xchg.h

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#ifndef _ALPHA_CMPXCHG_H
#error Do not include xchg.h directly!
#else
/*
 * xchg/xchg_local and cmpxchg/cmpxchg_local share the same code
 * except that local version do not have the expensive memory barrier.
 * So this file is included twice from asm/cmpxchg.h.
 */

/*
 * Atomic exchange.
 * Since it can be used to implement critical sections
 * it must clobber "memory" (also for interrupts in UP).
 */

static inline unsigned long
____xchg(_u8, volatile char *m, unsigned long val)
{
    unsigned long ret, tmp, addr64;

    __asm__ __volatile__(
    "   andnot  %4,7,%3\n"
    "   insbl   %1,%4,%1\n"
    "1: ldq_l   %2,0(%3)\n"
    "   extbl   %2,%4,%0\n"
    "   mskbl   %2,%4,%2\n"
    "   or  %1,%2,%2\n"
    "   stq_c   %2,0(%3)\n"
    "   beq %2,2f\n"
        __ASM__MB
    ".subsection 2\n"
    "2: br  1b\n"
    ".previous"
    : "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
    : "r" ((long)m), "1" (val) : "memory");

    return ret;
}

static inline unsigned long
____xchg(_u16, volatile short *m, unsigned long val)
{
    unsigned long ret, tmp, addr64;

    __asm__ __volatile__(
    "   andnot  %4,7,%3\n"
    "   inswl   %1,%4,%1\n"
    "1: ldq_l   %2,0(%3)\n"
    "   extwl   %2,%4,%0\n"
    "   mskwl   %2,%4,%2\n"
    "   or  %1,%2,%2\n"
    "   stq_c   %2,0(%3)\n"
    "   beq %2,2f\n"
        __ASM__MB
    ".subsection 2\n"
    "2: br  1b\n"
    ".previous"
    : "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
    : "r" ((long)m), "1" (val) : "memory");

    return ret;
}

static inline unsigned long
____xchg(_u32, volatile int *m, unsigned long val)
{
    unsigned long dummy;

    __asm__ __volatile__(
    "1: ldl_l %0,%4\n"
    "   bis $31,%3,%1\n"
    "   stl_c %1,%2\n"
    "   beq %1,2f\n"
        __ASM__MB
    ".subsection 2\n"
    "2: br 1b\n"
    ".previous"
    : "=&r" (val), "=&r" (dummy), "=m" (*m)
    : "rI" (val), "m" (*m) : "memory");

    return val;
}

static inline unsigned long
____xchg(_u64, volatile long *m, unsigned long val)
{
    unsigned long dummy;

    __asm__ __volatile__(
    "1: ldq_l %0,%4\n"
    "   bis $31,%3,%1\n"
    "   stq_c %1,%2\n"
    "   beq %1,2f\n"
        __ASM__MB
    ".subsection 2\n"
    "2: br 1b\n"
    ".previous"
    : "=&r" (val), "=&r" (dummy), "=m" (*m)
    : "rI" (val), "m" (*m) : "memory");

    return val;
}

/* This function doesn't exist, so you'll get a linker error
   if something tries to do an invalid xchg().  */
extern void __xchg_called_with_bad_pointer(void);

static __always_inline unsigned long
____xchg(, volatile void *ptr, unsigned long x, int size)
{
    switch (size) {
        case 1:
            return ____xchg(_u8, ptr, x);
        case 2:
            return ____xchg(_u16, ptr, x);
        case 4:
            return ____xchg(_u32, ptr, x);
        case 8:
            return ____xchg(_u64, ptr, x);
    }
    __xchg_called_with_bad_pointer();
    return x;
}

/*
 * Atomic compare and exchange.  Compare OLD with MEM, if identical,
 * store NEW in MEM.  Return the initial value in MEM.  Success is
 * indicated by comparing RETURN with OLD.
 *
 * The memory barrier should be placed in SMP only when we actually
 * make the change. If we don't change anything (so if the returned
 * prev is equal to old) then we aren't acquiring anything new and
 * we don't need any memory barrier as far I can tell.
 */

static inline unsigned long
____cmpxchg(_u8, volatile char *m, unsigned char old, unsigned char new)
{
    unsigned long prev, tmp, cmp, addr64;

