1/* This file is distributed under the University of Illinois Open Source
2 * License. See LICENSE.TXT for details.
3 */
4
5/* int64_t __fixunstfdi(long double x);
6 * This file implements the PowerPC 128-bit double-double -> int64_t conversion
7 */
8
9#include "DD.h"
10#include <stdint.h>
11
12uint64_t __fixtfdi(long double input)
13{
14	const DD x = { .ld = input };
15	const doublebits hibits = { .d = x.s.hi };
16
17	const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);
18	const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);
19
20	/* If (1.0 - tiny) <= input < 0x1.0p63: */
21	if (UINT32_C(0x03f00000) > absHighWordMinusOne)
22	{
23		/* Do an unsigned conversion of the absolute value, then restore the sign. */
24		const int unbiasedHeadExponent = absHighWordMinusOne >> 20;
25
26		int64_t result = hibits.x & INT64_C(0x000fffffffffffff); /* mantissa(hi) */
27		result |= INT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */
28		result <<= 10; /* mantissa(hi) with one zero preceeding bit. */
29
30		const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;
31
32		/* If the tail is non-zero, we need to patch in the tail bits. */
33		if (0.0 != x.s.lo)
34		{
35			const doublebits lobits = { .d = x.s.lo };
36			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
37			tailMantissa |= INT64_C(0x0010000000000000);
38
39			/* At this point we have the mantissa of |tail| */
40			/* We need to negate it if head and tail have different signs. */
41			const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;
42			const int64_t negationMask = loNegationMask ^ hiNegationMask;
43			tailMantissa = (tailMantissa ^ negationMask) - negationMask;
44
45			/* Now we have the mantissa of tail as a signed 2s-complement integer */
46
47			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
48
49			/* Shift the tail mantissa into the right position, accounting for the
50			 * bias of 10 that we shifted the head mantissa by.
51			 */
52			tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));
53
54			result += tailMantissa;
55		}
56
57		result >>= (62 - unbiasedHeadExponent);
58
59		/* Restore the sign of the result and return */
60		result = (result ^ hiNegationMask) - hiNegationMask;
61		return result;
62
63	}
64
65	/* Edge cases handled here: */
66
67	/* |x| < 1, result is zero. */
68	if (1.0 > __builtin_fabs(x.s.hi))
69		return INT64_C(0);
70
71	/* x very close to INT64_MIN, care must be taken to see which side we are on. */
72	if (x.s.hi == -0x1.0p63) {
73
74		int64_t result = INT64_MIN;
75
76		if (0.0 < x.s.lo)
77		{
78			/* If the tail is positive, the correct result is something other than INT64_MIN.
79			 * we'll need to figure out what it is.
80			 */
81
82			const doublebits lobits = { .d = x.s.lo };
83			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
84			tailMantissa |= INT64_C(0x0010000000000000);
85
86			/* Now we negate the tailMantissa */
87			tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);
88
89			/* And shift it by the appropriate amount */
90			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
91			tailMantissa >>= 1075 - biasedTailExponent;
92
93			result -= tailMantissa;
94		}
95
96		return result;
97	}
98
99	/* Signed overflows, infinities, and NaNs */
100	if (x.s.hi > 0.0)
101		return INT64_MAX;
102	else
103		return INT64_MIN;
104}
105