compiler-rt/lib/builtins/ashrdi3.c

   1 //===-- ashrdi3.c - Implement __ashrdi3 -----------------------------------===//
   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 __ashrdi3 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 // Returns: arithmetic a >> b
  16
  17 // Precondition:  0 <= b < bits_in_dword
  18
  19 COMPILER_RT_ABI di_int __ashrdi3(di_int a, int b) {
  20   const int bits_in_word = (int)(sizeof(si_int) * CHAR_BIT);
  21   dwords input;
  22   dwords result;
  23   input.all = a;
  24   if (b & bits_in_word) /* bits_in_word <= b < bits_in_dword */ {
  25     // result.s.high = input.s.high < 0 ? -1 : 0
  26     result.s.high = input.s.high >> (bits_in_word - 1);
  27     result.s.low = input.s.high >> (b - bits_in_word);
  28   } else /* 0 <= b < bits_in_word */ {
  29     if (b == 0)
  30       return a;
  31     result.s.high = input.s.high >> b;
  32     result.s.low =
  33         ((su_int)input.s.high << (bits_in_word - b)) | (input.s.low >> b);
  34   }
  35   return result.all;
  36 }
  37
  38 #if defined(__ARM_EABI__)
  39 COMPILER_RT_ALIAS(__ashrdi3, __aeabi_lasr)
  40 #endif