Executing LLVM IR during runtime on Windows

Question

During some research across the internet and Stackoverflow the only example on how to execute IR code during runtime was this one on SO. I have now compiled llvm and clang with Visual Studio 2012 and I was able to compile some source files I want to use to for "scripting" extensions with clang File.cpp -S -emit-llvm -O3 such that the output was the usual IR code like

; ModuleID = '.\Test.cpp'
target datalayout = "/* ... */"
target triple = "i686-pc-win32"
define i32 @test() #0 {
  ret i32 43
}
attributes #0 = { nounwind /* ... */ }

The post I referred to is really old and I would like to know two things:

1. How does one initialize an engine and execute such code (using C++) during runtime with llvm 3.2? Are still the same calls used for it?
2. During compilation a huge amount of libs were created. How do I know which ones have to be linked?

---

My code which works and could need some optimization

#include <iostream>
#include <llvm/IR/LLVMContext.h>
#include <llvm/ADT/Triple.h>
#include <llvm/Bitcode/ReaderWriter.h>
#include <llvm/CodeGen/LinkAllCodegenComponents.h>
#include <llvm/ExecutionEngine/GenericValue.h>
#include <llvm/ExecutionEngine/Interpreter.h>
#include <llvm/ExecutionEngine/JIT.h>
#include <llvm/ExecutionEngine/JITEventListener.h>
#include <llvm/ExecutionEngine/JITMemoryManager.h>
#include <llvm/ExecutionEngine/MCJIT.h>
#include <llvm/ExecutionEngine/SectionMemoryManager.h>
#include <llvm/IR/Module.h>
#include <llvm/IR/Type.h>
#include <llvm/Support/CommandLine.h>
#include <llvm/Support/Debug.h>
#include <llvm/Support/DynamicLibrary.h>
#include <llvm/Support/Format.h>
#include <llvm/Support/IRReader.h>
#include <llvm/Support/ManagedStatic.h>
#include <llvm/Support/MathExtras.h>
#include <llvm/Support/Memory.h>
#include <llvm/Support/MemoryBuffer.h>
#include <llvm/Support/PluginLoader.h>
#include <llvm/Support/PrettyStackTrace.h>
#include <llvm/Support/Process.h>
#include <llvm/Support/Signals.h>
#include <llvm/Support/TargetSelect.h>
#include <llvm/Support/raw_ostream.h>

#pragma comment(lib, "LLVMMCJIT.lib")
#pragma comment(lib, "LLVMInterpreter.lib")
#pragma comment(lib, "LLVMBitReader.lib")
#pragma comment(lib, "LLVMAsmParser.lib")
#pragma comment(lib, "LLVMX86CodeGen.lib")
#pragma comment(lib, "LLVMX86AsmParser.lib")
#pragma comment(lib, "LLVMX86Disassembler.lib")
#pragma comment(lib, "LLVMJIT.lib")
#pragma comment(lib, "LLVMAsmPrinter.lib")
#pragma comment(lib, "LLVMSelectionDAG.lib")
#pragma comment(lib, "LLVMX86Desc.lib")
#pragma comment(lib, "LLVMExecutionEngine.lib")
#pragma comment(lib, "LLVMRuntimeDyld.lib")
#pragma comment(lib, "LLVMMCParser.lib")
#pragma comment(lib, "LLVMCodeGen.lib")
#pragma comment(lib, "LLVMX86AsmPrinter.lib")
#pragma comment(lib, "LLVMX86Info.lib")
#pragma comment(lib, "LLVMObjCARCOpts.lib")
#pragma comment(lib, "LLVMScalarOpts.lib")
#pragma comment(lib, "LLVMX86Utils.lib")
#pragma comment(lib, "LLVMInstCombine.lib")
#pragma comment(lib, "LLVMTransformUtils.lib")
#pragma comment(lib, "LLVMipa.lib")
#pragma comment(lib, "LLVMAnalysis.lib")
#pragma comment(lib, "LLVMTarget.lib")
#pragma comment(lib, "LLVMCore.lib")
#pragma comment(lib, "LLVMMC.lib")
#pragma comment(lib, "LLVMObject.lib")
#pragma comment(lib, "LLVMSupport.lib")

using namespace llvm;

int main(int argc, char **argv) {
    InitializeNativeTarget();
    LLVMContext &context = getGlobalContext();
    ExecutionEngine *ee;
    SMDiagnostic diag;
    Module *m = ParseIRFile("Script.s", diag, context);
    if(!m) {
        diag.print("LLVMSandbox", errs());
        return 1;
    }
    m->MaterializeAllPermanently();
    ee = EngineBuilder(m).create();
    Function *func = ee->FindFunctionNamed("main");
    typedef int (*PFN)();
    PFN pfn = reinterpret_cast<PFN>(ee->getPointerToFunction(func));
    int i = pfn();
    std::cout << i;
    std::cin.get();
    delete ee;
    return 0;
}

Answer 1

LLVM is evolving at a break-neck pace and is difficult to keep up with. Therefore, the best way to find code that keeps working while LLVM keeps moving forward is look at code that is built and tested with LLVM.

In this case, you need the lli tool (tools/lli in the code). It's a generic "executor" for LLVM IR, using either the interpreter or one of the JIT engines. It should work on Windows as well. You can use it both as an example for instantiating all the required LLVM machinery (in terms of C++ code) and building a new stand-alone tool (you can mimic it's makefile or CMakeLists.txt)