[PATCH v6 0/5] Don't compute events that won't be used in a metric.

[PATCH v6 0/5] Don't compute events that won't be used in a metric.

[Ian Rogers]

    
For a metric like:
  EVENT1 if #smt_on else EVENT2
    
currently EVENT1 and EVENT2 will be measured and then when the metric
is reported EVENT1 or EVENT2 will be printed depending on the value
from smt_on() during the expr parsing. Computing both events is
unnecessary and can lead to multiplexing as discussed in this thread:
https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/

This change modifies expression parsing so that constants are
considered when building the set of ids (events) and only events not
contributing to a constant value are measured.

v6. rebases and fixes issues raised by Namhyung Kim <namhyung@kernel.org>,
a memory leak and a function comment.

v5. uses macros to reduce boiler plate in patch 5/5 as suggested by
Andi Kleen <ak@linux.intel.com>.

v4. reduces references to BOTTOM/NAN in patch 5/5 by using utility
functions. It improves comments and fixes an unnecessary union in a
peephole optimization.

v3. fixes an assignment in patch 2/5. In patch 5/5 additional comments
are added and useless frees are replaced by asserts. A new peephole
optimization is added for the case CONST IF expr ELSE CONST, where the
the constants are identical, as we don't need to evaluate the IF
condition.

v2. is a rebase.

Ian Rogers (5):
  perf metric: Restructure struct expr_parse_ctx.
  perf metric: Use NAN for missing event IDs.
  perf metric: Rename expr__find_other.
  perf metric: Add utilities to work on ids map.
  perf metric: Don't compute unused events.

 tools/perf/tests/expr.c       | 159 +++++++++++-----
 tools/perf/tests/pmu-events.c |  42 +++--
 tools/perf/util/expr.c        | 137 ++++++++++++--
 tools/perf/util/expr.h        |  21 ++-
 tools/perf/util/expr.l        |   9 -
 tools/perf/util/expr.y        | 343 ++++++++++++++++++++++++++--------
 tools/perf/util/metricgroup.c |  44 +++--
 tools/perf/util/stat-shadow.c |  54 ++++--
 8 files changed, 591 insertions(+), 218 deletions(-)

-- 
2.30.0.284.gd98b1dd5eaa7-goog

[PATCH v6 1/5] perf metric: Restructure struct expr_parse_ctx.

[Ian Rogers]

A later change to parsing the ids out (in expr__find_other) will
potentially drop hashmaps and so it is more convenient to move
expr_parse_ctx to have a hashmap pointer rather than a struct value. As
this pointer must be freed, rather than just going out of scope,
add expr__ctx_new and expr__ctx_free to manage expr_parse_ctx memory.
Adjust use of struct expr_parse_ctx accordingly.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c       | 81 ++++++++++++++++++-----------------
 tools/perf/tests/pmu-events.c | 37 +++++++++-------
 tools/perf/util/expr.c        | 38 ++++++++++++----
 tools/perf/util/expr.h        |  5 ++-
 tools/perf/util/metricgroup.c | 44 ++++++++++---------
 tools/perf/util/stat-shadow.c | 50 +++++++++++++--------
 6 files changed, 151 insertions(+), 104 deletions(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index 4d01051951cd..b0a3b5fd0c00 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -22,67 +22,70 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
 	const char *p;
 	double val;
 	int ret;
-	struct expr_parse_ctx ctx;
+	struct expr_parse_ctx *ctx;
 
-	expr__ctx_init(&ctx);
-	expr__add_id_val(&ctx, strdup("FOO"), 1);
-	expr__add_id_val(&ctx, strdup("BAR"), 2);
+	ctx = expr__ctx_new();
+	TEST_ASSERT_VAL("expr__ctx_new", ctx);
+	expr__add_id_val(ctx, strdup("FOO"), 1);
+	expr__add_id_val(ctx, strdup("BAR"), 2);
 
-	ret = test(&ctx, "1+1", 2);
-	ret |= test(&ctx, "FOO+BAR", 3);
-	ret |= test(&ctx, "(BAR/2)%2", 1);
-	ret |= test(&ctx, "1 - -4",  5);
-	ret |= test(&ctx, "(FOO-1)*2 + (BAR/2)%2 - -4",  5);
-	ret |= test(&ctx, "1-1 | 1", 1);
-	ret |= test(&ctx, "1-1 & 1", 0);
-	ret |= test(&ctx, "min(1,2) + 1", 2);
-	ret |= test(&ctx, "max(1,2) + 1", 3);
-	ret |= test(&ctx, "1+1 if 3*4 else 0", 2);
-	ret |= test(&ctx, "1.1 + 2.1", 3.2);
-	ret |= test(&ctx, ".1 + 2.", 2.1);
-	ret |= test(&ctx, "d_ratio(1, 2)", 0.5);
-	ret |= test(&ctx, "d_ratio(2.5, 0)", 0);
-	ret |= test(&ctx, "1.1 < 2.2", 1);
-	ret |= test(&ctx, "2.2 > 1.1", 1);
-	ret |= test(&ctx, "1.1 < 1.1", 0);
-	ret |= test(&ctx, "2.2 > 2.2", 0);
-	ret |= test(&ctx, "2.2 < 1.1", 0);
-	ret |= test(&ctx, "1.1 > 2.2", 0);
+	ret = test(ctx, "1+1", 2);
+	ret |= test(ctx, "FOO+BAR", 3);
+	ret |= test(ctx, "(BAR/2)%2", 1);
+	ret |= test(ctx, "1 - -4",  5);
+	ret |= test(ctx, "(FOO-1)*2 + (BAR/2)%2 - -4",  5);
+	ret |= test(ctx, "1-1 | 1", 1);
+	ret |= test(ctx, "1-1 & 1", 0);
+	ret |= test(ctx, "min(1,2) + 1", 2);
+	ret |= test(ctx, "max(1,2) + 1", 3);
+	ret |= test(ctx, "1+1 if 3*4 else 0", 2);
+	ret |= test(ctx, "1.1 + 2.1", 3.2);
+	ret |= test(ctx, ".1 + 2.", 2.1);
+	ret |= test(ctx, "d_ratio(1, 2)", 0.5);
+	ret |= test(ctx, "d_ratio(2.5, 0)", 0);
+	ret |= test(ctx, "1.1 < 2.2", 1);
+	ret |= test(ctx, "2.2 > 1.1", 1);
+	ret |= test(ctx, "1.1 < 1.1", 0);
+	ret |= test(ctx, "2.2 > 2.2", 0);
+	ret |= test(ctx, "2.2 < 1.1", 0);
+	ret |= test(ctx, "1.1 > 2.2", 0);
 
-	if (ret)
+	if (ret) {
+		expr__ctx_free(ctx);
 		return ret;
+	}
 
 	p = "FOO/0";
-	ret = expr__parse(&val, &ctx, p, 1);
+	ret = expr__parse(&val, ctx, p, 1);
 	TEST_ASSERT_VAL("division by zero", ret == -1);
 
 	p = "BAR/";
-	ret = expr__parse(&val, &ctx, p, 1);
+	ret = expr__parse(&val, ctx, p, 1);
 	TEST_ASSERT_VAL("missing operand", ret == -1);
 
