v.util.timers: improve tracing by supporting -d trace_timers_creation

vlib/v/util/timers.v

@@ -1,12 +1,16 @@
 // Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
 // Use of this source code is governed by an MIT license
 // that can be found in the LICENSE file.
+[has_globals]
 module util
 
 import time
 
+__global g_timers = new_timers(should_print: false, label: 'g_timers')
+
 [heap]
 pub struct Timers {
+	label string
 pub mut:
 	swatches     map[string]time.StopWatch
 	should_print bool
@@ -14,18 +18,26 @@ pub mut:
 	already_shown []string
 }
 
-pub fn new_timers(should_print bool) &Timers {
+[params]
+pub struct TimerParams {
+	should_print bool
+	label        string
+}
+
+pub fn new_timers(params TimerParams) &Timers {
+	$if trace_timers_creation ? {
+		eprintln('>>>> new_timers, should_print: $params.should_print | label: $params.label')
+	}
 	return &Timers{
+		label: params.label
 		swatches: map[string]time.StopWatch{}
-		should_print: should_print
+		should_print: params.should_print
 		already_shown: []string{cap: 100}
 	}
 }
 
-const timers = new_timers(false)
-
 pub fn get_timers() &Timers {
-	return util.timers
+	return g_timers
 }
 
 pub fn timing_start(label string) {
@@ -34,18 +46,15 @@ pub fn timing_start(label string) {
 }
 
 pub fn timing_measure(label string) {
-	mut t := get_timers()
-	t.show(label)
+	g_timers.show(label)
 }
 
 pub fn timing_measure_cumulative(label string) {
-	mut t := get_timers()
-	t.measure_cumulative(label)
+	g_timers.measure_cumulative(label)
 }
 
 pub fn timing_set_should_print(should_print bool) {
-	mut t := util.timers
-	t.should_print = should_print
+	g_timers.should_print = should_print
 }
 
 pub fn (mut t Timers) start(name string) {