    __asm__ __volatile__(
    "   andnot  %5,7,%4\n"
    "   insbl   %1,%5,%1\n"
    "1: ldq_l   %2,0(%4)\n"
    "   extbl   %2,%5,%0\n"
    "   cmpeq   %0,%6,%3\n"
    "   beq %3,2f\n"
    "   mskbl   %2,%5,%2\n"
    "   or  %1,%2,%2\n"
    "   stq_c   %2,0(%4)\n"
    "   beq %2,3f\n"
        __ASM__MB
    "2:\n"
    ".subsection 2\n"
    "3: br  1b\n"
    ".previous"
    : "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
    : "r" ((long)m), "Ir" (old), "1" (new) : "memory");

    return prev;
}

static inline unsigned long
____cmpxchg(_u16, volatile short *m, unsigned short old, unsigned short new)
{
    unsigned long prev, tmp, cmp, addr64;

    __asm__ __volatile__(
    "   andnot  %5,7,%4\n"
    "   inswl   %1,%5,%1\n"
    "1: ldq_l   %2,0(%4)\n"
    "   extwl   %2,%5,%0\n"
    "   cmpeq   %0,%6,%3\n"
    "   beq %3,2f\n"
    "   mskwl   %2,%5,%2\n"
    "   or  %1,%2,%2\n"
    "   stq_c   %2,0(%4)\n"
    "   beq %2,3f\n"
        __ASM__MB
    "2:\n"
    ".subsection 2\n"
    "3: br  1b\n"
    ".previous"
    : "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
    : "r" ((long)m), "Ir" (old), "1" (new) : "memory");

    return prev;
}

static inline unsigned long
____cmpxchg(_u32, volatile int *m, int old, int new)
{
    unsigned long prev, cmp;

    __asm__ __volatile__(
    "1: ldl_l %0,%5\n"
    "   cmpeq %0,%3,%1\n"
    "   beq %1,2f\n"
    "   mov %4,%1\n"
    "   stl_c %1,%2\n"
    "   beq %1,3f\n"
        __ASM__MB
    "2:\n"
    ".subsection 2\n"
    "3: br 1b\n"
    ".previous"
    : "=&r"(prev), "=&r"(cmp), "=m"(*m)
    : "r"((long) old), "r"(new), "m"(*m) : "memory");

    return prev;
}

static inline unsigned long
____cmpxchg(_u64, volatile long *m, unsigned long old, unsigned long new)
{
    unsigned long prev, cmp;

    __asm__ __volatile__(
    "1: ldq_l %0,%5\n"
    "   cmpeq %0,%3,%1\n"
    "   beq %1,2f\n"
    "   mov %4,%1\n"
    "   stq_c %1,%2\n"
    "   beq %1,3f\n"
        __ASM__MB
    "2:\n"
    ".subsection 2\n"
    "3: br 1b\n"
    ".previous"
    : "=&r"(prev), "=&r"(cmp), "=m"(*m)
    : "r"((long) old), "r"(new), "m"(*m) : "memory");

    return prev;
}

/* This function doesn't exist, so you'll get a linker error
   if something tries to do an invalid cmpxchg().  */
extern void __cmpxchg_called_with_bad_pointer(void);

static __always_inline unsigned long
____cmpxchg(, volatile void *ptr, unsigned long old, unsigned long new,
          int size)
{
    switch (size) {
        case 1:
            return ____cmpxchg(_u8, ptr, old, new);
        case 2:
            return ____cmpxchg(_u16, ptr, old, new);
        case 4:
            return ____cmpxchg(_u32, ptr, old, new);
        case 8:
            return ____cmpxchg(_u64, ptr, old, new);
    }
    __cmpxchg_called_with_bad_pointer();
    return old;
}

#endif