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/*===-- 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"))) _LIBCPP_EXPORTED_FROM_ABI
__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
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