1 /* This file is distributed under the University of Illinois Open Source 2 * License. See LICENSE.TXT for details. 3 */ 4 5 /* int64_t __fixunstfdi(long double x); 6 * This file implements the PowerPC 128-bit double-double -> int64_t conversion 7 */ 8 9 #include "DD.h" 10 #include <stdint.h> 11 12 uint64_t __fixtfdi(long double input) 13 { 14 const DD x = { .ld = input }; 15 const doublebits hibits = { .d = x.s.hi }; 16 17 const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff); 18 const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000); 19 20 /* If (1.0 - tiny) <= input < 0x1.0p63: */ 21 if (UINT32_C(0x03f00000) > absHighWordMinusOne) 22 { 23 /* Do an unsigned conversion of the absolute value, then restore the sign. */ 24 const int unbiasedHeadExponent = absHighWordMinusOne >> 20; 25 26 int64_t result = hibits.x & INT64_C(0x000fffffffffffff); /* mantissa(hi) */ 27 result |= INT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */ 28 result <<= 10; /* mantissa(hi) with one zero preceeding bit. */ 29 30 const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63; 31 32 /* If the tail is non-zero, we need to patch in the tail bits. */ 33 if (0.0 != x.s.lo) 34 { 35 const doublebits lobits = { .d = x.s.lo }; 36 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); 37 tailMantissa |= INT64_C(0x0010000000000000); 38 39 /* At this point we have the mantissa of |tail| */ 40 /* We need to negate it if head and tail have different signs. */ 41 const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63; 42 const int64_t negationMask = loNegationMask ^ hiNegationMask; 43 tailMantissa = (tailMantissa ^ negationMask) - negationMask; 44 45 /* Now we have the mantissa of tail as a signed 2s-complement integer */ 46 47 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; 48 49 /* Shift the tail mantissa into the right position, accounting for the 50 * bias of 10 that we shifted the head mantissa by. 51 */ 52 tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10))); 53 54 result += tailMantissa; 55 } 56 57 result >>= (62 - unbiasedHeadExponent); 58 59 /* Restore the sign of the result and return */ 60 result = (result ^ hiNegationMask) - hiNegationMask; 61 return result; 62 63 } 64 65 /* Edge cases handled here: */ 66 67 /* |x| < 1, result is zero. */ 68 if (1.0 > __builtin_fabs(x.s.hi)) 69 return INT64_C(0); 70 71 /* x very close to INT64_MIN, care must be taken to see which side we are on. */ 72 if (x.s.hi == -0x1.0p63) { 73 74 int64_t result = INT64_MIN; 75 76 if (0.0 < x.s.lo) 77 { 78 /* If the tail is positive, the correct result is something other than INT64_MIN. 79 * we'll need to figure out what it is. 80 */ 81 82 const doublebits lobits = { .d = x.s.lo }; 83 int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff); 84 tailMantissa |= INT64_C(0x0010000000000000); 85 86 /* Now we negate the tailMantissa */ 87 tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1); 88 89 /* And shift it by the appropriate amount */ 90 const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff; 91 tailMantissa >>= 1075 - biasedTailExponent; 92 93 result -= tailMantissa; 94 } 95 96 return result; 97 } 98 99 /* Signed overflows, infinities, and NaNs */ 100 if (x.s.hi > 0.0) 101 return INT64_MAX; 102 else 103 return INT64_MIN; 104 } 105
