cmd/go: distinguish packages built for different main packages in printing

In -pgo=auto mode, a package may be built multiple times. E.g. for

go build -pgo=auto cmd/a cmd/b

and both cmd/a and cmd/b imports package p, p may be built twice,
one using a's profile, one using b's. If we need to print p, e.g.
in "go list -deps" or when there is a build failure, p will be
printed twice, and currently we don't distinguish them.

We have a precedence for a similar case: for testing, there is the
original package, and the (internal) test version of the package
(which includes _test.go files). Packages that import the package
under testing may also have two versions (one imports the original,
one imports the testing version). In printing, the go command
distinguishes them by adding a "[p.test]" suffix for the latter,
as they are specifically built for the p.test binary.

We do the similar. When a package needs to be compiled multiple
times for different main packages, we attach the main package's
import path, like "p [cmd/a]" for package p built specifically
for cmd/a.

For #58099.

Change-Id: I4a040cf17e1dceb5ca1810c217f16e734c858ab6
Reviewed-on: https://go-review.googlesource.com/c/go/+/473275
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 6284955228..40278dda4d 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -195,6 +195,9 @@ func (p *Package) Desc() string {
 	if p.ForTest != "" {
 		return p.ImportPath + " [" + p.ForTest + ".test]"
 	}
+	if p.Internal.ForMain != "" {
+		return p.ImportPath + " [" + p.Internal.ForMain + "]"
+	}
 	return p.ImportPath
 }
 
@@ -234,6 +237,7 @@ type PackageInternal struct {
 	Embed             map[string][]string  // //go:embed comment mapping
 	OrigImportPath    string               // original import path before adding '_test' suffix
 	PGOProfile        string               // path to PGO profile
+	ForMain           string               // the main package if this package is built specifically for it
 
 	Asmflags   []string // -asmflags for this package
 	Gcflags    []string // -gcflags for this package
@@ -2944,6 +2948,7 @@ func setPGOProfilePath(pkgs []*Package) {
 					p1.Internal.Imports = slices.Clone(p.Internal.Imports)
 					copied[p] = p1
 					p = p1
+					p.Internal.ForMain = pmain.ImportPath
 				}
 				p.Internal.PGOProfile = file
 				// Recurse to dependencies.