llvm dev - Jun 2011 - [LLVMdev] LLVM analysis of Linux programs

Hey all,

I'm trying to do computations on the LLVM bitcode representations of various
Linux programs, and I'm running into some troubles. I have the source code
for various programs (tcpdump, gzip, curl, etc) and I want to compile each
program down into a single LLVM bitcode file. I've tried a few different
methods so far. Originally, I attempted to use the Makefiles of the projects
with llvm-gcc as the compiler (make CC="llvm-gcc -emit-llvm"), then
manually
link all the resulting bitcode files into a single one. This works on a few
examples, but not all of them. Next, I was pointed to Ben Hardekopf's work
on pointer analysis; it turns out he has a nifty perl script for doing
exactly the sort of thing I'm trying to do. Unfortunately, that script
doesn't seem to work on all programs either. It worked quite well on some of
my examples, but not at all on others.

So basically, I'm wondering if you all have any advice on how to go about
doing this. Is there some universal method of compiling entire source
packages into a single LLVM bitcode file, or possibly some mix of
tools/techniques that will work for the majority of programs? Or is my best
bet just to hack together the sort of things I've already been trying?

Thanks,
Ben
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On 11-06-16 4:20 PM, Ben Farley wrote:
> Hey all,
>
> I'm trying to do computations on the LLVM bitcode representations of
> various Linux programs, and I'm running into some troubles. I have the
> source code for various programs (tcpdump, gzip, curl, etc) and I want
> to compile each program down into a single LLVM bitcode file. I've
tried
> a few different methods so far. Originally, I attempted to use the
> Makefiles of the projects with llvm-gcc as the compiler (make
> CC="llvm-gcc -emit-llvm"), then manually link all the resulting
bitcode
> files into a single one. This works on a few examples, but not all of
> them. Next, I was pointed to Ben Hardekopf's work on pointer analysis;
> it turns out he has a nifty perl script for doing exactly the sort of
> thing I'm trying to do. Unfortunately, that script doesn't seem to
work
> on all programs either. It worked quite well on some of my examples, but
> not at all on others.
>
> So basically, I'm wondering if you all have any advice on how to go
> about doing this. Is there some universal method of compiling entire
> source packages into a single LLVM bitcode file, or possibly some mix of
> tools/techniques that will work for the majority of programs? Or is my
> best bet just to hack together the sort of things I've already been
trying?

What I would suggest is first setting up a regular LTO build with gold:
http://llvm.org/docs/GoldPlugin.html

Once you have that working, you can manually get the bitcode for the 
program you want by passing -plugin-arg=also-emit-llvm to the linker. 
Something like

$ rm bzip2
$ make bzip2
<will print the like used for linking>
$ <link line> -Wl,-plugin-arg=also-emit-llvm
> Thanks,
> Ben
Cheers,
Rafael