Skip to main content

Translating C Code to Executable using LLVM

LLVM provides a suite of tools to compile and execute code, including transforming C code into an executable format. This document outlines the basic steps involved in compiling a C file using LLVM tools such as clang, llvm-as, and llc.

Table of Contents​

Overview​

LLVM (Low-Level Virtual Machine) is a collection of modular and reusable compiler and toolchain technologies. The process of translating C code into an executable involves several steps, from compiling the C code to generating intermediate representations (IR) and finally creating machine code that can be executed.

Step 1: Write a Basic C Program​

Create a simple C program, hello.c, as follows:

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

Step 2: Compile the C Code to LLVM IR​

Use clang to compile the C file into an LLVM Intermediate Representation (IR):

clang -S -emit-llvm hello.c -o hello.ll

This command produces an LLVM IR file (hello.ll).

Step 3: Generate LLVM Assembly​

Once you have the LLVM IR file, you can generate LLVM assembly code using the llvm-as tool:

llvm-as hello.ll -o hello.bc

Step 4: Convert LLVM IR to Machine Code​

Next, convert the LLVM bytecode into machine code using the llc tool. This step will generate an assembly file for your target architecture.

llc hello.bc -o hello.s

Once you have the assembly file, the final step is to link it and create an executable. You can use either clang or gcc for this purpose:

clang hello.s -o hello

This command compiles the assembly file (hello.s) and links it with the C standard library to create an executable named hello.

You can run your program using the following command:

./hello

Conclusion​

In this document, we have walked through the steps required to translate C code into an executable using LLVM tools. By writing a simple C program, compiling it to LLVM Intermediate Representation, generating LLVM assembly, converting the assembly to machine code, and finally linking it to create an executable, you can harness the power of LLVM for your C projects. This process illustrates the modularity and versatility of LLVM in the compilation pipeline, enabling you to optimize and analyze your code effectively.

Summary of Steps​

  1. Write a Basic C Program: Create a simple hello.c file.
  2. Compile the C Code to LLVM IR: Use clang to generate an LLVM IR file (hello.ll).
  3. Generate LLVM Assembly: Convert LLVM IR to bytecode using llvm-as (hello.bc).
  4. Convert LLVM IR to Machine Code: Use llc to generate assembly code (hello.s).
  5. Link and Create Executable: Create the executable with clang or gcc (hello).

This structure should provide a clear and concise guide for users looking to translate C code to executable using LLVM tools. Let me know if you need any additional modifications or information!