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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 |