[PATCH] D145131: [Arm][AArch64] Setting IsX18ReservedByDefault() to true for Unknown OSes

[Murali Vijayaraghavan via Phabricator via llvm-commits]

vmurali added a comment.

In D145131#4164072 <https://reviews.llvm.org/D145131#4164072>, @DavidSpickett wrote:

> Please confirm that the CI failures are not due to this change and add/update an existing test case for this change. Presumably a triple of "aarch64-notarealos-gnueabi" will trigger this.

If it's indeed only from "aarch64-notarealos-gnueabi", then that can be fixed more easily.

> There is a chance someone out there is relying on this, but that seems like a risky position to begin with. If they are, they will probably just get less efficient code, so I don't object to the change.
>
> There should be a release note for this, for those minority of cases. I know there are command line options for reserving registers (`-ffixed-`?), please check if those would allow folks to override this and if so add that to the note. "if you do not want this behaviour you can use....".

It is currently an opt-out. I can make it an opt-in.

>> [Arm][AArch64]
>
> In the context of llvm, ARM = Arm 32 bit, AArch64 = Arm 64 bit (I know, it's hardly elegant). So you just need [AArch64]. Ideally `[llvm][AArch64]`.

Aah thanks.

> Finally, do we know what RISCV does for this? They have a method by the same name and we might as well make clang consistent if we can.

I haven't taken a look at RISCV.


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https://reviews.llvm.org/D145131