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See: * https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc/77319 * https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701 We're dropping support for C++03 for Zig due to the first change; it would be insane to ship 1018 duplicate header files just for this outdated use case. As a result of the second change, I had to bring in a subset of the headers from llvm-libc since libc++ now depends on these. Hopefully we can continue to get away with not copying the entirety of llvm-libc.
54 lines
1.6 KiB
C++
Vendored
54 lines
1.6 KiB
C++
Vendored
/*===-- int128_builtins.cpp - Implement __muloti4 --------------------------===
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*
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* Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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* See https://llvm.org/LICENSE.txt for license information.
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* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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*
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* ===----------------------------------------------------------------------===
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*
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* This file implements __muloti4, and is stolen from the compiler_rt library.
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*
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* FIXME: we steal and re-compile it into filesystem, which uses __int128_t,
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* and requires this builtin when sanitized. See llvm.org/PR30643
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*
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* ===----------------------------------------------------------------------===
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*/
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#include <__config>
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#include <climits>
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#if _LIBCPP_HAS_INT128
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extern "C" __attribute__((no_sanitize("undefined"))) _LIBCPP_EXPORTED_FROM_ABI __int128_t
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__muloti4(__int128_t a, __int128_t b, int* overflow) {
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const int N = (int)(sizeof(__int128_t) * CHAR_BIT);
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const __int128_t MIN = (__int128_t)1 << (N - 1);
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const __int128_t MAX = ~MIN;
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*overflow = 0;
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__int128_t result = a * b;
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if (a == MIN) {
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if (b != 0 && b != 1)
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*overflow = 1;
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return result;
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}
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if (b == MIN) {
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if (a != 0 && a != 1)
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*overflow = 1;
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return result;
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}
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__int128_t sa = a >> (N - 1);
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__int128_t abs_a = (a ^ sa) - sa;
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__int128_t sb = b >> (N - 1);
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__int128_t abs_b = (b ^ sb) - sb;
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if (abs_a < 2 || abs_b < 2)
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return result;
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if (sa == sb) {
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if (abs_a > MAX / abs_b)
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*overflow = 1;
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} else {
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if (abs_a > MIN / -abs_b)
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*overflow = 1;
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}
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return result;
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}
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#endif
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