1 //===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-C -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements converting a signed 128 bit integer to a 128bit IBM / 10 // PowerPC long double (double-double) value. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include <stdint.h> 15 16 // Conversions from signed and unsigned 64-bit int to long double. 17 long double __floatditf(int64_t); 18 long double __floatunditf(uint64_t); 19 20 // Convert a signed 128-bit integer to long double. 21 // This uses the following property: Let hi and lo be 64-bits each, 22 // and let signed_val_k() and unsigned_val_k() be the value of the 23 // argument interpreted as a signed or unsigned k-bit integer. Then, 24 // 25 // signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo) 26 // = (long double)hi * 2^64 + (long double)lo, 27 // 28 // where (long double)hi and (long double)lo are signed and 29 // unsigned 64-bit integer to long double conversions, respectively. 30 long double __floattitf(__int128_t arg) { 31 // Split the int128 argument into 64-bit high and low int64 parts. 32 int64_t ArgHiPart = (int64_t)(arg >> 64); 33 uint64_t ArgLoPart = (uint64_t)arg; 34 35 // Convert each 64-bit part into long double. The high part 36 // must be a signed conversion and the low part an unsigned conversion 37 // to ensure the correct result. 38 long double ConvertedHiPart = __floatditf(ArgHiPart); 39 long double ConvertedLoPart = __floatunditf(ArgLoPart); 40 41 // The low bit of ArgHiPart corresponds to the 2^64 bit in arg. 42 // Multiply the high part by 2^64 to undo the right shift by 64-bits 43 // done in the splitting. Then, add to the low part to obtain the 44 // final result. 45 return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart); 46 } 47