cmd/go: inital plumbing for PGO profiles preprocessing

The new go tool preprofile preprocesses a PGO pprof profile into an
intermediate representation that is more efficient for the compiler to
consume. Performing preprocessing avoids having every single compile
process from duplicating the same processing.

This CL prepares the initial plumbing to support automatic preprocessing
by cmd/go.

Each compile action takes a new dependency on a new "preprocess PGO
profile" action. The same action instance is shared by all compile
actions (assuming they have the same input profile), so the action only
executes once.

Builder.build retrieves the file to pass to -pgofile from the output of
the preprocessing action, rather than directly from
p.Internal.PGOProfile.

Builder.buildActionID also uses the preprocess output as the PGO
component of the cache key, rather than the original source. This
doesn't matter for normal toolchain releases, as the two files are
semantically equivalent, but it is useful for correct cache invalidation
in development. For example, if _only_ go tool preprofile changes
(potentially changing the output), then we must regenerate the output
and then rebuild all packages.

This CL does not actually invoke go tool preprocess. That will come in
the next CL. For now, it just copies the input pprof profile.

This CL shouldn't be submitted on its own, only with the children. Since
the new action doesn't yet use the build cache, every build (even fully
cached builds) unconditionally run the PGO action.

For #58102.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Change-Id: I594417cfb0164cd39439a03977c904e4c0c83b8b
Reviewed-on: https://go-review.googlesource.com/c/go/+/569423
Auto-Submit: Michael Pratt <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: prattmic

src/cmd/go/internal/work/action.go

@@ -461,6 +461,34 @@ func (ba *buildActor) Act(b *Builder, ctx context.Context, a *Action) error {
 	return b.build(ctx, a)
 }
 
+// pgoActor implements the Actor interface for preprocessing PGO profiles.
+type pgoActor struct {
+	// input is the path to the original pprof profile.
+	input string
+}
+
+func (p *pgoActor) Act(b *Builder, ctx context.Context, a *Action) error {
+	// TODO(prattmic): Integrate with build cache to cache output.
+
+	sh := b.Shell(a)
+
+	if err := sh.Mkdir(a.Objdir); err != nil {
+		return err
+	}
+
+	// TODO(prattmic): This should use go tool preprofile to actually
+	// preprocess the profile. For now, this is a dummy implementation that
+	// simply copies the input to the output. This is technically a valid
+	// implementation because go tool compile -pgofile accepts either a
+	// pprof file or preprocessed file.
+	if err := sh.CopyFile(a.Target, p.input, 0644, false); err != nil {
+		return err
+	}
+
+	a.built = a.Target
+	return nil
+}
+
 // CompileAction returns the action for compiling and possibly installing
 // (according to mode) the given package. The resulting action is only
 // for building packages (archives), never for linking executables.
@@ -494,6 +522,20 @@ func (b *Builder) CompileAction(mode, depMode BuildMode, p *load.Package) *Actio
 			}
 		}
 
+		if p.Internal.PGOProfile != "" {
+			pgoAction := b.cacheAction("preprocess PGO profile "+p.Internal.PGOProfile, nil, func() *Action {
+				a := &Action{
+					Mode:    "preprocess PGO profile",
+					Actor:   &pgoActor{input: p.Internal.PGOProfile},
+					Objdir:  b.NewObjdir(),
+				}
+				a.Target = filepath.Join(a.Objdir, "pgo.preprofile")
+
+				return a
+			})
+			a.Deps = append(a.Deps, pgoAction)
+		}
+
 		if p.Standard {
 			switch p.ImportPath {
 			case "builtin", "unsafe":

