Source Code → Frontend → Middle-End (Optimizer) → Backend → Machine Code
                ↓              ↓                      ↓
             AST/IR      LLVM IR Passes          Target Code

// Token types for a simple language
enum class TokenKind {
    Identifier,
    Number,
    String,
    Keyword,
    Operator,
    Punctuation,
    EndOfFile
};

struct Token {
    TokenKind kind;
    std::string value;
    SourceLocation location;
};

class Expr {
public:
    virtual ~Expr() = default;
    virtual llvm::Value* codegen() = 0;
};

class BinaryExpr : public Expr {
    std::unique_ptr<Expr> LHS, RHS;
    char Op;
public:
    llvm::Value* codegen() override {
        llvm::Value* L = LHS->codegen();
        llvm::Value* R = RHS->codegen();
        
        switch (Op) {
            case '+': return Builder.CreateFAdd(L, R, "addtmp");
            case '-': return Builder.CreateFSub(L, R, "subtmp");
            case '*': return Builder.CreateFMul(L, R, "multmp");
            case '/': return Builder.CreateFDiv(L, R, "divtmp");
        }
    }
};

#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/IRBuilder.h"

class CodeGen {
    std::unique_ptr<llvm::LLVMContext> Context;
    std::unique_ptr<llvm::Module> Module;
    std::unique_ptr<llvm::IRBuilder<>> Builder;
    
public:
    CodeGen() {
        Context = std::make_unique<llvm::LLVMContext>();
        Module = std::make_unique<llvm::Module>("my_module", *Context);
        Builder = std::make_unique<llvm::IRBuilder<>>(*Context);
    }
};

llvm::Function* createFunction(const std::string& name, 
                                llvm::Type* returnType,
                                std::vector<llvm::Type*> params) {
    llvm::FunctionType* FT = llvm::FunctionType::get(returnType, params, false);
    llvm::Function* F = llvm::Function::Create(
        FT, llvm::Function::ExternalLinkage, name, Module.get());
    
    llvm::BasicBlock* BB = llvm::BasicBlock::Create(*Context, "entry", F);
    Builder->SetInsertPoint(BB);
    
    return F;
}

#include "llvm/ExecutionEngine/Orc/LLJIT.h"

auto JIT = llvm::orc::LLJITBuilder().create();
if (!JIT) {
    handleError(JIT.takeError());
}

// Add module
(*JIT)->addIRModule(llvm::orc::ThreadSafeModule(
    std::move(Module), std::move(Context)));

// Look up symbol and execute
auto Sym = (*JIT)->lookup("main");
auto* MainFn = (int(*)())Sym->getAddress();
int result = MainFn();

#include "llvm/Passes/PassBuilder.h"

void optimizeModule(llvm::Module& M) {
    llvm::PassBuilder PB;
    llvm::LoopAnalysisManager LAM;
    llvm::FunctionAnalysisManager FAM;
    llvm::CGSCCAnalysisManager CGAM;
    llvm::ModuleAnalysisManager MAM;
    
    PB.registerModuleAnalyses(MAM);
    PB.registerCGSCCAnalyses(CGAM);
    PB.registerFunctionAnalyses(FAM);
    PB.registerLoopAnalyses(LAM);
    PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
    
    llvm::ModulePassManager MPM = PB.buildPerModuleDefaultPipeline(
        llvm::OptimizationLevel::O2);
    MPM.run(M, MAM);
}

struct MyPass : public llvm::PassInfoMixin<MyPass> {
    llvm::PreservedAnalyses run(llvm::Function& F, 
                                 llvm::FunctionAnalysisManager& FAM) {
        for (auto& BB : F) {
            for (auto& I : BB) {
                // Transform instructions
            }
        }
        return llvm::PreservedAnalyses::none();
    }
};

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