EXPECT)
+ {
+ int percent = PARAM_VALUE (BUILTIN_EXPECT_PROBABILITY);
+ gcc_assert (percent >= 0 && percent <= 100);
+ predict_edge (e, PRED_BUILTIN_EXPECT,
+ HITRATE (percent));
+ }
+ else
+ predict_edge_def (e, predictor, TAKEN);
+ }
+ }
+
+ if (gimple_code (stmt) != GIMPLE_COND)
return;
FOR_EACH_EDGE (then_edge, ei, bb->succs)
if (then_edge->flags & EDGE_TRUE_VALUE)
cmp = gimple_cond_code (stmt);
type = TREE_TYPE (op0);
val = expr_expected_value_1 (boolean_type_node, op0, cmp, op1, auto_bitmap (),
- &predictor);
+ &predictor, &probability);
if (val && TREE_CODE (val) == INTEGER_CST)
{
- if (predictor == PRED_BUILTIN_EXPECT)
- {
- int percent = PARAM_VALUE (BUILTIN_EXPECT_PROBABILITY);
-
- gcc_assert (percent >= 0 && percent <= 100);
- if (integer_zerop (val))
- percent = 100 - percent;
- predict_edge (then_edge, PRED_BUILTIN_EXPECT, HITRATE (percent));
- }
- else
- predict_edge_def (then_edge, predictor,
- integer_zerop (val) ? NOT_TAKEN : TAKEN);
+ HOST_WIDE_INT prob = get_predictor_value (predictor, probability);
+ if (integer_zerop (val))
+ prob = REG_BR_PROB_BASE - prob;
+ predict_edge (then_edge, predictor, prob);
}
/* Try "pointer heuristic."
A comparison ptr == 0 is predicted as false.
return PRED_NO_PREDICTION;
}
+/* Return zero if phi result could have values other than -1, 0 or 1,
+ otherwise return a bitmask, with bits 0, 1 and 2 set if -1, 0 and 1
+ values are used or likely. */
+
+static int
+zero_one_minusone (gphi *phi, int limit)
+{
+ int phi_num_args = gimple_phi_num_args (phi);
+ int ret = 0;
+ for (int i = 0; i < phi_num_args; i++)
+ {
+ tree t = PHI_ARG_DEF (phi, i);
+ if (TREE_CODE (t) != INTEGER_CST)
+ continue;
+ wide_int w = wi::to_wide (t);
+ if (w == -1)
+ ret |= 1;
+ else if (w == 0)
+ ret |= 2;
+ else if (w == 1)
+ ret |= 4;
+ else
+ return 0;
+ }
+ for (int i = 0; i < phi_num_args; i++)
+ {
+ tree t = PHI_ARG_DEF (phi, i);
+ if (TREE_CODE (t) == INTEGER_CST)
+ continue;
+ if (TREE_CODE (t) != SSA_NAME)
+ return 0;
+ gimple *g = SSA_NAME_DEF_STMT (t);
+ if (gimple_code (g) == GIMPLE_PHI && limit > 0)
+ if (int r = zero_one_minusone (as_a <gphi *> (g), limit - 1))
+ {
+ ret |= r;
+ continue;
+ }
+ if (!is_gimple_assign (g))
+ return 0;
+ if (gimple_assign_cast_p (g))
+ {
+ tree rhs1 = gimple_assign_rhs1 (g);
+ if (TREE_CODE (rhs1) != SSA_NAME
+ || !INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
+ || TYPE_PRECISION (TREE_TYPE (rhs1)) != 1
+ || !TYPE_UNSIGNED (TREE_TYPE (rhs1)))
+ return 0;
+ ret |= (2 | 4);
+ continue;
+ }
+ if (TREE_CODE_CLASS (gimple_assign_rhs_code (g)) != tcc_comparison)
+ return 0;
+ ret |= (2 | 4);
+ }
+ return ret;
+}
+
/* Find the basic block with return expression and look up for possible
return value trying to apply RETURN_PREDICTION heuristics. */
static void
phi_num_args = gimple_phi_num_args (phi);
pred = return_prediction (PHI_ARG_DEF (phi, 0), &direction);
+ /* Avoid the case where the function returns -1, 0 and 1 values and
+ nothing else. Those could be qsort etc. comparison functions
+ where the negative return isn't less probable than positive.
