muldi3.c revision 222656 
1/* ===-- muldi3.c - Implement __muldi3 -------------------------------------===
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 __muldi3 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14#include "abi.h"
15
16#include "int_lib.h"
17
18/* Returns: a * b */
19
20static
21di_int
22__muldsi3(su_int a, su_int b)
23{
24    dwords r;
25    const int bits_in_word_2 = (int)(sizeof(si_int) * CHAR_BIT) / 2;
26    const su_int lower_mask = (su_int)~0 >> bits_in_word_2;
27    r.s.low = (a & lower_mask) * (b & lower_mask);
28    su_int t = r.s.low >> bits_in_word_2;
29    r.s.low &= lower_mask;
30    t += (a >> bits_in_word_2) * (b & lower_mask);
31    r.s.low += (t & lower_mask) << bits_in_word_2;
32    r.s.high = t >> bits_in_word_2;
33    t = r.s.low >> bits_in_word_2;
34    r.s.low &= lower_mask;
35    t += (b >> bits_in_word_2) * (a & lower_mask);
36    r.s.low += (t & lower_mask) << bits_in_word_2;
37    r.s.high += t >> bits_in_word_2;
38    r.s.high += (a >> bits_in_word_2) * (b >> bits_in_word_2);
39    return r.all;
40}
41
42/* Returns: a * b */
43
44ARM_EABI_FNALIAS(lmul, muldi3);
45
46COMPILER_RT_ABI di_int
47__muldi3(di_int a, di_int b)
48{
49    dwords x;
50    x.all = a;
51    dwords y;
52    y.all = b;
53    dwords r;
54    r.all = __muldsi3(x.s.low, y.s.low);
55    r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
56    return r.all;
57}
58