[llvm-dev] CFI directives for callee saved registers

[Tim Northover via llvm-dev]

Hi Zaara,

On 6 October 2017 at 12:55, Zaara Syeda via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I've made changes to the prologue to not spill callee saved gprs to the
> stack but rather spill them to unused vector registers. I'm not sure how to
> handle this in the cfi directives.

It sounds like you want the ".cfi_register" directive. There's no way
you can write code that sensibly actually restores the register at any
point it might be needed.

It looks like there's already at least some support for this
directive, but I wouldn't bet on it being handled well (by either LLVM
or your debugger/unwinder) since it's not really used in anger as far
as I know.

Cheers.

Tim.