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qemu/atomic: Remove pre-C11 atomic fallbacks
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We now require c11, so the fallbacks are now dead code

Tested-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@rth7680
rth7680 committed Jul 21, 2021
1 parent 952fd67 commit 47345e7
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Showing 2 changed files with 10 additions and 201 deletions.
7 changes: 0 additions & 7 deletions configure
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Expand Up @@ -3991,18 +3991,11 @@ cat > $TMPC << EOF
int main(void)
{
uint64_t x = 0, y = 0;
#ifdef __ATOMIC_RELAXED
y = __atomic_load_n(&x, __ATOMIC_RELAXED);
__atomic_store_n(&x, y, __ATOMIC_RELAXED);
__atomic_compare_exchange_n(&x, &y, x, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED);
__atomic_exchange_n(&x, y, __ATOMIC_RELAXED);
__atomic_fetch_add(&x, y, __ATOMIC_RELAXED);
#else
typedef char is_host64[sizeof(void *) >= sizeof(uint64_t) ? 1 : -1];
__sync_lock_test_and_set(&x, y);
__sync_val_compare_and_swap(&x, y, 0);
__sync_fetch_and_add(&x, y);
#endif
return 0;
}
EOF
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204 changes: 10 additions & 194 deletions include/qemu/atomic.h
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Expand Up @@ -60,8 +60,9 @@
(unsigned short)1, \
(expr)+0))))))

#ifdef __ATOMIC_RELAXED
/* For C11 atomic ops */
#ifndef __ATOMIC_RELAXED
#error "Expecting C11 atomic ops"
#endif

/* Manual memory barriers
*
Expand Down Expand Up @@ -239,193 +240,8 @@
#define qatomic_xor(ptr, n) \
((void) __atomic_fetch_xor(ptr, n, __ATOMIC_SEQ_CST))

#else /* __ATOMIC_RELAXED */

#ifdef __alpha__
#define smp_read_barrier_depends() asm volatile("mb":::"memory")
#endif

#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__)

/*
* Because of the strongly ordered storage model, wmb() and rmb() are nops
* here (a compiler barrier only). QEMU doesn't do accesses to write-combining
* qemu memory or non-temporal load/stores from C code.
*/
#define smp_mb_release() barrier()
#define smp_mb_acquire() barrier()

/*
* __sync_lock_test_and_set() is documented to be an acquire barrier only,
* but it is a full barrier at the hardware level. Add a compiler barrier
* to make it a full barrier also at the compiler level.
*/
#define qatomic_xchg(ptr, i) (barrier(), __sync_lock_test_and_set(ptr, i))

#elif defined(_ARCH_PPC)

/*
* We use an eieio() for wmb() on powerpc. This assumes we don't
* need to order cacheable and non-cacheable stores with respect to
* each other.
*
* smp_mb has the same problem as on x86 for not-very-new GCC
* (http://patchwork.ozlabs.org/patch/126184/, Nov 2011).
*/
#define smp_wmb() ({ asm volatile("eieio" ::: "memory"); (void)0; })
#if defined(__powerpc64__)
#define smp_mb_release() ({ asm volatile("lwsync" ::: "memory"); (void)0; })
#define smp_mb_acquire() ({ asm volatile("lwsync" ::: "memory"); (void)0; })
#else
#define smp_mb_release() ({ asm volatile("sync" ::: "memory"); (void)0; })
#define smp_mb_acquire() ({ asm volatile("sync" ::: "memory"); (void)0; })
#endif
#define smp_mb() ({ asm volatile("sync" ::: "memory"); (void)0; })

#endif /* _ARCH_PPC */

/*
* For (host) platforms we don't have explicit barrier definitions
* for, we use the gcc __sync_synchronize() primitive to generate a
* full barrier. This should be safe on all platforms, though it may
* be overkill for smp_mb_acquire() and smp_mb_release().
*/
#ifndef smp_mb
#define smp_mb() __sync_synchronize()
#endif

#ifndef smp_mb_acquire
#define smp_mb_acquire() __sync_synchronize()
#endif

#ifndef smp_mb_release
#define smp_mb_release() __sync_synchronize()
#endif

#ifndef smp_read_barrier_depends
#define smp_read_barrier_depends() barrier()
#endif

#ifndef signal_barrier
#define signal_barrier() barrier()
#endif

/* These will only be atomic if the processor does the fetch or store
* in a single issue memory operation
*/
#define qatomic_read__nocheck(p) (*(__typeof__(*(p)) volatile*) (p))
#define qatomic_set__nocheck(p, i) ((*(__typeof__(*(p)) volatile*) (p)) = (i))

#define qatomic_read(ptr) qatomic_read__nocheck(ptr)
#define qatomic_set(ptr, i) qatomic_set__nocheck(ptr,i)

/**
* qatomic_rcu_read - reads a RCU-protected pointer to a local variable
* into a RCU read-side critical section. The pointer can later be safely
* dereferenced within the critical section.
*
* This ensures that the pointer copy is invariant thorough the whole critical
* section.
*
* Inserts memory barriers on architectures that require them (currently only
* Alpha) and documents which pointers are protected by RCU.
*
* qatomic_rcu_read also includes a compiler barrier to ensure that
* value-speculative optimizations (e.g. VSS: Value Speculation
* Scheduling) does not perform the data read before the pointer read
* by speculating the value of the pointer.
*
* Should match qatomic_rcu_set(), qatomic_xchg(), qatomic_cmpxchg().
*/
#define qatomic_rcu_read(ptr) ({ \
typeof(*ptr) _val = qatomic_read(ptr); \
smp_read_barrier_depends(); \
_val; \
})

