tree 80b561b5acd7a6eaab93774e1f48e5db33900d61
parent 56c22442ee369ddc6f44c2ff5e0664d47a3c6b0e
author Nico Weber <thakis@chromium.org> 1790230598 -0700
committer gn-scoped@luci-project-accounts.iam.gserviceaccount.com <gn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1790266112 -0700

Write phony rules for harddeps

Write a rule for each target with at least two hard deps,
similar to what WritePublicInputsStampOrPhony() does for public_inputs:

    build phony/foo/bar.harddeps: $
        phony phony/foo/action phony/foo/dep.harddeps

It lists the target's direct hard deps. This mirrors
ResolvedTargetData::ComputeHardDeps(), so it depends on the same set
of hard deps, but its size is proportional to the number of direct deps.
A target's input deps then just refer to its own .harddeps rule.

Results for a Chromium build (mac, arm64, is_debug=false):

                                      before         after
  size of all loaded .ninja files     1025 MB        427 MB
  gn gen (hyperfine, 6 runs)          2.065s ± .048  1.947s ± .050
    user / sys                        12.0s / 4.3s   10.1s / 4.5s

Chromium no-op builds of base_unittests (target already built, hyperfine, M-series Mac):

                                               before           after
  siso v1.6.0 (autoninja), -offline            735.5 ms ± 13.7  648.3 ms ± 22.8
    user / sys                                 3.7s / 1.9s      2.3s / 2.2s
  depot_tools ninja (1.12.1)                   4.37s ± .02      2.25s ± .02
  ninja v1.13.2                                2.755s ± .009    1.532s ± .007
  ninja with some local changes to tweak perf  535.8 ms ± 2.7   408.4 ms ± 8.1
  (`siso -n` and `ninja -n` are within 2% of the no-op times.)

No intended behavior change.

Bug: chromium:40278737
Change-Id: I163e6bea334c2e626bf7c96cd8d942848a6766bf
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/26741
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Reviewed-by: Nico Weber <thakis@google.com>
Commit-Queue: Nico Weber <thakis@chromium.org>