go/internal/gcimporter: avoid setting unnecessary lines in fakeFileSet

As discussed in golang/go#46586, the gcimporter spends large portion of
time just validating fake lines.

Fix this by only setting the lines we need. Benchcmd results for

name              old time/op         new time/op         delta
TestImportStdLib          1.11s ±40%          0.57s ±58%  -48.17%  (p=0.000 n=18+18)

name              old user-time/op    new user-time/op    delta
TestImportStdLib          1.24s ±46%          0.71s ±61%  -42.84%  (p=0.000 n=18+18)

name              old sys-time/op     new sys-time/op     delta
TestImportStdLib          249ms ±64%          139ms ±47%  -44.19%  (p=0.000 n=19+18)

name              old peak-RSS-bytes  new peak-RSS-bytes  delta
TestImportStdLib         80.1MB ±24%         86.6MB ±13%   +8.06%  (p=0.001 n=20+20)

Fixes golang/go#46586

Change-Id: I5ef99ea9f242fc80d2d17750a8d9b28f7fc71245
Reviewed-on: https://go-review.googlesource.com/c/tools/+/357291
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2 files changed
tree: 25c62b6baae248ec75c26f0408712fbd49fdc3aa
  1. .gitattributes
  2. .gitignore
  3. .prettierrc
  9. README.md
  10. benchmark/
  11. blog/
  12. cmd/
  13. codereview.cfg
  14. container/
  15. copyright/
  16. cover/
  17. go.mod
  18. go.sum
  19. go/
  20. godoc/
  21. gopls/
  22. imports/
  23. internal/
  24. playground/
  25. present/
  26. refactor/
  27. txtar/

Go Tools


This subrepository holds the source for various packages and tools that support the Go programming language.

Some of the tools, godoc and vet for example, are included in binary Go distributions.

Others, including the Go guru and the test coverage tool, can be fetched with go get.

Packages include a type-checker for Go and an implementation of the Static Single Assignment form (SSA) representation for Go programs.


The easiest way to install is to run go get -u golang.org/x/tools/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/tools.

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The version of prettier used is 1.18.2.

It is encouraged that all JS and CSS code be run through this before submitting a change. However, it is not a strict requirement enforced by CI.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.