Hello.
I'm sending updated version of the patch that is now built on
top of recent switch expansion changes.
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
Ready to be installed?
Martin
>From 1e362576dacb8a601f3362e033a725c234f6bc7c Mon Sep 17 00:00:00 2001
From: marxin <mli...@suse.cz>
Date: Thu, 16 Aug 2018 14:16:01 +0200
Subject: [PATCH] Make __builtin_expect effective in switch statements
(PR middle-end/59521).
gcc/ChangeLog:
2018-08-23 Martin Liska <mli...@suse.cz>
PR middle-end/59521
* predict.c (set_even_probabilities): Add likely_edges
argument and handle cases where we have precisely one
likely edge.
(combine_predictions_for_bb): Catch also likely_edges.
(tree_predict_by_opcode): Handle gswitch statements.
* tree-cfg.c (find_taken_edge_switch_expr): Remove
const quantifier.
(find_case_label_for_value): Likewise.
* tree-cfg.h (find_case_label_for_value): New declaration.
(find_taken_edge_switch_expr): Likewise.
* tree-switch-conversion.c (switch_decision_tree::balance_case_nodes):
Find pivot in decision tree based on probabily, not by number of
nodes.
gcc/testsuite/ChangeLog:
2018-08-23 Martin Liska <mli...@suse.cz>
PR middle-end/59521
* c-c++-common/pr59521-1.c: New test.
* c-c++-common/pr59521-2.c: New test.
* gcc.dg/tree-prof/pr59521-3.c: New test.
---
gcc/predict.c | 96 +++++++++++++++++-----
gcc/testsuite/c-c++-common/pr59521-1.c | 15 ++++
gcc/testsuite/c-c++-common/pr59521-2.c | 15 ++++
gcc/testsuite/gcc.dg/tree-prof/pr59521-3.c | 34 ++++++++
gcc/tree-cfg.c | 10 +--
gcc/tree-cfg.h | 2 +
gcc/tree-switch-conversion.c | 45 +++++-----
7 files changed, 168 insertions(+), 49 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/pr59521-1.c
create mode 100644 gcc/testsuite/c-c++-common/pr59521-2.c
create mode 100644 gcc/testsuite/gcc.dg/tree-prof/pr59521-3.c
diff --git a/gcc/predict.c b/gcc/predict.c
index 8c8e79153fc..db1fe737cb4 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -831,7 +831,8 @@ unlikely_executed_bb_p (basic_block bb)
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;
@@ -843,7 +844,7 @@ set_even_probabilities (basic_block bb,
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 ();
@@ -852,26 +853,54 @@ set_even_probabilities (basic_block bb,
}
/* 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;
-
- 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 ();
+ /* 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);
+ profile_probability remainder = prob.invert ();
+
+ if (prediction->ep_edge == e)
+ e->probability = prob;
+ else
+ e->probability = remainder.apply_scale (1, nedges - 1);
+ }
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. */
@@ -1175,6 +1204,7 @@ combine_predictions_for_bb (basic_block bb, bool dry_run)
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
@@ -1182,11 +1212,16 @@ combine_predictions_for_bb (basic_block bb, bool dry_run)
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)
+ unlikely_edges.add (pred->ep_edge);
+ if (pred->ep_probability >= PROB_VERY_LIKELY
+ || pred->ep_predictor == PRED_BUILTIN_EXPECT)
+ likely_edges.add (pred);
+ }
if (!dry_run)
- set_even_probabilities (bb, &unlikely_edges);
+ set_even_probabilities (bb, &unlikely_edges, &likely_edges);
