Generate LLVM code

[Matt Giuca]

There is currently no way to compile Mars code (either to a native executable or any other program format); it can only be interpreted. The program marsc (Mars compiler) is currently fairly useless; it just generates debugging output.

The marsc program should be able to produce LLVM bitcode files which could be interpreted with 'lli' or compiled to native code using 'llc'. LLVM (http://llvm.org/) is a generic low-level compiler infrastructure toolkit which has powerful optimisations built-in, and can generate native code for many platforms.

In addition, the mars program should be able to compile programs using LLVM and run them with the JIT framework, rather than using the current interpreter. This would allow programs run with 'mars' to run at the full speed of a compiled program, and also allow the LLVM backend to be tested using the Mars test framework (which runs programs through 'mars').

[Matt Giuca (mgiuca)]

Fixed in trunk r1334.