+ For this require that the function returns at least -1 or 1
+ or -1 and a boolean value or comparison result, so that functions
+ returning just -1 and 0 are treated as if -1 represents error value. */
+ if (INTEGRAL_TYPE_P (TREE_TYPE (return_val))
+ && !TYPE_UNSIGNED (TREE_TYPE (return_val))
+ && TYPE_PRECISION (TREE_TYPE (return_val)) > 1)
+ if (int r = zero_one_minusone (phi, 3))
+ if ((r & (1 | 4)) == (1 | 4))
+ return;
+
/* Avoid the degenerate case where all return values form the function
belongs to same category (ie they are all positive constants)
so we can hardly say something about them. */
preheaders. */
create_preheaders (CP_SIMPLE_PREHEADERS);
calculate_dominance_info (CDI_POST_DOMINATORS);
+ /* Decide which edges are known to be unlikely. This improves later
+ branch prediction. */
+ determine_unlikely_bbs ();
bb_predictions = new hash_map<const_basic_block, edge_prediction *>;
tree_bb_level_predictions ();
predict_paths_for_bb (basic_block cur, basic_block bb,
enum br_predictor pred,
enum prediction taken,
- bitmap visited, struct loop *in_loop = NULL)
+ bitmap visited, class loop *in_loop = NULL)
{
edge e;
edge_iterator ei;
static void
predict_paths_leading_to (basic_block bb, enum br_predictor pred,
- enum prediction taken, struct loop *in_loop)
+ enum prediction taken, class loop *in_loop)
{
predict_paths_for_bb (bb, bb, pred, taken, auto_bitmap (), in_loop);
}
static void
predict_paths_leading_to_edge (edge e, enum br_predictor pred,
- enum prediction taken, struct loop *in_loop)
+ enum prediction taken, class loop *in_loop)
{
bool has_nonloop_edge = false;
edge_iterator ei;
/* This is used to carry information about basic blocks. It is
attached to the AUX field of the standard CFG block. */
-struct block_info
+class block_info
{
+public:
/* Estimated frequency of execution of basic_block. */
sreal frequency;
};
/* Similar information for edges. */
-struct edge_prob_info
+class edge_prob_info
{
+public:
/* In case edge is a 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). */
/* Estimate frequencies in loops at same nest level. */
static void
-estimate_loops_at_level (struct loop *first_loop)
+estimate_loops_at_level (class loop *first_loop)
{
- struct loop *loop;
+ class loop *loop;
for (loop = first_loop; loop; loop = loop->next)
{
}
basic_block bb;
- push_cfun (DECL_STRUCT_FUNCTION (node->decl));
- if (flag_guess_branch_prob)
+ if (opt_for_fn (node->decl, flag_guess_branch_prob))
{
bool clear_zeros
- = ENTRY_BLOCK_PTR_FOR_FN
- (DECL_STRUCT_FUNCTION (node->decl))->count.nonzero_p ();
+ = !ENTRY_BLOCK_PTR_FOR_FN (fn)->count.nonzero_p ();
FOR_ALL_BB_FN (bb, fn)
if (clear_zeros || !(bb->count == profile_count::zero ()))
bb->count = bb->count.guessed_local ();
- DECL_STRUCT_FUNCTION (node->decl)->cfg->count_max =
- DECL_STRUCT_FUNCTION (node->decl)->cfg->count_max.guessed_local ();
+ fn->cfg->count_max = fn->cfg->count_max.guessed_local ();
}
else
{
FOR_ALL_BB_FN (bb, fn)
bb->count = profile_count::uninitialized ();
- DECL_STRUCT_FUNCTION (node->decl)->cfg->count_max
- = profile_count::uninitialized ();
+ fn->cfg->count_max = profile_count::uninitialized ();
}
- pop_cfun ();
struct cgraph_edge *e;
for (e = node->callees; e; e = e->next_callee)
e->count = gimple_bb (e->call_stmt)->count;
for (e = node->indirect_calls; e; e = e->next_callee)
e->count = gimple_bb (e->call_stmt)->count;
+ node->count = ENTRY_BLOCK_PTR_FOR_FN (fn)->count;
profile_status_for_fn (fn)
= (flag_guess_branch_prob ? PROFILE_GUESSED : PROFILE_ABSENT);
void
handle_missing_profiles (void)
{
+ const int unlikely_frac = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
