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Diffstat (limited to 'util/qfloat16-tables/gen_qfloat16_tables.cpp')
| -rw-r--r-- | util/qfloat16-tables/gen_qfloat16_tables.cpp | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/util/qfloat16-tables/gen_qfloat16_tables.cpp b/util/qfloat16-tables/gen_qfloat16_tables.cpp new file mode 100644 index 0000000000..faedb5073c --- /dev/null +++ b/util/qfloat16-tables/gen_qfloat16_tables.cpp @@ -0,0 +1,163 @@ +/**************************************************************************** +** +** Copyright (C) 2016 by Southwest Research Institute (R) +** Copyright (C) 2019 Intel Corporation. +** 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. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include <stdint.h> +#include <stdio.h> + +/* + * This tool generates the tables used by qfloat16 to implement a + * software-emulated version of IEEE 754 binary16. qfloat16 automatically uses + * CPU instructions to convert to and from float (IEEE 754 binary32), but if + * the CPU is not guaranteed to have those instructions available at compile + * time, then qfloat16 needs the tables to perform the conversion with + * reasonable performance. + * + * Because Qt requires float to be IEEE 754 binary32, these tables are + * platform-independent and will never change. + */ + +uint32_t convertmantissa(int32_t i) +{ + uint32_t m = i << 13; // Zero pad mantissa bits + uint32_t e = 0; // Zero exponent + + while (!(m & 0x00800000)) { // While not normalized + e -= 0x00800000; // Decrement exponent (1<<23) + m <<= 1; // Shift mantissa + } + m &= ~0x00800000; // Clear leading 1 bit + e += 0x38800000; // Adjust bias ((127-14)<<23) + return m | e; // Return combined number +} + +// we first build these tables up and then print them out as a separate step in order +// to more closely map the implementation given in the paper. +uint32_t basetable[512]; +uint32_t shifttable[512]; + +int main() +{ + uint32_t i; + + printf("/* This file was generated by util/qfloat16-tables/gen_qfloat16_tables.cpp */\n\n"); + printf("#include <QtCore/qfloat16.h>\n\n"); + + printf("QT_BEGIN_NAMESPACE\n\n"); + printf("#if !defined(__F16C__) && !defined(__ARM_FP16_FORMAT_IEEE)\n\n"); + + printf("const quint32 qfloat16::mantissatable[2048] = {\n"); + printf("0,\n"); + for (i = 1; i < 1024; i++) + printf("0x%XU,\n", convertmantissa(i)); + for (i = 1024; i < 2048; i++) + printf("0x%XU,\n", 0x38000000U + ((i - 1024) << 13)); + printf("};\n\n"); + + printf("const quint32 qfloat16::exponenttable[64] = {\n"); + printf("0,\n"); + for (i = 1; i < 31; i++) + printf("0x%XU,\n", i << 23); + printf("0x47800000U,\n"); // 31 + printf("0x80000000U,\n"); // 32 + for (i = 33; i < 63; i++) + printf("0x%XU,\n", 0x80000000U + ((i - 32) << 23)); + printf("0xC7800000U,\n"); // 63 + printf("};\n\n"); + + printf("const quint32 qfloat16::offsettable[64] = {\n"); + printf("0,\n"); + for (i = 1; i < 32; i++) + printf("1024U,\n"); + printf("0,\n"); + for (i = 33; i < 64; i++) + printf("1024U,\n"); + printf("};\n\n"); + + int32_t e; + for (i = 0; i < 256; ++i) { + e = i - 127; + if (e < -24) { // Very small numbers map to zero + basetable[i | 0x000] = 0x0000; + basetable[i | 0x100] = 0x8000; + shifttable[i | 0x000] = 24; + shifttable[i | 0x100] = 24; + + } else if (e < -14) { // Small numbers map to denorms + basetable[i | 0x000] = (0x0400 >> (-e - 14)); + basetable[i | 0x100] = (0x0400 >> (-e - 14)) | 0x8000; + shifttable[i | 0x000] = -e - 1; + shifttable[i | 0x100] = -e - 1; + + } else if (e <= 15) { // Normal numbers just lose precision + basetable[i | 0x000] = ((e + 15) << 10); + basetable[i | 0x100] = ((e + 15) << 10) | 0x8000; + shifttable[i | 0x000] = 13; + shifttable[i | 0x100] = 13; + + } else if (e < 128) { // Large numbers map to Infinity + basetable[i | 0x000] = 0x7C00; + basetable[i | 0x100] = 0xFC00; + shifttable[i | 0x000] = 24; + shifttable[i | 0x100] = 24; + + } else { // Infinity and NaN's stay Infinity and NaN's + basetable[i | 0x000] = 0x7C00; + basetable[i | 0x100] = 0xFC00; + shifttable[i | 0x000] = 13; + shifttable[i | 0x100] = 13; + } + } + + printf("const quint32 qfloat16::basetable[512] = {\n"); + for (i = 0; i < 512; i++) + printf("0x%XU,\n", basetable[i]); + + printf("};\n\n"); + + printf("const quint32 qfloat16::shifttable[512] = {\n"); + for (i = 0; i < 512; i++) + printf("0x%XU,\n", shifttable[i]); + + printf("};\n\n"); + + printf("#endif // !__F16C__ && !__ARM_FP16_FORMAT_IEEE\n\n"); + printf("QT_END_NAMESPACE\n"); + return 0; +} |