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// uint64_t __fixunstfdi(long double x);
6// This file implements the PowerPC 128-bit double-double -> uint64_t conversion
7
8#include "DD.h"
9
10uint64_t __fixunstfdi(long double input) {
11  const DD x = {.ld = input};
12  const doublebits hibits = {.d = x.s.hi};
13
14  const uint32_t highWordMinusOne =
15      (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000);
16
17  // If (1.0 - tiny) <= input < 0x1.0p64:
18  if (UINT32_C(0x04000000) > highWordMinusOne) {
19    const int unbiasedHeadExponent = highWordMinusOne >> 20;
20
21    uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); // mantissa(hi)
22    result |= UINT64_C(0x0010000000000000); // matissa(hi) with implicit bit
23    result <<= 11; // mantissa(hi) left aligned in the int64 field.
24
25    // If the tail is non-zero, we need to patch in the tail bits.
26    if (0.0 != x.s.lo) {
27      const doublebits lobits = {.d = x.s.lo};
28      int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
29      tailMantissa |= INT64_C(0x0010000000000000);
30
31      // At this point we have the mantissa of |tail|
32
33      const int64_t negationMask = ((int64_t)(lobits.x)) >> 63;
34      tailMantissa = (tailMantissa ^ negationMask) - negationMask;
35
36      // Now we have the mantissa of tail as a signed 2s-complement integer
37
38      const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
39
40      // Shift the tail mantissa into the right position, accounting for the
41      // bias of 11 that we shifted the head mantissa by.
42      tailMantissa >>=
43          (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11)));
44
45      result += tailMantissa;
46    }
47
48    result >>= (63 - unbiasedHeadExponent);
49    return result;
50  }
51
52  // Edge cases are handled here, with saturation.
53  if (1.0 > x.s.hi)
54    return UINT64_C(0);
55  else
56    return UINT64_MAX;
57}
58