LTO - AshokBhat/notes GitHub Wiki

LTO (Link Time Optimization)

• Advantages - Reduced binary size and higher performance.
• Disadvantages - Longer link time (even incremental), more memory usage

Usage

• Linux kernel - Starting Linux 5.12, Clang LTO-optimized kernel builds are enabled.
• RHEL - Starting RHEL 9, LTO is enabled by default in userspace.
• Android - Starting in 2018, Google Pixel devices run major kernel versions with LTO+CFI.
• Microsoft Windows heavily utilizes both LTO and PGO

Also known as

• LTCG, WPA/WPO/IPA

ThinLTO

• New approach designed to scale like a non-LTO build, while retaining most of the performance achievement of full LTO.
• Support in LLVM since 4.0 release.
• Resources: http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html

Usage

• Google Chrome team uses ThinLTO on MacOS (running on Apple hardware) and Windows builds.

See also

• GNU Toolchain
• LLVM