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Make lcm/gcd work better in edge cases. Fixes a UBSAN failure. 

llvm-svn: 294779
This commit is contained in:
Marshall Clow 2017-02-10 20:49:08 +00:00
parent 278890f85b
commit 58fc1b50d8
6 changed files with 52 additions and 28 deletions
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27
libcxx/include/experimental/numeric
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@ -45,18 +45,23 @@ inline namespace fundamentals_v2 {
_LIBCPP_BEGIN_NAMESPACE_LFTS_V2 _LIBCPP_BEGIN_NAMESPACE_LFTS_V2
template <typename _Tp, bool _IsSigned = is_signed<_Tp>::value> struct __abs; template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> struct __abs;
template <typename _Tp> template <typename _Result, typename _Source>
struct __abs<_Tp, true> { struct __abs<_Result, _Source, true> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t >= 0 ? __t : -__t; } _Result operator()(_Source __t) const noexcept
{
if (__t >= 0) return __t;
if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t);
return -__t;
}
}; };
template <typename _Tp> template <typename _Result, typename _Source>
struct __abs<_Tp, false> { struct __abs<_Result, _Source, false> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t; } _Result operator()(_Source __t) const noexcept { return __t; }
}; };
@ -79,8 +84,8 @@ gcd(_Tp __m, _Up __n)
static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" ); static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" );
using _Rp = common_type_t<_Tp,_Up>; using _Rp = common_type_t<_Tp,_Up>;
using _Wp = make_unsigned_t<_Rp>; using _Wp = make_unsigned_t<_Rp>;
return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Tp>()(__m)), return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Rp, _Tp>()(__m)),
static_cast<_Wp>(__abs<_Up>()(__n)))); static_cast<_Wp>(__abs<_Rp, _Up>()(__n))));
} }
template<class _Tp, class _Up> template<class _Tp, class _Up>
@ -95,8 +100,8 @@ lcm(_Tp __m, _Up __n)
return 0; return 0;
using _Rp = common_type_t<_Tp,_Up>; using _Rp = common_type_t<_Tp,_Up>;
_Rp __val1 = __abs<_Tp>()(__m) / gcd(__m,__n); _Rp __val1 = __abs<_Rp, _Tp>()(__m) / gcd(__m, __n);
_Up __val2 = __abs<_Up>()(__n); _Rp __val2 = __abs<_Rp, _Up>()(__n);
_LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm"); _LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
return __val1 * __val2; return __val1 * __val2;
} }

29
libcxx/include/numeric
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@ -201,18 +201,23 @@ iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value_)
#if _LIBCPP_STD_VER > 14 #if _LIBCPP_STD_VER > 14
template <typename _Tp, bool _IsSigned = is_signed<_Tp>::value> struct __abs; template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> struct __abs;
template <typename _Tp> template <typename _Result, typename _Source>
struct __abs<_Tp, true> { struct __abs<_Result, _Source, true> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t >= 0 ? __t : -__t; } _Result operator()(_Source __t) const noexcept
{
if (__t >= 0) return __t;
if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t);
return -__t;
}
}; };
template <typename _Tp> template <typename _Result, typename _Source>
struct __abs<_Tp, false> { struct __abs<_Result, _Source, false> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t; } _Result operator()(_Source __t) const noexcept { return __t; }
}; };
@ -220,7 +225,7 @@ template<class _Tp>
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp __gcd(_Tp __m, _Tp __n) _Tp __gcd(_Tp __m, _Tp __n)
{ {
static_assert((!is_signed<_Tp>::value), "" ); static_assert((!is_signed<_Tp>::value), "");
return __n == 0 ? __m : __gcd<_Tp>(__n, __m % __n); return __n == 0 ? __m : __gcd<_Tp>(__n, __m % __n);
} }
@ -235,8 +240,8 @@ gcd(_Tp __m, _Up __n)
static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" ); static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" );
using _Rp = common_type_t<_Tp,_Up>; using _Rp = common_type_t<_Tp,_Up>;
using _Wp = make_unsigned_t<_Rp>; using _Wp = make_unsigned_t<_Rp>;
return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Tp>()(__m)), return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Rp, _Tp>()(__m)),
static_cast<_Wp>(__abs<_Up>()(__n)))); static_cast<_Wp>(__abs<_Rp, _Up>()(__n))));
} }
template<class _Tp, class _Up> template<class _Tp, class _Up>
@ -251,8 +256,8 @@ lcm(_Tp __m, _Up __n)
return 0; return 0;
using _Rp = common_type_t<_Tp,_Up>; using _Rp = common_type_t<_Tp,_Up>;
_Rp __val1 = __abs<_Tp>()(__m) / gcd(__m,__n); _Rp __val1 = __abs<_Rp, _Tp>()(__m) / gcd(__m, __n);
_Up __val2 = __abs<_Up>()(__n); _Rp __val2 = __abs<_Rp, _Up>()(__n);
_LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm"); _LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
return __val1 * __val2; return __val1 * __val2;
} }