struct cgraph_node *node;
- int unlikely_count_fraction = PARAM_VALUE (UNLIKELY_BB_COUNT_FRACTION);
auto_vec<struct cgraph_node *, 64> worklist;
/* See if 0 count function has non-0 count callers. In this case we
gcov_type max_tp_first_run = 0;
struct function *fn = DECL_STRUCT_FUNCTION (node->decl);
- if (!(node->count == profile_count::zero ()))
+ if (node->count.ipa ().nonzero_p ())
continue;
for (e = node->callers; e; e = e->next_caller)
- if (e->count.initialized_p () && e->count > 0)
+ if (e->count.ipa ().initialized_p () && e->count.ipa () > 0)
{
- call_count = call_count + e->count;
+ call_count = call_count + e->count.ipa ();
if (e->caller->tp_first_run > max_tp_first_run)
max_tp_first_run = e->caller->tp_first_run;
if (call_count > 0
&& fn && fn->cfg
- && (call_count.apply_scale (unlikely_count_fraction, 1)
- >= profile_info->runs))
+ && call_count.apply_scale (unlikely_frac, 1) >= profile_info->runs)
{
drop_profile (node, call_count);
worklist.safe_push (node);
struct cgraph_node *callee = e->callee;
struct function *fn = DECL_STRUCT_FUNCTION (callee->decl);
- if (callee->count > 0)
+ if (!(e->count.ipa () == profile_count::zero ())
+ && callee->count.ipa ().nonzero_p ())
continue;
if ((DECL_COMDAT (callee->decl) || DECL_EXTERNAL (callee->decl))
&& fn && fn->cfg
while (worklist.length () > 0)
{
bb = worklist.pop ();
+ if (bb->count == profile_count::zero ())
+ continue;
if (bb != ENTRY_BLOCK_PTR_FOR_FN (cfun))
{
bool found = false;
if (found)
continue;
}
- if (!(bb->count == profile_count::zero ())
- && (dump_file && (dump_flags & TDF_DETAILS)))
+ if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Basic block %i is marked unlikely by backward prop\n",
bb->index);
{
if (!(e->src->count == profile_count::zero ()))
{
+ gcc_checking_assert (nsuccs[e->src->index] > 0);
nsuccs[e->src->index]--;
if (!nsuccs[e->src->index])
worklist.safe_push (e->src);
}
/* Finally all edges from non-0 regions to 0 are unlikely. */
FOR_ALL_BB_FN (bb, cfun)
- if (!(bb->count == profile_count::zero ()))
+ {
+ if (!(bb->count == profile_count::zero ()))
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (!(e->probability == profile_probability::never ())
+ && e->dest->count == profile_count::zero ())
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Edge %i->%i is unlikely because "
+ "it enters unlikely block\n",
+ bb->index, e->dest->index);
+ e->probability = profile_probability::never ();
+ }
+
+ edge other = NULL;
+
FOR_EACH_EDGE (e, ei, bb->succs)
- if (!(e->probability == profile_probability::never ())
- && e->dest->count == profile_count::zero ())
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "Edge %i->%i is unlikely because "
- "it enters unlikely block\n",
- bb->index, e->dest->index);
- e->probability = profile_probability::never ();
- }
+ if (e->probability == profile_probability::never ())
+ ;
+ else if (other)
+ {
+ other = NULL;
+ break;
+ }
+ else
+ other = e;
+ if (other
+ && !(other->probability == profile_probability::always ()))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Edge %i->%i is locally likely\n",
+ bb->index, other->dest->index);
+ other->probability = profile_probability::always ();
+ }
+ }
+ if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->count == profile_count::zero ())
+ cgraph_node::get (current_function_decl)->count = profile_count::zero ();
}
/* Estimate and propagate basic block frequencies using the given branch
{
real_values_initialized = 1;
real_br_prob_base = REG_BR_PROB_BASE;
- real_bb_freq_max = BB_FREQ_MAX;
+ /* Scaling frequencies up to maximal profile count may result in
+ frequent overflows especially when inlining loops.
