@@ -42,20 +42,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
constexpr _Tp
- __rotl(_Tp __x, unsigned int __s) noexcept
+ __rotl(_Tp __x, int __s) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- const unsigned __sN = __s % _Nd;
- return (__x << __sN) | (__x >> ((_Nd - __sN) % _Nd));
+ const int __r = __s % _Nd;
+ if (__r == 0)
+ return __x;
+ else if (__r > 0)
+ return (__x << __r) | (__x >> ((_Nd - __r) % _Nd));
+ else
+ return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r)
}
template<typename _Tp>
constexpr _Tp
- __rotr(_Tp __x, unsigned int __s) noexcept
+ __rotr(_Tp __x, int __s) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- const unsigned __sN = __s % _Nd;
- return (__x >> __sN) | (__x << ((_Nd - __sN) % _Nd));
+ const int __r = __s % _Nd;
+ if (__r == 0)
+ return __x;
+ else if (__r > 0)
+ return (__x >> __r) | (__x << ((_Nd - __r) % _Nd));
+ else
+ return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r)
}
template<typename _Tp>
@@ -244,20 +254,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using _If_is_unsigned_integer
= enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
-#if ! __STRICT_ANSI__
- // [bitops.rot], rotating
+ // [bit.rot], rotating
template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp>
- rotl(_Tp __x, unsigned int __s) noexcept
+ [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
+ rotl(_Tp __x, int __s) noexcept
{ return std::__rotl(__x, __s); }
template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp>
- rotr(_Tp __x, unsigned int __s) noexcept
+ [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
+ rotr(_Tp __x, int __s) noexcept
{ return std::__rotr(__x, __s); }
- // [bitops.count], counting
+ // [bit.count], counting
template<typename _Tp>
constexpr _If_is_unsigned_integer<_Tp, int>
@@ -283,9 +292,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr _If_is_unsigned_integer<_Tp, int>
popcount(_Tp __x) noexcept
{ return std::__popcount(__x); }
-#endif
- // Integral power-of-two operations
+ // [bit.pow.two], integral powers of 2
template<typename _Tp>
constexpr _If_is_unsigned_integer<_Tp, bool>
similarity index 89%
rename from libstdc++-v3/testsuite/26_numerics/bit/bitops.rot/rotl.cc
rename to libstdc++-v3/testsuite/26_numerics/bit/bit.rotate/rotl.cc
@@ -20,12 +20,27 @@
#include <bit>
+template<typename UInt>
+constexpr bool
+test_negative_shifts()
+{
+ constexpr unsigned digits = std::numeric_limits<UInt>::digits;
+
+ UInt xarr[] = { (UInt)-1, 0, 1, 3, 6, 7, 0x10, 0x11, 0x22, 0x44, 0x80 };
+ int sarr[] = { 1, 4, 5, digits - 1, digits };
+ for (UInt x : xarr)
+ for (int s : sarr)
+ if (std::rotl(x, -s) != std::rotr(x, s))
+ return false;
+ return true;
+}
+
template<typename UInt>
constexpr auto
test(UInt x)
--> decltype(std::rotl(x, 0u))
+-> decltype(std::rotl(x, 0))
{
- static_assert( noexcept(std::rotl(x, 0u)) );
+ static_assert( noexcept(std::rotl(x, 0)) );
constexpr unsigned digits = std::numeric_limits<UInt>::digits;
@@ -63,6 +78,8 @@ test(UInt x)
static_assert( std::rotl((UInt)0b1010'0101, 4) == 0b1010'0101'0000 );
}
+ static_assert( test_negative_shifts<UInt>() );
+
return true;
}
similarity index 89%
rename from libstdc++-v3/testsuite/26_numerics/bit/bitops.rot/rotr.cc
rename to libstdc++-v3/testsuite/26_numerics/bit/bit.rotate/rotr.cc
This proposal has now been accepted for C++20, with a few changes. This patch adjusts std::rotl and std::rotr to match the final specification and declares the additions for C++2a mode even when __STRICT_ANSI__ is defined. * include/std/bit (__rotl, __rotr): Change second parameter from unsigned int to int and handle negative values. (rotl, rotr): Remove check for __STRICT_ANSI__. Change second parameter from unsigned int to int. Add nodiscard attribute. * testsuite/26_numerics/bit/bitops.rot/rotl.cc: Rename to ... * testsuite/26_numerics/bit/bit.rotate/rotl.cc: Here. Test negative shifts. * testsuite/26_numerics/bit/bitops.rot/rotr.cc: Rename to ... * testsuite/26_numerics/bit/bit.rotate/rotr.cc: Here. Test negative shifts. Tested x86_64-linux, committed to trunk. I'll backport this to gcc-9-branch too. commit b58d3908b4fcf83343f93bba8c4f5e49e982b894 Author: redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4> Date: Mon Jul 22 16:53:36 2019 +0000 Adjust std::rotl, std::rotr etc to match final P0553R4 proposal This proposal has now been accepted for C++20, with a few changes. This patch adjusts std::rotl and std::rotr to match the final specification and declares the additions for C++2a mode even when __STRICT_ANSI__ is defined. * include/std/bit (__rotl, __rotr): Change second parameter from unsigned int to int and handle negative values. (rotl, rotr): Remove check for __STRICT_ANSI__. Change second parameter from unsigned int to int. Add nodiscard attribute. * testsuite/26_numerics/bit/bitops.rot/rotl.cc: Rename to ... * testsuite/26_numerics/bit/bit.rotate/rotl.cc: Here. Test negative shifts. * testsuite/26_numerics/bit/bitops.rot/rotr.cc: Rename to ... * testsuite/26_numerics/bit/bit.rotate/rotr.cc: Here. Test negative shifts. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@273706 138bc75d-0d04-0410-961f-82ee72b054a4 +++ b/libstdc++-v3/testsuite/26_numerics/bit/bit.rotate/rotr.cc @@ -20,12 +20,27 @@ #include <bit> +template<typename UInt> +constexpr bool +test_negative_shifts() +{ + constexpr unsigned digits = std::numeric_limits<UInt>::digits; + + UInt xarr[] = { (UInt)-1, 0, 1, 3, 6, 7, 0x10, 0x11, 0x22, 0x44, 0x80 }; + int sarr[] = { 1, 4, 5, digits - 1, digits }; + for (UInt x : xarr) + for (int s : sarr) + if (std::rotr(x, -s) != std::rotl(x, s)) + return false; + return true; +} + template<typename UInt> constexpr auto test(UInt x) --> decltype(std::rotr(x, 0u)) +-> decltype(std::rotr(x, 0)) { - static_assert( noexcept(std::rotr(x, 0u)) ); + static_assert( noexcept(std::rotr(x, 0)) ); constexpr unsigned digits = std::numeric_limits<UInt>::digits; @@ -65,6 +80,8 @@ test(UInt x) == (0b1010 | ((UInt)0b0101 << digits - 4)) ); } + static_assert( test_negative_shifts<UInt>() ); + return true; }