[LLVMdev] Insert Self Written Function Call from a FunctionPass?

[Arnamoy Bhattacharyya]

Hello all;

So my goal is to insert some (self-written) function calls in the LLVM IR. I can achieve it with a ModulePass and using the getOrInsertFunction() call.  For a ModulePass I follow the steps-

1.  Compile the code (in which call instructions are to be inserted) to LLVM IR

2.  Compile the file (which contains the *called* external function ) to LLVM IR

3.  Link them together and run the transformation pass to insert function calls.

But I have to use LoopInfo pass in my transformation pass as well and for that I have to have a FunctionPass (LoopInfo fails in a ModulePass).  So I am trying to follow the above steps for a FunctionPass class (with relevant modifications, as I can't use getOrInsertFunction() now (or can I)). And when I run my optimization pass now (step 3) to instrument, I am getting - 

Referencing function in another module!

  %1 = call i32 @print(i32 %0)

Broken module found, compilation aborted!

My Code:

#include "llvm/Pass.h"

#include "llvm/Module.h"

#include "llvm/Function.h"

#include "llvm/Support/raw_ostream.h"

#include "llvm/Type.h"

#include "llvm/Instructions.h"

#include "llvm/Instruction.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/IRBuilder.h"

using namespace llvm;

Module * M;

LLVMContext Context;

Twine * name = new Twine("print");

FunctionType *STy=FunctionType::get(Type::getInt32Ty(Context),Type::getInt32Ty(Context), false);

Function *check = Function::Create(STy, Function::ExternalLinkage, *name ,M);

AllocaInst* count;

namespace{

    struct bishe_insert : public FunctionPass{

        static char ID;   

        bishe_insert() : FunctionPass(ID) {}

        virtual bool runOnFunction(Function &func)

        {

count = new AllocaInst(IntegerType::getInt32Ty(Context), 0, "count");

  count->setAlignment(4);

       for(Function::iterator F = func.begin(), E = func.end(); F!= E; ++F)

        {

   if(F == func.begin())

   {

bishe_insert::insertOnFirstBlock(F);

   }

                    bishe_insert::runOnBasicBlock(F);

                }

            return false;

        }

/*insert alloca instruction in the start of the first basic block*/

        virtual bool insertOnFirstBlock(Function::iterator &BB)

        {

            for(BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI)           

            {

                    if(BI == BB->begin())

                    {

BB->getInstList().insert((Instruction*)BI, count);

break;

   }//end of if

                   

            }

            return true;

        }

        virtual bool runOnBasicBlock(Function::iterator &BB)

        {

            for(BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI)           

            {

                    if(isa<LoadInst>(&(*BI)))

                    {

LoadInst *CI = dyn_cast<LoadInst>(BI);

/*load count*/

LoadInst* load_count = new LoadInst(count, "", false);

load_count->setAlignment(4);

/*call print(count)*/

CallInst* call_print = CallInst::Create(check, load_count, "");

/*insert the instructions*/

BB->getInstList().insert((Instruction*)CI, load_count);

BB->getInstList().insert((Instruction*)CI, call_print);

    }//end of if

                   

            }

            return true;

        }

    };

}

char bishe_insert::ID = 0;

static RegisterPass<bishe_insert> X("bishe_insert", "insert print calls");

Thanks a lot;

--
Arnamoy Bhattacharyya
Athabasca Hall 143
Department of Computing Science - University of Alberta
Edmonton, Alberta, Canada, T6G 2E8
587-710-7073

[Iaroslav Markov]

I think, your check should get it's value like this:

check = M->getFunction(*name);
if (!check) {
check = Function::Create(
/*Type=*/FuncTy,
/*Linkage=*/GlobalValue::ExternalLinkage,
/*Name=*/*name, M); // (external, no body)
check->setCallingConv(CallingConv::C);
}
// The following two lines are not necessary
AttrListPtr check_PAL;
check->setAttributes(check_PAL);

Where M is a Module where this function was declared

--
Yaroslav Markov
PhD student in Computer Science
Stony Brook University
________________________________________
From: llvmdev...@cs.uiuc.edu [llvmdev...@cs.uiuc.edu] on behalf of Arnamoy Bhattacharyya [arn...@ualberta.ca]
Sent: Friday, August 24, 2012 8:44 PM
To: llv...@cs.uiuc.edu
Subject: [LLVMdev] Insert Self Written Function Call from a FunctionPass?

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