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