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/* uint64_t __fixunstfdi(long double x); */ 68bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan/* This file implements the PowerPC 128-bit double-double -> uint64_t conversion */ 7b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 8b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar#include "DD.h" 9b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 10b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbaruint64_t __fixunstfdi(long double input) 11b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar{ 12b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const DD x = { .ld = input }; 138bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan const doublebits hibits = { .d = x.s.hi }; 14b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 15b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const uint32_t highWordMinusOne = (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000); 16b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 178bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* If (1.0 - tiny) <= input < 0x1.0p64: */ 18b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar if (UINT32_C(0x04000000) > highWordMinusOne) 19b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 20b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const int unbiasedHeadExponent = highWordMinusOne >> 20; 21b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 228bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); /* mantissa(hi) */ 238bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan result |= UINT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */ 248bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan result <<= 11; /* mantissa(hi) left aligned in the int64 field. */ 25b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 268bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* If the tail is non-zero, we need to patch in the tail bits. */ 278bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan if (0.0 != x.s.lo) 28b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar { 298bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan const doublebits lobits = { .d = x.s.lo }; 30b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); 31b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar tailMantissa |= INT64_C(0x0010000000000000); 32b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 338bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* At this point we have the mantissa of |tail| */ 34b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 35b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const int64_t negationMask = ((int64_t)(lobits.x)) >> 63; 36b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar tailMantissa = (tailMantissa ^ negationMask) - negationMask; 37b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 388bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* Now we have the mantissa of tail as a signed 2s-complement integer */ 39b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 40b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; 41b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 428bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* Shift the tail mantissa into the right position, accounting for the 438bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan * bias of 11 that we shifted the head mantissa by. 448bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan */ 45b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11))); 46b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 47b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar result += tailMantissa; 48b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar } 49b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 50b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar result >>= (63 - unbiasedHeadExponent); 51b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return result; 52b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar } 53b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 548bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan /* Edge cases are handled here, with saturation. */ 558bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan if (1.0 > x.s.hi) 56b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return UINT64_C(0); 57b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar else 58b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar return UINT64_MAX; 59b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar} 60