https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110096
Bug ID: 110096
Summary: Would be nice if __builtin_ia32_pause had a portable
equivalent as it's applicable to ARM
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: pdimov at gmail dot com
Target Milestone: ---
This is more of a feature request than a bug.
Currently `__builtin_ia32_pause()` only applies to Intel/AMD CPUs (hence the
`ia32` in the name), but it has a straightforward and equivalent meaning for
ARM (issue a YIELD instruction, which is the exact ARM equivalent to the PAUSE
x86 one.)
This forces us to do things like
```
#if __has_builtin(__builtin_ia32_pause)
__builtin_ia32_pause();
#elif defined(__GNUC__) && ( (defined(__ARM_ARCH) && __ARM_ARCH >= 8) ||
defined(__ARM_ARCH_8A__) || defined(__aarch64__) )
__asm__ __volatile__( "yield" : : : "memory" );
// ...
```
(E.g.
https://github.com/boostorg/core/blob/3b96d237c0e3ada30c9beca0f60062a2576dcafd/include/boost/core/detail/sp_thread_pause.hpp)
This can be solved in one of two ways; one, extend `__builtin_ia32_pause` to do
the right thing for ARM - unprincipled because of ia32 in the name, but will
automagically "fix" all code using `#if __has_builtin(__builtin_ia32_pause)`.
Or two, add a portable spelling for the intrinsic, either `__builtin_pause()`
or `__builtin_yield()`.
(Failing that, an ARM-specific `__builtin_arm_yield()` would still be an
improvement over the above because it at least will allow us to not hardcode
the ARM target detection, which we are probably getting wrong.)
