1 | /*===-- int128_builtins.cpp - Implement __muloti4 --------------------------=== |
2 | * |
3 | * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | * See https://llvm.org/LICENSE.txt for license information. |
5 | * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | * |
7 | * ===----------------------------------------------------------------------=== |
8 | * |
9 | * This file implements __muloti4, and is stolen from the compiler_rt library. |
10 | * |
11 | * FIXME: we steal and re-compile it into filesystem, which uses __int128_t, |
12 | * and requires this builtin when sanitized. See llvm.org/PR30643 |
13 | * |
14 | * ===----------------------------------------------------------------------=== |
15 | */ |
16 | #include "__config" |
17 | #include "climits" |
18 | |
19 | #if !defined(_LIBCPP_HAS_NO_INT128) |
20 | |
21 | extern "C" __attribute__((no_sanitize("undefined" ))) _LIBCPP_FUNC_VIS |
22 | __int128_t __muloti4(__int128_t a, __int128_t b, int* overflow) { |
23 | const int N = (int)(sizeof(__int128_t) * CHAR_BIT); |
24 | const __int128_t MIN = (__int128_t)1 << (N - 1); |
25 | const __int128_t MAX = ~MIN; |
26 | *overflow = 0; |
27 | __int128_t result = a * b; |
28 | if (a == MIN) { |
29 | if (b != 0 && b != 1) |
30 | *overflow = 1; |
31 | return result; |
32 | } |
33 | if (b == MIN) { |
34 | if (a != 0 && a != 1) |
35 | *overflow = 1; |
36 | return result; |
37 | } |
38 | __int128_t sa = a >> (N - 1); |
39 | __int128_t abs_a = (a ^ sa) - sa; |
40 | __int128_t sb = b >> (N - 1); |
41 | __int128_t abs_b = (b ^ sb) - sb; |
42 | if (abs_a < 2 || abs_b < 2) |
43 | return result; |
44 | if (sa == sb) { |
45 | if (abs_a > MAX / abs_b) |
46 | *overflow = 1; |
47 | } else { |
48 | if (abs_a > MIN / -abs_b) |
49 | *overflow = 1; |
50 | } |
51 | return result; |
52 | } |
53 | |
54 | #endif |
55 | |