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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package objabi
import (
"fmt"
"os"
"reflect"
"strings"
"internal/goexperiment"
)
// Experiment contains the toolchain experiments enabled for the
// current build.
//
// (This is not necessarily the set of experiments the compiler itself
// was built with.)
var Experiment goexperiment.Flags = parseExperiments()
// experimentBaseline specifies the experiment flags that are enabled by
// default in the current toolchain. This is, in effect, the "control"
// configuration and any variation from this is an experiment.
var experimentBaseline goexperiment.Flags
// FramePointerEnabled enables the use of platform conventions for
// saving frame pointers.
//
// This used to be an experiment, but now it's always enabled on
// platforms that support it.
//
// Note: must agree with runtime.framepointer_enabled.
var FramePointerEnabled = GOARCH == "amd64" || GOARCH == "arm64"
func parseExperiments() goexperiment.Flags {
// Start with the statically enabled set of experiments.
flags := experimentBaseline
// Pick up any changes to the baseline configuration from the
// GOEXPERIMENT environment. This can be set at make.bash time
// and overridden at build time.
env := envOr("GOEXPERIMENT", defaultGOEXPERIMENT)
if env != "" {
// Create a map of known experiment names.
names := make(map[string]reflect.Value)
rv := reflect.ValueOf(&flags).Elem()
rt := rv.Type()
for i := 0; i < rt.NumField(); i++ {
field := rv.Field(i)
names[strings.ToLower(rt.Field(i).Name)] = field
}
// Parse names.
for _, f := range strings.Split(env, ",") {
if f == "" {
continue
}
if f == "none" {
// GOEXPERIMENT=none disables all experiment flags.
// This is used by cmd/dist, which doesn't know how
// to build with any experiment flags.
flags = goexperiment.Flags{}
continue
}
val := true
if strings.HasPrefix(f, "no") {
f, val = f[2:], false
}
field, ok := names[f]
if !ok {
fmt.Printf("unknown experiment %s\n", f)
os.Exit(2)
}
field.SetBool(val)
}
}
// regabi is only supported on amd64.
if GOARCH != "amd64" {
flags.Regabi = false
flags.RegabiWrappers = false
flags.RegabiG = false
flags.RegabiReflect = false
flags.RegabiDefer = false
flags.RegabiArgs = false
}
// Setting regabi sets working sub-experiments.
if flags.Regabi {
flags.RegabiWrappers = true
flags.RegabiG = true
flags.RegabiReflect = true
flags.RegabiDefer = true
// Not ready yet:
//flags.RegabiArgs = true
}
// Check regabi dependencies.
if flags.RegabiG && !flags.RegabiWrappers {
panic("GOEXPERIMENT regabig requires regabiwrappers")
}
if flags.RegabiArgs && !(flags.RegabiWrappers && flags.RegabiG && flags.RegabiReflect && flags.RegabiDefer) {
panic("GOEXPERIMENT regabiargs requires regabiwrappers,regabig,regabireflect,regabidefer")
}
return flags
}
// expList returns the list of lower-cased experiment names for
// experiments that differ from base. base may be nil to indicate no
// experiments. If all is true, then include all experiment flags,
// regardless of base.
func expList(exp, base *goexperiment.Flags, all bool) []string {
var list []string
rv := reflect.ValueOf(exp).Elem()
var rBase reflect.Value
if base != nil {
rBase = reflect.ValueOf(base).Elem()
}
rt := rv.Type()
for i := 0; i < rt.NumField(); i++ {
name := strings.ToLower(rt.Field(i).Name)
val := rv.Field(i).Bool()
baseVal := false
if base != nil {
baseVal = rBase.Field(i).Bool()
}
if all || val != baseVal {
if val {
list = append(list, name)
} else {
list = append(list, "no"+name)
}
}
}
return list
}
// GOEXPERIMENT is a comma-separated list of enabled or disabled
// experiments that differ from the baseline experiment configuration.
// GOEXPERIMENT is exactly what a user would set on the command line
// to get the set of enabled experiments.
func GOEXPERIMENT() string {
return strings.Join(expList(&Experiment, &experimentBaseline, false), ",")
}
// EnabledExperiments returns a list of enabled experiments, as
// lower-cased experiment names.
func EnabledExperiments() []string {
return expList(&Experiment, nil, false)
}
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