1/* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------===
2 *
3 *                     The LLVM Compiler Infrastructure
4 *
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 *
10 * This file implements __mulvti3 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15#include "int_lib.h"
16
17#ifdef CRT_HAS_128BIT
18
19/* Returns: a * b */
20
21/* Effects: aborts if a * b overflows */
22
23COMPILER_RT_ABI ti_int
24__mulvti3(ti_int a, ti_int b)
25{
26    const int N = (int)(sizeof(ti_int) * CHAR_BIT);
27    const ti_int MIN = (ti_int)1 << (N-1);
28    const ti_int MAX = ~MIN;
29    if (a == MIN)
30    {
31        if (b == 0 || b == 1)
32            return a * b;
33        compilerrt_abort();
34    }
35    if (b == MIN)
36    {
37        if (a == 0 || a == 1)
38            return a * b;
39        compilerrt_abort();
40    }
41    ti_int sa = a >> (N - 1);
42    ti_int abs_a = (a ^ sa) - sa;
43    ti_int sb = b >> (N - 1);
44    ti_int abs_b = (b ^ sb) - sb;
45    if (abs_a < 2 || abs_b < 2)
46        return a * b;
47    if (sa == sb)
48    {
49        if (abs_a > MAX / abs_b)
50            compilerrt_abort();
51    }
52    else
53    {
54        if (abs_a > MIN / -abs_b)
55            compilerrt_abort();
56    }
57    return a * b;
58}
59
60#endif /* CRT_HAS_128BIT */
61