blob: 35ce3a912fc1ac227c71d12999f4ba67fd2535b6 (
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
|
// 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"
#include <stdint.h>
uint64_t __fixunstfdi(long double input)
{
const DD x = { .ld = input };
const doublebits hibits = { .d = x.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.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|
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.hi)
return UINT64_C(0);
else
return UINT64_MAX;
}
|
