PVS-Studio warning V593 for Opus

opus_int silk_Encode(....)
{
  ....
  if( ( ret = check_control_input( encControl ) != 0 ) ) {
    silk_assert( 0 );
    RESTORE_STACK;
    return ret;
  }
  ....
}

This suspicious code was found in Opus project by PVS-Studio static code analyzer.
Warning message is:
V593 Consider reviewing the expression of the 'A = B != C' kind. The expression is calculated as following: 'A = (B != C)'. enc_api.c 168

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