lib/builtins/ashrti3.c

   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
  23 COMPILER_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 */