musl/arch/powerpc/atomic_arch.h

#define a_ll a_ll
static inline int a_ll(volatile int *p)
{
	int v;
	__asm__ __volatile__ ("lwarx %0, 0, %2" : "=r"(v) : "m"(*p), "r"(p));
	return v;
}

#define a_sc a_sc
static inline int a_sc(volatile int *p, int v)
{
	int r;
	__asm__ __volatile__ (
		"stwcx. %2, 0, %3 ; mfcr %0"
		: "=r"(r), "=m"(*p) : "r"(v), "r"(p) : "memory", "cc");
	return r & 0x20000000; /* "bit 2" of "cr0" (backwards bit order) */
}

#define a_barrier a_barrier
static inline void a_barrier()
{
	__asm__ __volatile__ ("sync" : : : "memory");
}

#define a_pre_llsc a_barrier

#define a_post_llsc a_post_llsc
static inline void a_post_llsc()
{
	__asm__ __volatile__ ("isync" : : : "memory");
}

#define a_store a_store
static inline void a_store(volatile int *p, int v)
{
	a_pre_llsc();
	*p = v;
	a_post_llsc();
}