Konstantin Tokarev
2012-Aug-01 10:21 UTC
[LLVMdev] Reading the AST from the bitcode generated by clang
> Hi all, > After reading the documentation on clang I still have the following > question: > How do I read the bitcode generated by clang from a C++ file? I need to > have all the AST information in memory.AST has nothing to do with LLVM bitcode. -- Regards, Konstantin
What is the best level to use for backend development? We do not need to
generate machine code, but rather an intermediate representation that will
give us the control flow graph.
Is this the llvm IR?
If so, how do I read into memory a file that was generated by clang++
-emit-llvm <source file>.
Thanks,
Sitvanit
Sitvanit Ruah
Formal Verification Group
IBM Haifa Research Laboratory
Tel: 972-4-828-1249
From: Konstantin Tokarev <annulen at yandex.ru>
To: Sitvanit Ruah/Haifa/IBM at IBMIL,
Cc: llvmdev at cs.uiuc.edu
Date: 01/08/2012 01:22 PM
Subject: Re:[LLVMdev] Reading the AST from the bitcode generated by
clang
> Hi all,
> After reading the documentation on clang I still have the following
> question:
> How do I read the bitcode generated by clang from a C++ file? I need to
> have all the AST information in memory.
AST has nothing to do with LLVM bitcode.
--
Regards,
Konstantin
Hi Sitvanit, You can create your own llvm pass as a shared library and use opt to run it. Take a look at the doc here http://llvm.org/docs/WritingAnLLVMPass.html. Ivan On 02/08/2012 09:41, Sitvanit Ruah wrote:> What is the best level to use for backend development? We do not need to > generate machine code, but rather an intermediate representation that will > give us the control flow graph. > Is this the llvm IR? > If so, how do I read into memory a file that was generated by clang++ > -emit-llvm<source file>. > > Thanks, > Sitvanit > > Sitvanit Ruah > Formal Verification Group > IBM Haifa Research Laboratory > Tel: 972-4-828-1249 > > > > > From: Konstantin Tokarev<annulen at yandex.ru> > To: Sitvanit Ruah/Haifa/IBM at IBMIL, > Cc: llvmdev at cs.uiuc.edu > Date: 01/08/2012 01:22 PM > Subject: Re:[LLVMdev] Reading the AST from the bitcode generated by > clang > > > > > >> Hi all, >> After reading the documentation on clang I still have the following >> question: >> How do I read the bitcode generated by clang from a C++ file? I need to >> have all the AST information in memory. > AST has nothing to do with LLVM bitcode. > > -- > Regards, > Konstantin > > > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
Hi Sitvanit, I assume you want to do some sort of formal verification and/or model checking of C++ programs. I've some experience on the subject, so let me give you some pointers. Some time ago I also asked here on the mailing list for opinions about where to do these kind of analyses: http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-May/005032.html Daniel Dunbar also provided some great comments: http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-May/005048.html To summarize, I believe the right way to go is to directly convert LLVM IR to your intermediate representation. The main advantages of using the LLVM IR are: - You can use LLVM's alias analysis to cheaply discard the simple aliasing queries - You can use LLVM to optimize the code (greatly reduces the verification time) - It supports multiple files (it's not something that is easy to do with clang ASTs directly) - LLVM IR is pretty low level, so all the complex C++ constructs are already desugared. For some analyses this may be a con, but for us it's great. I would suggest you to implement a ModulePass, which allows you to iterate over all global symbols (i.e., global variables and functions). You can then have an instruction visitor that encodes instructions to your intermediate representation. Nuno P.S.: BTW, there's a BMC tool (named LLBMC) implemented on top of LLVM. Our model checker is not (yet) based on LLVM because of historical reasons. ----- Original Message ----- From: "Sitvanit Ruah" <RUAH at il.ibm.com> To: "Konstantin Tokarev" <annulen at yandex.ru> Cc: <llvmdev at cs.uiuc.edu> Sent: Thursday, August 02, 2012 8:41 AM Subject: Re: [LLVMdev] Reading the output of clang> What is the best level to use for backend development? We do not need to > generate machine code, but rather an intermediate representation that will > give us the control flow graph. > Is this the llvm IR? > If so, how do I read into memory a file that was generated by clang++ > -emit-llvm <source file>. > > Thanks, > Sitvanit > > Sitvanit Ruah > Formal Verification Group > IBM Haifa Research Laboratory > Tel: 972-4-828-1249 > > > > From: Konstantin Tokarev <annulen at yandex.ru> > To: Sitvanit Ruah/Haifa/IBM at IBMIL, > Cc: llvmdev at cs.uiuc.edu > Date: 01/08/2012 01:22 PM > Subject: Re:[LLVMdev] Reading the AST from the bitcode generated by > clang > > > >> Hi all, >> After reading the documentation on clang I still have the following >> question: >> How do I read the bitcode generated by clang from a C++ file? I need to >> have all the AST information in memory. > > AST has nothing to do with LLVM bitcode. > > -- > Regards, > Konstantin