llvm dev - Feb 2010 - [LLVMdev] Programmatic compilation of C++ file into bitcode

I'm building a static analysis tool on top of LLVM. It needs to take  
in a C++ source file and have LLVM translate it into bitcode. In other  
words, it basically needs to do this:

   llvmc hello.cpp -emit-llvm -O0 -S -g

Except that instead of writing the bitcode to a file, it needs to load  
it into memory (presumably as an instance of Module) for further  
processing and analysis. So my goal is to do essentially what llvmc  
does, but programmatically by invoking the LLVM API directly.

I thought I could use lib/CompilerDriver/Main.cpp as a guide, but  
after studying the code and associated docs, I'm stumped. Much of the  
logic is woven through TableGen'd drivers, so I can't even figure out  
how the command line options are fed into the LLVM API.

Any suggestions? Thanks,

Trevor

Hi Trevor,
> I'm building a static analysis tool on top of LLVM. It needs to take
> in a C++ source file and have LLVM translate it into bitcode. In other
> words, it basically needs to do this:
>
>     llvmc hello.cpp -emit-llvm -O0 -S -g
behind the scenes it's actually llvm-gcc that is generating the
bitcode.
> Except that instead of writing the bitcode to a file, it needs to load
> it into memory (presumably as an instance of Module) for further
> processing and analysis.
You could just pipe it to your program:

llvm-gcc hello.cpp -emit-llvm -c -o - | analysis_program

So my goal is to do essentially what llvmc
> does, but programmatically by invoking the LLVM API directly.
You can add your static analysis to llvm-gcc as an LLVM pass.
If you write it as an LLVM pass then you can also use it from
"opt", which would be convenient.
> I thought I could use lib/CompilerDriver/Main.cpp as a guide, but
> after studying the code and associated docs, I'm stumped. Much of the
> logic is woven through TableGen'd drivers, so I can't even figure
out
> how the command line options are fed into the LLVM API.
>
> Any suggestions? Thanks,
I don't think you should bother with llvmc: it's a compiler driver,
that launches the real compiler.

Did you take a look at the clang static analyser?

Ciao,

Duncan.

On Feb 25, 2010, at 1:04 AM, Duncan Sands wrote:
> You can add your static analysis to llvm-gcc as an LLVM pass.
> If you write it as an LLVM pass then you can also use it from
> "opt", which would be convenient.
Thanks, that sounds like a good approach. It appears I can get a  
Module instance simply by inheriting from ModulePass.

There's one problem, however. I will at some point want to integrate  
this analysis tool with other tools. For example, an Eclipse plugin  
might run the analysis tool and then display the analysis results in  
an Eclipse window. I suppose the plugin could execute "opt" as a  
subprocess and then parse the output, but that seems brittle. I'd  
prefer to define an API in my analysis tool that other tools could  
then call. That's why I was trying to build upon projects/sample/*  
instead of lib/Transforms/Hello/*.

Is there perhaps some structured mechanism for retrieving the output  
of an LLVM pass? That is, something better than just parsing the  
output of "opt"...

Thanks,

Trevor