Re: [PATCH v5 resend 1/4] include: Define fast fail codes and the __fastfail() intrinsic.

[Thomas Faber]

Hi,

On 2022-01-19 12:06, Jinoh Kang wrote:
> +#if defined(__GNUC__)
> +#if defined(__x86_64__)
> +static FORCEINLINE DECLSPEC_NORETURN void __fastfail(unsigned int code)
> +{
> - register ULONGLONG val __asm__("rcx") = code;
> - __asm__ __volatile__( "int $0x29" :: "r" (val) : "memory" );

Any reason to prefer this "manual move" into a register over specifying 
r/ecx as an input into the assembly block? I.e.

__asm__ __volatile__( "int $0x29" :: "c" ((ULONG_PTR)code) : "memory" );

As an added bonus, that would make the function identical between x64 
and x86.
(The cast to ULONG_PTR is to make the compiler aware that the upper bits 
of rcx _must_ be zero, rather than just letting it happen incidentally.)

Something similar might be applicable to ARM, too, but I'm not sure.

Thanks,
Thomas