https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82641
--- Comment #6 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #5)
> My patch adds support for
>
>
> ```
> #pragma GCC push_options
> #pragma GCC target("arch=armv8-a+crc")
> __attribute__((target("arch=armv8-a+crc"))) uint32_t crc32cw(uint32_t crc,
> uint32_t val)
> ```
>
> and just
>
>
> ```
> #pragma GCC push_options
> #pragma GCC target("+crc")
> __attribute__((target("+crc"))) uint32_t crc32cw(uint32_t crc, uint32_t val)
> ```
>
> if the compiler was invoked with `-march=armv8-a`.
>
> However it currently doesn't allow
>
>
> ```
> #pragma GCC push_options
> #pragma GCC target("armv8-a+crc")
> __attribute__((target("armv8-a+crc"))) uint32_t crc32cw(uint32_t crc,
> uint32_t val)
> ```
>
> as it doesn't know if you wanted to change the `fpu` or `arch` here.
> Should I support this case as well?
No, I think we should insist on an arch= or fpu= prefix for all but the adding
extensions case.
Note that extensions can only modify the existing architecture if it supports
that extension. This is because the modifiers are context dependent: for
example the +fp extension (new in gcc-8) will enable floating-point
instructions that come with the specified architecture.
Also note that in the long-term -mfpu and pragma/attribute variants thereof are
likely to be deprecated in favour of specifying all this through the
architecture string.
