| //===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-C -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is dual licensed under the MIT and the University of Illinois Open |
| // Source Licenses. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements converting a signed 128 bit integer to a 128bit IBM / |
| // PowerPC long double (double-double) value. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include <stdint.h> |
| |
| /* Conversions from signed and unsigned 64-bit int to long double. */ |
| long double __floatditf(int64_t); |
| long double __floatunditf(uint64_t); |
| |
| /* Convert a signed 128-bit integer to long double. |
| * This uses the following property: Let hi and lo be 64-bits each, |
| * and let signed_val_k() and unsigned_val_k() be the value of the |
| * argument interpreted as a signed or unsigned k-bit integer. Then, |
| * |
| * signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo) |
| * = (long double)hi * 2^64 + (long double)lo, |
| * |
| * where (long double)hi and (long double)lo are signed and |
| * unsigned 64-bit integer to long double conversions, respectively. |
| */ |
| long double __floattitf(__int128_t arg) { |
| /* Split the int128 argument into 64-bit high and low int64 parts. */ |
| int64_t ArgHiPart = (int64_t)(arg >> 64); |
| uint64_t ArgLoPart = (uint64_t)arg; |
| |
| /* Convert each 64-bit part into long double. The high part |
| * must be a signed conversion and the low part an unsigned conversion |
| * to ensure the correct result. */ |
| long double ConvertedHiPart = __floatditf(ArgHiPart); |
| long double ConvertedLoPart = __floatunditf(ArgLoPart); |
| |
| /* The low bit of ArgHiPart corresponds to the 2^64 bit in arg. |
| * Multiply the high part by 2^64 to undo the right shift by 64-bits |
| * done in the splitting. Then, add to the low part to obtain the |
| * final result. */ |
| return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart); |
| } |