mirror of
git://git.musl-libc.org/musl
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06fbefd100
counts leading zero bits of a 64bit int, undefined on zero input. (has nothing to do with atomics, added to atomic.h so target specific helper functions are together.) there is a logarithmic generic implementation and another in terms of a 32bit a_clz_32 on targets where that's available.
83 lines
1.5 KiB
C
83 lines
1.5 KiB
C
#define a_ll a_ll
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static inline int a_ll(volatile int *p)
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{
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int v;
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__asm__ __volatile__ ("ldaxr %w0,%1" : "=r"(v) : "Q"(*p));
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return v;
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}
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#define a_sc a_sc
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static inline int a_sc(volatile int *p, int v)
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{
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int r;
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__asm__ __volatile__ ("stlxr %w0,%w2,%1" : "=&r"(r), "=Q"(*p) : "r"(v) : "memory");
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return !r;
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}
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#define a_barrier a_barrier
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static inline void a_barrier()
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{
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__asm__ __volatile__ ("dmb ish" : : : "memory");
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}
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#define a_cas a_cas
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static inline int a_cas(volatile int *p, int t, int s)
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{
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int old;
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do {
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old = a_ll(p);
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if (old != t) {
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a_barrier();
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break;
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}
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} while (!a_sc(p, s));
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return old;
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}
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#define a_ll_p a_ll_p
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static inline void *a_ll_p(volatile void *p)
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{
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void *v;
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__asm__ __volatile__ ("ldaxr %0, %1" : "=r"(v) : "Q"(*(void *volatile *)p));
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return v;
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}
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#define a_sc_p a_sc_p
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static inline int a_sc_p(volatile int *p, void *v)
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{
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int r;
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__asm__ __volatile__ ("stlxr %w0,%2,%1" : "=&r"(r), "=Q"(*(void *volatile *)p) : "r"(v) : "memory");
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return !r;
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}
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#define a_cas_p a_cas_p
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static inline void *a_cas_p(volatile void *p, void *t, void *s)
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{
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void *old;
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do {
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old = a_ll_p(p);
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if (old != t) {
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a_barrier();
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break;
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}
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} while (!a_sc_p(p, s));
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return old;
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}
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#define a_ctz_64 a_ctz_64
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static inline int a_ctz_64(uint64_t x)
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{
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__asm__(
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" rbit %0, %1\n"
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" clz %0, %0\n"
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: "=r"(x) : "r"(x));
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return x;
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}
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#define a_clz_64 a_clz_64
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static inline int a_clz_64(uint64_t x)
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{
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__asm__("clz %0, %1" : "=r"(x) : "r"(x));
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return x;
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}
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