compiler-rt/lib/builtins/ffsti2.c

   1 //===-- ffsti2.c - Implement __ffsti2 -------------------------------------===//
   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 __ffsti2 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 #ifdef CRT_HAS_128BIT
  16
  17 // Returns: the index of the least significant 1-bit in a, or
  18 // the value zero if a is zero. The least significant bit is index one.
  19
  20 COMPILER_RT_ABI int __ffsti2(ti_int a) {
  21   twords x;
  22   x.all = a;
  23   if (x.s.low == 0) {
  24     if (x.s.high == 0)
  25       return 0;
  26     return __builtin_ctzll(x.s.high) + (1 + sizeof(di_int) * CHAR_BIT);
  27   }
  28   return __builtin_ctzll(x.s.low) + 1;
  29 }
  30
  31 #endif // CRT_HAS_128BIT