/**
* qatomic_rcu_set - assigns (publicizes) a pointer to a new data structure
* meant to be read by RCU read-side critical sections.
*
* Documents which pointers will be dereferenced by RCU read-side critical
* sections and adds the required memory barriers on architectures requiring
* them. It also makes sure the compiler does not reorder code initializing the
* data structure before its publication.
*
* Should match qatomic_rcu_read().
*/
#define qatomic_rcu_set(ptr, i) do { \
smp_wmb(); \
qatomic_set(ptr, i); \
} while (0)

#define qatomic_load_acquire(ptr) ({ \
typeof(*ptr) _val = qatomic_read(ptr); \
smp_mb_acquire(); \
_val; \
})

#define qatomic_store_release(ptr, i) do { \
smp_mb_release(); \
qatomic_set(ptr, i); \
} while (0)

#ifndef qatomic_xchg
#if defined(__clang__)
#define qatomic_xchg(ptr, i) __sync_swap(ptr, i)
#else
/* __sync_lock_test_and_set() is documented to be an acquire barrier only. */
#define qatomic_xchg(ptr, i) (smp_mb(), __sync_lock_test_and_set(ptr, i))
#endif
#endif
#define qatomic_xchg__nocheck qatomic_xchg

/* Provide shorter names for GCC atomic builtins. */
#define qatomic_fetch_inc(ptr) __sync_fetch_and_add(ptr, 1)
#define qatomic_fetch_dec(ptr) __sync_fetch_and_add(ptr, -1)

#define qatomic_fetch_add(ptr, n) __sync_fetch_and_add(ptr, n)
#define qatomic_fetch_sub(ptr, n) __sync_fetch_and_sub(ptr, n)
#define qatomic_fetch_and(ptr, n) __sync_fetch_and_and(ptr, n)
#define qatomic_fetch_or(ptr, n) __sync_fetch_and_or(ptr, n)
#define qatomic_fetch_xor(ptr, n) __sync_fetch_and_xor(ptr, n)

#define qatomic_inc_fetch(ptr) __sync_add_and_fetch(ptr, 1)
#define qatomic_dec_fetch(ptr) __sync_add_and_fetch(ptr, -1)
#define qatomic_add_fetch(ptr, n) __sync_add_and_fetch(ptr, n)
#define qatomic_sub_fetch(ptr, n) __sync_sub_and_fetch(ptr, n)
#define qatomic_and_fetch(ptr, n) __sync_and_and_fetch(ptr, n)
#define qatomic_or_fetch(ptr, n) __sync_or_and_fetch(ptr, n)
#define qatomic_xor_fetch(ptr, n) __sync_xor_and_fetch(ptr, n)

#define qatomic_cmpxchg(ptr, old, new) \
__sync_val_compare_and_swap(ptr, old, new)
#define qatomic_cmpxchg__nocheck(ptr, old, new) qatomic_cmpxchg(ptr, old, new)

/* And even shorter names that return void. */
#define qatomic_inc(ptr) ((void) __sync_fetch_and_add(ptr, 1))
#define qatomic_dec(ptr) ((void) __sync_fetch_and_add(ptr, -1))
#define qatomic_add(ptr, n) ((void) __sync_fetch_and_add(ptr, n))
#define qatomic_sub(ptr, n) ((void) __sync_fetch_and_sub(ptr, n))
#define qatomic_and(ptr, n) ((void) __sync_fetch_and_and(ptr, n))
#define qatomic_or(ptr, n) ((void) __sync_fetch_and_or(ptr, n))
#define qatomic_xor(ptr, n) ((void) __sync_fetch_and_xor(ptr, n))

#endif /* __ATOMIC_RELAXED */

#ifndef smp_wmb
#define smp_wmb() smp_mb_release()
#endif
#ifndef smp_rmb
#define smp_rmb() smp_mb_acquire()
#endif

/* This is more efficient than a store plus a fence. */
#if !defined(__SANITIZE_THREAD__)
#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__)
#define qatomic_mb_set(ptr, i) ((void)qatomic_xchg(ptr, i))
#endif
#endif

/* qatomic_mb_read/set semantics map Java volatile variables. They are
* less expensive on some platforms (notably POWER) than fully
Expand All @@ -435,16 +251,16 @@
* use. See docs/devel/atomics.rst for more discussion.
*/

#ifndef qatomic_mb_read
#define qatomic_mb_read(ptr) \
qatomic_load_acquire(ptr)
#endif

#ifndef qatomic_mb_set
#define qatomic_mb_set(ptr, i) do { \
qatomic_store_release(ptr, i); \
smp_mb(); \
} while(0)
#if !defined(__SANITIZE_THREAD__) && \
(defined(__i386__) || defined(__x86_64__) || defined(__s390x__))
/* This is more efficient than a store plus a fence. */
# define qatomic_mb_set(ptr, i) ((void)qatomic_xchg(ptr, i))
#else
# define qatomic_mb_set(ptr, i) \
({ qatomic_store_release(ptr, i); smp_mb(); })
#endif

#define qatomic_fetch_inc_nonzero(ptr) ({ \
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