[llvm] [AArch64, ELF] Allow implicit $d/$x at section beginning (PR #99718)
Peter Smith via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 13 09:07:53 PDT 2024
smithp35 wrote:
To give you a summary of my thoughts so far:
* I don't think we'll be able to change the AArch64 ABI as I don't think there's enough consensus on the GNU side for a relocatable object based solution.
* An alternative, likely LLVM only, opt-in option for users with large projects, in control of their own toolchain to reduce mapping symbols could be valuable to those projects.
* I'd like to discourage use of the opt-in option where portability of the relocatable objects is a concern. For example, while there are no plans to do so, I couldn't guarantee the AArch64 ABI might make changes that would retain backwards compatibility.
* If the option becomes LLVM only then I'd prefer we gave the option a more neutral name. For example `-mimplicit-mapsyms` or `-malternative-mapsyms` as `-moptimize-mapsyms` doesn't imply a, small, trade-off in portability.
* I'd like to see the help for the option mention compatibility. For example "Allow mapping symbol at section beginning to be implicit, lowers number of mapping symbols at the expense of some portability. Recommended for large projects that can build all their objects using this option."
* I'd like to find a way of recording that implicit mapping symbols have been used, I don't think we need a compatibility check.
https://github.com/llvm/llvm-project/pull/99718
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