perf tools: Factor out prepare_metric function

Factoring out prepare_metric function so it can be used in test
interface coming in following changes.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200602214741.1218986-10-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/stat-shadow.c

@@ -730,25 +730,16 @@ static void print_smi_cost(struct perf_stat_config *config,
 	out->print_metric(config, out->ctx, NULL, "%4.0f", "SMI#", smi_num);
 }
 
-static void generic_metric(struct perf_stat_config *config,
-			   const char *metric_expr,
-			   struct evsel **metric_events,
-			   char *name,
-			   const char *metric_name,
-			   const char *metric_unit,
-			   int runtime,
-			   int cpu,
-			   struct perf_stat_output_ctx *out,
-			   struct runtime_stat *st)
+static int prepare_metric(struct evsel **metric_events,
+			  struct expr_parse_ctx *pctx,
+			  int cpu,
+			  struct runtime_stat *st)
 {
-	print_metric_t print_metric = out->print_metric;
-	struct expr_parse_ctx pctx;
-	double ratio, scale;
-	int i;
-	void *ctxp = out->ctx;
+	double scale;
 	char *n, *pn;
+	int i;
 
-	expr__ctx_init(&pctx);
+	expr__ctx_init(pctx);
 	for (i = 0; metric_events[i]; i++) {
 		struct saved_value *v;
 		struct stats *stats;
@@ -771,7 +762,7 @@ static void generic_metric(struct perf_stat_config *config,
 
 		n = strdup(metric_events[i]->name);
 		if (!n)
-			return;
+			return -ENOMEM;
 		/*
 		 * This display code with --no-merge adds [cpu] postfixes.
 		 * These are not supported by the parser. Remove everything
@@ -782,11 +773,35 @@ static void generic_metric(struct perf_stat_config *config,
 			*pn = 0;
 
 		if (metric_total)
-			expr__add_id(&pctx, n, metric_total);
+			expr__add_id(pctx, n, metric_total);
 		else
-			expr__add_id(&pctx, n, avg_stats(stats)*scale);
+			expr__add_id(pctx, n, avg_stats(stats)*scale);
 	}
 
+	return i;
+}
+
+static void generic_metric(struct perf_stat_config *config,
+			   const char *metric_expr,
+			   struct evsel **metric_events,
+			   char *name,
+			   const char *metric_name,
+			   const char *metric_unit,
+			   int runtime,
+			   int cpu,
+			   struct perf_stat_output_ctx *out,
+			   struct runtime_stat *st)
+{
+	print_metric_t print_metric = out->print_metric;
+	struct expr_parse_ctx pctx;
+	double ratio, scale;
+	int i;
+	void *ctxp = out->ctx;
+
+	i = prepare_metric(metric_events, &pctx, cpu, st);
+	if (i < 0)
+		return;
+
 	if (!metric_events[i]) {
 		if (expr__parse(&ratio, &pctx, metric_expr, runtime) == 0) {
 			char *unit;