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Move LLVM bitcode destination #70458

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wants to merge 8 commits into from
Closed

Move LLVM bitcode destination #70458

wants to merge 8 commits into from

Commits on Apr 16, 2020

  1. Remove BitcodeSection::Marker. 

    It existed to minimize compile time of debug builds, but the subsequent
commits in rust-lang#70458 and corresponding changes to Cargo mean that bitcode
will be omitted in most cases anyway.

As a result, we just embed full bitcode whenever embedded bitcode is
necessary.

This commit also removes `BitcodeSection`, using just a `bool` instead
now to indicate the presence of bitcode in an object file.
    @nnethercote
    nnethercote committed Apr 16, 2020
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  2. Promote -Zembed-bitcode to -Cembed-bitcode and default to true. 

    This means that bitcode embedding now occurs by default. Subsequent
commits in this PR will remove the production of compressed bitcode in
rlibs, and Cargo will soon start using this flag to avoid bitcode
embedding when it's not necessary, which is most of the time.

Also, produce an early error if `-Cembed-bitcode=no` is used with
`-Clto`.
    @nnethercote
    nnethercote committed Apr 16, 2020
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  3. Use embedded bitcode for LTO. 

    Instead of `.bc.z` files. This requires adding some code that calls into
LLVM to find the bitcode section within an object file. The name
used for the LTO module is now the full filename, rather than a
substring of the filename, which accounts for one test change.
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    nnethercote committed Apr 16, 2020
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  4. Remove .bc.z files. 

    These were needed for LTO, but LTO now uses bitcode embedded in `.o`
files.
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    nnethercote committed Apr 16, 2020
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  5. Don't copy bytecode files into the incr. comp. cache. 

    It's no longer necessary now that bitcode is embedded into object files.

This change meant that `WorkProductFileKind::Bytecode` is no longer
necessary, which means that type is no longer necessary, which allowed
several places in the code to become simpler.
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    nnethercote committed Apr 16, 2020
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  6. Document -C embed-bitcode in the rustc book.

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    nnethercote committed Apr 16, 2020
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  7. Build libstd with -Cembed-bitcode=yes. 

    So that the artifacts will work with both LTO and non-LTO builds.
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    nnethercote committed Apr 16, 2020
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  8. Update llvm-project. 

    In order to get rust-lang/llvm-project#48, which is needed for wasm to
work in this PR (rust-lang#70458).
    @nnethercote
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