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