compiler-rt/lib/builtins/lshrti3.c

   1 //===-- lshrti3.c - Implement __lshrti3 -----------------------------------===//
   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 __lshrti3 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 #ifdef CRT_HAS_128BIT
  16
  17 // Returns: logical a >> b
  18
  19 // Precondition:  0 <= b < bits_in_tword
  20
  21 COMPILER_RT_ABI ti_int __lshrti3(ti_int a, int b) {
  22   const int bits_in_dword = (int)(sizeof(di_int) * CHAR_BIT);
  23   utwords input;
  24   utwords result;
  25   input.all = a;
  26   if (b & bits_in_dword) /* bits_in_dword <= b < bits_in_tword */ {
  27     result.s.high = 0;
  28     result.s.low = input.s.high >> (b - bits_in_dword);
  29   } else /* 0 <= b < bits_in_dword */ {
  30     if (b == 0)
  31       return a;
  32     result.s.high = input.s.high >> b;
  33     result.s.low = (input.s.high << (bits_in_dword - b)) | (input.s.low >> b);
  34   }
  35   return result.all;
  36 }
  37
  38 #endif // CRT_HAS_128BIT