1 //===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-C -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements converting a signed 128 bit integer to a 128bit IBM /
11 // PowerPC long double (double-double) value.
13 //===----------------------------------------------------------------------===//
17 /* Conversions from signed and unsigned 64-bit int to long double. */
18 long double __floatditf(int64_t);
19 long double __floatunditf(uint64_t);
21 /* Convert a signed 128-bit integer to long double.
22 * This uses the following property: Let hi and lo be 64-bits each,
23 * and let signed_val_k() and unsigned_val_k() be the value of the
24 * argument interpreted as a signed or unsigned k-bit integer. Then,
26 * signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo)
27 * = (long double)hi * 2^64 + (long double)lo,
29 * where (long double)hi and (long double)lo are signed and
30 * unsigned 64-bit integer to long double conversions, respectively.
32 long double __floattitf(__int128_t arg) {
33 /* Split the int128 argument into 64-bit high and low int64 parts. */
34 int64_t ArgHiPart = (int64_t)(arg >> 64);
35 uint64_t ArgLoPart = (uint64_t)arg;
37 /* Convert each 64-bit part into long double. The high part
38 * must be a signed conversion and the low part an unsigned conversion
39 * to ensure the correct result. */
40 long double ConvertedHiPart = __floatditf(ArgHiPart);
41 long double ConvertedLoPart = __floatunditf(ArgLoPart);
43 /* The low bit of ArgHiPart corresponds to the 2^64 bit in arg.
44 * Multiply the high part by 2^64 to undo the right shift by 64-bits
45 * done in the splitting. Then, add to the low part to obtain the
47 return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart);