I went searching through perl's pre and post preprocessor headers. I found some interesting things which prove that automatic IPO, on Perl, in C with any compiler is simply impossible.

But LLVM isn't a C compiler. It can compile C (amongst many other languages), but it doesn't (have to) follow C conventions.

LLVM is a far more an assembler targeting a user definable virtual processor. As an illustration of the sorts of things it can and does do, can you think of any other compiler technology that will generate 832-bit integers as a part of its optimisation pass?

You have to stop thinking of LLVM as a C compiler before can even begin to appreciate what it is potentially capable of. It is weird, and to my knowledge unique.

In a world where everything -- processors, memory, disk, networking et al. -- are being virtualised; why not virtualise the compiler, have it target a (user configurable) virtual processor, and produce not just platform independence, but processor architecture independence, and source language independence?

Can it really tackle a hoarey ol' dynamic language and apply those principles to it successfully? The simple answer is: I do not know. But neither does anyone else!

Stop nay-saying based upon your knowledge of what C compilers do, and follow the matra: (Let someone else) Try it!

I first installed LLVM here (going by the date on the subdirectory) on the 6th May 2010:

C:\test>dir /t:c .| find "llvm"
06/05/2010  20:35    <DIR>          llvm
06/05/2010  20:55    <DIR>          llvm-2.7
[download]

I've been playing with it and reading about it on and off ever since, I still keep learning new things about it all the time. It is unlike anything I've come across before, and defies my attempts at description. Virtual compiler, virtual interpreter, virtual assembler. Take your pick; or all 3.

Give it a try, (or at least a read) before you summarily dismiss it it out of hand.