Switch pipelining metadata action to hollow rlib (-Zno-codegen)#3870
Switch pipelining metadata action to hollow rlib (-Zno-codegen)#3870walter-zeromatter wants to merge 1 commit intobazelbuild:mainfrom
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Replace the --rustc-quit-on-rmeta / .rmeta approach with Buck2-style hollow rlibs: the RustcMetadata action runs rustc to completion with -Zno-codegen, emitting a .rlib archive (named -hollow.rlib) that contains only metadata and optimized MIR. Key fixes: - Main Rustc action uses full rlib --extern deps so the SVH embedded in the full rlib matches what downstream binaries expect (avoiding E0460 with non-deterministic proc macros). - RUSTC_BOOTSTRAP=1 is set on both actions: it changes the crate hash, so inconsistent use would cause SVH mismatch even for deterministic crates. - -Ldependency= points to the _hollow/ subdirectory so the full rlib and hollow rlib never appear in the same search path (avoids E0463). - transitive_metadata_outputs are always included in the sandbox so rustc can resolve transitive -Ldependency= references. Adds an SVH mismatch test that demonstrates the problem with non-deterministic proc macros (uses a HashMap-based derive macro whose output varies by OS-seeded random seed).
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Hey @walter-zeromatter, we'll need a signed CLA to proceed with the review, could you let us know if that works for you? |
scentini
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It's Walter's work. We just merged it to my fork a while ago so the world can benefit from it via rules_rs. |
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Thanks for the clarification! In that case we only need to wait for the CLA. |
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Sorry, I've been waiting on our legal. Just got approval, should have the cla signed later today |
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Replace the --rustc-quit-on-rmeta / .rmeta approach with Buck2-style hollow rlibs: the RustcMetadata action runs rustc to completion with -Zno-codegen, emitting a .rlib archive (named -hollow.rlib) that contains only metadata and optimized MIR.
Key fixes:
Adds an SVH mismatch test that demonstrates the problem with non-deterministic proc macros (uses a HashMap-based derive macro whose output varies by OS-seeded random seed).
I've been using this locally, and it seems to be a notable improvement - I've been able to remove all
disable_pipelining=Trueattributes and enable pipelining globally while still having good performance