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 <mpratt@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>