floatditf.c revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0 
1/* This file is distributed under the University of Illinois Open Source
2 * License. See LICENSE.TXT for details.
3 */
4
5/* long double __floatditf(long long x); */
6/* This file implements the PowerPC long long -> long double conversion */
7
8#include "DD.h"
9
10long double __floatditf(int64_t a) {
11
12	static const double twop32 = 0x1.0p32;
13	static const double twop52 = 0x1.0p52;
14
15	doublebits low  = { .d = twop52 };
16	low.x |= a & UINT64_C(0x00000000ffffffff);	/* 0x1.0p52 + low 32 bits of a. */
17
18	const double high_addend = (double)((int32_t)(a >> 32))*twop32 - twop52;
19
20	/* At this point, we have two double precision numbers
21	 * high_addend and low.d, and we wish to return their sum
22	 * as a canonicalized long double:
23	 */
24
25	/* This implementation sets the inexact flag spuriously.
26	 * This could be avoided, but at some substantial cost.
27	*/
28
29	DD result;
30
31	result.s.hi = high_addend + low.d;
32	result.s.lo = (high_addend - result.s.hi) + low.d;
33
34	return result.ld;
35
36}
37