[llvm-dev] How to enable AArch64 V8.3A support in clang?

[Ahmed Bougacha via llvm-dev]

Hi Zhang,

On Tue, Apr 23, 2019 at 10:22 AM Zhang via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Hey:
> Apple's version of Clang has support for ``-arch arm64e``which enables ARM PAC support. IIRC a few years ago someone from Apple/ARM says they are planning to merge the support back to upstream and judging by my very limited experience with backend it seems to be the case. However I just couldn't get that part to work. Directly using ``-arch arm64e`` doesn't seem to work and results in a ``invalid arch name '-arch arm64e'``.
>
> I then tried multiple combinations like ``-target arm64-apple-ios5.0.0 -march=armv8.3-a`` but has no effect. The binary still doesn't have any V8.3A instructions. Am I missing something here?

arm64e is only supported by Apple Clang at this time.
Upstream LLVM/Clang has various bits and pieces, including: full
assembler/disassembler for v8.3a, some basic codegen (for return
address signing and v8.5a BTI), and minimal MachO object reading.

Let me know if you have any questions,
-Ahmed

>
> Thanks
>
>
> Zhang
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