Insert Self Written Function Call from a FunctionPass?

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);
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”);

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

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);
}//end of if

return true;
virtual bool runOnBasicBlock(Function::iterator &BB)
for(BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI)
LoadInst CI = dyn_cast(BI);
/load count/
load_count = new LoadInst(count, “”, false);
/call print(count)/
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;

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

check = M->getFunction(*name);
if (!check) {
  check = Function::Create(
  /*Name=*/*name, M); // (external, no body)
// The following two lines are not necessary
AttrListPtr check_PAL;

Where M is a Module where this function was declared