assert: Mark `__assert_fail` as `cold`

[Sam James]

Noah Goldstein <goldstein.w.n@gmail.com> writes:

> This helps compilers split the codegen for setting up the arguments
> (`__expression`, `__filename`, etc...) from the potentially hot cold
> where the `assert` is to a presumably cold region on the assertion
> failure path.

It looks good to me too, but I'm a little surprised this didn't come up
before.

I dug a bit more and found
https://inbox.sourceware.org/libc-alpha/BYAPR08MB4232749003F118FA852BA0E5B6730@BYAPR08MB4232.namprd08.prod.outlook.com/,
but nothing else.

Reviewed-by: Sam James <sam@gentoo.org>

> ---
>  assert/assert.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/assert/assert.h b/assert/assert.h
> index 266a41df06..3261eb4202 100644
> --- a/assert/assert.h
> +++ b/assert/assert.h
> @@ -71,13 +71,13 @@ extern void __assert_fail (const char *__assertion, const char *__file,
>  /* Likewise, but prints the error text for ERRNUM.  */
>  extern void __assert_perror_fail (int __errnum, const char *__file,
>  				  unsigned int __line, const char *__function)
> -     __THROW __attribute__ ((__noreturn__));
> +     __THROW __attribute__ ((__noreturn__)) __COLD;
>  
>  
>  /* The following is not at all used here but needed for standard
>     compliance.  */
>  extern void __assert (const char *__assertion, const char *__file, int __line)
> -     __THROW __attribute__ ((__noreturn__));
> +     __THROW __attribute__ ((__noreturn__)) __COLD;
>  
>  
>  __END_DECLS
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