ashrti3.c revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0 
1/* ===-- ashrti3.c - Implement __ashrti3 -----------------------------------===
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 __ashrti3 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15#include "int_lib.h"
16
17#ifdef CRT_HAS_128BIT
18
19/* Returns: arithmetic a >> b */
20
21/* Precondition:  0 <= b < bits_in_tword */
22
23COMPILER_RT_ABI ti_int
24__ashrti3(ti_int a, si_int b)
25{
26    const int bits_in_dword = (int)(sizeof(di_int) * CHAR_BIT);
27    twords input;
28    twords result;
29    input.all = a;
30    if (b & bits_in_dword)  /* bits_in_dword <= b < bits_in_tword */
31    {
32        /* result.s.high = input.s.high < 0 ? -1 : 0 */
33        result.s.high = input.s.high >> (bits_in_dword - 1);
34        result.s.low = input.s.high >> (b - bits_in_dword);
35    }
36    else  /* 0 <= b < bits_in_dword */
37    {
38        if (b == 0)
39            return a;
40        result.s.high  = input.s.high >> b;
41        result.s.low = (input.s.high << (bits_in_dword - b)) | (input.s.low >> b);
42    }
43    return result.all;
44}
45
46#endif /* CRT_HAS_128BIT */
47