-	expr__ctx_clear(&ctx);
+	expr__ctx_clear(ctx);
 	TEST_ASSERT_VAL("find other",
 			expr__find_other("FOO + BAR + BAZ + BOZO", "FOO",
-					 &ctx, 1) == 0);
-	TEST_ASSERT_VAL("find other", hashmap__size(&ctx.ids) == 3);
-	TEST_ASSERT_VAL("find other", hashmap__find(&ctx.ids, "BAR",
+					 ctx, 1) == 0);
+	TEST_ASSERT_VAL("find other", hashmap__size(ctx->ids) == 3);
+	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BAR",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(&ctx.ids, "BAZ",
+	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BAZ",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(&ctx.ids, "BOZO",
+	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BOZO",
 						    (void **)&val_ptr));
 
-	expr__ctx_clear(&ctx);
+	expr__ctx_clear(ctx);
 	TEST_ASSERT_VAL("find other",
 			expr__find_other("EVENT1\\,param\\=?@ + EVENT2\\,param\\=?@",
-					 NULL, &ctx, 3) == 0);
-	TEST_ASSERT_VAL("find other", hashmap__size(&ctx.ids) == 2);
-	TEST_ASSERT_VAL("find other", hashmap__find(&ctx.ids, "EVENT1,param=3/",
+					 NULL, ctx, 3) == 0);
+	TEST_ASSERT_VAL("find other", hashmap__size(ctx->ids) == 2);
+	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "EVENT1,param=3/",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(&ctx.ids, "EVENT2,param=3/",
+	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "EVENT2,param=3/",
 						    (void **)&val_ptr));
 
-	expr__ctx_clear(&ctx);
+	expr__ctx_free(ctx);
 
 	return 0;
 }
diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
index 0ca6a5a53523..cf5afd126934 100644
--- a/tools/perf/tests/pmu-events.c
+++ b/tools/perf/tests/pmu-events.c
@@ -478,9 +478,14 @@ static int test_parsing(void)
 	struct pmu_event *pe;
 	int i, j, k;
 	int ret = 0;
-	struct expr_parse_ctx ctx;
+	struct expr_parse_ctx *ctx;
 	double result;
 
+	ctx = expr__ctx_new();
+	if (!ctx) {
+		pr_debug("expr__ctx_new failed");
+		return TEST_FAIL;
+	}
 	i = 0;
 	for (;;) {
 		map = &pmu_events_map[i++];
@@ -496,8 +501,8 @@ static int test_parsing(void)
 				break;
 			if (!pe->metric_expr)
 				continue;
-			expr__ctx_init(&ctx);
-			if (expr__find_other(pe->metric_expr, NULL, &ctx, 0)
+			expr__ctx_clear(ctx);
+			if (expr__find_other(pe->metric_expr, NULL, ctx, 0)
 				  < 0) {
 				expr_failure("Parse other failed", map, pe);
 				ret++;
@@ -510,22 +515,22 @@ static int test_parsing(void)
 			 * make them unique.
 			 */
 			k = 1;
-			hashmap__for_each_entry((&ctx.ids), cur, bkt)
-				expr__add_id_val(&ctx, strdup(cur->key), k++);
+			hashmap__for_each_entry(ctx->ids, cur, bkt)
+				expr__add_id_val(ctx, strdup(cur->key), k++);
 
-			hashmap__for_each_entry((&ctx.ids), cur, bkt) {
+			hashmap__for_each_entry(ctx->ids, cur, bkt) {
 				if (check_parse_cpu(cur->key, map == cpus_map,
 						   pe))
 					ret++;
 			}
 
-			if (expr__parse(&result, &ctx, pe->metric_expr, 0)) {
+			if (expr__parse(&result, ctx, pe->metric_expr, 0)) {
 				expr_failure("Parse failed", map, pe);
 				ret++;
 			}
-			expr__ctx_clear(&ctx);
 		}
 	}
+	expr__ctx_free(ctx);
 	/* TODO: fail when not ok */
 	return ret == 0 ? TEST_OK : TEST_SKIP;
 }
@@ -544,7 +549,7 @@ static struct test_metric metrics[] = {
 
 static int metric_parse_fake(const char *str)
 {
-	struct expr_parse_ctx ctx;
+	struct expr_parse_ctx *ctx;
 	struct hashmap_entry *cur;
 	double result;
 	int ret = -1;
@@ -553,8 +558,8 @@ static int metric_parse_fake(const char *str)
 
 	pr_debug("parsing '%s'\n", str);
 
-	expr__ctx_init(&ctx);
-	if (expr__find_other(str, NULL, &ctx, 0) < 0) {
+	ctx = expr__ctx_new();
+	if (expr__find_other(str, NULL, ctx, 0) < 0) {
 		pr_err("expr__find_other failed\n");
 		return -1;
 	}
@@ -565,23 +570,23 @@ static int metric_parse_fake(const char *str)
 	 * make them unique.
 	 */
 	i = 1;
-	hashmap__for_each_entry((&ctx.ids), cur, bkt)
-		expr__add_id_val(&ctx, strdup(cur->key), i++);
+	hashmap__for_each_entry(ctx->ids, cur, bkt)
+		expr__add_id_val(ctx, strdup(cur->key), i++);
 
-	hashmap__for_each_entry((&ctx.ids), cur, bkt) {
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
 		if (check_parse_fake(cur->key)) {
 			pr_err("check_parse_fake failed\n");
 			goto out;
 		}
 	}
 
-	if (expr__parse(&result, &ctx, str, 0))
+	if (expr__parse(&result, ctx, str, 0))
 		pr_err("expr__parse failed\n");
 	else
 		ret = 0;
 
 out:
-	expr__ctx_clear(&ctx);
+	expr__ctx_free(ctx);
 	return ret;
 }
 
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index a850fd0be3ee..e0623d38e6ee 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -73,7 +73,7 @@ int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
 	data_ptr->parent = ctx->parent;
 	data_ptr->kind = EXPR_ID_DATA__PARENT;
 
-	ret = hashmap__set(&ctx->ids, id, data_ptr,
+	ret = hashmap__set(ctx->ids, id, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	if (ret)
 		free(data_ptr);
@@ -95,7 +95,7 @@ int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val)
 	data_ptr->val = val;
 	data_ptr->kind = EXPR_ID_DATA__VALUE;
 
-	ret = hashmap__set(&ctx->ids, id, data_ptr,
+	ret = hashmap__set(ctx->ids, id, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	if (ret)
 		free(data_ptr);
@@ -140,7 +140,7 @@ int expr__add_ref(struct expr_parse_ctx *ctx, struct metric_ref *ref)
 	data_ptr->ref.metric_expr = ref->metric_expr;
 	data_ptr->kind = EXPR_ID_DATA__REF;
 
-	ret = hashmap__set(&ctx->ids, name, data_ptr,
+	ret = hashmap__set(ctx->ids, name, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	if (ret)
 		free(data_ptr);
@@ -156,7 +156,7 @@ int expr__add_ref(struct expr_parse_ctx *ctx, struct metric_ref *ref)
 int expr__get_id(struct expr_parse_ctx *ctx, const char *id,
 		 struct expr_id_data **data)
 {
-	return hashmap__find(&ctx->ids, id, (void **)data) ? 0 : -1;
+	return hashmap__find(ctx->ids, id, (void **)data) ? 0 : -1;
 }
 
 int expr__resolve_id(struct expr_parse_ctx *ctx, const char *id,
@@ -205,15 +205,23 @@ void expr__del_id(struct expr_parse_ctx *ctx, const char *id)
 	struct expr_id_data *old_val = NULL;
 	char *old_key = NULL;
 
-	hashmap__delete(&ctx->ids, id,
+	hashmap__delete(ctx->ids, id,
 			(const void **)&old_key, (void **)&old_val);
 	free(old_key);
 	free(old_val);
 }
 
