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Use may_alias attribute to silence gcc warnings about breaking strict aliasing.

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We need to mark the uint32_t and uint64_t that are used to load parts of the
double-width values into registers.
This commit is contained in:
Andrey Semashev
2018-02-03 23:20:39 +03:00
parent 9768684841
commit ceadfbcea2
1 changed files with 16 additions and 14 deletions
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30
include/boost/atomic/detail/ops_gcc_x86_dcas.hpp
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@@ -48,6 +48,7 @@ struct gcc_dcas_x86
{
typedef typename make_storage_type< 8u, Signed >::type storage_type;
typedef typename make_storage_type< 8u, Signed >::aligned aligned_storage_type;
typedef uint32_t BOOST_ATOMIC_DETAIL_MAY_ALIAS aliasing_uint32_t;
static BOOST_CONSTEXPR_OR_CONST bool is_always_lock_free = true;
@@ -111,7 +112,7 @@ struct gcc_dcas_x86
".align 16\n\t"
"1: lock; cmpxchg8b %[dest_lo]\n\t"
"jne 1b\n\t"
: [dest_lo] "=m" (storage), [dest_hi] "=m" (reinterpret_cast< volatile uint32_t* >(&storage)[1])
: [dest_lo] "=m" (storage), [dest_hi] "=m" (reinterpret_cast< volatile aliasing_uint32_t* >(&storage)[1])
: [value_lo] "b" ((uint32_t)v), "c" ((uint32_t)(v >> 32))
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "eax", "edx", "memory"
);
@@ -325,7 +326,7 @@ struct gcc_dcas_x86
".align 16\n\t"
"1: lock; cmpxchg8b %[dest_lo]\n\t"
"jne 1b\n\t"
: "=&a" (old_bits[0]), "=&d" (old_bits[1]), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile uint32_t* >(&storage)[1])
: "=&a" (old_bits[0]), "=&d" (old_bits[1]), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile aliasing_uint32_t* >(&storage)[1])
: "b" ((uint32_t)v), "c" ((uint32_t)(v >> 32))
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
@@ -344,7 +345,7 @@ struct gcc_dcas_x86
".align 16\n\t"
"1: lock; cmpxchg8b %[dest_lo]\n\t"
"jne 1b\n\t"
: "=&A" (old_value), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile uint32_t* >(&storage)[1])
: "=&A" (old_value), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile aliasing_uint32_t* >(&storage)[1])
: "b" ((uint32_t)v), "c" ((uint32_t)(v >> 32))
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
@@ -364,6 +365,7 @@ struct gcc_dcas_x86_64
{
typedef typename make_storage_type< 16u, Signed >::type storage_type;
typedef typename make_storage_type< 16u, Signed >::aligned aligned_storage_type;
typedef uint64_t BOOST_ATOMIC_DETAIL_MAY_ALIAS aliasing_uint64_t;
static BOOST_CONSTEXPR_OR_CONST bool is_always_lock_free = true;
@@ -376,8 +378,8 @@ struct gcc_dcas_x86_64
".align 16\n\t"
"1: lock; cmpxchg16b %[dest_lo]\n\t"
"jne 1b\n\t"
: [dest_lo] "=m" (storage), [dest_hi] "=m" (reinterpret_cast< volatile uint64_t* >(&storage)[1])
: "b" (reinterpret_cast< const uint64_t* >(&v)[0]), "c" (reinterpret_cast< const uint64_t* >(&v)[1])
: [dest_lo] "=m" (storage), [dest_hi] "=m" (reinterpret_cast< volatile aliasing_uint64_t* >(&storage)[1])
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&v)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&v)[1])
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "rax", "rdx", "memory"
);
}
@@ -450,8 +452,8 @@ struct gcc_dcas_x86_64
(
"lock; cmpxchg16b %[dest]\n\t"
"sete %[success]\n\t"
: [dest] "+m" (storage), "+a" (reinterpret_cast< uint64_t* >(&expected)[0]), "+d" (reinterpret_cast< uint64_t* >(&expected)[1]), [success] "=q" (success)
: "b" (reinterpret_cast< const uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const uint64_t* >(&desired)[1])
: [dest] "+m" (storage), "+a" (reinterpret_cast< aliasing_uint64_t* >(&expected)[0]), "+d" (reinterpret_cast< aliasing_uint64_t* >(&expected)[1]), [success] "=q" (success)
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[1])
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
@@ -466,7 +468,7 @@ struct gcc_dcas_x86_64
(
"lock; cmpxchg16b %[dest]\n\t"
: "+A" (expected), [dest] "+m" (storage), "=@ccz" (success)
: "b" (reinterpret_cast< const uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const uint64_t* >(&desired)[1])
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[1])
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
#else // defined(BOOST_ATOMIC_DETAIL_ASM_HAS_FLAG_OUTPUTS)
@@ -476,10 +478,10 @@ struct gcc_dcas_x86_64
"sete %[success]\n\t"
#if !defined(BOOST_ATOMIC_DETAIL_NO_ASM_CONSTRAINT_ALTERNATIVES)
: "+A,A" (expected), [dest] "+m,m" (storage), [success] "=q,m" (success)
: "b,b" (reinterpret_cast< const uint64_t* >(&desired)[0]), "c,c" (reinterpret_cast< const uint64_t* >(&desired)[1])
: "b,b" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[0]), "c,c" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[1])
#else
: "+A" (expected), [dest] "+m" (storage), [success] "=q" (success)
: "b" (reinterpret_cast< const uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const uint64_t* >(&desired)[1])
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&desired)[1])
#endif
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
@@ -507,8 +509,8 @@ struct gcc_dcas_x86_64
".align 16\n\t"
"1: lock; cmpxchg16b %[dest_lo]\n\t"
"jne 1b\n\t"
: [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile uint64_t* >(&storage)[1]), "=&a" (old_bits[0]), "=&d" (old_bits[1])
: "b" (reinterpret_cast< const uint64_t* >(&v)[0]), "c" (reinterpret_cast< const uint64_t* >(&v)[1])
: [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile aliasing_uint64_t* >(&storage)[1]), "=&a" (old_bits[0]), "=&d" (old_bits[1])
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&v)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&v)[1])
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);
@@ -524,8 +526,8 @@ struct gcc_dcas_x86_64
".align 16\n\t"
"1: lock; cmpxchg16b %[dest_lo]\n\t"
"jne 1b\n\t"
: "=&A" (old_value), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile uint64_t* >(&storage)[1])
: "b" (reinterpret_cast< const uint64_t* >(&v)[0]), "c" (reinterpret_cast< const uint64_t* >(&v)[1])
: "=&A" (old_value), [dest_lo] "+m" (storage), [dest_hi] "+m" (reinterpret_cast< volatile aliasing_uint64_t* >(&storage)[1])
: "b" (reinterpret_cast< const aliasing_uint64_t* >(&v)[0]), "c" (reinterpret_cast< const aliasing_uint64_t* >(&v)[1])
: BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
);