Platform Preprocessor Definitions

[John E]

Using VS2005 I'm building a source library that was originally written to be compiled using gcc. A couple of modules have code that looks like this:-

#if defined(__i386__) || defined(__x86_64__)
    // Do something
#elif defined(__powerpc__)
    // Do something else
#elif defined(__alpha__)
    // Do something else
#elif defined(__mips__)
    // etc, etc
#endif

For most of the above I wouldn't expect them to be recognised by VC++ because it can't cross-compile for powerpc, mips alpha or whatever. However, VC++ doesn't even recognise __i386__ or __x86_64__

Are there any equivalent identifiers that VC++ will recognise?