-void expr__ctx_init(struct expr_parse_ctx *ctx)
+struct expr_parse_ctx *expr__ctx_new(void)
 {
-	hashmap__init(&ctx->ids, key_hash, key_equal, NULL);
+	struct expr_parse_ctx *ctx;
+
+	ctx = malloc(sizeof(struct expr_parse_ctx));
+	if (!ctx)
+		return NULL;
+
+	ctx->ids = hashmap__new(key_hash, key_equal, NULL);
+	ctx->parent = NULL;
+	return ctx;
 }
 
 void expr__ctx_clear(struct expr_parse_ctx *ctx)
@@ -221,11 +229,23 @@ void expr__ctx_clear(struct expr_parse_ctx *ctx)
 	struct hashmap_entry *cur;
 	size_t bkt;
 
-	hashmap__for_each_entry((&ctx->ids), cur, bkt) {
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
+		free((char *)cur->key);
+		free(cur->value);
+	}
+	hashmap__clear(ctx->ids);
+}
+
+void expr__ctx_free(struct expr_parse_ctx *ctx)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
 		free((char *)cur->key);
 		free(cur->value);
 	}
-	hashmap__clear(&ctx->ids);
+	hashmap__free(ctx->ids);
 }
 
 static int
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index dcf8d19b83c8..00b941cfe6a6 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -19,7 +19,7 @@ struct expr_id {
 };
 
 struct expr_parse_ctx {
-	struct hashmap	 ids;
+	struct hashmap	*ids;
 	struct expr_id	*parent;
 };
 
@@ -30,8 +30,9 @@ struct expr_scanner_ctx {
 	int runtime;
 };
 
-void expr__ctx_init(struct expr_parse_ctx *ctx);
+struct expr_parse_ctx *expr__ctx_new(void);
 void expr__ctx_clear(struct expr_parse_ctx *ctx);
+void expr__ctx_free(struct expr_parse_ctx *ctx);
 void expr__del_id(struct expr_parse_ctx *ctx, const char *id);
 int expr__add_id(struct expr_parse_ctx *ctx, const char *id);
 int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val);
diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index ee94d3e8dd65..014c0fd7d670 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -118,7 +118,7 @@ struct metric_ref_node {
 
 struct metric {
 	struct list_head nd;
-	struct expr_parse_ctx pctx;
+	struct expr_parse_ctx *pctx;
 	const char *metric_name;
 	const char *metric_expr;
 	const char *metric_unit;
@@ -190,7 +190,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 	struct evsel *ev, *current_leader = NULL;
 	struct expr_id_data *val_ptr;
 	int i = 0, matched_events = 0, events_to_match;
-	const int idnum = (int)hashmap__size(&pctx->ids);
+	const int idnum = (int)hashmap__size(pctx->ids);
 
 	/*
 	 * duration_time is always grouped separately, when events are grouped
@@ -198,7 +198,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 	 * add it to metric_events at the end.
 	 */
 	if (!has_constraint &&
-	    hashmap__find(&pctx->ids, "duration_time", (void **)&val_ptr))
+	    hashmap__find(pctx->ids, "duration_time", (void **)&val_ptr))
 		events_to_match = idnum - 1;
 	else
 		events_to_match = idnum;
@@ -234,7 +234,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 		if (contains_event(metric_events, matched_events, ev->name))
 			continue;
 		/* Does this event belong to the parse context? */
-		if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr))
+		if (hashmap__find(pctx->ids, ev->name, (void **)&val_ptr))
 			metric_events[matched_events++] = ev;
 
 		if (matched_events == events_to_match)
@@ -315,12 +315,12 @@ static int metricgroup__setup_events(struct list_head *groups,
 		struct metric_ref *metric_refs = NULL;
 
 		metric_events = calloc(sizeof(void *),
-				hashmap__size(&m->pctx.ids) + 1);
+				hashmap__size(m->pctx->ids) + 1);
 		if (!metric_events) {
 			ret = -ENOMEM;
 			break;
 		}
-		evsel = find_evsel_group(perf_evlist, &m->pctx,
+		evsel = find_evsel_group(perf_evlist, m->pctx,
 					 metric_no_merge,
 					 m->has_constraint, metric_events,
 					 evlist_used);
@@ -686,7 +686,7 @@ static void metricgroup__add_metric_weak_group(struct strbuf *events,
 	size_t bkt;
 	bool no_group = true, has_duration = false;
 
-	hashmap__for_each_entry((&ctx->ids), cur, bkt) {
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
 		pr_debug("found event %s\n", (const char *)cur->key);
 		/*
 		 * Duration time maps to a software event and can make
@@ -717,7 +717,7 @@ static void metricgroup__add_metric_non_group(struct strbuf *events,
 	size_t bkt;
 	bool first = true;
 
-	hashmap__for_each_entry((&ctx->ids), cur, bkt) {
+	hashmap__for_each_entry(ctx->ids, cur, bkt) {
 		if (!first)
 			strbuf_addf(events, ",");
 		strbuf_addf(events, "%s", (const char *)cur->key);
@@ -793,7 +793,11 @@ static int __add_metric(struct list_head *metric_list,
 		if (!m)
 			return -ENOMEM;
 
-		expr__ctx_init(&m->pctx);
+		m->pctx = expr__ctx_new();
+		if (!m->pctx) {
+			free(m);
+			return -ENOMEM;
+		}
 		m->metric_name = pe->metric_name;
 		m->metric_expr = pe->metric_expr;
 		m->metric_unit = pe->unit;
@@ -841,15 +845,15 @@ static int __add_metric(struct list_head *metric_list,
 
 	/* Force all found IDs in metric to have us as parent ID. */
 	WARN_ON_ONCE(!parent);
-	m->pctx.parent = parent;
+	m->pctx->parent = parent;
 
 	/*
 	 * For both the parent and referenced metrics, we parse
 	 * all the metric's IDs and add it to the parent context.
 	 */
-	if (expr__find_other(pe->metric_expr, NULL, &m->pctx, runtime) < 0) {
+	if (expr__find_other(pe->metric_expr, NULL, m->pctx, runtime) < 0) {
 		if (m->metric_refs_cnt == 0) {
-			expr__ctx_clear(&m->pctx);
+			expr__ctx_free(m->pctx);
 			free(m);
 			*mp = NULL;
 		}
@@ -872,8 +876,8 @@ static int __add_metric(struct list_head *metric_list,
 		list_for_each_prev(pos, metric_list) {
 			struct metric *old = list_entry(pos, struct metric, nd);
 
-			if (hashmap__size(&m->pctx.ids) <=
-			    hashmap__size(&old->pctx.ids))
+			if (hashmap__size(m->pctx->ids) <=
+			    hashmap__size(old->pctx->ids))
 				break;
 		}
 		list_add(&m->nd, pos);
@@ -920,7 +924,7 @@ static int recursion_check(struct metric *m, const char *id, struct expr_id **pa
 	 * if we already processed 'id', if we did, it's recursion
 	 * and we fail.
 	 */
-	ret = expr__get_id(&m->pctx, id, &data);
+	ret = expr__get_id(m->pctx, id, &data);
 	if (ret)
 		return ret;
 
@@ -975,7 +979,7 @@ static int __resolve_metric(struct metric *m,
 	 */
 	do {
 		all = true;
-		hashmap__for_each_entry((&m->pctx.ids), cur, bkt) {
+		hashmap__for_each_entry(m->pctx->ids, cur, bkt) {
 			struct expr_id *parent;
 			struct pmu_event *pe;
 
