[LLVMdev] Re: C to C++

[Chris Lattner]

On Mon, 28 Jun 2004, Surupa Biswas wrote:

> I am at the University of Maryland, College Park, working with Prof.
> Rajeev Barua. Someone just told me that LLVM includes a C++ to C
> source-to-source compiler. I was hoping you could tell me something about
> that - I am trying to run some C++ benchmarks on the Motorola Mcore
> simulator and my compiler only has a C front-end.

Yup, LLVM can do that and more.  Use commands like this:

#1. Compile your program as normal with llvmg++

$ llvmg++ x.cpp -o program

or:
 llvmg++ a.cpp -c
 llvmg++ b.cpp -c
 llvmg++ a.o b.o -o program

This will generate program and program.bc.  The .bc file is the LLVM
version of the program all linked together.

#2. Convert the LLVM code to C code, using the LLC tool with the C
backend:

$ llc -march=c program.bc -o program.c

#3. Then compile the c file:

$ cc x.c

Note that, by default, the C backend does not support exception handling.
If you want/need it for a certain program, you can enable it by passing
"-enable-correct-eh-support" to the llc program.  The resultant code will
use setjmp/longjmp to implement exception support that is correct but
relatively slow.

LLVM will eventually also have Java and other front-ends, which will allow
you to convert java code to C as well.

-Chris

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