1/* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------===
2 *
3 *                     The LLVM Compiler Infrastructure
4 *
5 * This file is distributed under the University of Illinois Open Source
6 * License. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 *
10 * This file implements __mulvti3 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15#if __x86_64
16
17#include "int_lib.h"
18#include <stdlib.h>
19
20/* Returns: a * b */
21
22/* Effects: aborts if a * b overflows */
23
24ti_int
25__mulvti3(ti_int a, ti_int b)
26{
27    const int N = (int)(sizeof(ti_int) * CHAR_BIT);
28    const ti_int MIN = (ti_int)1 << (N-1);
29    const ti_int MAX = ~MIN;
30    if (a == MIN)
31    {
32        if (b == 0 || b == 1)
33            return a * b;
34        abort();
35    }
36    if (b == MIN)
37    {
38        if (a == 0 || a == 1)
39            return a * b;
40        abort();
41    }
42    ti_int sa = a >> (N - 1);
43    ti_int abs_a = (a ^ sa) - sa;
44    ti_int sb = b >> (N - 1);
45    ti_int abs_b = (b ^ sb) - sb;
46    if (abs_a < 2 || abs_b < 2)
47        return a * b;
48    if (sa == sb)
49    {
50        if (abs_a > MAX / abs_b)
51            abort();
52    }
53    else
54    {
55        if (abs_a > MIN / -abs_b)
56            abort();
57    }
58    return a * b;
59}
60
61#endif
62