@@ -989,7 +993,7 @@ static int __resolve_metric(struct metric *m,
 
 			all = false;
 			/* The metric key itself needs to go out.. */
-			expr__del_id(&m->pctx, cur->key);
+			expr__del_id(m->pctx, cur->key);
 
 			/* ... and it gets resolved to the parent context. */
 			ret = add_metric(metric_list, pe, metric_no_group, &m, parent, ids);
@@ -1135,10 +1139,10 @@ static int metricgroup__add_metric(const char *metric, bool metric_no_group,
 
 		if (m->has_constraint) {
 			metricgroup__add_metric_non_group(events,
-							  &m->pctx);
+							  m->pctx);
 		} else {
 			metricgroup__add_metric_weak_group(events,
-							   &m->pctx);
+							   m->pctx);
 		}
 	}
 
@@ -1201,7 +1205,7 @@ static void metricgroup__free_metrics(struct list_head *metric_list)
 
 	list_for_each_entry_safe (m, tmp, metric_list, nd) {
 		metric__free_refs(m);
-		expr__ctx_clear(&m->pctx);
+		expr__ctx_free(m->pctx);
 		list_del_init(&m->nd);
 		free(m);
 	}
diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index 901265127e36..bea7b5c6b1c0 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -1,8 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <math.h>
 #include <stdio.h>
 #include "evsel.h"
 #include "stat.h"
 #include "color.h"
+#include "debug.h"
 #include "pmu.h"
 #include "rblist.h"
 #include "evlist.h"
@@ -335,12 +337,16 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 {
 	struct evsel *counter, *leader, **metric_events, *oc;
 	bool found;
-	struct expr_parse_ctx ctx;
+	struct expr_parse_ctx *ctx;
 	struct hashmap_entry *cur;
 	size_t bkt;
 	int i;
 
-	expr__ctx_init(&ctx);
+	ctx = expr__ctx_new();
+	if (!ctx) {
+		pr_debug("expr__ctx_new failed");
+		return;
+	}
 	evlist__for_each_entry(evsel_list, counter) {
 		bool invalid = false;
 
@@ -348,25 +354,25 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 		if (!counter->metric_expr)
 			continue;
 
-		expr__ctx_clear(&ctx);
+		expr__ctx_clear(ctx);
 		metric_events = counter->metric_events;
 		if (!metric_events) {
 			if (expr__find_other(counter->metric_expr,
 					     counter->name,
-					     &ctx, 1) < 0)
+					     ctx, 1) < 0)
 				continue;
 
 			metric_events = calloc(sizeof(struct evsel *),
-					       hashmap__size(&ctx.ids) + 1);
+					       hashmap__size(ctx->ids) + 1);
 			if (!metric_events) {
-				expr__ctx_clear(&ctx);
+				expr__ctx_free(ctx);
 				return;
 			}
 			counter->metric_events = metric_events;
 		}
 
 		i = 0;
-		hashmap__for_each_entry((&ctx.ids), cur, bkt) {
+		hashmap__for_each_entry(ctx->ids, cur, bkt) {
 			const char *metric_name = (const char *)cur->key;
 
 			found = false;
@@ -418,7 +424,7 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 			counter->metric_expr = NULL;
 		}
 	}
-	expr__ctx_clear(&ctx);
+	expr__ctx_free(ctx);
 }
 
 static double runtime_stat_avg(struct runtime_stat *st,
@@ -793,7 +799,6 @@ static int prepare_metric(struct evsel **metric_events,
 	char *n, *pn;
 	int i, j, ret;
 
-	expr__ctx_init(pctx);
 	for (i = 0; metric_events[i]; i++) {
 		struct saved_value *v;
 		struct stats *stats;
@@ -854,17 +859,22 @@ static void generic_metric(struct perf_stat_config *config,
 			   struct runtime_stat *st)
 {
 	print_metric_t print_metric = out->print_metric;
-	struct expr_parse_ctx pctx;
+	struct expr_parse_ctx *pctx;
 	double ratio, scale;
 	int i;
 	void *ctxp = out->ctx;
 
-	i = prepare_metric(metric_events, metric_refs, &pctx, cpu, st);
-	if (i < 0)
+	pctx = expr__ctx_new();
+	if (!pctx)
 		return;
 
+	i = prepare_metric(metric_events, metric_refs, pctx, cpu, st);
+	if (i < 0) {
+		expr__ctx_free(pctx);
+		return;
+	}
 	if (!metric_events[i]) {
-		if (expr__parse(&ratio, &pctx, metric_expr, runtime) == 0) {
+		if (expr__parse(&ratio, pctx, metric_expr, runtime) == 0) {
 			char *unit;
 			char metric_bf[64];
 
@@ -900,22 +910,26 @@ static void generic_metric(struct perf_stat_config *config,
 			     (metric_name ? metric_name : name) : "", 0);
 	}
 
-	expr__ctx_clear(&pctx);
+	expr__ctx_free(pctx);
 }
 
 double test_generic_metric(struct metric_expr *mexp, int cpu, struct runtime_stat *st)
 {
-	struct expr_parse_ctx pctx;
+	struct expr_parse_ctx *pctx;
 	double ratio = 0.0;
 
-	if (prepare_metric(mexp->metric_events, mexp->metric_refs, &pctx, cpu, st) < 0)
+	pctx = expr__ctx_new();
+	if (!pctx)
+		return NAN;
+
+	if (prepare_metric(mexp->metric_events, mexp->metric_refs, pctx, cpu, st) < 0)
 		goto out;
 
-	if (expr__parse(&ratio, &pctx, mexp->metric_expr, 1))
+	if (expr__parse(&ratio, pctx, mexp->metric_expr, 1))
 		ratio = 0.0;
 
 out:
-	expr__ctx_clear(&pctx);
+	expr__ctx_free(pctx);
 	return ratio;
 }
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog

[PATCH v6 2/5] perf metric: Use NAN for missing event IDs.

[Ian Rogers]

If during computing a metric an event (id) is missing the parsing
aborts. A later patch will make it so that events that aren't used in
the output are deliberately omitted, in which case we don't want the
abort. Modify the missing ID case to report NAN for these cases.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/expr.y | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index b2ada8f8309a..41c9cd4efadd 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -1,6 +1,7 @@
 /* Simple expression parser */
 %{
 #define YYDEBUG 1
+#include <math.h>
 #include <stdio.h>
 #include "util.h"
 #include "util/debug.h"
@@ -88,12 +89,10 @@ expr:	  NUMBER
 	| ID			{
 					struct expr_id_data *data;
 
-					if (expr__resolve_id(ctx, $1, &data)) {
-						free($1);
-						YYABORT;
-					}
+					$$ = NAN;
+					if (expr__resolve_id(ctx, $1, &data) == 0)
+						$$ = expr_id_data__value(data);
 
-					$$ = expr_id_data__value(data);
 					free($1);
 				}
 	| expr '|' expr		{ $$ = (long)$1 | (long)$3; }
-- 
2.30.0.284.gd98b1dd5eaa7-goog

[PATCH v6 3/5] perf metric: Rename expr__find_other.

