compiler-rt/lib/builtins/ffsdi2.c

   1 //===-- ffsdi2.c - Implement __ffsdi2 -------------------------------------===//
   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 __ffsdi2 for the compiler_rt library.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "int_lib.h"
  14
  15 // Returns: the index of the least significant 1-bit in a, or
  16 // the value zero if a is zero. The least significant bit is index one.
  17
  18 COMPILER_RT_ABI int __ffsdi2(di_int a) {
  19   dwords x;
  20   x.all = a;
  21   if (x.s.low == 0) {
  22     if (x.s.high == 0)
  23       return 0;
  24     return ctzsi(x.s.high) + (1 + sizeof(si_int) * CHAR_BIT);
  25   }
  26   return ctzsi(x.s.low) + 1;
  27 }