Commit 392a4d5b authored by Peter Maydell's avatar Peter Maydell Committed by Paolo Bonzini
Browse files

atomic.h: Fix build with clang 



clang defines __ATOMIC_SEQ_CST but its implementation of the
__atomic_exchange() builtin differs from that of gcc. Move the
__clang__ branch of the ifdef ladder to the top and fix its
implementation (there is no such builtin as __sync_exchange),
so we can compile with clang again.

Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7839ff59

include/qemu/atomic.h

+3 −3
Original line number Diff line number Diff line
@@ -168,14 +168,14 @@ 
#endif



#ifndef atomic_xchg

#ifdef __ATOMIC_SEQ_CST

#if defined(__clang__)

#define atomic_xchg(ptr, i)    __sync_swap(ptr, i)

#elif defined(__ATOMIC_SEQ_CST)

#define atomic_xchg(ptr, i)    ({                           \

    typeof(*ptr) _new = (i), _old;                          \

    __atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \

    _old;                                                   \

})

#elif defined __clang__

#define atomic_xchg(ptr, i)    __sync_exchange(ptr, i)

#else

/* __sync_lock_test_and_set() is documented to be an acquire barrier only.  */

#define atomic_xchg(ptr, i)    (smp_mb(), __sync_lock_test_and_set(ptr, i))