| /*===-- int128_builtins.cpp - Implement __muloti4 --------------------------=== |
| * |
| * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| * See https://llvm.org/LICENSE.txt for license information. |
| * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| * |
| * ===----------------------------------------------------------------------=== |
| * |
| * This file implements __muloti4, and is stolen from the compiler_rt library. |
| * |
| * FIXME: we steal and re-compile it into filesystem, which uses __int128_t, |
| * and requires this builtin when sanitized. See llvm.org/PR30643 |
| * |
| * ===----------------------------------------------------------------------=== |
| */ |
| #include "__config" |
| #include "climits" |
| |
| #if !defined(_LIBCPP_HAS_NO_INT128) |
| |
| extern "C" __attribute__((no_sanitize("undefined"))) |
| __int128_t __muloti4(__int128_t a, __int128_t b, int* overflow) { |
| const int N = (int)(sizeof(__int128_t) * CHAR_BIT); |
| const __int128_t MIN = (__int128_t)1 << (N - 1); |
| const __int128_t MAX = ~MIN; |
| *overflow = 0; |
| __int128_t result = a * b; |
| if (a == MIN) { |
| if (b != 0 && b != 1) |
| *overflow = 1; |
| return result; |
| } |
| if (b == MIN) { |
| if (a != 0 && a != 1) |
| *overflow = 1; |
| return result; |
| } |
| __int128_t sa = a >> (N - 1); |
| __int128_t abs_a = (a ^ sa) - sa; |
| __int128_t sb = b >> (N - 1); |
| __int128_t abs_b = (b ^ sb) - sb; |
| if (abs_a < 2 || abs_b < 2) |
| return result; |
| if (sa == sb) { |
| if (abs_a > MAX / abs_b) |
| *overflow = 1; |
| } else { |
| if (abs_a > MIN / -abs_b) |
| *overflow = 1; |
| } |
| return result; |
| } |
| |
| #endif |