New qfloat16 class

This constitutes a fairly complete submission of an entirely new
floating point type which conforms to IEEE 754 as a 16-bit storage
class.  Conversion between qfloat16 and float is currently performed
through a sequence of lookup tables.  Global-level functions
qRound(), qRound64(), qFuzzyCompare(), qFuzzyIsNull(), and
qIsNull() each with a qfloat16 parameter have been included
for completeness.

[ChangeLog][QtCore] Added new qfloat16 class.

Change-Id: Ia52eb27846965c14f8140c00faf5ba33c9443976
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 225 insertions, 0 deletions

diff --git a/src/corelib/global/qfloat16.h b/src/corelib/global/qfloat16.h
new file mode 100644
index 0000000000..5059108fb8
--- /dev/null
+++ b/src/corelib/global/qfloat16.h
@@ -0,0 +1,225 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 by Southwest Research Institute (R)
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QFLOAT16_H
+#define QFLOAT16_H
+
+#include <QtCore/qglobal.h>
+#include <QtCore/qmetatype.h>
+#include <string.h>
+
+QT_BEGIN_NAMESPACE
+
+#if 0
+#pragma qt_class(QFloat16)
+#endif
+
+class qfloat16
+{
+public:
+#ifndef Q_QDOC
+    Q_DECL_CONSTEXPR inline qfloat16() Q_DECL_NOTHROW : b16(0) { }
+    inline qfloat16(float f) Q_DECL_NOTHROW;
+    inline operator float() const Q_DECL_NOTHROW;
+    inline operator double() const Q_DECL_NOTHROW;
+    inline operator long double() const Q_DECL_NOTHROW;
+#endif
+
+private:
+    quint16 b16;
+
+    Q_CORE_EXPORT static const quint32 mantissatable[];
+    Q_CORE_EXPORT static const quint32 exponenttable[];
+    Q_CORE_EXPORT static const quint32 offsettable[];
+    Q_CORE_EXPORT static const quint32 basetable[];
+    Q_CORE_EXPORT static const quint32 shifttable[];
+
+    friend bool qIsNull(qfloat16 f) Q_DECL_NOTHROW;
+    friend qfloat16 operator-(qfloat16 a) Q_DECL_NOTHROW;
+};
+
+Q_DECLARE_TYPEINFO(qfloat16, Q_PRIMITIVE_TYPE);
+
+Q_CORE_EXPORT Q_REQUIRED_RESULT bool qIsInf(qfloat16 f) Q_DECL_NOTHROW;    // complements qnumeric.h
+Q_CORE_EXPORT Q_REQUIRED_RESULT bool qIsNaN(qfloat16 f) Q_DECL_NOTHROW;    // complements qnumeric.h
+Q_CORE_EXPORT Q_REQUIRED_RESULT bool qIsFinite(qfloat16 f) Q_DECL_NOTHROW; // complements qnumeric.h
+
+// The remainder of these utility functions complement qglobal.h
+inline Q_REQUIRED_RESULT int qRound(qfloat16 d) Q_DECL_NOTHROW
+{ return qRound(static_cast<float>(d)); }
+
+inline Q_REQUIRED_RESULT qint64 qRound64(qfloat16 d) Q_DECL_NOTHROW
+{ return qRound64(static_cast<float>(d)); }
+
+inline Q_REQUIRED_RESULT bool qFuzzyCompare(qfloat16 p1, qfloat16 p2) Q_DECL_NOTHROW
+{
+    float f1 = static_cast<float>(p1);
+    float f2 = static_cast<float>(p2);
+    // The significand precision for IEEE754 half precision is
+    // 11 bits (10 explicitly stored), or approximately 3 decimal
+    // digits.  In selecting the fuzzy comparison factor of 102.5f
+    // (that is, (2^10+1)/10) below, we effectively select a
+    // window of about 1 (least significant) decimal digit about
+    // which the two operands can vary and still return true.
+    return (qAbs(f1 - f2) * 102.5f <= qMin(qAbs(f1), qAbs(f2)));
+}
+
+inline Q_REQUIRED_RESULT bool qIsNull(qfloat16 f) Q_DECL_NOTHROW
+{
+    return (f.b16 & static_cast<quint16>(0x7fff)) == 0;
+}
+
+inline int qIntCast(qfloat16 f) Q_DECL_NOTHROW
+{ return int(static_cast<float>(f)); }
+
+inline qfloat16::qfloat16(float f) Q_DECL_NOTHROW
+{
+    quint32 u;
+    memcpy(&u, &f, sizeof(quint32));
+    b16 = basetable[(u >> 23) & 0x1ff]
+          + ((u & 0x007fffff) >> shifttable[(u >> 23) & 0x1ff]);
+}
+
+inline qfloat16::operator float() const Q_DECL_NOTHROW
+{
+    quint32 u = mantissatable[offsettable[b16 >> 10] + (b16 & 0x3ff)]
+                + exponenttable[b16 >> 10];
+    float f;
+    memcpy(&f, &u, sizeof(quint32));
+    return f;
+}
+
+inline qfloat16::operator double() const Q_DECL_NOTHROW
+{
+    return static_cast<double>(float(*this));
+}
+
+inline qfloat16::operator long double() const Q_DECL_NOTHROW
+{
+    return static_cast<long double>(float(*this));
+}
+
+inline qfloat16 operator-(qfloat16 a) Q_DECL_NOTHROW
