llvm-project/compiler-rt/lib/builtins/ctzti2.c

//===-- ctzti2.c - Implement __ctzti2 -------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements __ctzti2 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//

#include "int_lib.h"

#ifdef CRT_HAS_128BIT

// Returns: the number of trailing 0-bits

// Precondition: a != 0

COMPILER_RT_ABI int __ctzti2(ti_int a) {
  twords x;
  x.all = a;
  const di_int f = -(x.s.low == 0);
  return __builtin_ctzll((x.s.high & f) | (x.s.low & ~f)) +
         ((si_int)f & ((si_int)(sizeof(di_int) * CHAR_BIT)));
}

#endif // CRT_HAS_128BIT