1 /* This file is distributed under the University of Illinois Open Source 2 * License. See LICENSE.TXT for details. 3 */ 4 5 /* uint64_t __fixunstfdi(long double x); */ 6 /* This file implements the PowerPC 128-bit double-double -> uint64_t conversion */ 7 8 #include "DD.h" 9 10 uint64_t __fixunstfdi(long double input) 11 { 12 const DD x = { .ld = input }; 13 const doublebits hibits = { .d = x.s.hi }; 14 15 const uint32_t highWordMinusOne = (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000); 16 17 /* If (1.0 - tiny) <= input < 0x1.0p64: */ 18 if (UINT32_C(0x04000000) > highWordMinusOne) 19 { 20 const int unbiasedHeadExponent = highWordMinusOne >> 20; 21 22 uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); /* mantissa(hi) */ 23 result |= UINT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */ 24 result <<= 11; /* mantissa(hi) left aligned in the int64 field. */ 25 26 /* If the tail is non-zero, we need to patch in the tail bits. */ 27 if (0.0 != x.s.lo) 28 { 29 const doublebits lobits = { .d = x.s.lo }; 30 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); 31 tailMantissa |= INT64_C(0x0010000000000000); 32 33 /* At this point we have the mantissa of |tail| */ 34 35 const int64_t negationMask = ((int64_t)(lobits.x)) >> 63; 36 tailMantissa = (tailMantissa ^ negationMask) - negationMask; 37 38 /* Now we have the mantissa of tail as a signed 2s-complement integer */ 39 40 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; 41 42 /* Shift the tail mantissa into the right position, accounting for the 43 * bias of 11 that we shifted the head mantissa by. 44 */ 45 tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11))); 46 47 result += tailMantissa; 48 } 49 50 result >>= (63 - unbiasedHeadExponent); 51 return result; 52 } 53 54 /* Edge cases are handled here, with saturation. */ 55 if (1.0 > x.s.hi) 56 return UINT64_C(0); 57 else 58 return UINT64_MAX; 59 } 60
