================
@@ -416,6 +416,12 @@ added in the future:
This calling convention, like the `PreserveMost` calling convention, will
be
used by a future version of the ObjectiveC runtime and should be considered
experimental at this time.
+"``preserve_nonecc``" - The `PreserveNone` calling convention
+ This calling convention doesn't preserve any general registers. So all
+ general registers are caller saved registers. It also uses all general
+ registers to pass arguments. This attribute doesn't impact floating-point
----------------
weiguozhi wrote:
> I suspect this should say any `non-general purpose registers (e.g. floating
> point registers, on x86 XMMs/YMMs)`. Rather than `floating-point registers`.
Thanks for the correction! Will change it.
> Also isn't this just a hack to increase the number of registers used to pass
> arguments? If so there has to be a better way of doing this. Maybe a
> non-exposed attribute which is used only for non-exposed functions? e.g. on
> x86 (not 64bit), regparm could be used internally there.
It's not a hack, it's a natural extension. Because we don't preserve general
registers, we can use all of them to pass arguments without the extra cost to
save/restore those registers, they are clobbered by the function call anyway.
https://github.com/llvm/llvm-project/pull/76868
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