src/cmd/go/internal/work/exec.go

@@ -395,14 +395,14 @@ func (b *Builder) buildActionID(a *Action) cache.ActionID {
 	for _, file := range inputFiles {
 		fmt.Fprintf(h, "file %s %s\n", file, b.fileHash(filepath.Join(p.Dir, file)))
 	}
-	if p.Internal.PGOProfile != "" {
-		fmt.Fprintf(h, "pgofile %s\n", b.fileHash(p.Internal.PGOProfile))
-	}
 	for _, a1 := range a.Deps {
 		p1 := a1.Package
 		if p1 != nil {
 			fmt.Fprintf(h, "import %s %s\n", p1.ImportPath, contentID(a1.buildID))
 		}
+		if a1.Mode == "preprocess PGO profile" {
+			fmt.Fprintf(h, "pgofile %s\n", b.fileHash(a1.built))
+		}
 	}
 
 	return h.Sum()
@@ -864,6 +864,18 @@ OverlayLoop:
 		embedcfg = js
 	}
 
+	// Find PGO profile if needed.
+	var pgoProfile string
+	for _, a1 := range a.Deps {
+		if a1.Mode != "preprocess PGO profile" {
+			continue
+		}
+		if pgoProfile != "" {
+			return fmt.Errorf("action contains multiple PGO profile dependencies")
+		}
+		pgoProfile = a1.built
+	}
+
 	if p.Internal.BuildInfo != nil && cfg.ModulesEnabled {
 		prog := modload.ModInfoProg(p.Internal.BuildInfo.String(), cfg.BuildToolchainName == "gccgo")
 		if len(prog) > 0 {
@@ -876,7 +888,7 @@ OverlayLoop:
 
 	// Compile Go.
 	objpkg := objdir + "_pkg_.a"
-	ofile, out, err := BuildToolchain.gc(b, a, objpkg, icfg.Bytes(), embedcfg, symabis, len(sfiles) > 0, gofiles)
+	ofile, out, err := BuildToolchain.gc(b, a, objpkg, icfg.Bytes(), embedcfg, symabis, len(sfiles) > 0, pgoProfile, gofiles)
 	if err := sh.reportCmd("", "", out, err); err != nil {
 		return err
 	}
@@ -2041,7 +2053,7 @@ func mkAbs(dir, f string) string {
 type toolchain interface {
 	// gc runs the compiler in a specific directory on a set of files
 	// and returns the name of the generated output file.
-	gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, gofiles []string) (ofile string, out []byte, err error)
+	gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, pgoProfile string, gofiles []string) (ofile string, out []byte, err error)
 	// cc runs the toolchain's C compiler in a directory on a C file
 	// to produce an output file.
 	cc(b *Builder, a *Action, ofile, cfile string) error
@@ -2081,7 +2093,7 @@ func (noToolchain) linker() string {
 	return ""
 }
 
-func (noToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, gofiles []string) (ofile string, out []byte, err error) {
+func (noToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, pgoProfile string, gofiles []string) (ofile string, out []byte, err error) {
 	return "", nil, noCompiler()
 }
 
@@ -3252,7 +3264,7 @@ func (b *Builder) swigDoIntSize(objdir string) (intsize string, err error) {
 
 	p := load.GoFilesPackage(context.TODO(), load.PackageOpts{}, srcs)
 
-	if _, _, e := BuildToolchain.gc(b, &Action{Mode: "swigDoIntSize", Package: p, Objdir: objdir}, "", nil, nil, "", false, srcs); e != nil {
+	if _, _, e := BuildToolchain.gc(b, &Action{Mode: "swigDoIntSize", Package: p, Objdir: objdir}, "", nil, nil, "", false, "", srcs); e != nil {
 		return "32", nil
 	}
 	return "64", nil

src/cmd/go/internal/work/gc.go

@@ -53,7 +53,7 @@ func pkgPath(a *Action) string {
 	return ppath
 }
 
-func (gcToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, gofiles []string) (ofile string, output []byte, err error) {
+func (gcToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, pgoProfile string, gofiles []string) (ofile string, output []byte, err error) {
 	p := a.Package
 	sh := b.Shell(a)
 	objdir := a.Objdir
@@ -112,8 +112,8 @@ func (gcToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg
 	if p.Internal.Cover.Cfg != "" {
 		defaultGcFlags = append(defaultGcFlags, "-coveragecfg="+p.Internal.Cover.Cfg)
 	}
-	if p.Internal.PGOProfile != "" {
-		defaultGcFlags = append(defaultGcFlags, "-pgoprofile="+p.Internal.PGOProfile)
+	if pgoProfile != "" {
+		defaultGcFlags = append(defaultGcFlags, "-pgoprofile="+pgoProfile)
 	}
 	if symabis != "" {
 		defaultGcFlags = append(defaultGcFlags, "-symabis", symabis)

