Some events are dependent on firmware/kernel enablement. Allow such
events to be detected when the metric is parsed so that the metric's
event parsing doesn't fail.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c |  4 ++++
 tools/perf/util/expr.c  | 19 +++++++++++++++++++
 tools/perf/util/expr.h  |  1 +
 tools/perf/util/expr.l  |  1 +
 tools/perf/util/expr.y  |  8 +++++++-
 5 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index 3d01eb5e2512..c1c3fcbc2753 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -254,6 +254,10 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
 	TEST_ASSERT_VAL("source count", hashmap__size(ctx->ids) == 1);
 	TEST_ASSERT_VAL("source count", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
 
+	/* has_event returns 1 when an event exists. */
+	expr__add_id_val(ctx, strdup("cycles"), 2);
+	ret = test(ctx, "has_event(cycles)", 1);
+
 	expr__ctx_free(ctx);
 
 	return 0;
diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index f4e52919324e..47b881e566f0 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -8,6 +8,7 @@
 #include "cpumap.h"
 #include "cputopo.h"
 #include "debug.h"
+#include "evlist.h"
 #include "expr.h"
 #include "expr-bison.h"
 #include "expr-flex.h"
@@ -474,3 +475,21 @@ double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx
 	pr_debug2("literal: %s = %f\n", literal, result);
 	return result;
 }
+
+/* Does the event 'id' parse? Determine via ctx->ids if possible. */
+double expr__has_event(const struct expr_parse_ctx *ctx, bool compute_ids, const char *id)
+{
+	struct evlist *tmp;
+	double ret;
+
+	if (hashmap__find(ctx->ids, id, /*value=*/NULL))
+		return 1.0;
+
+	if (!compute_ids)
+		return 0.0;
+
+	tmp = evlist__new();
+	ret = parse_event(tmp, id) ? 0 : 1;
+	evlist__delete(tmp);
+	return ret;
+}
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index eaa44b24c555..3c1e49b3e35d 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -54,5 +54,6 @@ int expr__find_ids(const char *expr, const char *one,
 double expr_id_data__value(const struct expr_id_data *data);
 double expr_id_data__source_count(const struct expr_id_data *data);
 double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx);
+double expr__has_event(const struct expr_parse_ctx *ctx, bool compute_ids, const char *id);
 
 #endif
diff --git a/tools/perf/util/expr.l b/tools/perf/util/expr.l
index 4fbf353e78e7..dbb117414710 100644
--- a/tools/perf/util/expr.l
+++ b/tools/perf/util/expr.l
@@ -113,6 +113,7 @@ min		{ return MIN; }
 if		{ return IF; }
 else		{ return ELSE; }
 source_count	{ return SOURCE_COUNT; }
+has_event	{ return HAS_EVENT; }
 {literal}	{ return literal(yyscanner, sctx); }
 {number}	{ return value(yyscanner); }
 {symbol}	{ return str(yyscanner, ID, sctx->runtime); }
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index f04963eb6be0..dd504afd8f36 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -37,7 +37,7 @@
 	} ids;
 }
 
-%token ID NUMBER MIN MAX IF ELSE LITERAL D_RATIO SOURCE_COUNT EXPR_ERROR
+%token ID NUMBER MIN MAX IF ELSE LITERAL D_RATIO SOURCE_COUNT HAS_EVENT EXPR_ERROR
 %left MIN MAX IF
 %left '|'
 %left '^'
@@ -199,6 +199,12 @@ expr: NUMBER
 }
 | ID				{ $$ = handle_id(ctx, $1, compute_ids, /*source_count=*/false); }
 | SOURCE_COUNT '(' ID ')'	{ $$ = handle_id(ctx, $3, compute_ids, /*source_count=*/true); }
+| HAS_EVENT '(' ID ')'
+{
+	$$.val = expr__has_event(ctx, compute_ids, $3);
+	$$.ids = NULL;
+	free($3);
+}
 | expr '|' expr
 {
 	if (is_const($1.val) && is_const($3.val)) {
-- 
2.41.0.162.gfafddb0af9-goog

On 23/06/2023 01:33, Ian Rogers wrote:
> +	if (!compute_ids)
> +		return 0.0;
> +
> +	tmp = evlist__new();

tmp may be NULL, and parse_event() is not NULL safe, so I assume that we 
need to handle tmp == NULL

> +	ret = parse_event(tmp, id) ? 0 : 1;
> +	evlist__delete(tmp);
> +	return ret;

On Fri, Jun 23, 2023 at 7:40 AM John Garry <john.g.garry@oracle.com> wrote:
>
> On 23/06/2023 01:33, Ian Rogers wrote:
> > +     if (!compute_ids)
> > +             return 0.0;
> > +
> > +     tmp = evlist__new();
>
> tmp may be NULL, and parse_event() is not NULL safe, so I assume that we
> need to handle tmp == NULL

I'm not sure there's much sensible we can do with this, so I'll turn
it into a NAN for v2 - the normal error case.

Thanks,
Ian

> > +     ret = parse_event(tmp, id) ? 0 : 1;
> > +     evlist__delete(tmp);
> > +     return ret;
>