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cmd/dist: build bootstrap without GOEXPERIMENT

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Currently, dist attempts to build the bootstrap with the GOEXPERIMENT
set in the environment. However, the logic is incomplete and notably
requires a hack to enable the appropriate build tags for
GOEXPERIMENT=regabi. Without this hack, the build becomes skewed
between a compiler that uses regabi and a runtime that doesn't when
building toolchain2.

We could try to improve the GOEXPERIMENT processing in cmd/dist, but
it will always chase cmd/internal/objabi and it's quite difficult to
share the logic with objabi because of the constraints on building
cmd/dist.

Instead, we switch to building go_bootstrap without any GOEXPERIMENT
and only start using GOEXPERIMENT once we have a working, modern
cmd/go (which has all the GOEXPERIMENT logic in it). We also build
toolchain1 without any GOEXPERIMENT set, in case the bootstrap
toolchain is recent enough to understand build-time GOEXPERIMENT
settings.

As part of this, we make GOEXPERIMENT=none mean "no experiments". This
is necessary since, now that we support setting GOEXPERIMENT at build
time, we need an explicit way to say "ignore all baked-in experiments".

For #40724.

Change-Id: I115399579b766a7a8b2f352f7e5efea5305666cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/302050
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Austin Clements 2021-03-15 15:53:21 -04:00
parent 06ca809410
commit 6461d74bf2
2 changed files with 22 additions and 8 deletions
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21
src/cmd/dist/build.go vendored
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@ -974,11 +974,6 @@ func matchtag(tag string) bool {
}
return !matchtag(tag[1:])
}
if os.Getenv("GOEXPERIMENT") == "regabi" && tag == "goexperiment.regabi" {
// TODO: maybe we can handle GOEXPERIMENT more generally.
// Or remove once we commit to regabi (#40724).
return true
}
return tag == "gc" || tag == goos || tag == goarch || tag == "cmd_go_bootstrap" || tag == "go1.1" ||
(goos == "android" && tag == "linux") ||
(goos == "illumos" && tag == "solaris") ||
@ -1268,6 +1263,20 @@ func cmdbootstrap() {
// go tool may complain.
os.Setenv("GOPATH", pathf("%s/pkg/obj/gopath", goroot))
// Disable GOEXPERIMENT when building toolchain1 and
// go_bootstrap. We don't need any experiments for the
// bootstrap toolchain, and this lets us avoid duplicating the
// GOEXPERIMENT-related build logic from cmd/go here. If the
// bootstrap toolchain is < Go 1.17, it will ignore this
// anyway since GOEXPERIMENT is baked in; otherwise it will
// pick it up from the environment we set here. Once we're
// using toolchain1 with dist as the build system, we need to
// override this to keep the experiments assumed by the
// toolchain and by dist consistent. Once go_bootstrap takes
// over the build process, we'll set this back to the original
// GOEXPERIMENT.
os.Setenv("GOEXPERIMENT", "none")
if debug {
// cmd/buildid is used in debug mode.
toolchain = append(toolchain, "cmd/buildid")
@ -1345,6 +1354,8 @@ func cmdbootstrap() {
}
xprintf("Building Go toolchain2 using go_bootstrap and Go toolchain1.\n")
os.Setenv("CC", compilerEnvLookup(defaultcc, goos, goarch))
// Now that cmd/go is in charge of the build process, enable GOEXPERIMENT.
os.Setenv("GOEXPERIMENT", goexperiment)
goInstall(goBootstrap, append([]string{"-i"}, toolchain...)...)
if debug {
run("", ShowOutput|CheckExit, pathf("%s/compile", tooldir), "-V=full")

3
src/cmd/internal/objabi/util.go
View File

@ -135,11 +135,14 @@ func init() {
goexperiment := envOr("GOEXPERIMENT", defaultGOEXPERIMENT)
// GOEXPERIMENT=none overrides all experiments enabled at dist time.
if goexperiment != "none" {
for _, f := range strings.Split(goexperiment, ",") {
if f != "" {
addexp(f)
}
}
}
// regabi is only supported on amd64.
if GOARCH != "amd64" {