[LLVMdev] Inserting a function call into bitcode

[Eli Friedman]

On Thu, Jun 3, 2010 at 9:43 PM, Nehal Gandhi <nbg2k7 at gmail.com> wrote:
> Hi All,
>
>
>
> I am trying to write code for simple instrumentation. What I want to do is
> to insert a call to an external function for result of each conditional
> branch instruction. This external function simply print true or false based
> on the result of condition. The modified code is then written into new file.
> However when I try to link that file with another bitcode file (containing
> external function), it results “llvm-link: error loading file 'newfile.bc'”
> error. This error is inconsistent. It appears for some programs and not for
> some other. If it links with other file, during execution it produces
> following error -  Assertion `Addr && "Code generation didn't add function
> to GlobalAddress table!"' failed
>
>
>
> Below is the code of my pass. It inherits ModulePass and does not have any
> other method except runOnModule. Am I missing something during call
> insertion or bitcode modification? I am using LLVM-2.6. The same code in
> LLVM-2.5 works correctly. (except Type::getInt32Ty, llvm-2.5 has
> Type::Int32Ty and no LLVMContext object)
>
>
>
> Thanks,
>
> Nehal
>
>
>
>     bool ConditionProfile::runOnModule(Module &M)
>
>     {
>
>         // Iterates through all functions of the module
>
>         for(Module::iterator mi = M.begin(), me = M.end(); mi!=me; mi++)
>
>         {
>
>             // Iterates through all basic blocks of the function
>
>             for(Function::iterator fi = mi->begin(), fe = mi->end(); fi!=fe;
> fi++)
>
>             {
>
>                     BasicBlock::iterator bi = fi->end();
>
>                     bi--;                 // Getting the terminator/last
> instruction of BasicBlock
>
>
>
>                     if(isa<BranchInst>(bi))
>
>                     {
>
>                         BranchInst *brInst = cast<BranchInst>(bi);
>
>
>
>                         // We are interested in conditional branch only
>
>                         if(brInst->isUnconditional()) continue;
>
>
>
>                         Value *condRes = brInst->getCondition();
>
>
> errs()<<"Type:"<<condRes->getType()->getDescription()<<"\n";
>
>
>
>                        // Looking for a function in Module Symbol
> table
>
>                         Constant *PrintFn =
> M.getOrInsertFunction("_Z12PrintCondResb", Type::getInt32Ty(context),
> condRes->getType(), (Type *)0);
>
>                         if(!PrintFn) {
>
>                             errs()<<"GetOrInsertFailed\n";
>
>                             continue;
>
>                         }
>
>
>
>                         std::vector<Value *> args(1);
>
>                             args[0] = condRes;
>
>
>
>                         // Creating a call instruction to above function.
>
>                         CallInst *callInst =
>
>                            CallInst::Create(PrintFn, args.begin(),
> args.end(), "", bi);
>
>
>
>                         callInst->setCallingConv(CallingConv::Fast);
>
>                     }
>
>             }
>
>         }
>
>
>
>        // Writing modified module to new file.
>
>         std::ostream *os = new std::ofstream("newfile.bc");
>
>         WriteBitcodeToFile(&M, *os);

Try putting "delete os" here?

-Eli

>         return true;
>
>     }
>
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