7
libcxx/test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
View File

@ -129,4 +129,11 @@ int main()
assert((do_test<long, int>(non_cce))); assert((do_test<long, int>(non_cce)));
assert((do_test<int, long long>(non_cce))); assert((do_test<int, long long>(non_cce)));
assert((do_test<long long, int>(non_cce))); assert((do_test<long long, int>(non_cce)));
// LWG#2792
{
auto res = std::gcd((int64_t)1234, (int32_t)-2147483648);
static_assert( std::is_same<decltype(res), std::common_type<int64_t, int32_t>::type>::value, "");
assert(res == 2);
}
} }

8
libcxx/test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.pass.cpp
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@ -128,4 +128,12 @@ int main()
assert((do_test<long, int>(non_cce))); assert((do_test<long, int>(non_cce)));
assert((do_test<int, long long>(non_cce))); assert((do_test<int, long long>(non_cce)));
assert((do_test<long long, int>(non_cce))); assert((do_test<long long, int>(non_cce)));
// LWG#2792
{
auto res1 = std::lcm((int64_t)1234, (int32_t)-2147483648);
(void) std::lcm<int, unsigned long>(INT_MIN, 2); // this used to trigger UBSAN
static_assert( std::is_same<decltype(res1), std::common_type<int64_t, int32_t>::type>::value, "");
assert(res1 == 1324997410816LL);
}
} }

1
libcxx/test/std/numerics/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
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@ -8,7 +8,6 @@
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
// //
// UNSUPPORTED: c++98, c++03, c++11, c++14 // UNSUPPORTED: c++98, c++03, c++11, c++14
// XFAIL: ubsan
// <numeric> // <numeric>

8
libcxx/test/std/numerics/numeric.ops/numeric.ops.lcm/lcm.pass.cpp
View File

@ -8,7 +8,6 @@
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
// //
// UNSUPPORTED: c++98, c++03, c++11, c++14 // UNSUPPORTED: c++98, c++03, c++11, c++14
// XFAIL: ubsan
// <numeric> // <numeric>
// template<class _M, class _N> // template<class _M, class _N>
@ -132,8 +131,9 @@ int main()
// LWG#2837 // LWG#2837
{ {
auto res = std::lcm((int64_t)1234, (int32_t)-2147483648); auto res1 = std::lcm((int64_t)1234, (int32_t)-2147483648);
static_assert( std::is_same<decltype(res), std::common_type<int64_t, int32_t>::type>::value, ""); (void) std::lcm<int, unsigned long>(INT_MIN, 2); // this used to trigger UBSAN
assert(res == -1324997410816LL); static_assert( std::is_same<decltype(res1), std::common_type<int64_t, int32_t>::type>::value, "");
assert(res1 == 1324997410816LL);
} }
} }