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| |
| #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(__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 // !__ARM_FP16_FORMAT_IEEE\n\n"); |
| printf("QT_END_NAMESPACE\n"); |
| return 0; |
| } |