[Ian Rogers]

A later change will remove the notion of other, rename the function to
expr__find_ids as this is what it populates.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c       | 26 +++++++++++++-------------
 tools/perf/tests/pmu-events.c |  9 ++++-----
 tools/perf/util/expr.c        |  4 ++--
 tools/perf/util/expr.h        |  2 +-
 tools/perf/util/metricgroup.c |  2 +-
 tools/perf/util/stat-shadow.c |  6 +++---
 6 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index b0a3b5fd0c00..7ccb97c73347 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -64,25 +64,25 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
 	TEST_ASSERT_VAL("missing operand", ret == -1);
 
 	expr__ctx_clear(ctx);
-	TEST_ASSERT_VAL("find other",
-			expr__find_other("FOO + BAR + BAZ + BOZO", "FOO",
-					 ctx, 1) == 0);
-	TEST_ASSERT_VAL("find other", hashmap__size(ctx->ids) == 3);
-	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BAR",
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("FOO + BAR + BAZ + BOZO", "FOO",
+					ctx, 1) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 3);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BAR",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BAZ",
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BAZ",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "BOZO",
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "BOZO",
 						    (void **)&val_ptr));
 
 	expr__ctx_clear(ctx);
-	TEST_ASSERT_VAL("find other",
-			expr__find_other("EVENT1\\,param\\=?@ + EVENT2\\,param\\=?@",
-					 NULL, ctx, 3) == 0);
-	TEST_ASSERT_VAL("find other", hashmap__size(ctx->ids) == 2);
-	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "EVENT1,param=3/",
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1\\,param\\=?@ + EVENT2\\,param\\=?@",
+					NULL, ctx, 3) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 2);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1,param=3/",
 						    (void **)&val_ptr));
-	TEST_ASSERT_VAL("find other", hashmap__find(ctx->ids, "EVENT2,param=3/",
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT2,param=3/",
 						    (void **)&val_ptr));
 
 	expr__ctx_free(ctx);
diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
index cf5afd126934..d14a42406549 100644
--- a/tools/perf/tests/pmu-events.c
+++ b/tools/perf/tests/pmu-events.c
@@ -502,9 +502,8 @@ static int test_parsing(void)
 			if (!pe->metric_expr)
 				continue;
 			expr__ctx_clear(ctx);
-			if (expr__find_other(pe->metric_expr, NULL, ctx, 0)
-				  < 0) {
-				expr_failure("Parse other failed", map, pe);
+			if (expr__find_ids(pe->metric_expr, NULL, ctx, 0) < 0) {
+				expr_failure("Parse find ids failed", map, pe);
 				ret++;
 				continue;
 			}
@@ -559,8 +558,8 @@ static int metric_parse_fake(const char *str)
 	pr_debug("parsing '%s'\n", str);
 
 	ctx = expr__ctx_new();
-	if (expr__find_other(str, NULL, ctx, 0) < 0) {
-		pr_err("expr__find_other failed\n");
+	if (expr__find_ids(str, NULL, ctx, 0) < 0) {
+		pr_err("expr__find_ids failed\n");
 		return -1;
 	}
 
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index e0623d38e6ee..a248d14882cc 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -287,8 +287,8 @@ int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
 	return __expr__parse(final_val, ctx, expr, EXPR_PARSE, runtime) ? -1 : 0;
 }
 
-int expr__find_other(const char *expr, const char *one,
-		     struct expr_parse_ctx *ctx, int runtime)
+int expr__find_ids(const char *expr, const char *one,
+		   struct expr_parse_ctx *ctx, int runtime)
 {
 	int ret = __expr__parse(NULL, ctx, expr, EXPR_OTHER, runtime);
 
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index 00b941cfe6a6..955d5adb7ca4 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -43,7 +43,7 @@ int expr__resolve_id(struct expr_parse_ctx *ctx, const char *id,
 		     struct expr_id_data **datap);
 int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
 		const char *expr, int runtime);
-int expr__find_other(const char *expr, const char *one,
+int expr__find_ids(const char *expr, const char *one,
 		struct expr_parse_ctx *ids, int runtime);
 
 double expr_id_data__value(const struct expr_id_data *data);
diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 014c0fd7d670..69cfd717ab05 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -851,7 +851,7 @@ static int __add_metric(struct list_head *metric_list,
 	 * For both the parent and referenced metrics, we parse
 	 * all the metric's IDs and add it to the parent context.
 	 */
-	if (expr__find_other(pe->metric_expr, NULL, m->pctx, runtime) < 0) {
+	if (expr__find_ids(pe->metric_expr, NULL, m->pctx, runtime) < 0) {
 		if (m->metric_refs_cnt == 0) {
 			expr__ctx_free(m->pctx);
 			free(m);
diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index bea7b5c6b1c0..91bb7245f8b1 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -357,9 +357,9 @@ void perf_stat__collect_metric_expr(struct evlist *evsel_list)
 		expr__ctx_clear(ctx);
 		metric_events = counter->metric_events;
 		if (!metric_events) {
-			if (expr__find_other(counter->metric_expr,
-					     counter->name,
-					     ctx, 1) < 0)
+			if (expr__find_ids(counter->metric_expr,
+					   counter->name,
+					   ctx, 1) < 0)
 				continue;
 
 			metric_events = calloc(sizeof(struct evsel *),
-- 
2.30.0.284.gd98b1dd5eaa7-goog

[PATCH v6 4/5] perf metric: Add utilities to work on ids map.

[Ian Rogers]

Add utilities to new/free an ids hashmap, as well as to union. Add
testing of the union. Unioning hashmaps will be used when parsing the
metric, if a value is known then the hashmap is unnecessary, otherwise
we need to union together all the event ids to compute their values for
reporting.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c | 47 ++++++++++++++++++++++
 tools/perf/util/expr.c  | 87 +++++++++++++++++++++++++++++++++++++++--
 tools/perf/util/expr.h  | 13 ++++++
 3 files changed, 143 insertions(+), 4 deletions(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index 7ccb97c73347..1c881bea7fca 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -6,6 +6,51 @@
 #include <string.h>
 #include <linux/zalloc.h>
 
+static int test_ids_union(void)
+{
+	struct hashmap *ids1, *ids2;
+
+	/* Empty union. */
+	ids1 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids1);
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 0);
+
+	/* Union {foo, bar} against {}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids1, strdup("foo"), NULL), 0);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids1, strdup("bar"), NULL), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 2);
+
+	/* Union {foo, bar} against {foo}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("foo"), NULL), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 2);
+
+	/* Union {foo, bar} against {bar,baz}. */
+	ids2 = ids__new();
+	TEST_ASSERT_VAL("ids__new", ids2);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("bar"), NULL), 0);
+	TEST_ASSERT_EQUAL("ids__insert", ids__insert(ids2, strdup("baz"), NULL), 0);
+
+	ids1 = ids__union(ids1, ids2);
+	TEST_ASSERT_EQUAL("union", (int)hashmap__size(ids1), 3);
+
+	ids__free(ids1);
+
+	return 0;
+}
+
 static int test(struct expr_parse_ctx *ctx, const char *e, double val2)
 {
 	double val;
@@ -24,6 +69,8 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
 	int ret;
 	struct expr_parse_ctx *ctx;
 
+	TEST_ASSERT_EQUAL("ids_union", test_ids_union(), 0);
+
 	ctx = expr__ctx_new();
 	TEST_ASSERT_VAL("expr__ctx_new", ctx);
 	expr__add_id_val(ctx, strdup("FOO"), 1);
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index a248d14882cc..1adb6cd202e0 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -59,8 +59,48 @@ static bool key_equal(const void *key1, const void *key2,
 	return !strcmp((const char *)key1, (const char *)key2);
 }
 
