2 files changed, 41 insertions, 0 deletions
diff --git a/src/internal/buildcfg/cfg.go b/src/internal/buildcfg/cfg.go
index 9fe7f211fb..68c10a2824 100644
--- a/src/internal/buildcfg/cfg.go
+++ b/src/internal/buildcfg/cfg.go
@@ -25,6 +25,7 @@ var (
 	GOARCH   = envOr("GOARCH", defaultGOARCH)
 	GOOS     = envOr("GOOS", defaultGOOS)
 	GO386    = envOr("GO386", defaultGO386)
+	GOAMD64  = goamd64()
 	GOARM    = goarm()
 	GOMIPS   = gomips()
 	GOMIPS64 = gomips64()
@@ -52,6 +53,21 @@ func envOr(key, value string) string {
 	return value
 }
 
+func goamd64() int {
+	switch v := envOr("GOAMD64", defaultGOAMD64); v {
+	case "v1":
+		return 1
+	case "v2":
+		return 2
+	case "v3":
+		return 3
+	case "v4":
+		return 4
+	}
+	Error = fmt.Errorf("invalid GOAMD64: must be v1, v2, v3, v4")
+	return int(defaultGOAMD64[len("v")] - '0')
+}
+
 func goarm() int {
 	def := defaultGOARM
 	if GOOS == "android" && GOARCH == "arm" {
diff --git a/src/internal/buildcfg/cfg_test.go b/src/internal/buildcfg/cfg_test.go
new file mode 100644
index 0000000000..9180441c28
--- /dev/null
+++ b/src/internal/buildcfg/cfg_test.go
@@ -0,0 +1,25 @@
+// 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 buildcfg
+
+import (
+	"os"
+	"testing"
+)
+
+func TestConfigFlags(t *testing.T) {
+	os.Setenv("GOAMD64", "v1")
+	if goamd64() != 1 {
+		t.Errorf("Wrong parsing of GOAMD64=v1")
+	}
+	os.Setenv("GOAMD64", "v4")
+	if goamd64() != 4 {
+		t.Errorf("Wrong parsing of GOAMD64=v4")
+	}
+	os.Setenv("GOAMD64", "1")
+	if goamd64() != 1 {
+		t.Errorf("Wrong parsing of GOAMD64=1")
+	}
+}