1// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
2// See https://llvm.org/LICENSE.txt for license information.
3// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
4
5// int64_t __fixunstfdi(long double x);
6// This file implements the PowerPC 128-bit double-double -> int64_t conversion
7
8#include "../int_math.h"
9#include "DD.h"
10
11uint64_t __fixtfdi(long double input) {
12  const DD x = {.ld = input};
13  const doublebits hibits = {.d = x.s.hi};
14
15  const uint32_t absHighWord =
16      (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);
17  const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);
18
19  // If (1.0 - tiny) <= input < 0x1.0p63:
20  if (UINT32_C(0x03f00000) > absHighWordMinusOne) {
21    // Do an unsigned conversion of the absolute value, then restore the sign.
22    const int unbiasedHeadExponent = absHighWordMinusOne >> 20;
23
24    int64_t result = hibits.x & INT64_C(0x000fffffffffffff); // mantissa(hi)
25    result |= INT64_C(0x0010000000000000); // matissa(hi) with implicit bit
26    result <<= 10; // mantissa(hi) with one zero preceding bit.
27
28    const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;
29
30    // If the tail is non-zero, we need to patch in the tail bits.
31    if (0.0 != x.s.lo) {
32      const doublebits lobits = {.d = x.s.lo};
33      int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
34      tailMantissa |= INT64_C(0x0010000000000000);
35
36      // At this point we have the mantissa of |tail|
37      // We need to negate it if head and tail have different signs.
38      const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;
39      const int64_t negationMask = loNegationMask ^ hiNegationMask;
40      tailMantissa = (tailMantissa ^ negationMask) - negationMask;
41
42      // Now we have the mantissa of tail as a signed 2s-complement integer
43
44      const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
45
46      // Shift the tail mantissa into the right position, accounting for the
47      // bias of 10 that we shifted the head mantissa by.
48      tailMantissa >>=
49          (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));
50
51      result += tailMantissa;
52    }
53
54    result >>= (62 - unbiasedHeadExponent);
55
56    // Restore the sign of the result and return
57    result = (result ^ hiNegationMask) - hiNegationMask;
58    return result;
59  }
60
61  // Edge cases handled here:
62
63  // |x| < 1, result is zero.
64  if (1.0 > crt_fabs(x.s.hi))
65    return INT64_C(0);
66
67  // x very close to INT64_MIN, care must be taken to see which side we are on.
68  if (x.s.hi == -0x1.0p63) {
69
70    int64_t result = INT64_MIN;
71
72    if (0.0 < x.s.lo) {
73      // If the tail is positive, the correct result is something other than
74      // INT64_MIN. we'll need to figure out what it is.
75
76      const doublebits lobits = {.d = x.s.lo};
77      int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
78      tailMantissa |= INT64_C(0x0010000000000000);
79
80      // Now we negate the tailMantissa
81      tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);
82
83      // And shift it by the appropriate amount
84      const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
85      tailMantissa >>= 1075 - biasedTailExponent;
86
87      result -= tailMantissa;
88    }
89
90    return result;
91  }
92
93  // Signed overflows, infinities, and NaNs
94  if (x.s.hi > 0.0)
95    return INT64_MAX;
96  else
97    return INT64_MIN;
98}
99