-/* Caller must make sure id is allocated */
-int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
+struct hashmap *ids__new(void)
+{
+	return hashmap__new(key_hash, key_equal, NULL);
+}
+
+void ids__free(struct hashmap *ids)
+{
+	struct hashmap_entry *cur;
+	size_t bkt;
+
+	if (ids == NULL)
+		return;
+
+#ifdef PARSER_DEBUG
+	fprintf(stderr, "freeing ids: ");
+	ids__print(ids);
+	fprintf(stderr, "\n");
+#endif
+
+	hashmap__for_each_entry(ids, cur, bkt) {
+		free((char *)cur->key);
+		free(cur->value);
+	}
+
+	hashmap__free(ids);
+}
+
+void ids__print(struct hashmap *ids)
+{
+	size_t bkt;
+	struct hashmap_entry *cur;
+
+	if (!ids)
+		return;
+
+	hashmap__for_each_entry(ids, cur, bkt) {
+		fprintf(stderr, "key:%s, ", (const char *)cur->key);
+	}
+}
+
+int ids__insert(struct hashmap *ids, const char *id,
+		struct expr_id *parent)
 {
 	struct expr_id_data *data_ptr = NULL, *old_data = NULL;
 	char *old_key = NULL;
@@ -70,10 +110,10 @@ int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
 	if (!data_ptr)
 		return -ENOMEM;
 
-	data_ptr->parent = ctx->parent;
+	data_ptr->parent = parent;
 	data_ptr->kind = EXPR_ID_DATA__PARENT;
 
-	ret = hashmap__set(ctx->ids, id, data_ptr,
+	ret = hashmap__set(ids, id, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	if (ret)
 		free(data_ptr);
@@ -82,6 +122,45 @@ int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
 	return ret;
 }
 
+struct hashmap *ids__union(struct hashmap *ids1, struct hashmap *ids2)
+{
+	size_t bkt;
+	struct hashmap_entry *cur;
+	int ret;
+	struct expr_id_data *old_data = NULL;
+	char *old_key = NULL;
+
+	if (!ids1)
+		return ids2;
+
+	if (!ids2)
+		return ids1;
+
+	if (hashmap__size(ids1) <  hashmap__size(ids2)) {
+		struct hashmap *tmp = ids1;
+
+		ids1 = ids2;
+		ids2 = tmp;
+	}
+	hashmap__for_each_entry(ids2, cur, bkt) {
+		ret = hashmap__set(ids1, cur->key, cur->value,
+				(const void **)&old_key, (void **)&old_data);
+		free(old_key);
+		free(old_data);
+
+		if (ret)
+			break;
+	}
+	hashmap__free(ids2);
+	return ids1;
+}
+
+/* Caller must make sure id is allocated */
+int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
+{
+	return ids__insert(ctx->ids, id, ctx->parent);
+}
+
 /* Caller must make sure id is allocated */
 int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val)
 {
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index 955d5adb7ca4..f201889d1136 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -30,9 +30,20 @@ struct expr_scanner_ctx {
 	int runtime;
 };
 
+struct hashmap *ids__new(void);
+void ids__free(struct hashmap *ids);
+void ids__print(struct hashmap *ids);
+int ids__insert(struct hashmap *ids, const char *id, struct expr_id *parent);
+/*
+ * Union two sets of ids (hashmaps) and construct a third, freeing ids1 and
+ * ids2.
+ */
+struct hashmap *ids__union(struct hashmap *ids1, struct hashmap *ids2);
+
 struct expr_parse_ctx *expr__ctx_new(void);
 void expr__ctx_clear(struct expr_parse_ctx *ctx);
 void expr__ctx_free(struct expr_parse_ctx *ctx);
+
 void expr__del_id(struct expr_parse_ctx *ctx, const char *id);
 int expr__add_id(struct expr_parse_ctx *ctx, const char *id);
 int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val);
@@ -41,8 +52,10 @@ int expr__get_id(struct expr_parse_ctx *ctx, const char *id,
 		 struct expr_id_data **data);
 int expr__resolve_id(struct expr_parse_ctx *ctx, const char *id,
 		     struct expr_id_data **datap);
+
 int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
 		const char *expr, int runtime);
+
 int expr__find_ids(const char *expr, const char *one,
 		struct expr_parse_ctx *ids, int runtime);
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog

[PATCH v6 5/5] perf metric: Don't compute unused events.

[Ian Rogers]

For a metric like:
  EVENT1 if #smt_on else EVENT2

currently EVENT1 and EVENT2 will be measured and then when the metric is
reported EVENT1 or EVENT2 will be printed depending on the value from
smt_on() during the expr parsing. Computing both events is unnecessary and
can lead to multiplexing as discussed in this thread:
https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/

This change modifies the expression parsing code by:
 - getting rid of the "other" parsing and introducing a boolean argument
   to say whether ids should be computed or not.
 - expressions are changed so that a pair of value and ids are returned.
 - when computing the metric value the ids are unused.
 - when computing the ids, constant values and smt_on are assigned to
   the value.
 - If the value is from an event ID then the event is added to the ids
   hashmap and the value set to bottom (encoded as NAN).
 - Typically operators union IDs for their inputs and set the value to
   bottom, however, if the inputs are constant then these are computed and
   propagated as the value.
 - If the input is constant to certain operators like:
 IDS1 if CONST else IDS2
   then the result will be either IDS1 or IDS2 depending on CONST (which
   may be evaluated from an entire expression), and so IDS1 or IDS2 may
   be discarded avoiding events from being programmed.
 - The ids at the end of parsing are added to the context.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c |  17 ++
 tools/perf/util/expr.c  |  10 +-
 tools/perf/util/expr.h  |   1 -
 tools/perf/util/expr.l  |   9 --
 tools/perf/util/expr.y  | 340 ++++++++++++++++++++++++++++++----------
 5 files changed, 283 insertions(+), 94 deletions(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index 1c881bea7fca..5cab5960b257 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "util/debug.h"
 #include "util/expr.h"
+#include "util/smt.h"
 #include "tests.h"
 #include <stdlib.h>
 #include <string.h>
@@ -132,6 +133,22 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
 	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT2,param=3/",
 						    (void **)&val_ptr));
 
+	/* Only EVENT1 or EVENT2 need be measured depending on the value of smt_on. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("EVENT1 if #smt_on else EVENT2",
+				NULL, ctx, 0) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
+	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids,
+						  smt_on() ? "EVENT1" : "EVENT2",
+						  (void **)&val_ptr));
+
+	/* The expression is a constant 1.0 without needing to evaluate EVENT1. */
+	expr__ctx_clear(ctx);
+	TEST_ASSERT_VAL("find ids",
+			expr__find_ids("1.0 if EVENT1 > 100.0 else 1.0",
+				NULL, ctx, 0) == 0);
+	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
 	expr__ctx_free(ctx);
 
 	return 0;
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 1adb6cd202e0..e9396a309fb7 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -325,14 +325,14 @@ void expr__ctx_free(struct expr_parse_ctx *ctx)
 		free(cur->value);
 	}
 	hashmap__free(ctx->ids);
+	free(ctx);
 }
 
 static int
 __expr__parse(double *val, struct expr_parse_ctx *ctx, const char *expr,
-	      int start, int runtime)
+	      bool compute_ids, int runtime)
 {
 	struct expr_scanner_ctx scanner_ctx = {
-		.start_token = start,
 		.runtime = runtime,
 	};
 	YY_BUFFER_STATE buffer;
@@ -352,7 +352,7 @@ __expr__parse(double *val, struct expr_parse_ctx *ctx, const char *expr,
 	expr_set_debug(1, scanner);
 #endif
 
