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 "../int_math.h"
11 
__fixtfdi(long double input)12 uint64_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 preceding 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 > crt_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