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1 /* ===-- multi3.c - Implement __multi3 -------------------------------------===
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 __multi3 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 static
22 ti_int
__mulddi3(du_int a,du_int b)23 __mulddi3(du_int a, du_int b)
24 {
25     twords r;
26     const int bits_in_dword_2 = (int)(sizeof(di_int) * CHAR_BIT) / 2;
27     const du_int lower_mask = (du_int)~0 >> bits_in_dword_2;
28     r.s.low = (a & lower_mask) * (b & lower_mask);
29     du_int t = r.s.low >> bits_in_dword_2;
30     r.s.low &= lower_mask;
31     t += (a >> bits_in_dword_2) * (b & lower_mask);
32     r.s.low += (t & lower_mask) << bits_in_dword_2;
33     r.s.high = t >> bits_in_dword_2;
34     t = r.s.low >> bits_in_dword_2;
35     r.s.low &= lower_mask;
36     t += (b >> bits_in_dword_2) * (a & lower_mask);
37     r.s.low += (t & lower_mask) << bits_in_dword_2;
38     r.s.high += t >> bits_in_dword_2;
39     r.s.high += (a >> bits_in_dword_2) * (b >> bits_in_dword_2);
40     return r.all;
41 }
42 
43 /* Returns: a * b */
44 
45 COMPILER_RT_ABI ti_int
__multi3(ti_int a,ti_int b)46 __multi3(ti_int a, ti_int b)
47 {
48     twords x;
49     x.all = a;
50     twords y;
51     y.all = b;
52     twords r;
53     r.all = __mulddi3(x.s.low, y.s.low);
54     r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
55     return r.all;
56 }
57 
58 #endif /* CRT_HAS_128BIT */
59