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Minor refactoring in <bit> header 

* include/std/bit (__countl_zero, __countr_zero, __popcount): Use
	local variables for number of digits instead of type aliases.
	(__log2p1): Remove redundant branch also checked in __countl_zero.

From-SVN: r262947
This commit is contained in:
Jonathan Wakely 2018-07-24 14:51:50 +01:00 committed by Jonathan Wakely
parent 6ec96dcb6b
commit 337dc30754
2 changed files with 48 additions and 45 deletions
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4
libstdc++-v3/ChangeLog
View File

@ -1,5 +1,9 @@
2018-07-24 Jonathan Wakely <jwakely@redhat.com>
* include/std/bit (__countl_zero, __countr_zero, __popcount): Use
local variables for number of digits instead of type aliases.
(__log2p1): Remove redundant branch also checked in __countl_zero.
* include/bits/uses_allocator.h (__is_erased_or_convertible): Reorder
conditions. Add comments.
* testsuite/20_util/uses_allocator/69293_neg.cc: Adjust dg-error line.

89
libstdc++-v3/include/std/bit
View File

@ -62,45 +62,44 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr int
__countl_zero(_Tp __x) noexcept
{
using __limits = numeric_limits<_Tp>;
constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
return __limits::digits;
return _Nd;
using __limits_ull = numeric_limits<unsigned long long>;
using __limits_ul = numeric_limits<unsigned long>;
using __limits_u = numeric_limits<unsigned>;
constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_u::digits)
if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
{
constexpr int __diff = __limits_u::digits - __limits::digits;
constexpr int __diff = _Nd_u - _Nd;
return __builtin_clz(__x) - __diff;
}
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
{
constexpr int __diff = __limits_ul::digits - __limits::digits;
constexpr int __diff = _Nd_ul - _Nd;
return __builtin_clzl(__x) - __diff;
}
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
{
constexpr int __diff = __limits_ull::digits - __limits::digits;
constexpr int __diff = _Nd_ull - _Nd;
return __builtin_clzll(__x) - __diff;
}
else // (__limits::digits > __limits_ull::digits)
else // (_Nd > _Nd_ull)
{
static_assert(__limits::digits <= (2 * __limits_ull::digits),
static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
unsigned long long __high = __x >> __limits_ull::digits;
unsigned long long __high = __x >> _Nd_ull;
if (__high != 0)
{
constexpr int __diff
= (2 * __limits_ull::digits) - __limits::digits;
constexpr int __diff = (2 * _Nd_ull) - _Nd;
return __builtin_clzll(__high) - __diff;
}
unsigned long long __low = __x & __limits_ull::max();
return (__limits::digits - __limits_ull::digits)
+ __builtin_clzll(__low);
constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
unsigned long long __low = __x & __max_ull;
return (_Nd - _Nd_ull) + __builtin_clzll(__low);
}
}
@ -117,31 +116,32 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr int
__countr_zero(_Tp __x) noexcept
{
using __limits = numeric_limits<_Tp>;
constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
return __limits::digits;
return _Nd;
using __limits_ull = numeric_limits<unsigned long long>;
using __limits_ul = numeric_limits<unsigned long>;
using __limits_u = numeric_limits<unsigned>;
constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_u::digits)
if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
return __builtin_ctz(__x);
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
return __builtin_ctzl(__x);
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
return __builtin_ctzll(__x);
else // (__limits::digits > __limits_ull::digits)
else // (_Nd > _Nd_ull)
{
static_assert(__limits::digits <= (2 * __limits_ull::digits),
static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
unsigned long long __low = __x & __limits_ull::max();
constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
unsigned long long __low = __x & __max_ull;
if (__low != 0)
return __builtin_ctzll(__low);
unsigned long long __high = __x >> __limits_ull::digits;
return __builtin_ctzll(__high) + __limits_ull::digits;
unsigned long long __high = __x >> _Nd_ull;
return __builtin_ctzll(__high) + _Nd_ull;
}
}
@ -158,28 +158,29 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr int
__popcount(_Tp __x) noexcept
{
using __limits = numeric_limits<_Tp>;
constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
return 0;
using __limits_ull = numeric_limits<unsigned long long>;
using __limits_ul = numeric_limits<unsigned long>;
using __limits_u = numeric_limits<unsigned>;
constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_u::digits)
if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
return __builtin_popcount(__x);
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
return __builtin_popcountl(__x);
else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
return __builtin_popcountll(__x);
else // (__limits::digits > __limits_ull::digits)
else // (_Nd > _Nd_ull)
{
static_assert(__limits::digits <= (2 * __limits_ull::digits),
static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
unsigned long long __low = __x & __limits_ull::max();
unsigned long long __high = __x >> __limits_ull::digits;
constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
unsigned long long __low = __x & __max_ull;
unsigned long long __high = __x >> _Nd_ull;
return __builtin_popcountll(__low) + __builtin_popcountll(__high);
}
}
@ -214,8 +215,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__log2p1(_Tp __x) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
return 0;
return _Nd - std::__countl_zero(__x);
}