[PATCH] D158322: [ELF] Add -Bsymbolic-non-weak

Fri Aug 18 16:28:16 PDT 2023

smeenai added a comment.

In D158322#4600532 <https://reviews.llvm.org/D158322#4600532>, @MaskRay wrote:

> Glad to know see more adoption of the `-Bsymbolic-non-weak*` idea:) (https://maskray.me/blog/2021-05-16-elf-interposition-and-bsymbolic)

Yup :) It seems like the nicest solution for maintaining preemptibility in the small amount of cases which need it while not unnecessarily slowing down everything else.

>> We have use cases for which making weak data preemptible is useful, but we don't want to pessimize access to non-weak data. (For a large internal app, we measured 2000+ data symbols whose accesses would be unnecessarily pessimized by -Bsymbolic-functions.)
>
> The main problem is copy relocations, which is incompatible with making non-weak data non-preemptible.
> Are you able to rule out all copy relocations  (default ELF codegen for -fno-pic)?

Thankfully yes, because we build everything as PIC/PIE (and IIRC modern Android versions require PIE).

Repository:
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  https://reviews.llvm.org/D158322/new/

https://reviews.llvm.org/D158322