+{
+    qfloat16 f;
+    f.b16 = a.b16 ^ quint16(0x8000);
+    return f;
+}
+
+inline qfloat16 operator+(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return qfloat16(static_cast<float>(a) + static_cast<float>(b)); }
+inline qfloat16 operator-(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return qfloat16(static_cast<float>(a) - static_cast<float>(b)); }
+inline qfloat16 operator*(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return qfloat16(static_cast<float>(a) * static_cast<float>(b)); }
+inline qfloat16 operator/(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return qfloat16(static_cast<float>(a) / static_cast<float>(b)); }
+
+#define QF16_MAKE_ARITH_OP_FP(FP, OP) \
+    inline FP operator OP(qfloat16 lhs, FP rhs) Q_DECL_NOTHROW { return static_cast<FP>(lhs) OP rhs; } \
+    inline FP operator OP(FP lhs, qfloat16 rhs) Q_DECL_NOTHROW { return lhs OP static_cast<FP>(rhs); }
+#define QF16_MAKE_ARITH_OP_EQ_FP(FP, OP_EQ, OP) \
+    inline qfloat16& operator OP_EQ(qfloat16& lhs, FP rhs) Q_DECL_NOTHROW { lhs = qfloat16(static_cast<FP>(lhs) OP rhs); return lhs; }
+#define QF16_MAKE_ARITH_OP(FP) \
+    QF16_MAKE_ARITH_OP_FP(FP, +) \
+    QF16_MAKE_ARITH_OP_FP(FP, -) \
+    QF16_MAKE_ARITH_OP_FP(FP, *) \
+    QF16_MAKE_ARITH_OP_FP(FP, /) \
+    QF16_MAKE_ARITH_OP_EQ_FP(FP, +=, +) \
+    QF16_MAKE_ARITH_OP_EQ_FP(FP, -=, -) \
+    QF16_MAKE_ARITH_OP_EQ_FP(FP, *=, *) \
+    QF16_MAKE_ARITH_OP_EQ_FP(FP, /=, /)
+QF16_MAKE_ARITH_OP(long double)
+QF16_MAKE_ARITH_OP(double)
+QF16_MAKE_ARITH_OP(float)
+#undef QF16_MAKE_ARITH_OP
+#undef QF16_MAKE_ARITH_OP_FP
+
+#define QF16_MAKE_ARITH_OP_INT(OP) \
+    inline double operator OP(qfloat16 lhs, int rhs) Q_DECL_NOTHROW { return static_cast<double>(lhs) OP rhs; } \
+    inline double operator OP(int lhs, qfloat16 rhs) Q_DECL_NOTHROW { return lhs OP static_cast<double>(rhs); }
+QF16_MAKE_ARITH_OP_INT(+)
+QF16_MAKE_ARITH_OP_INT(-)
+QF16_MAKE_ARITH_OP_INT(*)
+QF16_MAKE_ARITH_OP_INT(/)
+#undef QF16_MAKE_ARITH_OP_INT
+
+inline bool operator>(qfloat16 a, qfloat16 b)  Q_DECL_NOTHROW { return static_cast<float>(a) >  static_cast<float>(b); }
+inline bool operator<(qfloat16 a, qfloat16 b)  Q_DECL_NOTHROW { return static_cast<float>(a) <  static_cast<float>(b); }
+inline bool operator>=(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return static_cast<float>(a) >= static_cast<float>(b); }
+inline bool operator<=(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return static_cast<float>(a) <= static_cast<float>(b); }
+inline bool operator==(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return static_cast<float>(a) == static_cast<float>(b); }
+inline bool operator!=(qfloat16 a, qfloat16 b) Q_DECL_NOTHROW { return static_cast<float>(a) != static_cast<float>(b); }
+
+#define QF16_MAKE_BOOL_OP_FP(FP, OP) \
+    inline bool operator OP(qfloat16 lhs, FP rhs) Q_DECL_NOTHROW { return static_cast<FP>(lhs) OP rhs; } \
+    inline bool operator OP(FP lhs, qfloat16 rhs) Q_DECL_NOTHROW { return lhs OP static_cast<FP>(rhs); }
+#define QF16_MAKE_BOOL_OP(FP) \
+    QF16_MAKE_BOOL_OP_FP(FP, <) \
+    QF16_MAKE_BOOL_OP_FP(FP, >) \
+    QF16_MAKE_BOOL_OP_FP(FP, >=) \
+    QF16_MAKE_BOOL_OP_FP(FP, <=) \
+    QF16_MAKE_BOOL_OP_FP(FP, ==) \
+    QF16_MAKE_BOOL_OP_FP(FP, !=)
+QF16_MAKE_BOOL_OP(long double)
+QF16_MAKE_BOOL_OP(double)
+QF16_MAKE_BOOL_OP(float)
+#undef QF16_MAKE_BOOL_OP
+#undef QF16_MAKE_BOOL_OP_FP
+
+#define QF16_MAKE_BOOL_OP_INT(OP) \
+    inline bool operator OP(qfloat16 a, int b) Q_DECL_NOTHROW { return static_cast<float>(a) OP b; } \
+    inline bool operator OP(int a, qfloat16 b) Q_DECL_NOTHROW { return a OP static_cast<float>(b); }
+QF16_MAKE_BOOL_OP_INT(>)
+QF16_MAKE_BOOL_OP_INT(<)
+QF16_MAKE_BOOL_OP_INT(>=)
+QF16_MAKE_BOOL_OP_INT(<=)
+QF16_MAKE_BOOL_OP_INT(==)
+QF16_MAKE_BOOL_OP_INT(!=)
+#undef QF16_MAKE_BOOL_OP_INT
+
+/*!
+  \internal
+*/
+inline Q_REQUIRED_RESULT bool qFuzzyIsNull(qfloat16 f) Q_DECL_NOTHROW
+{
+    return qAbs(static_cast<float>(f)) <= 0.001f;
+}
+
+QT_END_NAMESPACE
+
+Q_DECLARE_METATYPE(qfloat16)
+
+#endif // QFLOAT16_H