+ Small scalling results in unnecesary precision loss. Stay in
+ the half of the (exponential) range. */
+ real_bb_freq_max = (uint64_t)1 << (profile_count::n_bits / 2);
real_one_half = sreal (1, -1);
real_inv_br_prob_base = sreal (1) / real_br_prob_base;
real_almost_one = sreal (1) - real_inv_br_prob_base;
to outermost to examine frequencies for back edges. */
estimate_loops ();
- bool global0 = ENTRY_BLOCK_PTR_FOR_FN (cfun)->count.initialized_p ()
- && ENTRY_BLOCK_PTR_FOR_FN (cfun)->count.ipa_p ();
-
freq_max = 0;
FOR_EACH_BB_FN (bb, cfun)
if (freq_max < BLOCK_INFO (bb)->frequency)
freq_max = BLOCK_INFO (bb)->frequency;
freq_max = real_bb_freq_max / freq_max;
+ if (freq_max < 16)
+ freq_max = 16;
+ profile_count ipa_count = ENTRY_BLOCK_PTR_FOR_FN (cfun)->count.ipa ();
cfun->cfg->count_max = profile_count::uninitialized ();
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun), NULL, next_bb)
{
/* If we have profile feedback in which this function was never
executed, then preserve this info. */
- if (global0)
- bb->count = count.global0 ();
- else if (!(bb->count == profile_count::zero ()))
- bb->count = count.guessed_local ();
+ if (!(bb->count == profile_count::zero ()))
+ bb->count = count.guessed_local ().combine_with_ipa_count (ipa_count);
cfun->cfg->count_max = cfun->cfg->count_max.max (bb->count);
}
return;
}
- /* Only first time try to drop function into unlikely executed.
- After inlining the roundoff errors may confuse us.
- Ipa-profile pass will drop functions only called from unlikely
- functions to unlikely and that is most of what we care about. */
- if (!cfun->after_inlining)
- {
- node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED;
- warn_function_cold (current_function_decl);
- }
+ node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED;
+ warn_function_cold (current_function_decl);
+ if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->count.ipa() == profile_count::zero ())
+ return;
FOR_EACH_BB_FN (bb, cfun)
{
if (maybe_hot_bb_p (cfun, bb))
profile_status_for_fn (fun) = PROFILE_GUESSED;
if (dump_file && (dump_flags & TDF_DETAILS))
{
- struct loop *loop;
+ class loop *loop;
FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
if (loop->header->count.initialized_p ())
fprintf (dump_file, "Loop got predicted %d to iterate %i times.\n",
return new pass_profile (ctxt);
}
-namespace {
-
-const pass_data pass_data_strip_predict_hints =
-{
- GIMPLE_PASS, /* type */
- "*strip_predict_hints", /* name */
- OPTGROUP_NONE, /* optinfo_flags */
- TV_BRANCH_PROB, /* tv_id */
- PROP_cfg, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- 0, /* todo_flags_finish */
-};
+/* Return true when PRED predictor should be removed after early
+ tree passes. Most of the predictors are beneficial to survive
+ as early inlining can also distribute then into caller's bodies. */
-class pass_strip_predict_hints : public gimple_opt_pass
+static bool
+strip_predictor_early (enum br_predictor pred)
{
-public:
- pass_strip_predict_hints (gcc::context *ctxt)
- : gimple_opt_pass (pass_data_strip_predict_hints, ctxt)
- {}
-
- /* opt_pass methods: */
- opt_pass * clone () { return new pass_strip_predict_hints (m_ctxt); }
- virtual unsigned int execute (function *);
-
-}; // class pass_strip_predict_hints
+ switch (pred)
+ {
+ case PRED_TREE_EARLY_RETURN:
+ return true;
+ default:
+ return false;
+ }
+}
/* Get rid of all builtin_expect calls and GIMPLE_PREDICT statements
- we no longer need. */
+ we no longer need. EARLY is set to true when called from early
+ optimizations. */
+
unsigned int
-pass_strip_predict_hints::execute (function *fun)
+strip_predict_hints (function *fun, bool early)
{
basic_block bb;
gimple *ass_stmt;
if (gimple_code (stmt) == GIMPLE_PREDICT)
{
- gsi_remove (&bi, true);
- changed = true;
- continue;
+ if (!early
+ || strip_predictor_early (gimple_predict_predictor (stmt)))
+ {
+ gsi_remove (&bi, true);
+ changed = true;
+ continue;
+ }
}
else if (is_gimple_call (stmt))
{
tree fndecl = gimple_call_fndecl (stmt);
- if ((fndecl
- && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
- && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT
- && gimple_call_num_args (stmt) == 2)
- || (gimple_call_internal_p (stmt)
