18bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan/* This file is distributed under the University of Illinois Open Source 28bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan * License. See LICENSE.TXT for details. 38bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan */ 4b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 58bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan/* long double __floatunditf(unsigned long long x); */ 68bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan/* This file implements the PowerPC unsigned long long -> long double conversion */ 7b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 8b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar#include "DD.h" 9b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 10b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbarlong double __floatunditf(uint64_t a) { 11b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 128bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* Begins with an exact copy of the code from __floatundidf */ 13b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 14b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar static const double twop52 = 0x1.0p52; 15b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar static const double twop84 = 0x1.0p84; 16b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar static const double twop84_plus_twop52 = 0x1.00000001p84; 17b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 18b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar doublebits high = { .d = twop84 }; 19b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar doublebits low = { .d = twop52 }; 20b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 218bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan high.x |= a >> 32; /* 0x1.0p84 + high 32 bits of a */ 228bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan low.x |= a & UINT64_C(0x00000000ffffffff); /* 0x1.0p52 + low 32 bits of a */ 23b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 24b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const double high_addend = high.d - twop84_plus_twop52; 25b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 268bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* At this point, we have two double precision numbers 278bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan * high_addend and low.d, and we wish to return their sum 288bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan * as a canonicalized long double: 298bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan */ 308bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan 318bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* This implementation sets the inexact flag spuriously. */ 328bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* This could be avoided, but at some substantial cost. */ 33b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 34b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar DD result; 35b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 368bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan result.s.hi = high_addend + low.d; 378bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan result.s.lo = (high_addend - result.s.hi) + low.d; 38b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 39b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return result.ld; 40b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 41b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar} 42