musl/arch/sh/atomic_arch.h

#define LLSC_CLOBBERS "r0", "t", "memory"
#define LLSC_START(mem) "synco\n"  \
	"0:	movli.l @" mem ", r0\n"
#define LLSC_END(mem)              \
	"1:	movco.l r0, @" mem "\n"    \
	"	bf 0b\n"                   \
	"	synco\n"

static inline int __sh_cas_llsc(volatile int *p, int t, int s)
{
	int old;
	__asm__ __volatile__(
		LLSC_START("%1")
		"	mov r0, %0\n"
		"	cmp/eq %0, %2\n"
		"	bf 1f\n"
		"	mov %3, r0\n"
		LLSC_END("%1")
		: "=&r"(old) : "r"(p), "r"(t), "r"(s) : LLSC_CLOBBERS);
	return old;
}

static inline int __sh_swap_llsc(volatile int *x, int v)
{
	int old;
	__asm__ __volatile__(
		LLSC_START("%1")
		"	mov r0, %0\n"
		"	mov %2, r0\n"
		LLSC_END("%1")
		: "=&r"(old) : "r"(x), "r"(v) : LLSC_CLOBBERS);
	return old;
}

static inline int __sh_fetch_add_llsc(volatile int *x, int v)
{
	int old;
	__asm__ __volatile__(
		LLSC_START("%1")
		"	mov r0, %0\n"
		"	add %2, r0\n"
		LLSC_END("%1")
		: "=&r"(old) : "r"(x), "r"(v) : LLSC_CLOBBERS);
	return old;
}

static inline void __sh_store_llsc(volatile int *p, int x)
{
	__asm__ __volatile__(
		"	synco\n"
		"	mov.l %1, @%0\n"
		"	synco\n"
		: : "r"(p), "r"(x) : "memory");
}

static inline void __sh_and_llsc(volatile int *x, int v)
{
	__asm__ __volatile__(
		LLSC_START("%0")
		"	and %1, r0\n"
		LLSC_END("%0")
		: : "r"(x), "r"(v) : LLSC_CLOBBERS);
}

static inline void __sh_or_llsc(volatile int *x, int v)
{
	__asm__ __volatile__(
		LLSC_START("%0")
		"	or %1, r0\n"
		LLSC_END("%0")
		: : "r"(x), "r"(v) : LLSC_CLOBBERS);
}

#ifdef __SH4A__
#define a_cas(p,t,s)     __sh_cas_llsc(p,t,s)
#define a_swap(x,v)      __sh_swap_llsc(x,v)
#define a_fetch_add(x,v) __sh_fetch_add_llsc(x, v)
#define a_store(x,v)     __sh_store_llsc(x, v)
#define a_and(x,v)       __sh_and_llsc(x, v)
#define a_or(x,v)        __sh_or_llsc(x, v)
#else

int  __sh_cas(volatile int *, int, int);
int  __sh_swap(volatile int *, int);
int  __sh_fetch_add(volatile int *, int);
void __sh_store(volatile int *, int);
void __sh_and(volatile int *, int);
void __sh_or(volatile int *, int);

#define a_cas(p,t,s)     __sh_cas(p,t,s)
#define a_swap(x,v)      __sh_swap(x,v)
#define a_fetch_add(x,v) __sh_fetch_add(x, v)
#define a_store(x,v)     __sh_store(x, v)
#define a_and(x,v)       __sh_and(x, v)
#define a_or(x,v)        __sh_or(x, v)
#endif