[llvm-branch-commits] [Driver] Add -Wa, options -mmapsyms={default, implicit} (PR #104542)

[Fangrui Song via llvm-branch-commits]

https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/104542

-Wa,-mapsyms=implicit enables the alternative mapping symbol scheme
discussed at #99718.

While not conforming to the current aaelf64 ABI, the option is
invaluable for those with full control over their toolchain, no reliance
on weird relocatable files, and a strong focus on minimizing both
relocatable and executable sizes.

The option is discouraged when portability of the relocatable objects is
a concern.
https://maskray.me/blog/2024-07-21-mapping-symbols-rethinking-for-efficiency
elaborates the risk.