https://github.com/marcospb19/mini-c

My first try at writing a LLVM compiler
https://github.com/marcospb19/mini-c

Last synced: 25 days ago
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My first try at writing a LLVM compiler

• Host: GitHub
• URL: https://github.com/marcospb19/mini-c
• Owner: marcospb19
• Created: 2023-02-15T22:01:45.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2023-10-04T17:44:29.000Z (about 1 year ago)
• Last Synced: 2024-04-19T15:30:54.872Z (7 months ago)
• Language: Rust
• Homepage:
• Size: 77.1 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# mini-c

My (_initial_) experiments building compilers with LLVM.

# Examples:

```c

int fibonacci(int n) {

  if (n <= 1) {

    return 1;

  }

  return fibonacci(n - 2) + fibonacci(n - 1);

}

int factorial(int n) {

  if (n <= 1) {

    return 1;

  }

  return n * factorial(n - 1);

}

```

# How

I'm generating LLVM-IR using `inkwell`, it's the only decent library I found.

After generating the IR, there are two options:

1. Running in LLVM's JIT execution engine (commented out in the code).

2. Dumping the IR into a file and using several utils to create the final binary.

I'm doing the latter, which is cumbersome but let's me inspect the generated assembly.

Here's the huge command I'm running:

```sh

clear \

    && cargo run -- file.c \

    && llc llvm-ir.ll -o assembly.s \

    && clang assembly.s -o a.out \

    && bat file.c \

    && (./a.out ; echo "\$? = $?")

```

Here's the oneliner:

```sh

clear && cargo run -- file.c && llc llvm-ir.ll -o assembly.s && clang assembly.s -o a.out && bat file.c && (./a.out ; echo "\$? = $?")

```

1. My program compiles file.c to LLVM IR and dumps it to the file `llvm-ir.ll`.

2. `llc` compiles `llvm-ir.ll` into the assembly file `assembly.s`.

3. `clang` compiles `assembly.s` into machine-code, `a.out`.

4. Show the source code, run the program (output appears here) and then print the return code.

You need `llvm` installed for `lcc` and `clang`.

You can also use `gcc` instead of `clang` here.

# Dependencies for building

If you try running `cargo run` you'll meet a unpleasant linking error.

In some systems, installing `llvm` may solve, in Arch Linux you need to download a LLVM release tarball and unpack it.

https://github.com/llvm/llvm-project/releases/tag/llvmorg-15.0.0

Then point an env var to the resulting folder like so:

```sh

export LLVM_SYS_150_PREFIX=$(realpath ../llvm/clang+llvm-15.0.0-x86_64-linux-gnu-rhel-8.4)

```

Now `llvm-sys` and `inkwell` will compile fine, make sure you open your text editor of choice after setting this env var.