src/cmd/go/internal/work/gccgo.go

@@ -59,7 +59,7 @@ func checkGccgoBin() {
 	base.Exit()
 }
 
-func (tools gccgoToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, gofiles []string) (ofile string, output []byte, err error) {
+func (tools gccgoToolchain) gc(b *Builder, a *Action, archive string, importcfg, embedcfg []byte, symabis string, asmhdr bool, pgoProfile string, gofiles []string) (ofile string, output []byte, err error) {
 	p := a.Package
 	sh := b.Shell(a)
 	objdir := a.Objdir

src/cmd/go/testdata/script/build_pgo.txt

@@ -9,7 +9,8 @@ go build triv.go
 # build with PGO, should trigger rebuild
 # starting with an empty profile (the compiler accepts it)
 go build -x -pgo=prof -o triv.exe triv.go
-stderr 'compile.*-pgoprofile=.*prof.*triv.go'
+stderr 'cp.*prof' # preprocess PGO profile
+stderr 'compile.*-pgoprofile=.*triv.go'
 
 # check that PGO appears in build info
 # N.B. we can't start the stdout check with -pgo because the script assumes that
@@ -33,9 +34,11 @@ cmp stdout list.out
 # overwrite the prof
 go run overwrite.go
 
-# build again, profile content changed, should trigger rebuild
+# build again, profile content changed, should trigger rebuild, including std
 go build -n -pgo=prof triv.go
-stderr 'compile.*-pgoprofile=.*prof.*p.go'
+stderr 'cp.*prof' # preprocess PGO profile
+stderr 'compile.*-pgoprofile=.*triv.go'
+stderr 'compile.*-p runtime.*-pgoprofile=.*'
 
 # check that the build ID is different
 go list -export -json=BuildID -pgo=prof triv.go

src/cmd/go/testdata/script/build_pgo_auto.txt

@@ -4,10 +4,11 @@
 
 # use default.pgo for a single main package
 go build -n -pgo=auto -o a1.exe ./a/a1
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go'
+stderr 'cp.*default\.pgo' # preprocess PGO profile
+stderr 'compile.*-pgoprofile=.*a1.go'
 
 # check that pgo applied to dependencies
-stderr 'compile.*-p test/dep.*-pgoprofile=.*default\.pgo'
+stderr 'compile.*-p test/dep.*-pgoprofile=.*'
 
 # check that pgo appears in build info
 # N.B. we can't start the stdout check with -pgo because the script assumes that
@@ -19,7 +20,7 @@ stderr 'build\\t-pgo=.*default\.pgo'
 
 # use default.pgo for ... with a single main package
 go build -n -pgo=auto ./a/...
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go'
+stderr 'compile.*-pgoprofile=.*a1.go'
 
 # check that pgo appears in build info
 stderr 'build\\t-pgo=.*default\.pgo'
@@ -34,14 +35,14 @@ stderr 'compile.*nopgo.go'
 
 # other build-related commands
 go install -a -n -pgo=auto ./a/a1
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go'
+stderr 'compile.*-pgoprofile=.*a1.go'
 
 go run -a -n -pgo=auto ./a/a1
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go'
+stderr 'compile.*-pgoprofile=.*a1.go'
 
 go test -a -n -pgo=auto ./a/a1
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go.*a1_test.go'
-stderr 'compile.*-pgoprofile=.*default\.pgo.*external_test.go'
+stderr 'compile.*-pgoprofile=.*a1.go.*a1_test.go'
+stderr 'compile.*-pgoprofile=.*external_test.go'
 
