llvm dev - May 2004 - [LLVMdev] Question about insert function or instruction.

Hi llvmer,

I am trying to learn how to use llvm. My question is
described as the following,
there has already a testcase code, and I get bytecode
by using llvmgcc. What I want to do is to insert a
call funcation into each basic block, which is for
statistic some information. 
1) I implement call function in another c/cpp file and
can I insert the external call function to existed
bytecode ? if it is valid. Can you give me a simple
example to show how to do it or just give me a url
which can show how to do it? 

2) If I'd like to insert the function in the same
bytecode, how to do it?

3) for opt commamnd, there have -trace -tracem options
,how can I see the detailed direction to use it.

I went through a LowerInvoke.cpp and EdgeCode.cpp file
which have examples to do what I want. Although I can
learn the main flow how to insert a call funcation or
instruction, but I still cannot implement it. Shame.
Another thing is that I am not sure the method I used
is correct or not? Can you give me some suggestion?


Thanks in advance for any response.

--fengy--

The following code is what I do
#include "llvm/Pass.h"
#include "llvm/Function.h"
#include "llvm/BasicBlock.h"
#include "llvm/Instruction.h"
#include "llvm/iOther.h"


namespace llvm {

 
  struct cntPass : public FunctionPass{
    virtual bool runOnFunction(Function &F){
      std::cerr <<"funtion name : "<<
F.getName()<<"\n";
      for(Function::iterator BB = F.begin(),E=F.end();
BB != E;++BB){
	std::cerr<< "BB name :
"<<BB->getName()<<"\n";
      // here, the problem is how can I get external
function pointer.
      //Instruction *callInst = new
CallInst(pCallfunction, "","");
      //BB->getInstList().push_back(callInst);
      //BB->getInstList().insert(callInst);
      }

      return false;
    }
    // can I  insert print() function?
    void print(){
      printf("Insert test\n");
    }
  };
  RegisterOpt<cntPass> X("cntPass", "insert printf
function");
}






	
		
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> What I want to do is to insert a call funcation into each basic
> block, which is for statistic some information.
I recommend that you look at the various pieces of code under
llvm/lib/Transforms/Instrumentation, e.g. BlockProfiling.cpp and
TraceBasicBlocks.cpp. They do essentially the same thing as you are
trying to do.
> 1) I implement call function in another c/cpp file and
> can I insert the external call function to existed
> bytecode ? if it is valid. Can you give me a simple
> example to show how to do it or just give me a url
> which can show how to do it? 
Yes; in the case of BlockProfiling, it calls into the library defined
in llvm/runtime/libprofile, which is linked against the resulting LLVM
binary.
> 2) If I'd like to insert the function in the same
> bytecode, how to do it?
In the above example, you would generate a bytecode version of
libprofile using the standard Makefile, then link it with the bytecode
version of your program using gccld or llvm-link.
> 3) for opt commamnd, there have -trace -tracem options
> ,how can I see the detailed direction to use it.
Short answer:

1. Compile the program in question to bytecode using llvmgcc.
Assume the result is 

2. Run the bytecode of the program through opt -tracem, and then
generate C code for the result.
 % opt -tracem bytecode.llvm.bc | llc -f -march=c -o bytecode.tracem.cbe.c

3. Compile the C code with tracing instrumentation using gcc.
 % gcc -o bytecode.tracem.cbe bytecode.tracem.cbe.c
You may have to link it with the libtrace library provided in
llvm/runtime/libtrace, in addition to any other libraries that
the program needs.
>       // here, the problem is how can I get external
> function pointer.
Look at the 'getOrInsertFunction' method of class llvm::Module.
>       //Instruction *callInst = new
> CallInst(pCallfunction, "","");
>       //BB->getInstList().push_back(callInst);
This is basically OK.
>       //BB->getInstList().insert(callInst);
This second insert is not necessary.

-Brian Gaeke

-- 
gaeke at uiuc.edu

> 1. Compile the program in question to bytecode using llvmgcc.
> Assume the result is 
I meant to say "Assume the result is in the bytecode file named
bytecode.llvm.bc".
> 2. Run the bytecode of the program through opt -tracem, and then
> generate C code for the result.
>  % opt -tracem bytecode.llvm.bc | llc -f -march=c -o bytecode.tracem.cbe.c
-Brian

-- 
gaeke at uiuc.edu