text: ////////////////////////////////////////////////////////////////////////////////
  ///
  /// Generic version of the x86 CPU extension detection routine.
  ///
  /// This file is for GNU & other non-Windows compilers, see 'cpu_detect_x86_win.cpp' 
  /// for the Microsoft compiler version.
  ///
  /// Author        : Copyright (c) Olli Parviainen
  /// Author e-mail : oparviai 'at' iki.fi
  /// SoundTouch WWW: http://www.surina.net/soundtouch
  ///
  ////////////////////////////////////////////////////////////////////////////////
  //
  // Last changed  : $Date$
  // File revision : $Revision: 4 $
  //
  // $Id$
  //
  ////////////////////////////////////////////////////////////////////////////////
  //
  // License :
  //
  //  SoundTouch audio processing library
  //  Copyright (c) Olli Parviainen
  //
  //  This library is free software; you can redistribute it and/or
  //  modify it under the terms of the GNU Lesser General Public
  //  License as published by the Free Software Foundation; either
  //  version 2.1 of the License, or (at your option) any later version.
  //
  //  This library is distributed in the hope that it will be useful,
  //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  //  Lesser General Public License for more details.
  //
  //  You should have received a copy of the GNU Lesser General Public
  //  License along with this library; if not, write to the Free Software
  //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //
  ////////////////////////////////////////////////////////////////////////////////
  
  #include "cpu_detect.h"
  #include "STTypes.h"
  
  #if defined(SOUNDTOUCH_ALLOW_X86_OPTIMIZATIONS)
  
      #if defined(__GNUC__) && defined(__i386__)
          // gcc
          #include "cpuid.h"
      #elif defined(_M_IX86)
          // windows non-gcc
          #include <intrin.h>
          #define bit_MMX     (1 << 23)
          #define bit_SSE     (1 << 25)
          #define bit_SSE2    (1 << 26)
      #endif
  
  #endif
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // processor instructions extension detection routines
  //
  //////////////////////////////////////////////////////////////////////////////
  
  // Flag variable indicating whick ISA extensions are disabled (for debugging)
  static uint _dwDisabledISA = 0x00;      // 0xffffffff; //<- use this to disable all extensions
  
  // Disables given set of instruction extensions. See SUPPORT_... defines.
  void disableExtensions(uint dwDisableMask)
  {
      _dwDisabledISA = dwDisableMask;
  }
  
  
  
  /// Checks which instruction set extensions are supported by the CPU.
  uint detectCPUextensions(void)
  {
  /// If building for a 64bit system (no Itanium) and the user wants optimizations.
  /// Return the OR of SUPPORT_{MMX,SSE,SSE2}. 11001 or 0x19.
  /// Keep the _dwDisabledISA test (2 more operations, could be eliminated).
  #if ((defined(__GNUC__) && defined(__x86_64__)) \
      || defined(_M_X64))  \
      && defined(SOUNDTOUCH_ALLOW_X86_OPTIMIZATIONS)
      return 0x19 & ~_dwDisabledISA;
  
  /// If building for a 32bit system and the user wants optimizations.
  /// Keep the _dwDisabledISA test (2 more operations, could be eliminated).
  #elif ((defined(__GNUC__) && defined(__i386__)) \
      || defined(_M_IX86))  \
      && defined(SOUNDTOUCH_ALLOW_X86_OPTIMIZATIONS)
  
      if (_dwDisabledISA == 0xffffffff) return 0;
   
      uint res = 0;
   
  #if defined(__GNUC__)
      // GCC version of cpuid. Requires GCC 4.3.0 or later for __cpuid intrinsic support.
      uint eax, ebx, ecx, edx;  // unsigned int is the standard type. uint is defined by the compiler and not guaranteed to be portable.
  
      // Check if no cpuid support.
      if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx)) return 0; // always disable extensions.
  
      if (edx & bit_MMX)  res = res | SUPPORT_MMX;
      if (edx & bit_SSE)  res = res | SUPPORT_SSE;
      if (edx & bit_SSE2) res = res | SUPPORT_SSE2;
  
  #else
      // Window / VS version of cpuid. Notice that Visual Studio 2005 or later required 
      // for __cpuid intrinsic support.
      int reg[4] = {-1};
  
      // Check if no cpuid support.
      __cpuid(reg,0);
      if ((unsigned int)reg[0] == 0) return 0; // always disable extensions.
  
      __cpuid(reg,1);
      if ((unsigned int)reg[3] & bit_MMX)  res = res | SUPPORT_MMX;
      if ((unsigned int)reg[3] & bit_SSE)  res = res | SUPPORT_SSE;
      if ((unsigned int)reg[3] & bit_SSE2) res = res | SUPPORT_SSE2;
  
  #endif
  
      return res & ~_dwDisabledISA;
  
  #else
  
  /// One of these is true:
  /// 1) We don't want optimizations.
  /// 2) Using an unsupported compiler.
  /// 3) Running on a non-x86 platform.
      return 0;
  
  #endif
  }
  