checker,cgen: implement v.profile.on/1, support `[if profile]` and `-d no_profile_startup` (#13232)

cmd/v/help/build.txt

@@ -84,8 +84,16 @@ NB: the build flags are shared with the run command too:
          b) how much *nanoseconds in total* it took
          c) an average for each function (i.e. (b) / (a) )
          d) the function name
+         
       NB: if you want to output the profile info to stdout, use `-profile -`.
 
+      NB: you can use `import v.profile`, and then calls to `profile.on(false)`
+           and `profile.on(true)` to temporarily turn it off and on again.
+
+      NB: if you do NOT want the profile to contain information from before your
+           program's `fn main()` starts, pass `-d no_profile_startup` too.
+           (V constants, and module init() functions are evaluated before `main()` is called)
+
    -message-limit <limit>
       The maximum amount of warnings / errors / notices, that will be accumulated (defaults to 100).
       The checker will abort prematurely once this limit has been reached.

vlib/v/checker/checker.v

@@ -26,7 +26,7 @@ const (
 	valid_comptime_if_cpu_features   = ['x64', 'x32', 'little_endian', 'big_endian']
 	valid_comptime_if_other          = ['apk', 'js', 'debug', 'prod', 'test', 'glibc', 'prealloc',
 		'no_bounds_checking', 'freestanding', 'threads', 'js_node', 'js_browser', 'js_freestanding',
-		'interpreter', 'es5']
+		'interpreter', 'es5', 'profile']
 	valid_comptime_not_user_defined  = all_valid_comptime_idents()
 	array_builtin_methods            = ['filter', 'clone', 'repeat', 'reverse', 'map', 'slice',
 		'sort', 'contains', 'index', 'wait', 'any', 'all', 'first', 'last', 'pop']

vlib/v/checker/comptime.v

@@ -532,6 +532,7 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Position) bool {
 					'js' { return !c.pref.backend.is_js() }
 					'debug' { return !c.pref.is_debug }
 					'prod' { return !c.pref.is_prod }
+					'profile' { return !c.pref.is_prof }
 					'test' { return !c.pref.is_test }
 					'glibc' { return false } // TODO
 					'threads' { return c.table.gostmts == 0 }

vlib/v/gen/c/cgen.v

@@ -703,6 +703,9 @@ pub fn (mut g Gen) init() {
 	if g.pref.is_test || 'test' in g.pref.compile_defines {
 		g.comptime_definitions.writeln('#define _VTEST (1)')
 	}
+	if g.pref.is_prof || 'profile' in g.pref.compile_defines {
+		g.comptime_definitions.writeln('#define _VPROFILE (1)')
+	}
 	if g.pref.autofree {
 		g.comptime_definitions.writeln('#define _VAUTOFREE (1)')
 		// g.comptime_definitions.writeln('unsigned char* g_cur_str;')

vlib/v/gen/c/cmain.v

@@ -96,6 +96,9 @@ fn (mut g Gen) gen_c_main_header() {
 	if g.pref.is_livemain {
 		g.generate_hotcode_reloading_main_caller()
 	}
+	if 'no_profile_startup' in g.pref.compile_defines {
+		g.writeln('vreset_profile_stats();')
+	}
 }
 
 pub fn (mut g Gen) gen_c_main_footer() {

vlib/v/gen/c/comptime.v

@@ -650,6 +650,9 @@ fn (mut g Gen) comptime_if_to_ifdef(name string, is_comptime_optional bool) ?str
 		'prod' {
 			return '_VPROD'
 		}
+		'profile' {
+			return '_VPROFILE'
+		}
 		'test' {
 			return '_VTEST'
 		}

vlib/v/gen/c/profile.v

@@ -14,16 +14,17 @@ fn (mut g Gen) profile_fn(fn_decl ast.FnDecl) {
 		return
 	}
 	fn_name := fn_decl.name
-	if fn_name.starts_with('time.vpc_now') {
+	if fn_name.starts_with('time.vpc_now') || fn_name.starts_with('v.profile.') {
 		g.defer_profile_code = ''
 	} else {
 		measure_fn_name := if g.pref.os == .macos { 'time__vpc_now_darwin' } else { 'time__vpc_now' }
 		fn_profile_counter_name := 'vpc_$g.last_fn_c_name'
 		fn_profile_counter_name_calls := '${fn_profile_counter_name}_calls'
 		g.writeln('')
-		g.writeln('\tdouble _PROF_FN_START = ${measure_fn_name}(); $fn_profile_counter_name_calls++; // $fn_name')
+		g.writeln('\tdouble _PROF_FN_START = ${measure_fn_name}();')
+		g.writeln('\tif(v__profile_enabled) { $fn_profile_counter_name_calls++; } // $fn_name')
 		g.writeln('')
-		g.defer_profile_code = '\t$fn_profile_counter_name += ${measure_fn_name}() - _PROF_FN_START;'
+		g.defer_profile_code = '\tif(v__profile_enabled) { $fn_profile_counter_name += ${measure_fn_name}() - _PROF_FN_START; }'
 		g.pcs_declarations.writeln('double $fn_profile_counter_name = 0.0; u64 $fn_profile_counter_name_calls = 0;')
 		g.pcs << ProfileCounterMeta{
 			fn_name: g.last_fn_c_name
@@ -49,4 +50,12 @@ pub fn (mut g Gen) gen_vprint_profile_stats() {
 		g.pcs_declarations.writeln('\tfclose(fp);')
 	}
 	g.pcs_declarations.writeln('}')
+	g.pcs_declarations.writeln('')
+	g.pcs_declarations.writeln('void vreset_profile_stats(){')
+	for pc_meta in g.pcs {
+		g.pcs_declarations.writeln('\t$pc_meta.vpc_calls = 0;')
+		g.pcs_declarations.writeln('\t$pc_meta.vpc_name = 0.0;')
+	}
+	g.pcs_declarations.writeln('}')
+	g.pcs_declarations.writeln('')
 }

vlib/v/preludes/profiled_program.v

@@ -1,7 +1,8 @@
 module main
 
 import time
+import v.profile
 
-const (
-	profiled_program_time_used = time.seconds_per_minute
-)
+const profiled_program_time_used = time.seconds_per_minute
+
+const profiled_program_profile_used = profile.state()

vlib/v/profile/api.v

@@ -0,0 +1,13 @@
+[has_globals]
+module profile
+
+__global v__profile_enabled = true
+
+pub fn state() bool {
+	return v__profile_enabled
+}
+
+[if profile]
+pub fn on(state bool) {
+	v__profile_enabled = state
+}

vlib/v/tests/profile/profile_test.v

@@ -21,3 +21,29 @@ fn test_v_profile_works() {
 	assert res.output.contains(' println')
 	assert res.output.contains(' strconv__atoi')
 }
+
+fn test_v_profile_on_off_api_works() {
+	os.chdir(vroot) or {}
+	program_source := os.join_path(vroot, 'vlib/v/tests/profile/profile_test_2.v')
+	res := os.execute('"$vexe" -profile - run $program_source')
+	// eprintln('res: $res')
+	assert res.exit_code == 0
+	assert res.output.len > 0
+	assert res.output.contains(' builtin_init')
+	assert res.output.contains(' main__main')
+	assert res.output.contains(' main__abc')
+	res_lines := res.output.split_into_lines()
+	abc_count := res_lines.filter(it.contains('main__abc'))[0].trim_space().all_before(' ').int()
+	assert abc_count == 1
+
+	// test that `-d no_profile_startup` *also* works:
+	res2 := os.execute('"$vexe" -d no_profile_startup -profile - run $program_source')
+	assert res2.exit_code == 0
+	assert res2.output.len > 0
+	assert !res2.output.contains(' builtin_init')
+	assert res2.output.contains(' main__main')
+	assert res2.output.contains(' main__abc')
+	res2_lines := res2.output.split_into_lines()
+	assert res_lines.len > res2_lines.len
+	// dump(res2_lines)
+}

vlib/v/tests/profile/profile_test_2.v

@@ -0,0 +1,23 @@
+import v.profile
+
+fn abc() {
+	eprintln(@FN)
+}
+
+fn main() {
+	profile.on(false)
+	for _ in 0 .. 3 {
+		abc()
+	}
+	println('>>>>>>>>>>')
+
+	profile.on(true)
+	abc()
+	profile.on(false)
+
+	println('>>>>>>>>>>')
+	for _ in 0 .. 3 {
+		abc()
+	}
+	profile.on(true)
+}