-	ret = expr_parse(val, ctx, scanner);
+	ret = expr_parse(val, ctx, compute_ids, scanner);
 
 	expr__flush_buffer(buffer, scanner);
 	expr__delete_buffer(buffer, scanner);
@@ -363,13 +363,13 @@ __expr__parse(double *val, struct expr_parse_ctx *ctx, const char *expr,
 int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
 		const char *expr, int runtime)
 {
-	return __expr__parse(final_val, ctx, expr, EXPR_PARSE, runtime) ? -1 : 0;
+	return __expr__parse(final_val, ctx, expr, /*compute_ids=*/false, runtime) ? -1 : 0;
 }
 
 int expr__find_ids(const char *expr, const char *one,
 		   struct expr_parse_ctx *ctx, int runtime)
 {
-	int ret = __expr__parse(NULL, ctx, expr, EXPR_OTHER, runtime);
+	int ret = __expr__parse(NULL, ctx, expr, /*compute_ids=*/true, runtime);
 
 	if (one)
 		expr__del_id(ctx, one);
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index f201889d1136..0d08b34285ba 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -26,7 +26,6 @@ struct expr_parse_ctx {
 struct expr_id_data;
 
 struct expr_scanner_ctx {
-	int start_token;
 	int runtime;
 };
 
diff --git a/tools/perf/util/expr.l b/tools/perf/util/expr.l
index 13e5e3c75f56..702fdf6456ca 100644
--- a/tools/perf/util/expr.l
+++ b/tools/perf/util/expr.l
@@ -91,15 +91,6 @@ symbol		({spec}|{sym})+
 %%
 	struct expr_scanner_ctx *sctx = expr_get_extra(yyscanner);
 
-	{
-		int start_token = sctx->start_token;
-
-		if (sctx->start_token) {
-			sctx->start_token = 0;
-			return start_token;
-		}
-	}
-
 d_ratio		{ return D_RATIO; }
 max		{ return MAX; }
 min		{ return MIN; }
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index 41c9cd4efadd..907fe135c080 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -1,43 +1,55 @@
 /* Simple expression parser */
 %{
 #define YYDEBUG 1
+#include <assert.h>
 #include <math.h>
-#include <stdio.h>
-#include "util.h"
 #include "util/debug.h"
-#include <stdlib.h> // strtod()
+#include "smt.h"
 #define IN_EXPR_Y 1
 #include "expr.h"
-#include "smt.h"
-#include <string.h>
-
-static double d_ratio(double val0, double val1)
-{
-	if (val1 == 0) {
-		return 0;
-	}
-	return  val0 / val1;
-}
-
 %}
 
 %define api.pure full
 
 %parse-param { double *final_val }
 %parse-param { struct expr_parse_ctx *ctx }
+%parse-param { bool compute_ids }
 %parse-param {void *scanner}
 %lex-param {void* scanner}
 
 %union {
 	double	 num;
 	char	*str;
+	struct ids {
+		/*
+		 * When creating ids, holds the working set of event ids. NULL
+		 * implies the set is empty.
+		 */
+		struct hashmap *ids;
+		/*
+		 * The metric value. When not creating ids this is the value
+		 * read from a counter, a constant or some computed value. When
+		 * creating ids the value is either a constant or BOTTOM. NAN is
+		 * used as the special BOTTOM value, representing a "set of all
+		 * values" case. Consider:
+		 *   1.0 if event1 > 50.0 else 2.0
+		 * The set of values {1.0, 2.0} is possible from this
+		 * expression, but we conservatively use BOTTOM to say any value
+		 * is possible. By tracking constants an expression like:
+		 *   1.0 if event1 > 50.0 else 1.0
+		 * can avoid computing event1 as only the value 1.0 is a
+		 * possible value.
+		 * It is much more likely we're evaluating:
+		 *   EVENT1 if #smt_on else EVENT2
+		 * where we don't want to compute two events, but we track
+		 * constants in a more general framework to allow for more
+		 * complicated expressions.
+		 */
+		double val;
+	} ids;
 }
 
-%token EXPR_PARSE EXPR_OTHER EXPR_ERROR
-%token <num> NUMBER
-%token <str> ID
-%destructor { free ($$); } <str>
-%token MIN MAX IF ELSE SMT_ON D_RATIO
+%token ID NUMBER MIN MAX IF ELSE SMT_ON D_RATIO EXPR_ERROR
 %left MIN MAX IF
 %left '|'
 %left '^'
@@ -46,81 +58,251 @@ static double d_ratio(double val0, double val1)
 %left '-' '+'
 %left '*' '/' '%'
 %left NEG NOT
-%type <num> expr if_expr
+%type <num> NUMBER
+%type <str> ID
+%destructor { free ($$); } <str>
+%type <ids> expr if_expr
+%destructor { ids__free($$.ids); } <ids>
 
 %{
 static void expr_error(double *final_val __maybe_unused,
 		       struct expr_parse_ctx *ctx __maybe_unused,
+		       bool compute_ids __maybe_unused,
 		       void *scanner,
 		       const char *s)
 {
 	pr_debug("%s\n", s);
 }
 
+/*
+ * During compute ids, the special "bottom" value uses NAN to represent the set
+ * of all values. NAN is selected as it isn't a useful constant value.
+ */
+#define BOTTOM NAN
+
+/* During computing ids, does val represent a constant (non-BOTTOM) value? */
+static bool is_const(double val)
+{
+	return isfinite(val);
+}
+
+static struct ids union_expr(struct ids ids1, struct ids ids2)
+{
+	struct ids result = {
+		.val = BOTTOM,
+		.ids = ids__union(ids1.ids, ids2.ids),
+	};
+	return result;
+}
+
+/*
+ * If we're not computing ids or $1 and $3 are constants, compute the new
+ * constant value using OP. Its invariant that there are no ids.  If computing
+ * ids for non-constants union the set of IDs that must be computed.
+ */
+#define BINARY_LONG_OP(RESULT, OP, LHS, RHS)				\
+	if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \
+		assert(LHS.ids == NULL);				\
+		assert(RHS.ids == NULL);				\
+		RESULT.val = (long)LHS.val OP (long)RHS.val;		\
+		RESULT.ids = NULL;					\
+	} else {							\
+	        RESULT = union_expr(LHS, RHS);				\
+	}
+
+#define BINARY_OP(RESULT, OP, LHS, RHS)					\
+	if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \
+		assert(LHS.ids == NULL);				\
+		assert(RHS.ids == NULL);				\
+		RESULT.val = LHS.val OP RHS.val;			\
+		RESULT.ids = NULL;					\
+	} else {							\
+	        RESULT = union_expr(LHS, RHS);				\
+	}
+
 %}
 %%
 
-start:
-EXPR_PARSE all_expr
-|
-EXPR_OTHER all_other
+start: if_expr
+{
+	if (compute_ids)
+		ctx->ids = ids__union($1.ids, ctx->ids);
 
-all_other: all_other other
-|
+	if (final_val)
+		*final_val = $1.val;
+}
+;
+
+if_expr: expr IF expr ELSE expr
+{
+	if (fpclassify($3.val) == FP_ZERO) {
+		/*
+		 * The IF expression evaluated to 0 so treat as false, take the
+		 * ELSE and discard everything else.
+		 */
+		$$.val = $5.val;
+		$$.ids = $5.ids;
+		ids__free($1.ids);
+		ids__free($3.ids);
+	} else if (!compute_ids || is_const($3.val)) {
+		/*
+		 * If ids aren't computed then treat the expression as true. If
+		 * ids are being computed and the IF expr is a non-zero
+		 * constant, then also evaluate the true case.
+		 */
+		$$.val = $1.val;
+		$$.ids = $1.ids;
+		ids__free($3.ids);
+		ids__free($5.ids);
+	} else if ($1.val == $5.val) {
+		/*
+		 * LHS == RHS, so both are an identical constant. No need to
+		 * evaluate any events.
+		 */
+		$$.val = $1.val;
+		$$.ids = NULL;
+		ids__free($1.ids);
+		ids__free($3.ids);
+		ids__free($5.ids);
+	} else {
+		/*
+		 * Value is either the LHS or RHS and we need the IF expression
+		 * to compute it.
+		 */
+		$$ = union_expr($1, union_expr($3, $5));
+	}
+}
+| expr
+;
 
