[LLVMdev] LLVM IR and CFG

[Rajendra]

Hi,

I want to know few things:

1) is LLVM IR (obtained from -emit-llvm option) an in-memory CFG?

Say, I have hello.c and I generate bit-code using:
clang -O3 -emit-llvm hello.c -c -o hello.bc

Next, I redirect this bit code to opt:
opt -load ../../Release+Asserts/lib/Hello.so -hello  < hello.bc > 
/dev/null

I have attached a example.tar.gz with one simple iterator.cpp and 
output from opt command and clang analyzer-checker.
Are these two - LLVM IR and CFG from clang analyzer-checker equivalent?

2) how to get/print original program back from this LLVM IR?

3) what about `clang -emit-llvm hello.c -c -o hello.bc'
- without using -O3 optimization flag, is this LLVM IR an in-memory 
CFG?

These queries may be trivial but I need this info to proceed further.


Thank you.

Rajendra

http://www.cse.iitb.ac.in/~rks

-------- Original Message --------
Subject: LLVMdev Digest, Vol 99, Issue 65
Date: 28-09-2012 10:26 PM
 From: llvmdev-request at cs.uiuc.edu
To: llvmdev at cs.uiuc.edu
Reply-To: llvmdev at cs.uiuc.edu

Message: 8
Date: Fri, 28 Sep 2012 17:45:23 +0200
 From: Duncan Sands <baldrick at free.fr>
To: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] [LLVM-Clang CFG] - generating CFG of a C
program and llvm iterators

Hi Rajendra, you want to get hold of the LLVM IR produced by clang (use 
the
-flto option to have clang produce LLVM IR), and pipe it to the "opt" 
command
line tool, into which you will have loaded your logic as a plugin pass. 
So I
suggest you read about writing plugins for opt.

Ciao, Duncan.

> Hi,
>
> I want to generate Control Flow Graph (in memory CFG object) of any
> given C program and then iterate over this CFG (all function, basic
> blocks and instructions) using llvm iterators.
>
> I can see text output of CFG on screen, using following command:
> `clang -cc1 -Idummyh -analyze -analyzer-checker=debug.DumpCFG 
> hello/hello.c'
> where dummyh has en empty stdio.h to remove this error:
> `fatal error: 'stdio.h' file not found'
>
> I see CFG.h and CFG.cpp that clang uses and have seen some docs on
> ModulePass, FunctionPass, BasicBlockPass, etc. But I have not figured
> out how to put together things to generate CFG and then write 
> iterators.
>
> All help is much appreciated.
>
> Thank you.
>
> Rajendra
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