[Qemu-devel] [FreeBSD] Host build i386 failing to build aarch64 targets

[Sean Bruno <sbruno@freebsd.org>]

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aarch64 targets are now failing to build on i386 hosts due to missing
__atomic_load_8() calls since this commit:

https://github.com/qemu/qemu/commit/a0aa44b488b3601415d55041e4619aef5f3a4ba8#diff-c143d686899ae51d7b927d9c682e12fd

I'm unsure if Linux is disabling aarch64 targets for i386 hosts or if
this commit works "just fine" on Linux hosts right now, as it doesn't
work with clang or gcc.

More or less, the code in question ends up looking like this bit of
test code:

#include <stdio.h>
#include <sys/types.h>
#include <machine/atomic.h>

#define atomic_read(ptr)                          \
    ({                                            \
    typeof(*ptr) _val;                            \
     __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
    _val;                                         \
    })

int main ()
{
	int foo;
	int64_t foo64;

	atomic_read(&foo);
	atomic_read(&foo64);

	return(0);
}


This test code will manifest the same issue as the aarch64 target
building on FreeBSD i386 with the error:

undefined reference to `__atomic_load_8'
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