Make use of __detail::_Select_uint_least_t<d>::type for
std::generate_canonical, so that we have a 128-bit integer type even on
32-bit targets.
libstdc++-v3/ChangeLog:
* include/bits/random.tcc (__generate_canonical_pow2): Elide
variable into poopcount call. Cast floating-point literal to
_RealT.
(__generate_canonical_any): Use direct-initialization for _UInt
variables. Cast floating-point literal to _RealT.
(generate_canonical): Remove unused typedef. Use
_Select_uint_least_t to select the unsigned integer type to use.
Co-authored-by: Jakub Jelinek <[email protected]>
---
Tested x86_64-linux
Also checked -m32 and -D_GLIBCXX_USE_OLD_GENERATE_CANONICAL
libstdc++-v3/include/bits/random.tcc | 51 +++++++---------------------
1 file changed, 12 insertions(+), 39 deletions(-)
diff --git a/libstdc++-v3/include/bits/random.tcc
b/libstdc++-v3/include/bits/random.tcc
index 68eae419b721..6d9ce7d6a623 100644
--- a/libstdc++-v3/include/bits/random.tcc
+++ b/libstdc++-v3/include/bits/random.tcc
@@ -3522,10 +3522,9 @@ namespace __detail
// r = 2; // Redundant, we only support radix 2.
using _Rng = decltype(_Urbg::max());
const _Rng __rng_range_less_1 = _Urbg::max() - _Urbg::min();
- const _UInt __uint_range_less_1 = ~_UInt(0);
// R = _UInt(__rng_range_less_1) + 1; // May wrap to 0.
const auto __log2_R = __builtin_popcountg(__rng_range_less_1);
- const auto __log2_uint_max = __builtin_popcountg(__uint_range_less_1);
+ const auto __log2_uint_max = __builtin_popcountg(~_UInt(0));
// rd = _UInt(1) << __d; // Could overflow, UB.
const unsigned __k = (__d + __log2_R - 1) / __log2_R;
const unsigned __log2_Rk_max = __k * __log2_R;
@@ -3533,7 +3532,7 @@ namespace __detail
__log2_uint_max < __log2_Rk_max ? __log2_uint_max : __log2_Rk_max;
static_assert(__log2_Rk >= __d);
// Rk = _UInt(1) << __log2_Rk; // Likely overflows, UB.
- constexpr _RealT __Rk = _RealT(_UInt(1) << (__log2_Rk - 1)) * 2.0;
+ constexpr _RealT __Rk = _RealT(_UInt(1) << (__log2_Rk - 1)) *
_RealT(2.0);
#if defined(_GLIBCXX_GENERATE_CANONICAL_STRICT)
const unsigned __log2_x = __log2_Rk - __d; // # of spare entropy bits.
#else
@@ -3586,25 +3585,25 @@ namespace __detail
_RealT
__generate_canonical_any(_Urbg& __urng)
{
- static_assert(__d < __builtin_popcountg(~_UInt(0)));
// Names below are chosen to match the description in the Standard.
// Parameter d is the actual target number of bits.
- const _UInt __r = 2;
+ const _UInt __r{2};
const _UInt __R = _UInt(_Urbg::max() - _Urbg::min()) + 1;
const _UInt __rd = _UInt(1) << __d;
const unsigned __k = __gen_can_rng_calls_needed(__R, __rd);
const _UInt __Rk = __gen_can_pow(__R, __k);
- const _UInt __x = __Rk/__rd;
+ const _UInt __x = __Rk / __rd;
while (true)
{
- _UInt __Ri = 1, __sum = __urng() - _Urbg::min();
+ _UInt __Ri{1};
+ _UInt __sum{__urng() - _Urbg::min()};
for (int __i = __k - 1; __i > 0; --__i)
{
__Ri *= __R;
- __sum += (__urng() - _Urbg::min()) * __Ri;
+ __sum += _UInt{__urng() - _Urbg::min()} * __Ri;
}
- const _RealT __ret = _RealT(__sum / __x) / __rd;
+ const _RealT __ret = _RealT(__sum / __x) / _RealT(__rd);
if (__ret < _RealT(1.0))
return __ret;
}
@@ -3660,7 +3659,6 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
"float16_t type is not supported, consider using bfloat16_t");
#endif
- using _Rng = decltype(_Urbg::max());
const unsigned __d_max = std::numeric_limits<_RealT>::digits;
const unsigned __d = __digits > __d_max ? __d_max : __digits;
@@ -3668,38 +3666,13 @@ _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
// is enough bits. If not, we need more.
if constexpr (__is_power_of_2_less_1(_Urbg::max() - _Urbg::min()))
{
- if constexpr (__d <= 32)
- return __generate_canonical_pow2<_RealT, uint32_t, __d>(__urng);
- else if constexpr (__d <= 64)
- return __generate_canonical_pow2<_RealT, uint64_t, __d>(__urng);
- else
- {
-#if defined(__SIZEOF_INT128__)
- // Accommodate double double or float128.
- return __extension__ __generate_canonical_pow2<
- _RealT, unsigned __int128, __d>(__urng);
-#else
- static_assert(false,
- "float precision >64 requires __int128 support");
-#endif
- }
+ using type = typename __detail::_Select_uint_least_t<__d>::type;
+ return __generate_canonical_pow2<_RealT, type, __d>(__urng);
}
else // Need up to 2x bits.
{
- if constexpr (__d <= 32)
- return __generate_canonical_any<_RealT, uint64_t, __d>(__urng);
- else
- {
-#if defined(__SIZEOF_INT128__)
- static_assert(__d <= 64,
- "irregular RNG with float precision >64 is not supported");
- return __extension__ __generate_canonical_any<
- _RealT, unsigned __int128, __d>(__urng);
-#else
- static_assert(false, "irregular RNG with float precision"
- " >32 requires __int128 support");
-#endif
- }
+ using type = typename __detail::_Select_uint_least_t<__d * 2>::type;
+ return __generate_canonical_any<_RealT, type, __d>(__urng);
}
}
_GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
--
2.52.0
