compiler-rt/lib/builtins/ashrti3.c

   1 //===-- ashrti3.c - Implement __ashrti3 -----------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements __ashrti3 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 #ifdef CRT_HAS_128BIT
  16
  17 // Returns: arithmetic a >> b
  18
  19 // Precondition:  0 <= b < bits_in_tword
  20
  21 COMPILER_RT_ABI ti_int __ashrti3(ti_int a, int b) {
  22   const int bits_in_dword = (int)(sizeof(di_int) * CHAR_BIT);
  23   twords input;
  24   twords result;
  25   input.all = a;
  26   if (b & bits_in_dword) /* bits_in_dword <= b < bits_in_tword */ {
  27     // result.s.high = input.s.high < 0 ? -1 : 0
  28     result.s.high = input.s.high >> (bits_in_dword - 1);
  29     result.s.low = input.s.high >> (b - bits_in_dword);
  30   } else /* 0 <= b < bits_in_dword */ {
  31     if (b == 0)
  32       return a;
  33     result.s.high = input.s.high >> b;
  34     result.s.low =
  35         ((du_int)input.s.high << (bits_in_dword - b)) | (input.s.low >> b);
  36   }
  37   return result.all;
  38 }
  39
  40 #endif // CRT_HAS_128BIT