clear_bb_predictions (bb);
if (dump_file)
{
@@ -2575,7 +2610,30 @@ tree_predict_by_opcode (basic_block bb)
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)
diff --git a/gcc/testsuite/c-c++-common/pr59521-1.c b/gcc/testsuite/c-c++-common/pr59521-1.c
new file mode 100644
index 00000000000..32320b57052
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr59521-1.c
@@ -0,0 +1,15 @@
+/* { dg-options "-O2" } */
+/* { dg-do compile } */
+
+extern int puts (const char *);
+
+void
+f(int ch) {
+ switch (ch) {
+ case 3: puts("a"); break;
+ case 42: puts("e"); break;
+ case 333: puts("i"); break;
+ }
+}
+
+/* { dg-final { scan-assembler "cmp.*42,.*cmp.*333,.*cmp.*3," { target i?86-*-* x86_64-*-* } } } */
diff --git a/gcc/testsuite/c-c++-common/pr59521-2.c b/gcc/testsuite/c-c++-common/pr59521-2.c
new file mode 100644
index 00000000000..3c48825b347
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr59521-2.c
@@ -0,0 +1,15 @@
+/* { dg-options "-O2" } */
+/* { dg-do compile } */
+
+extern int puts (const char *);
+
+void
+f(int ch) {
+ switch (__builtin_expect(ch, 333)) {
+ case 3: puts("a"); break;
+ case 42: puts("e"); break;
+ case 333: puts("i"); break;
+ }
+}
+
+/* { dg-final { scan-assembler "cmp.*333,.*cmp.*3,.*cmp.*42," { target i?86-*-* x86_64-*-* } } } */
diff --git a/gcc/testsuite/gcc.dg/tree-prof/pr59521-3.c b/gcc/testsuite/gcc.dg/tree-prof/pr59521-3.c
new file mode 100644
index 00000000000..497643bed3d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-prof/pr59521-3.c
@@ -0,0 +1,34 @@
+/* { dg-options "-O2 -save-temps" } */
+
+#include <stdio.h>
+
+__attribute__((noinline,noclone)) void
+sink(const char *s) {
+ asm("" :: "r"(s));
+}
+
+void
+foo(int ch) {
+ switch (ch) {
+ case 100: sink("100"); break;
+ case 10: sink("10"); break;
+ case 1: sink("1"); break;
+ }
+}
+
+int main()
+{
+ for (int i = 0; i < 10000; i++)
+ {
+ int v;
+ if (i % 100 == 0)
+ v = 100;
+ else if(i % 10 == 0)
+ v = 10;
+ else
+ v = 1;
+ foo(v);
+ }
+}
+
+/* { dg-final-use-not-autofdo { scan-assembler "\nfoo:\n.*cmp.*1,.*cmp.*10,.*cmp.*100" { target i?86-*-* x86_64-*-* } } } */
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index b021fb0f97b..738e0e7fe7f 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -171,8 +171,6 @@ static bool gimple_can_merge_blocks_p (basic_block, basic_block);
static void remove_bb (basic_block);
static edge find_taken_edge_computed_goto (basic_block, tree);
static edge find_taken_edge_cond_expr (const gcond *, tree);
-static edge find_taken_edge_switch_expr (const gswitch *, tree);
-static tree find_case_label_for_value (const gswitch *, tree);
static void lower_phi_internal_fn ();
void
@@ -2436,8 +2434,8 @@ find_taken_edge_cond_expr (const gcond *cond_stmt, tree val)
If VAL is NULL_TREE, then the current value of SWITCH_STMT's index
is used. */
-static edge
-find_taken_edge_switch_expr (const gswitch *switch_stmt, tree val)
+edge
+find_taken_edge_switch_expr (gswitch *switch_stmt, tree val)
{
basic_block dest_bb;
edge e;
@@ -2466,8 +2464,8 @@ find_taken_edge_switch_expr (const gswitch *switch_stmt, tree val)
We can make optimal use here of the fact that the case labels are
sorted: We can do a binary search for a case matching VAL. */
-static tree
