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libstdc++: Avoid vector casts while still avoiding PR90424

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Signed-off-by: Matthias Kretz <m.kretz@gsi.de>

libstdc++-v3/ChangeLog:

	PR libstdc++/109822
	* include/experimental/bits/simd_builtin.h (_S_store): Rewrite
	to avoid casts to other vector types. Implement store as
	succession of power-of-2 sized memcpy to avoid PR90424.
This commit is contained in:
Matthias Kretz 2023-06-02 21:33:04 +02:00
parent 27e45b7597
commit 9165ede56a
1 changed files with 15 additions and 25 deletions
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40
libstdc++-v3/include/experimental/bits/simd_builtin.h
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@ -1295,6 +1295,18 @@ struct _CommonImplBuiltin
// }}}
// _S_store {{{
template <size_t _Bytes>
_GLIBCXX_SIMD_INTRINSIC static void
_S_memcpy(char* __dst, const char* __src)
{
if constexpr (_Bytes > 0)
{
constexpr size_t _Ns = std::__bit_floor(_Bytes);
__builtin_memcpy(__dst, __src, _Ns);
_S_memcpy<_Bytes - _Ns>(__dst + _Ns, __src + _Ns);
}
}
template <size_t _ReqBytes = 0, typename _TV>
_GLIBCXX_SIMD_INTRINSIC static void
_S_store(_TV __x, void* __addr)
@ -1302,33 +1314,11 @@ struct _CommonImplBuiltin
constexpr size_t _Bytes = _ReqBytes == 0 ? sizeof(__x) : _ReqBytes;
static_assert(sizeof(__x) >= _Bytes);
#if !defined __clang__ && _GLIBCXX_SIMD_WORKAROUND_PR90424
if constexpr (__is_vector_type_v<_TV>)
{
using _Tp = typename _VectorTraits<_TV>::value_type;
constexpr size_t _Np = _Bytes / sizeof(_Tp);
static_assert(_Np * sizeof(_Tp) == _Bytes);
#ifdef _GLIBCXX_SIMD_WORKAROUND_PR90424
using _Up = conditional_t<
(is_integral_v<_Tp> || _Bytes < 4),
conditional_t<(sizeof(__x) > sizeof(long long)), long long, _Tp>,
float>;
const auto __v = __vector_bitcast<_Up>(__x);
#else // _GLIBCXX_SIMD_WORKAROUND_PR90424
const __vector_type_t<_Tp, _Np> __v = __x;
#endif // _GLIBCXX_SIMD_WORKAROUND_PR90424
if constexpr ((_Bytes & (_Bytes - 1)) != 0)
{
constexpr size_t _MoreBytes = std::__bit_ceil(_Bytes);
alignas(decltype(__v)) char __tmp[_MoreBytes];
__builtin_memcpy(__tmp, &__v, _MoreBytes);
__builtin_memcpy(__addr, __tmp, _Bytes);
}
else
__builtin_memcpy(__addr, &__v, _Bytes);
}
_S_memcpy<_Bytes>(reinterpret_cast<char*>(__addr), reinterpret_cast<const char*>(&__x));
else
#endif // _GLIBCXX_SIMD_WORKAROUND_PR90424
__builtin_memcpy(__addr, &__x, _Bytes);
}