blob: 56e7b3fbf3e5aa5559486b830cc6746fbafb1247 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
|
/* 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;
}
|
