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| author | Michael Woerister <michaelwoerister@posteo> | 2019-10-14 10:34:21 +0200 |
|---|---|---|
| committer | Michael Woerister <michaelwoerister@posteo> | 2019-10-14 10:34:21 +0200 |
| commit | f81b1548ddf886449d8ea95f82b56274b60fbac7 (patch) | |
| tree | 41a397a5729a4a99207b455a3d6226ca0174f5fe /src/doc | |
| parent | d28a9c38fe14396e86ae274c7847e20ee0f78ca9 (diff) | |
| download | rust-f81b1548ddf886449d8ea95f82b56274b60fbac7.tar.gz rust-f81b1548ddf886449d8ea95f82b56274b60fbac7.zip | |
Add troubleshooting section to PGO chapter in rustc book.
Diffstat (limited to 'src/doc')
| -rw-r--r-- | src/doc/rustc/src/profile-guided-optimization.md | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/src/doc/rustc/src/profile-guided-optimization.md b/src/doc/rustc/src/profile-guided-optimization.md index 38be07a6440..d066f4a9cf5 100644 --- a/src/doc/rustc/src/profile-guided-optimization.md +++ b/src/doc/rustc/src/profile-guided-optimization.md @@ -125,6 +125,17 @@ RUSTFLAGS="-Cprofile-use=/tmp/pgo-data/merged.profdata" \ cargo build --release --target=x86_64-unknown-linux-gnu ``` +### Troubleshooting + +- It is recommended to pass `-Cllvm-args=-pgo-warn-missing-function` during the + `-Cprofile-use` phase. LLVM by default does not warn if it cannot find + profiling data for a given function. Enabling this warning will make it + easier to spot errors in your setup. + +- There is a [known issue](https://github.com/rust-lang/cargo/issues/7416) in + Cargo prior to version 1.39 that will prevent PGO from working correctly. Be + sure to use Cargo 1.39 or newer when doing PGO. + ## Further Reading `rustc`'s PGO support relies entirely on LLVM's implementation of the feature |