LLVM’s BOLT enabled by default for Linux x86/AArch64 test builds

BOLT as the Technology developed by Facebook/Meta to optimize binaries behalf better performance by optimizing code layout merged with mainline LLVM earlier this year. Now that we are approaching the end of the year, BOLT is getting a small promotion by being enabled by default for Linux x86_64 and AArch64 test builds.

The LLVM test build script used to generate LLVM resources for testing new compiler release candidates has been updated to generate BOLT by default. This default BOLT for LLVM test builds currently only applies to Linux and AArch64 and x86_64 architectures.

The default change was merged yesterday for future test version consumption.

Those who want to know more about this post-link optimizer developed by Facebook can find the code in-tree here. Generating an optimized binary works for large apps with Faceobok/Meta having even worked on optimized linux kernel images, but either way one needs to first profile the app/software with linux perf so that BOLT can make appropriate optimizations to the code layout. The linked GitHub page describes more BOLT optimization steps and other details for those who want to play around with this LLVM tool.

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