 # go list commands should succeed as usual
 go list -pgo=auto ./a/a1
@@ -53,8 +54,8 @@ go list -deps -pgo=auto ./a/a1
 # -pgo=auto is the default. Commands without explicit -pgo=auto
 # should work as -pgo=auto.
 go build -a -n -o a1.exe ./a/a1
-stderr 'compile.*-pgoprofile=.*default\.pgo.*a1.go'
-stderr 'compile.*-p test/dep.*-pgoprofile=.*default\.pgo'
+stderr 'compile.*-pgoprofile=.*a1.go'
+stderr 'compile.*-p test/dep.*-pgoprofile=.*'
 
 # check that pgo appears in build info
 stderr 'build\\t-pgo=.*default\.pgo'

src/cmd/go/testdata/script/build_pgo_auto_multi.txt

@@ -2,24 +2,21 @@
 
 go install -a -n -pgo=auto ./a ./b ./nopgo
 
-# a/default.pgo applies to package a and (transitive)
-# dependencies.
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*a(/|\\\\)a\.go'
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*dep(/|\\\\)dep\.go'
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*dep2(/|\\\\)dep2\.go'
-stderr -count=1 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*dep3(/|\\\\)dep3\.go'
+# a/default.pgo and b/default.pgo are both preprocessed
+stderr 'cp.*a(/|\\)default\.pgo'
+stderr 'cp.*b(/|\\)default\.pgo'
 
-# b/default.pgo applies to package b and (transitive)
-# dependencies.
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*b(/|\\\\)b\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*dep(/|\\\\)dep\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*dep2(/|\\\\)dep2\.go'
-stderr -count=1 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*dep3(/|\\\\)dep3\.go'
+# a and b built once each with PGO.
+# Ideally we would check that the passed profile is the expected profile (here
+# and for dependencies). Unfortunately there is no nice way to map the expected
+# paths after preprocessing.
+stderr -count=1 'compile.*-pgoprofile=.*a(/|\\\\)a\.go'
+stderr -count=1 'compile.*-pgoprofile=.*b(/|\\\\)b\.go'
 
 # nopgo should be built without PGO.
 ! stderr 'compile.*-pgoprofile=.*nopgo(/|\\\\)nopgo\.go'
 
-# Dependencies should also be built without PGO.
+# Dependencies should also be built with and without PGO.
 # Here we want to match a compile action without -pgoprofile,
 # by matching 3 occurrences of "compile dep.go", among which
 # 2 of them have -pgoprofile (therefore one without).
@@ -39,17 +36,14 @@ stderr 'path\\ttest/b\\n.*build\\t-pgo=.*b(/|\\\\)default\.pgo'
 
 # go test works the same way
 go test -a -n -pgo=auto ./a ./b ./nopgo
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*a(/|\\\\)a_test\.go'
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*dep(/|\\\\)dep\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*b(/|\\\\)b_test\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*dep(/|\\\\)dep\.go'
+stderr -count=1 'compile.*-pgoprofile=.*a(/|\\\\)a_test\.go'
+stderr -count=1 'compile.*-pgoprofile=.*b(/|\\\\)b_test\.go'
+stderr -count=2 'compile.*-pgoprofile=.*dep(/|\\\\)dep\.go'
 ! stderr 'compile.*-pgoprofile=.*nopgo(/|\\\\)nopgo_test\.go'
 
 # test-only dependencies also have profiles attached
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*testdep(/|\\\\)testdep\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*testdep(/|\\\\)testdep\.go'
-stderr 'compile.*-pgoprofile=.*a(/|\\\\)default\.pgo.*testdep2(/|\\\\)testdep2\.go'
-stderr 'compile.*-pgoprofile=.*b(/|\\\\)default\.pgo.*testdep2(/|\\\\)testdep2\.go'
+stderr -count=2 'compile.*-pgoprofile=.*testdep(/|\\\\)testdep\.go'
+stderr -count=2 'compile.*-pgoprofile=.*testdep2(/|\\\\)testdep2\.go'
 
 # go list -deps prints packages built multiple times.
 go list -pgo=auto -deps ./a ./b ./nopgo