1 //===-- mulosi4.c - Implement __mulosi4 -----------------------------------===//
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
7 //===----------------------------------------------------------------------===//
9 // This file implements __mulosi4 for the compiler_rt library.
11 //===----------------------------------------------------------------------===//
17 // Effects: sets *overflow to 1 if a * b overflows
19 COMPILER_RT_ABI si_int __mulosi4(si_int a, si_int b, int *overflow) {
20 const int N = (int)(sizeof(si_int) * CHAR_BIT);
21 const si_int MIN = (si_int)1 << (N - 1);
22 const si_int MAX = ~MIN;
24 si_int result = a * b;
35 si_int sa = a >> (N - 1);
36 si_int abs_a = (a ^ sa) - sa;
37 si_int sb = b >> (N - 1);
38 si_int abs_b = (b ^ sb) - sb;
39 if (abs_a < 2 || abs_b < 2)
42 if (abs_a > MAX / abs_b)
45 if (abs_a > MIN / -abs_b)