bors 0c72c0d11a Auto merge of #133250 - DianQK:embed-bitcode-pgo, r=nikic
The embedded bitcode should always be prepared for LTO/ThinLTO

Fixes #115344. Fixes #117220.

There are currently two methods for generating bitcode that used for LTO. One method involves using `-C linker-plugin-lto` to emit object files as bitcode, which is the typical setting used by cargo. The other method is through `-C embed-bitcode=yes`.

When using with `-C embed-bitcode=yes -C lto=no`, we run a complete non-LTO LLVM pipeline to obtain bitcode, then the bitcode is used for LTO. We run the Call Graph Profile Pass twice on the same module.

This PR is doing something similar to LLVM's `buildFatLTODefaultPipeline`, obtaining the bitcode for embedding after running `buildThinLTOPreLinkDefaultPipeline`.

r? nikic
2025-03-01 08:22:18 +00:00
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The run-make test suite

The run-make test suite contains tests which are the most flexible out of all the rust-lang/rust test suites. run-make tests can basically contain arbitrary code, and are supported by the run_make_support library.

Infrastructure

There are two kinds of run-make tests:

  1. The new rmake.rs version: this allows run-make tests to be written in Rust (with rmake.rs as the main test file).
  2. The legacy Makefile version: this is what run-make tests were written with before support for rmake.rs was introduced.

The implementation for collecting and building the rmake.rs recipes (or Makefiles) are in src/tools/compiletest/src/runtest.rs, in run_rmake_v2_test and run_rmake_legacy_test.

Rust-based run-make tests: rmake.rs

The setup for the rmake.rs version is a 3-stage process:

  1. First, we build the run_make_support library in bootstrap as a tool lib.

  2. Then, we compile the rmake.rs "recipe" linking the support library and its dependencies in, and provide a bunch of env vars. We setup a directory structure within build/<target>/test/run-make/

    <test-name>/
        rmake.exe              # recipe binary
        rmake_out/             # sources from test sources copied over
    

    and copy non-rmake.rs input support files over to rmake_out/. The support library is made available as an extern prelude.

  3. Finally, we run the recipe binary and set rmake_out/ as the working directory.

Formatting

Note that files under tests/ are not formatted by ./x fmt, use rustfmt tests/path/to/file.rs to format a specific file if desired.