Profile-Guided Optimization (PGO) and Post-Link Optimization (PLO) for Odin lang

[zamazan4ik]

Hi!

Odin aims to be a high-performance programming language. One of the optimizations that can help with achieving better software performance is Profile-Guided Optimization (PGO) (Wiki).

Regarding Odin, there are several ways where PGO can be integrated:

• Implement PGO into the Odin compiler so Odin programs can be compiled and optimized with PGO. Probably, the Odin compiler can try to reuse the existing LLVM PGO ecosystem to implement PGO for Odin programs (like it's done in other LLVM-based compilers like Clang, Rustc, LDC (LLVM-based D compiler), etc.). Many languages like C, C++, Rust, C#, Java (with GraalVM), Go already support building applications with PGO.
• Optimize the Odin compiler itself with PGO. So Odin will compile programs faster. According to the multiple tests, PGO measurably improves compilers performance. As an additional optimization, I suggest testing Post-Link Optimization techniques (like LLVM BOLT) would be interesting too (Clang and Rustc already use BOLT as an addition to PGO). Still, I recommend starting from the usual PGO.

Here are some examples of how PGO optimization is integrated into other projects:

• Rustc: a CI script for the multi-stage build
• GCC:
  • Official docs, section "Building with profile feedback" (even AutoFDO build is supported)
  • A part in a "wonderful" configure script
• Clang: Docs
• Python:
  • CPython: README
  • Pyston: README
• Go: Bash script
• V8: Bazel flag
• ChakraCore: Scripts
• Chromium: Script
• Firefox: Docs
• PHP: Makefile command and old Centminmod scripts
• MySQL: CMake script
• YugabyteDB: GitHub commit
• FoundationDB: Script
• Zstd: Makefile
• Foot: Scripts
• Windows Terminal: GitHub PR
• Pydantic-core: GitHub PR
• file.d: GitHub PR
• OceanBase: CMake flag

Much more information about PGO in other projects, its caveats, etc can be found in my repo. I would be happy to answer your questions about PGO.