[bazel] Enable dead code stripping on macOS #537
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
fhanau
force-pushed
the
felix/dead_strip
branch
from
e5fe18a to
a8a8607
Compare
ohodson
reviewed
Apr 13, 2023
.bazelrc
Outdated
| @@ -63,6 +63,7 @@ build:unix --per_file_copt='external/zlib[~/].*\.c@-std=c90' --host_per_file_cop | |||
| build:unix --@capnp-cpp//src/kj:openssl=True --@capnp-cpp//src/kj:zlib=True --@capnp-cpp//src/kj:libdl=True | |||
|
|
|||
| build:linux --config=unix | |||
| build:macos --linkopt=-Wl,-dead_strip --host_linkopt=-Wl,-dead_strip | |||
There was a problem hiding this comment.
Nice saving!
Last time I checked we were close to exceeding github disk quotas on CI and we're using fastbuild there. It seems reasonable here to enable for all non-dbg builds because of this (and the timing data). On the overall time of our builds, the small increase in linking time likely doesn't change much. If we leave a comment there, we can tune it if necessary.
There was a problem hiding this comment.
Enabled the flag for all non-debug builds – having it for both workerd and test targets turned out to be complex but the changes in BUILD.bazel should be useful as a blueprint for future build configuration changes.
fhanau
force-pushed
the
felix/dead_strip
branch
2 times, most recently
from
d73264e to
15b8982
Compare
fhanau
force-pushed
the
felix/dead_strip
branch
from
15b8982 to
de1de0b
Compare
ohodson
approved these changes
Apr 14, 2023
# for free
to join this conversation on GitHub.
Already have an account?
# to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This adds the
-dead_stripflag to the linker options on macOS when optimization is enabled, effectively replicating bazel's approach on Linux where--ffunction-sections--gc-sectionsflags are enabled by default under theoptconfiguration.Based on the Mach-O binary format no compiler flag changes are needed, dead code stripping is linker-only.
optimized workerd binary size:
67.9MB -> 60.2MBUp for discussion: I wasn't planning to enable this for fastbuild mode and only modified the .bazelrc file to show that the change won't break test cases, but based on local testing it might be a tiny bit faster since the linker generates and writes binaries with much fewer symbols. For
crypto-impl-asymmetric-test, linking takes 1.5s instead of 1.8s and fastbuild binary size is down from 172MB to 116MB. While these results may not be representative – I expected dead_strip builds to be slower – this may reduce CI disk usage and improve the local build experience.