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Changed memory_order constant values to simplify checks for success/failure orders in compare_exchange methods. Fixed incorrect cas_failure_order_must_not_be_stronger_than_success_order check.

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This commit is contained in:
Andrey Semashev
2014-06-01 02:10:44 +04:00
parent a721aa468f
commit abdce8f1bb
3 changed files with 13 additions and 8 deletions
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5
include/boost/atomic/detail/atomic_template.hpp
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@@ -51,8 +51,9 @@ BOOST_FORCEINLINE BOOST_CONSTEXPR memory_order deduce_failure_order(memory_order
BOOST_FORCEINLINE BOOST_CONSTEXPR bool cas_failure_order_must_not_be_stronger_than_success_order(memory_order success_order, memory_order failure_order) BOOST_NOEXCEPT
{
return ((failure_order | success_order) & ~memory_order_consume) == (success_order & ~memory_order_consume)
&& (failure_order & memory_order_consume) <= (success_order & memory_order_consume);
// 15 == (memory_order_seq_cst | memory_order_consume), see memory_order.hpp
// Given the enum values we can test the strength of memory order requirements with this single condition.
return (failure_order & 15u) <= (success_order & 15u);
}
template< typename T, bool IsInt = boost::is_integral< T >::value >

2
include/boost/atomic/detail/ops_msvc_arm.hpp
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@@ -81,7 +81,7 @@ struct msvc_arm_operations_base
static BOOST_FORCEINLINE BOOST_CONSTEXPR memory_order cas_common_order(memory_order success_order, memory_order failure_order) BOOST_NOEXCEPT
{
// Combine order flags together and transform memory_order_consume to memory_order_acquire
return static_cast< memory_order >(((failure_order | success_order) & ~memory_order_consume) | (((failure_order | success_order) & memory_order_consume) >> 3u));
return static_cast< memory_order >(((failure_order | success_order) & ~memory_order_consume) | (((failure_order | success_order) & memory_order_consume) << 1u));
}
};

14
include/boost/memory_order.hpp
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@@ -37,15 +37,19 @@ namespace boost
//
// if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... }
//
// The values are also in the order of increasing "strength"
// of the fences so that success/failure orders can be checked
// efficiently in compare_exchange methods.
//
enum memory_order
{
memory_order_relaxed = 0,
memory_order_acquire = 1,
memory_order_release = 2,
memory_order_acq_rel = 3, // acquire | release
memory_order_seq_cst = 7, // acq_rel | 4
memory_order_consume = 8
memory_order_consume = 1,
memory_order_acquire = 2,
memory_order_release = 4,
memory_order_acq_rel = 6, // acquire | release
memory_order_seq_cst = 14 // acq_rel | 8
};
} // namespace boost