[libcxx-commits] [libcxx] [libc++] Turn off PIE when running libc++ premerge tests. (PR #155689)

[Aiden Grossman via libcxx-commits]

https://github.com/boomanaiden154 commented:

This won't have much of an effect. libc++ doesn't build any binaries as part of their build.

The PIE costs for libc++ come from invoking the compiler (if it is compiled with PIE) during testing, and running the just compiled binaries for execution tests. This won't control whether or not the host compiler is built with PIE (other than for a bootstrapping build, which we only do one of).

Controlling the link flags for execution tests would be done somewhere like https://github.com/llvm/llvm-project/blob/0e3319537972d284e94a183899f15b40a798fd1f/libcxx/test/configs/llvm-libc%2B%2B-shared.cfg.in#L13
I already tried disabling PIE on the execution tests on Linux and measured virtually no difference on test runtime. I would think turning off PIE for the host compiler would be even less likely to have any gains as I would imagine a large part of the test time is spent doing standard C++ things like parsing headers, dominating startup time. Profiling there wouldn't hurt though.



https://github.com/llvm/llvm-project/pull/155689