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cmath: Skip Libc for integral types in isinf, etc.

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For std::isinf, the standard requires effectively calling isinf as
double from Libc for integral types. But integral types are never
infinite; we don't need to call Libc to return false.

Also short-circuit other functions where Libc won't have interesting
answers: signbit, fpclassify, isfinite, isnan, and isnormal.

I added correctness tests for integral types since we're no longer
deferring to Libc.

In review it was pointed out that in future revisions of the C++
standard we may add more types to std::is_arithmetic (e.g.,
std::is_fixed_point).  I'll leave it to a future commit to hack this to
allow using math functions on those.  We'll need to change things like
__libcpp_fpclassify anyway, so I'm not sure anything here would really
be future-proof.

https://reviews.llvm.org/D31561
rdar://problem/31361223

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@301060 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2017-04-21 23:14:55 +00:00
parent fba865a217
commit 5df171df50
2 changed files with 114 additions and 8 deletions
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89
include/math.h
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@@ -307,6 +307,7 @@ long double truncl(long double x);
extern "C++" {
#include <type_traits>
#include <limits>
// signbit
@@ -324,22 +325,50 @@ __libcpp_signbit(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
signbit(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_signbit((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_integral<_A1>::value && std::is_signed<_A1>::value, bool>::type
signbit(_A1 __lcpp_x) _NOEXCEPT
{ return __lcpp_x < 0; }
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_integral<_A1>::value && !std::is_signed<_A1>::value, bool>::type
signbit(_A1) _NOEXCEPT
{ return false; }
#elif defined(_LIBCPP_MSVCRT)
template <typename _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
signbit(_A1 __lcpp_x) _NOEXCEPT
{
return ::signbit(static_cast<typename std::__promote<_A1>::type>(__lcpp_x));
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_integral<_A1>::value && std::is_signed<_A1>::value, bool>::type
signbit(_A1 __lcpp_x) _NOEXCEPT
{ return __lcpp_x < 0; }
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_integral<_A1>::value && !std::is_signed<_A1>::value, bool>::type
signbit(_A1) _NOEXCEPT
{ return false; }
#endif // signbit
// fpclassify
@@ -358,22 +387,34 @@ __libcpp_fpclassify(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, int>::type
typename std::enable_if<std::is_floating_point<_A1>::value, int>::type
fpclassify(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_fpclassify((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_integral<_A1>::value, int>::type
fpclassify(_A1 __lcpp_x) _NOEXCEPT
{ return __lcpp_x == 0 ? FP_ZERO : FP_NORMAL; }
#elif defined(_LIBCPP_MSVCRT)
template <typename _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, int>::type
typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
fpclassify(_A1 __lcpp_x) _NOEXCEPT
{
return ::fpclassify(static_cast<typename std::__promote<_A1>::type>(__lcpp_x));
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_integral<_A1>::value, int>::type
fpclassify(_A1 __lcpp_x) _NOEXCEPT
{ return __lcpp_x == 0 ? FP_ZERO : FP_NORMAL; }
#endif // fpclassify
// isfinite
@@ -392,12 +433,22 @@ __libcpp_isfinite(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<
std::is_arithmetic<_A1>::value && std::numeric_limits<_A1>::has_infinity,
bool>::type
isfinite(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_isfinite((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_arithmetic<_A1>::value && !std::numeric_limits<_A1>::has_infinity,
bool>::type
isfinite(_A1) _NOEXCEPT
{ return true; }
#endif // isfinite
// isinf
@@ -416,12 +467,22 @@ __libcpp_isinf(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<
std::is_arithmetic<_A1>::value && std::numeric_limits<_A1>::has_infinity,
bool>::type
isinf(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_isinf((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<
std::is_arithmetic<_A1>::value && !std::numeric_limits<_A1>::has_infinity,
bool>::type
isinf(_A1) _NOEXCEPT
{ return false; }
#endif // isinf
// isnan
@@ -440,12 +501,18 @@ __libcpp_isnan(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
isnan(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_isnan((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_integral<_A1>::value, bool>::type
isnan(_A1) _NOEXCEPT
{ return false; }
#endif // isnan
// isnormal
@@ -464,12 +531,18 @@ __libcpp_isnormal(_A1 __lcpp_x) _NOEXCEPT
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
isnormal(_A1 __lcpp_x) _NOEXCEPT
{
return __libcpp_isnormal((typename std::__promote<_A1>::type)__lcpp_x);
}
template <class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename std::enable_if<std::is_integral<_A1>::value, bool>::type
isnormal(_A1 __lcpp_x) _NOEXCEPT
{ return __lcpp_x != 0; }
#endif // isnormal
// isgreater