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// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// int64_t __fixunstfdi(long double x);
// This file implements the PowerPC 128-bit double-double -> int64_t conversion
#include "DD.h"
#include <stdint.h>
uint64_t __fixtfdi(long double input)
{
const DD x = { .ld = input };
const doublebits hibits = { .d = x.hi };
const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);
const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);
// If (1.0 - tiny) <= input < 0x1.0p63:
if (UINT32_C(0x03f00000) > absHighWordMinusOne)
{
// Do an unsigned conversion of the absolute value, then restore the sign.
const int unbiasedHeadExponent = absHighWordMinusOne >> 20;
int64_t result = hibits.x & INT64_C(0x000fffffffffffff); // mantissa(hi)
result |= INT64_C(0x0010000000000000); // matissa(hi) with implicit bit
result <<= 10; // mantissa(hi) with one zero preceeding bit.
const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;
// If the tail is non-zero, we need to patch in the tail bits.
if (0.0 != x.lo)
{
const doublebits lobits = { .d = x.lo };
int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
tailMantissa |= INT64_C(0x0010000000000000);
// At this point we have the mantissa of |tail|
// We need to negate it if head and tail have different signs.
const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;
const int64_t negationMask = loNegationMask ^ hiNegationMask;
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 10 that we shifted the head mantissa by.
tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));
result += tailMantissa;
}
result >>= (62 - unbiasedHeadExponent);
// Restore the sign of the result and return
result = (result ^ hiNegationMask) - hiNegationMask;
return result;
}
// Edge cases handled here:
// |x| < 1, result is zero.
if (1.0 > __builtin_fabs(x.hi))
return INT64_C(0);
// x very close to INT64_MIN, care must be taken to see which side we are on.
if (x.hi == -0x1.0p63) {
int64_t result = INT64_MIN;
if (0.0 < x.lo)
{
// If the tail is positive, the correct result is something other than INT64_MIN.
// we'll need to figure out what it is.
const doublebits lobits = { .d = x.lo };
int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
tailMantissa |= INT64_C(0x0010000000000000);
// Now we negate the tailMantissa
tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);
// And shift it by the appropriate amount
const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
tailMantissa >>= 1075 - biasedTailExponent;
result -= tailMantissa;
}
return result;
}
// Signed overflows, infinities, and NaNs
if (x.hi > 0.0)
return INT64_MAX;
else
return INT64_MIN;
}
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