- && gimple_call_internal_fn (stmt) == IFN_BUILTIN_EXPECT))
+ if (!early
+ && ((fndecl != NULL_TREE
+ && fndecl_built_in_p (fndecl, BUILT_IN_EXPECT)
+ && gimple_call_num_args (stmt) == 2)
+ || (fndecl != NULL_TREE
+ && fndecl_built_in_p (fndecl,
+ BUILT_IN_EXPECT_WITH_PROBABILITY)
+ && gimple_call_num_args (stmt) == 3)
+ || (gimple_call_internal_p (stmt)
+ && gimple_call_internal_fn (stmt) == IFN_BUILTIN_EXPECT)))
{
var = gimple_call_lhs (stmt);
changed = true;
return changed ? TODO_cleanup_cfg : 0;
}
+namespace {
+
+const pass_data pass_data_strip_predict_hints =
+{
+ GIMPLE_PASS, /* type */
+ "*strip_predict_hints", /* name */
+ OPTGROUP_NONE, /* optinfo_flags */
+ TV_BRANCH_PROB, /* tv_id */
+ PROP_cfg, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ 0, /* todo_flags_finish */
+};
+
+class pass_strip_predict_hints : public gimple_opt_pass
+{
+public:
+ pass_strip_predict_hints (gcc::context *ctxt)
+ : gimple_opt_pass (pass_data_strip_predict_hints, ctxt)
+ {}
+
+ /* opt_pass methods: */
+ opt_pass * clone () { return new pass_strip_predict_hints (m_ctxt); }
+ void set_pass_param (unsigned int n, bool param)
+ {
+ gcc_assert (n == 0);
+ early_p = param;
+ }
+
+ virtual unsigned int execute (function *);
+
+private:
+ bool early_p;
+
+}; // class pass_strip_predict_hints
+
+unsigned int
+pass_strip_predict_hints::execute (function *fun)
+{
+ return strip_predict_hints (fun, early_p);
+}
+
} // anon namespace
gimple_opt_pass *
}
else if (profile_status_for_fn (cfun) == PROFILE_READ)
update_max_bb_count ();
+ else if (profile_status_for_fn (cfun) == PROFILE_ABSENT
+ && !flag_guess_branch_prob)
+ ;
else
gcc_unreachable ();
timevar_pop (TV_REBUILD_FREQUENCIES);
we are not 100% sure.
This function locally updates profile without attempt to keep global
- consistency which can not be reached in full generality without full profile
+ consistency which cannot be reached in full generality without full profile
rebuild from probabilities alone. Doing so is not necessarily a good idea
because frequencies and counts may be more realistic then probabilities.
edge e2;
bool uninitialized_exit = false;
+ /* When branch probability guesses are not known, then do nothing. */
+ if (!impossible && !e->count ().initialized_p ())
+ return;
+
profile_probability goal = (impossible ? profile_probability::never ()
: profile_probability::very_unlikely ());
FOR_EACH_EDGE (e2, ei, e->src->succs)
if (e2 != e)
{
+ if (e->flags & EDGE_FAKE)
+ continue;
if (e2->count ().initialized_p ())
count_sum += e2->count ();
- else
- uninitialized_exit = true;
if (e2->probability.initialized_p ())
prob_sum += e2->probability;
+ else
+ uninitialized_exit = true;
}
+ /* If we are not guessing profiles but have some other edges out,
+ just assume the control flow goes elsewhere. */
+ if (uninitialized_exit)
+ e->probability = goal;
/* If there are other edges out of e->src, redistribute probabilitity
there. */
- if (prob_sum > profile_probability::never ())
+ else if (prob_sum > profile_probability::never ())
{
if (!(e->probability < goal))
e->probability = goal;
{
if (impossible)
e->probability = profile_probability::never ();
- /* If BB has some edges out that are not impossible, we can not
+ /* If BB has some edges out that are not impossible, we cannot
assume that BB itself is. */
impossible = false;
}
update_br_prob_note (e->src);
if (e->src->count == profile_count::zero ())
return;
- if (count_sum == profile_count::zero () && !uninitialized_exit
- && impossible)
+ if (count_sum == profile_count::zero () && impossible)
{
bool found = false;
if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
struct branch_predictor
{
const char *name;
- unsigned probability;
+ int probability;
};
#define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) { NAME, HITRATE },
{
branch_predictor predictors[] = {
#include "predict.def"
- {NULL, -1U}
+ { NULL, PROB_UNINITIALIZED }
};
for (unsigned i = 0; predictors[i].name != NULL; i++)
{
+ if (predictors[i].probability == PROB_UNINITIALIZED)
+ continue;
+
unsigned p = 100 * predictors[i].probability / REG_BR_PROB_BASE;
- ASSERT_TRUE (p > 50 && p <= 100);
+ ASSERT_TRUE (p >= 50 && p <= 100);
}
}
projects / thirdparty / gcc.git / blobdiff