Implement a simple Hello World with LLVM

.gitignore

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+build

.vscode/c_cpp_properties.json

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+{
+    "configurations": [
+        {
+            "name": "Linux",
+            "includePath": [
+                "${workspaceFolder}/**"
+            ],
+            "defines": [],
+            "compilerPath": "/usr/bin/clang",
+            "cStandard": "c17",
+            "cppStandard": "c++20",
+            "intelliSenseMode": "linux-clang-x86"
+        }
+    ],
+    "version": 4
+}

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20.0)
+project(SimpleProject)
+
+set(PROJECT_NAME llvm_c_compiler)
+project(${PROJECT_NAME} VERSION 1.0.0 LANGUAGES CXX)
+
+# Include LLVM as library
+find_package(LLVM 21.1.0 CONFIG)
+
+message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
+message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
+
+include_directories(${LLVM_INCLUDE_DIRS})
+separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
+add_definitions(${LLVM_DEFINITIONS_LIST})
+
+# Executable
+add_executable(${PROJECT_NAME} src/main.cpp)
+target_compile_features(${PROJECT_NAME} PRIVATE cxx_std_20)
+
+# Find the libraries that correspond to the LLVM components
+# that we wish to use
+llvm_map_components_to_libnames(llvm_libs support core irreader)
+
+# Link
+target_link_libraries(${PROJECT_NAME} LLVM)

src/main.cpp

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+#include <llvm/IR/LLVMContext.h>
+#include <llvm/ADT/StringRef.h>
+#include <llvm/Support/TargetSelect.h>
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetOptions.h"
+#include <llvm/MC/TargetRegistry.h>
+#include <llvm/IR/IRBuilder.h>
+#include <llvm/IR/Module.h>
+#include <llvm/TargetParser/Host.h>
+#include <llvm/Support/raw_ostream.h>
+#include <llvm/Support/FileSystem.h>
+#include <llvm/IR/LegacyPassManager.h>
+#include <llvm/IR/Verifier.h>
+
+#include <iostream>
+
+int main() {
+    auto Context = std::make_unique<llvm::LLVMContext>();
+    auto Module = std::make_unique<llvm::Module>("my cool module", *Context);
+
+    auto Builder = std::make_unique<llvm::IRBuilder<>>(*Context);
+
+    llvm::FunctionType* FunType = llvm::FunctionType::get(llvm::Type::getInt32Ty(*Context), false);
+    llvm::Function* Function = llvm::Function::Create(
+        FunType, llvm::GlobalValue::LinkageTypes::ExternalLinkage, "main", *Module);
+
+    llvm::BasicBlock* BB = llvm::BasicBlock::Create(*Context, "entry", Function, nullptr);
+
+    Builder->SetInsertPoint(BB);
+    llvm::Value* value = llvm::ConstantInt::get(llvm::Type::getInt32Ty(*Context), 5);
+    Builder->CreateRet(value);
+
+    llvm::verifyFunction(*Function);
+
+    llvm::InitializeAllTargetInfos();
+    llvm::InitializeAllTargets();
+    llvm::InitializeAllTargetMCs();
+    llvm::InitializeAllAsmParsers();
+    llvm::InitializeAllAsmPrinters();
+
+    auto TargetTriple = llvm::sys::getDefaultTargetTriple();
+    std::string Error;
+    auto Target = llvm::TargetRegistry::lookupTarget(TargetTriple, Error);
+
+    llvm::TargetOptions opt;
+    auto TargetMachine = Target->createTargetMachine(TargetTriple, "generic", "", opt, llvm::Reloc::PIC_);
+    Module->setDataLayout(TargetMachine->createDataLayout());
+
+    // auto Filename = "output.o";
+    // std::error_code EC;
+    // llvm::raw_fd_ostream dest(Filename, EC, llvm::sys::fs::OpenFlags::OF_Text);
+
+    // if (EC) {
+    //     llvm::errs() << "Could not open file: " << EC.message();
+    //     return 1;
+    // }
+    std::string out;
+    llvm::raw_string_ostream dest{ out };
+
+    Module->print(dest, nullptr);
+    dest.flush();
+
+    std::cout << out << std::endl;
+    std::cout << "hello" << std::endl;
+    return 0;
+}