1 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2 // See https://llvm.org/LICENSE.txt for license information.
3 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4 
5 // long double __floatunditf(unsigned long long x);
6 // This file implements the PowerPC unsigned long long -> long double conversion
7 
8 #include "DD.h"
9 
__floatunditf(uint64_t a)10 long double __floatunditf(uint64_t a) {
11 
12   // Begins with an exact copy of the code from __floatundidf
13 
14   static const double twop52 = 0x1.0p52;
15   static const double twop84 = 0x1.0p84;
16   static const double twop84_plus_twop52 = 0x1.00000001p84;
17 
18   doublebits high = {.d = twop84};
19   doublebits low = {.d = twop52};
20 
21   high.x |= a >> 32;                         // 0x1.0p84 + high 32 bits of a
22   low.x |= a & UINT64_C(0x00000000ffffffff); // 0x1.0p52 + low 32 bits of a
23 
24   const double high_addend = high.d - twop84_plus_twop52;
25 
26   // At this point, we have two double precision numbers
27   // high_addend and low.d, and we wish to return their sum
28   // as a canonicalized long double:
29 
30   // This implementation sets the inexact flag spuriously.
31   // This could be avoided, but at some substantial cost.
32 
33   DD result;
34 
35   result.s.hi = high_addend + low.d;
36   result.s.lo = (high_addend - result.s.hi) + low.d;
37 
38   return result.ld;
39 }
40