-other: ID
+expr: NUMBER
 {
-	expr__add_id(ctx, $1);
-}
-|
-MIN | MAX | IF | ELSE | SMT_ON | NUMBER | '|' | '^' | '&' | '-' | '+' | '*' | '/' | '%' | '(' | ')' | ','
-|
-'<' | '>' | D_RATIO
-
-all_expr: if_expr			{ *final_val = $1; }
-	;
-
-if_expr:
-	expr IF expr ELSE expr { $$ = $3 ? $1 : $5; }
-	| expr
-	;
-
-expr:	  NUMBER
-	| ID			{
-					struct expr_id_data *data;
-
-					$$ = NAN;
-					if (expr__resolve_id(ctx, $1, &data) == 0)
-						$$ = expr_id_data__value(data);
-
-					free($1);
-				}
-	| expr '|' expr		{ $$ = (long)$1 | (long)$3; }
-	| expr '&' expr		{ $$ = (long)$1 & (long)$3; }
-	| expr '^' expr		{ $$ = (long)$1 ^ (long)$3; }
-	| expr '<' expr		{ $$ = $1 < $3; }
-	| expr '>' expr		{ $$ = $1 > $3; }
-	| expr '+' expr		{ $$ = $1 + $3; }
-	| expr '-' expr		{ $$ = $1 - $3; }
-	| expr '*' expr		{ $$ = $1 * $3; }
-	| expr '/' expr		{ if ($3 == 0) {
-					pr_debug("division by zero\n");
-					YYABORT;
-				  }
-				  $$ = $1 / $3;
-	                        }
-	| expr '%' expr		{ if ((long)$3 == 0) {
-					pr_debug("division by zero\n");
-					YYABORT;
-				  }
-				  $$ = (long)$1 % (long)$3;
-	                        }
-	| '-' expr %prec NEG	{ $$ = -$2; }
-	| '(' if_expr ')'	{ $$ = $2; }
-	| MIN '(' expr ',' expr ')' { $$ = $3 < $5 ? $3 : $5; }
-	| MAX '(' expr ',' expr ')' { $$ = $3 > $5 ? $3 : $5; }
-	| SMT_ON		 { $$ = smt_on() > 0; }
-	| D_RATIO '(' expr ',' expr ')' { $$ = d_ratio($3,$5); }
-	;
+	$$.val = $1;
+	$$.ids = NULL;
+}
+| ID
+{
+	if (!compute_ids) {
+		/*
+		 * Compute the event's value from ID. If the ID isn't known then
+		 * it isn't used to compute the formula so set to NAN.
+		 */
+		struct expr_id_data *data;
+
+		$$.val = NAN;
+		if (expr__resolve_id(ctx, $1, &data) == 0)
+			$$.val = expr_id_data__value(data);
+
+		$$.ids = NULL;
+		free($1);
+	} else {
+		/*
+		 * Set the value to BOTTOM to show that any value is possible
+		 * when the event is computed. Create a set of just the ID.
+		 */
+		$$.val = BOTTOM;
+		$$.ids = ids__new();
+		if (!$$.ids || ids__insert($$.ids, $1, ctx->parent))
+			YYABORT;
+	}
+}
+| expr '|' expr { BINARY_LONG_OP($$, |, $1, $3); }
+| expr '&' expr { BINARY_LONG_OP($$, &, $1, $3); }
+| expr '^' expr { BINARY_LONG_OP($$, ^, $1, $3); }
+| expr '<' expr { BINARY_OP($$, <, $1, $3); }
+| expr '>' expr { BINARY_OP($$, >, $1, $3); }
+| expr '+' expr { BINARY_OP($$, +, $1, $3); }
+| expr '-' expr { BINARY_OP($$, -, $1, $3); }
+| expr '*' expr { BINARY_OP($$, *, $1, $3); }
+| expr '/' expr
+{
+	if (fpclassify($3.val) == FP_ZERO) {
+		pr_debug("division by zero\n");
+		YYABORT;
+	} else if (!compute_ids || (is_const($1.val) && is_const($3.val))) {
+		assert($1.ids == NULL);
+		assert($3.ids == NULL);
+		$$.val = $1.val / $3.val;
+		$$.ids = NULL;
+	} else {
+		/* LHS and/or RHS need computing from event IDs so union. */
+		$$ = union_expr($1, $3);
+	}
+}
+| expr '%' expr
+{
+	if (fpclassify($3.val) == FP_ZERO) {
+		pr_debug("division by zero\n");
+		YYABORT;
+	} else if (!compute_ids || (is_const($1.val) && is_const($3.val))) {
+		assert($1.ids == NULL);
+		assert($3.ids == NULL);
+		$$.val = (long)$1.val % (long)$3.val;
+		$$.ids = NULL;
+	} else {
+		/* LHS and/or RHS need computing from event IDs so union. */
+		$$ = union_expr($1, $3);
+	}
+}
+| D_RATIO '(' expr ',' expr ')'
+{
+	if (fpclassify($5.val) == FP_ZERO) {
+		/*
+		 * Division by constant zero always yields zero and no events
+		 * are necessary.
+		 */
+		assert($5.ids == NULL);
+		$$.val = 0.0;
+		$$.ids = NULL;
+		ids__free($3.ids);
+	} else if (!compute_ids || (is_const($3.val) && is_const($5.val))) {
+		assert($3.ids == NULL);
+		assert($5.ids == NULL);
+		$$.val = $3.val / $5.val;
+		$$.ids = NULL;
+	} else {
+		/* LHS and/or RHS need computing from event IDs so union. */
+		$$ = union_expr($3, $5);
+	}
+}
+| '-' expr %prec NEG
+{
+	$$.val = -$2.val;
+	$$.ids = $2.ids;
+}
+| '(' if_expr ')'
+{
+	$$ = $2;
+}
+| MIN '(' expr ',' expr ')'
+{
+	if (!compute_ids || (is_const($3.val) && is_const($5.val))) {
+		assert($3.ids == NULL);
+		assert($5.ids == NULL);
+		$$.val = $3.val < $5.val ? $3.val : $5.val;
+		$$.ids = NULL;
+	} else {
+		/* LHS and/or RHS need computing from event IDs so union. */
+		$$ = union_expr($3, $5);
+	}
+}
+| MAX '(' expr ',' expr ')'
+{
+	if (!compute_ids || (is_const($3.val) && is_const($5.val))) {
+		assert($3.ids == NULL);
+		assert($5.ids == NULL);
+		$$.val = $3.val > $5.val ? $3.val : $5.val;
+		$$.ids = NULL;
+	} else {
+		/* LHS and/or RHS need computing from event IDs so union. */
+		$$ = union_expr($3, $5);
+	}
+}
+| SMT_ON
+{
+	$$.val = smt_on() > 0 ? 1.0 : 0.0;
+	$$.ids = NULL;
+}
+;
 
 %%
-- 
2.30.0.284.gd98b1dd5eaa7-goog