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Implement qt_is_{inf,nan,finite} using std. library functions.

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The previous implementations did not check the full mantissa. The result
was that certain NaN values were seen as +/-Infinity.

A nice benefit is that the generated code for this implementation is also
faster.

Task-number: QTBUG-47692
Change-Id: I1507ec579ccd9a2ab97da8cf83dabbc5d6e28597
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
This commit is contained in:
Erik Verbruggen 2015-08-10 13:15:24 +02:00
parent 0659bb810b
commit a2b58c1643
2 changed files with 71 additions and 40 deletions
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99
src/corelib/global/qnumeric_p.h
View File

@ -47,7 +47,7 @@
//
#include "QtCore/qglobal.h"
#include <cmath>
#include <limits>
#if defined(Q_OS_WIN) && !defined(Q_OS_WINCE)
@ -56,7 +56,56 @@
# include <immintrin.h> // for _addcarry_u<nn>
#endif
#if defined(Q_CC_MSVC)
#include <float.h>
#endif
#if !defined(Q_CC_MSVC) && (defined(Q_OS_QNX) || !defined(__cplusplus) || __cplusplus < 201103L)
#include <math.h>
QT_BEGIN_NAMESPACE
namespace qnumeric_std_wrapper {
// the 'using namespace std' below is cases where the stdlib already put the math.h functions in the std namespace and undefined the macros.
static inline bool math_h_isnan(double d) { using namespace std; return isnan(d); }
static inline bool math_h_isinf(double d) { using namespace std; return isinf(d); }
static inline bool math_h_isfinite(double d) { using namespace std; return isfinite(d); }
static inline bool math_h_isnan(float f) { using namespace std; return isnan(f); }
static inline bool math_h_isinf(float f) { using namespace std; return isinf(f); }
static inline bool math_h_isfinite(float f) { using namespace std; return isfinite(f); }
}
QT_END_NAMESPACE
// These macros from math.h conflict with the real functions in the std namespace.
#undef signbit
#undef isnan
#undef isinf
#undef isfinite
#endif
QT_BEGIN_NAMESPACE
namespace qnumeric_std_wrapper {
#if defined(Q_CC_MSVC) && _MSC_VER < 1800
static inline bool isnan(double d) { return !!_isnan(d); }
static inline bool isinf(double d) { return !_finite(d) && !_isnan(d); }
static inline bool isfinite(double d) { return !!_finite(d); }
static inline bool isnan(float f) { return !!_isnanf(f); }
static inline bool isinf(float f) { return !_finitef(f) && !_isnan(f); }
static inline bool isfinite(float f) { return !!_finite(f); }
#elif !defined(Q_CC_MSVC) && (defined(Q_OS_QNX) || !defined(__cplusplus) || __cplusplus < 201103L)
static inline bool isnan(double d) { return math_h_isnan(d); }
static inline bool isinf(double d) { return math_h_isinf(d); }
static inline bool isfinite(double d) { return math_h_isfinite(d); }
static inline bool isnan(float f) { return math_h_isnan(f); }
static inline bool isinf(float f) { return math_h_isinf(f); }
static inline bool isfinite(float f) { return math_h_isfinite(f); }
#else
static inline bool isnan(double d) { return std::isnan(d); }
static inline bool isinf(double d) { return std::isinf(d); }
static inline bool isfinite(double d) { return std::isfinite(d); }
static inline bool isnan(float f) { return std::isnan(f); }
static inline bool isinf(float f) { return std::isinf(f); }
static inline bool isfinite(float f) { return std::isfinite(f); }
#endif
}
#if !defined(Q_CC_MIPS)
@ -139,62 +188,32 @@ static inline double qt_qnan()
static inline bool qt_is_inf(double d)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) == 0x7f && ch[1] == 0xf0;
} else {
return (ch[7] & 0x7f) == 0x7f && ch[6] == 0xf0;
}
return qnumeric_std_wrapper::isinf(d);
}
static inline bool qt_is_nan(double d)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) == 0x7f && ch[1] > 0xf0;
} else {
return (ch[7] & 0x7f) == 0x7f && ch[6] > 0xf0;
}
return qnumeric_std_wrapper::isnan(d);
}
static inline bool qt_is_finite(double d)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) != 0x7f || (ch[1] & 0xf0) != 0xf0;
} else {
return (ch[7] & 0x7f) != 0x7f || (ch[6] & 0xf0) != 0xf0;
}
return qnumeric_std_wrapper::isfinite(d);
}
static inline bool qt_is_inf(float d)
static inline bool qt_is_inf(float f)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) == 0x7f && ch[1] == 0x80;
} else {
return (ch[3] & 0x7f) == 0x7f && ch[2] == 0x80;
}
return qnumeric_std_wrapper::isinf(f);
}
static inline bool qt_is_nan(float d)
static inline bool qt_is_nan(float f)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) == 0x7f && ch[1] > 0x80;
} else {
return (ch[3] & 0x7f) == 0x7f && ch[2] > 0x80;
}
return qnumeric_std_wrapper::isnan(f);
}
static inline bool qt_is_finite(float d)
static inline bool qt_is_finite(float f)
{
uchar *ch = (uchar *)&d;
if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
return (ch[0] & 0x7f) != 0x7f || (ch[1] & 0x80) != 0x80;
} else {
return (ch[3] & 0x7f) != 0x7f || (ch[2] & 0x80) != 0x80;
}
return qnumeric_std_wrapper::isfinite(f);
}
//

12
tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp
View File

@ -105,6 +105,18 @@ void tst_QNumeric::qNan()
QVERIFY(qIsNaN(nan));
QVERIFY(qIsNaN(nan + 1));
QVERIFY(qIsNaN(-nan));
Q_STATIC_ASSERT(sizeof(double) == 8);
#ifdef Q_LITTLE_ENDIAN
const uchar bytes[] = { 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0, 0x7f };
#else
const uchar bytes[] = { 0x7f, 0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 };
#endif
memcpy(&nan, bytes, 8);
QVERIFY(!qIsFinite(nan));
QVERIFY(!qIsInf(nan));
QVERIFY(qIsNaN(nan));
double inf = qInf();
QVERIFY(inf > 0);
QVERIFY(-inf < 0);