1336819Sdim/*===-- int128_builtins.cpp - Implement __muloti4 --------------------------===
2336819Sdim *
3353358Sdim * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4353358Sdim * See https://llvm.org/LICENSE.txt for license information.
5353358Sdim * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6336819Sdim *
7336819Sdim * ===----------------------------------------------------------------------===
8336819Sdim *
9336819Sdim * This file implements __muloti4, and is stolen from the compiler_rt library.
10336819Sdim *
11336819Sdim * FIXME: we steal and re-compile it into filesystem, which uses __int128_t,
12336819Sdim * and requires this builtin when sanitized. See llvm.org/PR30643
13336819Sdim *
14336819Sdim * ===----------------------------------------------------------------------===
15336819Sdim */
16336819Sdim#include "__config"
17336819Sdim#include "climits"
18336819Sdim
19336819Sdim#if !defined(_LIBCPP_HAS_NO_INT128)
20336819Sdim
21360784Sdimextern "C" __attribute__((no_sanitize("undefined"))) _LIBCPP_FUNC_VIS
22336819Sdim__int128_t __muloti4(__int128_t a, __int128_t b, int* overflow) {
23336819Sdim  const int N = (int)(sizeof(__int128_t) * CHAR_BIT);
24336819Sdim  const __int128_t MIN = (__int128_t)1 << (N - 1);
25336819Sdim  const __int128_t MAX = ~MIN;
26336819Sdim  *overflow = 0;
27336819Sdim  __int128_t result = a * b;
28336819Sdim  if (a == MIN) {
29336819Sdim    if (b != 0 && b != 1)
30336819Sdim      *overflow = 1;
31336819Sdim    return result;
32336819Sdim  }
33336819Sdim  if (b == MIN) {
34336819Sdim    if (a != 0 && a != 1)
35336819Sdim      *overflow = 1;
36336819Sdim    return result;
37336819Sdim  }
38336819Sdim  __int128_t sa = a >> (N - 1);
39336819Sdim  __int128_t abs_a = (a ^ sa) - sa;
40336819Sdim  __int128_t sb = b >> (N - 1);
41336819Sdim  __int128_t abs_b = (b ^ sb) - sb;
42336819Sdim  if (abs_a < 2 || abs_b < 2)
43336819Sdim    return result;
44336819Sdim  if (sa == sb) {
45336819Sdim    if (abs_a > MAX / abs_b)
46336819Sdim      *overflow = 1;
47336819Sdim  } else {
48336819Sdim    if (abs_a > MIN / -abs_b)
49336819Sdim      *overflow = 1;
50336819Sdim  }
51336819Sdim  return result;
52336819Sdim}
53336819Sdim
54336819Sdim#endif
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