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//===-- muloti4.c - 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 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
#ifdef CRT_HAS_128BIT
// Returns: a * b
// Effects: sets *overflow to 1 if a * b overflows
COMPILER_RT_ABI ti_int __muloti4(ti_int a, ti_int b, int *overflow) {
const int N = (int)(sizeof(ti_int) * CHAR_BIT);
const ti_int MIN = (ti_int)1 << (N - 1);
const ti_int MAX = ~MIN;
*overflow = 0;
ti_int 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;
}
ti_int sa = a >> (N - 1);
ti_int abs_a = (a ^ sa) - sa;
ti_int sb = b >> (N - 1);
ti_int 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 // CRT_HAS_128BIT
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