-find_case_label_for_value (const gswitch *switch_stmt, tree val)
+tree
+find_case_label_for_value (gswitch *switch_stmt, tree val)
{
size_t low, high, n = gimple_switch_num_labels (switch_stmt);
tree default_case = gimple_switch_default_label (switch_stmt);
diff --git a/gcc/tree-cfg.h b/gcc/tree-cfg.h
index 349a9543168..10ec50e95fd 100644
--- a/gcc/tree-cfg.h
+++ b/gcc/tree-cfg.h
@@ -102,6 +102,8 @@ extern tree gimplify_build2 (gimple_stmt_iterator *, enum tree_code,
extern tree gimplify_build1 (gimple_stmt_iterator *, enum tree_code,
tree, tree);
extern void extract_true_false_edges_from_block (basic_block, edge *, edge *);
+extern tree find_case_label_for_value (gswitch *switch_stmt, tree val);
+extern edge find_taken_edge_switch_expr (gswitch *switch_stmt, tree val);
extern unsigned int execute_fixup_cfg (void);
extern unsigned int split_critical_edges (void);
extern basic_block insert_cond_bb (basic_block, gimple *, gimple *,
diff --git a/gcc/tree-switch-conversion.c b/gcc/tree-switch-conversion.c
index a31ff94b895..5e4876474f9 100644
--- a/gcc/tree-switch-conversion.c
+++ b/gcc/tree-switch-conversion.c
@@ -1921,6 +1921,7 @@ switch_decision_tree::balance_case_nodes (case_tree_node **head,
int ranges = 0;
case_tree_node **npp;
case_tree_node *left;
+ profile_probability prob = profile_probability::never ();
/* Count the number of entries on branch. Also count the ranges. */
@@ -1930,6 +1931,7 @@ switch_decision_tree::balance_case_nodes (case_tree_node **head,
ranges++;
i++;
+ prob += np->m_c->m_prob;
np = np->m_right;
}
@@ -1938,39 +1940,34 @@ switch_decision_tree::balance_case_nodes (case_tree_node **head,
/* Split this list if it is long enough for that to help. */
npp = head;
left = *npp;
+ profile_probability pivot_prob = prob.apply_scale (1, 2);
- /* If there are just three nodes, split at the middle one. */
- if (i == 3)
- npp = &(*npp)->m_right;
- else
+ /* Find the place in the list that bisects the list's total cost,
+ where ranges count as 2. */
+ while (1)
{
- /* Find the place in the list that bisects the list's total cost,
- where ranges count as 2.
- Here I gets half the total cost. */
- i = (i + ranges + 1) / 2;
- while (1)
- {
- /* Skip nodes while their cost does not reach that amount. */
- if (!tree_int_cst_equal ((*npp)->m_c->get_low (),
- (*npp)->m_c->get_high ()))
- i--;
- i--;
- if (i <= 0)
- break;
- npp = &(*npp)->m_right;
- }
+ /* Skip nodes while their probability does not reach
+ that amount. */
+ prob -= (*npp)->m_c->m_prob;
+ if (prob <= pivot_prob || ! (*npp)->m_right)
+ break;
+ npp = &(*npp)->m_right;
}
- *head = np = *npp;
- *npp = 0;
+
+ np = *npp;
+ *npp = 0;
+ *head = np;
np->m_parent = parent;
- np->m_left = left;
+ np->m_left = left == np ? NULL : left;
/* Optimize each of the two split parts. */
balance_case_nodes (&np->m_left, np);
balance_case_nodes (&np->m_right, np);
np->m_c->m_subtree_prob = np->m_c->m_prob;
- np->m_c->m_subtree_prob += np->m_left->m_c->m_subtree_prob;
- np->m_c->m_subtree_prob += np->m_right->m_c->m_subtree_prob;
+ if (np->m_left)
+ np->m_c->m_subtree_prob += np->m_left->m_c->m_subtree_prob;
+ if (np->m_right)
+ np->m_c->m_subtree_prob += np->m_right->m_c->m_subtree_prob;
}
else
{
--
2.18.0
