1 | /* ===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------=== |
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 __mulvsi3 for the compiler_rt library. |
11 | * |
12 | * ===----------------------------------------------------------------------=== |
13 | */ |
14 | |
15 | #include "int_lib.h" |
16 | |
17 | /* Returns: a * b */ |
18 | |
19 | /* Effects: aborts if a * b overflows */ |
20 | |
21 | COMPILER_RT_ABI si_int |
22 | __mulvsi3(si_int a, si_int b) |
23 | { |
24 | const int N = (int)(sizeof(si_int) * CHAR_BIT); |
25 | const si_int MIN = (si_int)1 << (N-1); |
26 | const si_int MAX = ~MIN; |
27 | if (a == MIN) |
28 | { |
29 | if (b == 0 || b == 1) |
30 | return a * b; |
31 | compilerrt_abort(); |
32 | } |
33 | if (b == MIN) |
34 | { |
35 | if (a == 0 || a == 1) |
36 | return a * b; |
37 | compilerrt_abort(); |
38 | } |
39 | si_int sa = a >> (N - 1); |
40 | si_int abs_a = (a ^ sa) - sa; |
41 | si_int sb = b >> (N - 1); |
42 | si_int abs_b = (b ^ sb) - sb; |
43 | if (abs_a < 2 || abs_b < 2) |
44 | return a * b; |
45 | if (sa == sb) |
46 | { |
47 | if (abs_a > MAX / abs_b) |
48 | compilerrt_abort(); |
49 | } |
50 | else |
51 | { |
52 | if (abs_a > MIN / -abs_b) |
53 | compilerrt_abort(); |
54 | } |
55 | return a * b; |
56 | } |
57 | |