Use V8's zlib

[npaun]

This PR changes the source of zlib to match what V8 is using, so that we don't have version conflicts between workerd and the internal edgeworker repo.

zlib is built from source. The build config is a translation from the BUILD.gn file into bazel syntax.

Note that this is a bit of a different build process from edgeworker, which uses precompiled binaries from v8 for zlib.

[fhanau]

Couple thoughts on this –

• we could use our own high-performance zlib fork (cloudflare/zlib) here, but I think using Chromium zlib is better for consistency since we use V8 a lot. Chromium zlib also has a number of performance optimizations (in fact some of the decompression optimizations in Cloudflare zlib originate from Chromium zlib) and should work well.
• I looked into switching a while back but got bogged down by configuring the build to configure SIMD support properly. I think we should do this eventually but it's not required for now – the GN build file is pretty complex and we'd also have to properly document what level of hardware extensions workerd requires. This is best done together with compiling with e.g. x86-64-v3 by default.
• I don't think we should test for ZLIB_VERNUM at all – in my experience it is not relevant to developers, except when checking if some C-level API that got added in a certain version will be available, or perhaps if a bug fix added in a certain version is added. Either way, we don't depend on zlib being a specific fixed version and shouldn't have to update a test every time the zlib version is incremented.

Change LGTM but it looks like there's SIMD-related compile errors on Windows so building this using Bazel might be more complex

[jasnell]

@anonrig ... your experience with simd may be helpful in the longer term effort here

[npaun]

Thanks for the notes @fhanau

I don't care about ZLIB_VERNUM itself, just that there is consistency between what is being used in workerd and edgeworker, so as to eliminate a possible source of trouble.

I'll have a look tomorrow into what is going wrong on Windows. Fingers crossed that it's not too hard to fix.

[anonrig]

Node.js ZLIB configuration might give you a better understanding for the SIMD related issues. If you couldn't solve this in a reasonable amount of time, I have a Windows machine at home.

https://github.com/anonrig/node/blob/main/deps/zlib/zlib.gyp

[npaun]

May resolve #2540 if we decide to go with this approach.

[npaun]

Note for reviewers: In this file, I try to keep everything as similar as possible to the original BUILD.gn even if it looks strange in bazel

[npaun]

Internal PR passes

[fhanau]

Thank you for doing this! Should certainly improve performance in use cases where developers use compression APIs within workerd a lot.

[fhanau]

These should really be local_defines – defines are added to every target that depends on zlib otherwise, which is really polluting the global defines namespace and unnecessarily making the command line of workerd longer. https://bazel.build/reference/be/c-cpp#cc_library.local_defines

[npaun]

I agree; the main reason I left it all as define is to match BUILD.gn. I can take a crack at limiting the scope in another PR.

[npaun]

There's also another nuisance: I'm using defines to avoid nested selects which don't work in bazel. I am actually not entirely sure how to get around this.

[fhanau]

Great question! We use selects.config_setting_group (https://bazel.build/docs/configurable-attributes#and-chaining) for this. Started with a PR on converting those.

[fhanau]

This adds a requirement on ISA extensions that we didn't have before – IMHO this is reasonable since these extensions have been around for a long time but we need to document it.
If we're doing that it's reasonable to define the same set of extensions for the entire build and remove the individual flags from here (I agree that we should follow the structure of BUILD.gn for the individual targets but to make the file less complex we should not have to define ISA extension flags for each target). I will prepare a PR for this.