A small sample using LLJIT

main.rs

use llvm_sys::orc2;
use std::{ffi::{CStr, CString}, mem::MaybeUninit, ops::Deref};

struct LLJIT(orc2::lljit::LLVMOrcLLJITRef);
impl Drop for LLJIT {
    fn drop(&mut self) {
        unsafe { orc2::lljit::LLVMOrcDisposeLLJIT(self.0) };
    }
}
impl Deref for LLJIT {
    type Target = orc2::lljit::LLVMOrcLLJITRef;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl LLJIT {
    fn add_module(&self, m : llvm_sys::prelude::LLVMModuleRef) {
        unsafe {
            let thread_safe_ctx = orc2::LLVMOrcCreateNewThreadSafeContext();
            let thread_safe = orc2::LLVMOrcCreateNewThreadSafeModule(m, thread_safe_ctx);
            let dylib = orc2::lljit::LLVMOrcLLJITGetMainJITDylib(**self);
            orc2::lljit::LLVMOrcLLJITAddLLVMIRModule(**self, dylib, thread_safe);
        }
    }
}

#[repr(transparent)]
struct LLJITBuilder(orc2::lljit::LLVMOrcLLJITBuilderRef);
impl Drop for LLJITBuilder {
    fn drop(&mut self) {
        if !self.0.is_null() {
            unsafe { orc2::lljit::LLVMOrcDisposeLLJITBuilder(self.0) };
        }
    }
}
impl Deref for LLJITBuilder {
    type Target = orc2::lljit::LLVMOrcLLJITBuilderRef;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}


impl LLJITBuilder {
    fn new() -> Self {
        Self(unsafe { orc2::lljit::LLVMOrcCreateLLJITBuilder() })
    }
    fn create(mut self) -> LLJIT {
        let mut lljit = MaybeUninit::uninit();
        let err = unsafe { orc2::lljit::LLVMOrcCreateLLJIT(lljit.as_mut_ptr(), *self) };
        self.0 = std::ptr::null_mut();
        if !err.is_null() {
            let err_msg = unsafe { error::LLVMGetErrorMessage(err) };
            let err_msg = unsafe { CStr::from_ptr(err_msg) };
            panic!("{err_msg:?}");
        }
        let ptr = unsafe { lljit.assume_init() };
        if ptr.is_null() {
            panic!("lljit wasn't initialized?")
        }
        LLJIT(ptr)
    }
}


fn main() {
    unsafe {
        llvm_sys::target::LLVM_InitializeNativeTarget();
        llvm_sys::target::LLVM_InitializeNativeAsmPrinter();
        let ctx = llvm_sys::core::LLVMContextCreate();
        let module = llvm_sys::core::LLVMModuleCreateWithNameInContext(std::ptr::null(), ctx);
        let ty = llvm_sys::core::LLVMVoidType();
        let ty = llvm_sys::core::LLVMFunctionType(ty, std::ptr::null_mut(), 0, 0);
        let name = CString::new("foo").unwrap();
        let fun = llvm_sys::core::LLVMAddFunction(module, name.as_ptr(), ty);
        let bb = llvm_sys::core::LLVMAppendBasicBlock(fun, std::ptr::null());
        let builder = llvm_sys::core::LLVMCreateBuilder();
        llvm_sys::core::LLVMPositionBuilderAtEnd(builder, bb);
        llvm_sys::core::LLVMBuildRet(builder,std::ptr::null_mut());
        let llbuilder = LLJITBuilder::new();
        let lljit = llbuilder.create();
        lljit.add_module(module);
        let mut executor_addr = MaybeUninit::uninit();
        orc2::lljit::LLVMOrcLLJITLookup(*lljit, executor_addr.as_mut_ptr(), name.as_ptr());
        let fun = std::mem::transmute::<u64,unsafe extern "C" fn()>(executor_addr.assume_init());
        fun()
    }
}