forked from OSchip/llvm-project
105 lines
3.2 KiB
C
105 lines
3.2 KiB
C
/* 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 "../int_math.h"
|
|
|
|
uint64_t __fixtfdi(long double input)
|
|
{
|
|
const DD x = { .ld = input };
|
|
const doublebits hibits = { .d = x.s.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.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| */
|
|
/* 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 > crt_fabs(x.s.hi))
|
|
return INT64_C(0);
|
|
|
|
/* x very close to INT64_MIN, care must be taken to see which side we are on. */
|
|
if (x.s.hi == -0x1.0p63) {
|
|
|
|
int64_t result = INT64_MIN;
|
|
|
|
if (0.0 < x.s.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.s.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.s.hi > 0.0)
|
|
return INT64_MAX;
|
|
else
|
|
return INT64_MIN;
|
|
}
|