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/* This file is distributed under the University of Illinois Open Source
* License. See LICENSE.TXT for details.
*/
/* uint64_t __fixunstfdi(long double x); */
/* This file implements the PowerPC 128-bit double-double -> uint64_t conversion */
#include "DD.h"
uint64_t __fixunstfdi(long double input)
{
const DD x = { .ld = input };
const doublebits hibits = { .d = x.s.hi };
const uint32_t highWordMinusOne = (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000);
/* If (1.0 - tiny) <= input < 0x1.0p64: */
if (UINT32_C(0x04000000) > highWordMinusOne)
{
const int unbiasedHeadExponent = highWordMinusOne >> 20;
uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); /* mantissa(hi) */
result |= UINT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */
result <<= 11; /* mantissa(hi) left aligned in the int64 field. */
/* If the tail is non-zero, we need to patch in the tail bits. */
if (0.0 != x.s.lo)
{
const doublebits lobits = { .d = x.s.lo };
int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
tailMantissa |= INT64_C(0x0010000000000000);
/* At this point we have the mantissa of |tail| */
const int64_t negationMask = ((int64_t)(lobits.x)) >> 63;
tailMantissa = (tailMantissa ^ negationMask) - negationMask;
/* Now we have the mantissa of tail as a signed 2s-complement integer */
const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
/* Shift the tail mantissa into the right position, accounting for the
* bias of 11 that we shifted the head mantissa by.
*/
tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11)));
result += tailMantissa;
}
result >>= (63 - unbiasedHeadExponent);
return result;
}
/* Edge cases are handled here, with saturation. */
if (1.0 > x.s.hi)
return UINT64_C(0);
else
return UINT64_MAX;
}
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