perf expr: Add has_event function

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 <[e-mail]>
Tested-by: Namhyung Kim <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Eduard Zingerman <[e-mail]>
Cc: Sohom Datta <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Caleb Biggers <[e-mail]>
Cc: Edward Baker <[e-mail]>
Cc: Perry Taylor <[e-mail]>
Cc: Samantha Alt <[e-mail]>
Cc: Weilin Wang <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Jing Zhang <[e-mail]>
Cc: Kajol Jain <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Zhengjun Xing <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/tests/expr.c

···
 	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;

tools/perf/util/expr.c

···
 #include "cpumap.h"
 #include "cputopo.h"
 #include "debug.h"
+#include "evlist.h"
 #include "expr.h"
 #include "expr-bison.h"
 #include "expr-flex.h"
···
 out:
 	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();
+	if (!tmp)
+		return NAN;
+	ret = parse_event(tmp, id) ? 0 : 1;
+	evlist__delete(tmp);
+	return ret;
 }

tools/perf/util/expr.h

···
 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

tools/perf/util/expr.l

···
 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); }

tools/perf/util/expr.y

···
 	} 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 '^'
···
 }
 | 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)) {