BasicBlockExtractorFromIR.cpp

#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/IR/LLVMContext.h" // added to fix LLVMContext problem
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

// use of cl namespace (command line) for setting
// a variable we need
static cl::opt<std::string> FileName(cl::Positional, cl::desc("Bitcode file"), cl::Required);

int
main(int argc, char **argv)
{
    // Parse the command line
    cl::ParseCommandLineOptions(argc, argv, "LLVM Hello World\n");
    LLVMContext context;

    // obtain the file to a MemoryBuffer
    ErrorOr<std::unique_ptr<MemoryBuffer>> mb = MemoryBuffer::getFile(FileName);

    if (std::error_code ec = mb.getError())
    {
        errs() << ec.message();
        return -1;
    }

    // get the memory buffer and parse its bitcode (the compiled IR).
    ErrorOr<Module *> m = parseBitcodeFile(mb->get(), context);
    if (std::error_code ec = m.getError())
    {
        errs() << "Error reading bitcode: " << ec.message() << "\n";
        return -1;
    }

    // The module now contain all the functions
    // from the code, and from each function
    // we can extract name and basic blocks
    for (Module::const_iterator I = (*m)->getFunctionList().begin(),
         E = (*m)->getFunctionList().end(); I != E; ++I)
    {
        outs() << "Function: " << I->getName() << "(";
        for (Function::const_arg_iterator arg = I->getArgumentList().begin(),
                arg_end = I->getArgumentList().end(); arg != arg_end; ++arg)
        {
            arg->getType()->print(outs());
            outs() << " %" << arg->getName();
            if (arg->getNextNode() != arg_end)
                outs() << ",";
        }
        outs() << ")";

        if (!I->isDeclaration())
        // if it's an internal declaration LLVM
        // has analyzed how many basic blocks contain
        {
            outs() << " has " << I->size() << " basic blocks.\n";
        }
        // in other case is an external function
        else
        {
            outs() << " is used but it's external to this code.\n";
        }
    }

    return 0;
}