main.rs

use llvm_sys::analysis::*;
use llvm_sys::core::*;
use llvm_sys::execution_engine::*;
use llvm_sys::prelude::*;
use llvm_sys::target::*;
use llvm_sys::*;
use std::ptr;

macro_rules! c {
    ($s:expr) => {
        cstr::cstr!($s).as_ptr()
    };
}

pub unsafe fn init() {
    LLVM_InitializeNativeTarget();
    LLVM_InitializeNativeAsmPrinter();
    LLVM_InitializeNativeAsmParser();
    LLVMLinkInMCJIT();
}

unsafe fn create_and_run(module: LLVMModuleRef, exec: LLVMExecutionEngineRef) {
    // Create and add function
    let fun_ty = LLVMFunctionType(LLVMVoidType(), ptr::null_mut(), 0, 0);
    let function = LLVMAddFunction(module, c!("jit"), fun_ty);
    LLVMSetFunctionCallConv(function, LLVMCallConv::LLVMCCallConv as u32);

    // Add some instructions
    let builder = LLVMCreateBuilder();
    let bb = LLVMAppendBasicBlock(function, c!("entry"));
    LLVMPositionBuilderAtEnd(builder, bb);
    LLVMBuildRetVoid(builder);

    // Verify & print for debugging
    LLVMPrintModuleToFile(module, c!("out.ll"), ptr::null_mut());
    LLVMVerifyModule(module, LLVMVerifierFailureAction::LLVMAbortProcessAction, ptr::null_mut());

    // Trigger codegen, get function pointer, call
    let mut length = 0;
    let name = LLVMGetValueName2(function, &mut length);

    let address = LLVMGetFunctionAddress(exec, name);
    assert!(address != 0);
    let fun = std::mem::transmute::<u64, extern "C" fn()>(address);
    fun();
    println!("Done");
}

fn main() {
    unsafe {
        init();

        // Create module & EE
        let module = LLVMModuleCreateWithName(c!("test"));
        let mut exec = ptr::null_mut();
        let mut err = ptr::null_mut();
        assert!(LLVMCreateExecutionEngineForModule(&mut exec, module, &mut err) == 0);
        assert!(err.is_null());

        create_and_run(module, exec);
        create_and_run(module, exec);
    }
}