luaur-code-gen 0.1.1

Native (A64/X64) code generation for Luau (Rust).
Documentation 
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use crate::functions::visit_fde_entries::visit_fde_entries;
use crate::macros::codegen_assert::CODEGEN_ASSERT;

#[cfg(not(target_os = "windows"))]
extern "C" {
    fn __register_frame(begin: *const core::ffi::c_void);
}

#[cfg(all(target_os = "macos", target_arch = "aarch64"))]
extern "C" {
    fn dlsym(
        handle: *mut core::ffi::c_void,
        symbol: *const core::ffi::c_char,
    ) -> *mut core::ffi::c_void;
}

#[cfg(target_os = "windows")]
extern "system" {
    fn RtlAddFunctionTable(
        function_table: *mut core::ffi::c_void,
        entry_count: u32,
        base_address: usize,
    ) -> i32;
}

pub unsafe extern "C" fn create_block_unwind_info(
    context: *mut core::ffi::c_void,
    block: *mut u8,
    block_size: usize,
    begin_offset: &mut usize,
) -> *mut core::ffi::c_void {
    const K_CODE_ALIGNMENT: usize = 32;

    #[cfg(target_os = "windows")]
    let (function_count, builder_begin_offset, unwind_size) = {
        let unwind = &mut *(context.cast::<crate::records::unwind_builder_win::UnwindBuilderWin>());
        let unwind_size = (unwind.get_unwind_info_size(block_size) + (K_CODE_ALIGNMENT - 1))
            & !(K_CODE_ALIGNMENT - 1);

        CODEGEN_ASSERT!(block_size >= unwind_size);

        let function_count = unwind.finalize(block.cast(), unwind_size, block.cast(), block_size);

        (function_count, unwind.get_begin_offset(), unwind_size)
    };

    #[cfg(not(target_os = "windows"))]
    let (builder_begin_offset, unwind_size) = {
        let unwind =
            &mut *(context.cast::<crate::records::unwind_builder_dwarf_2::UnwindBuilderDwarf2>());
        let unwind_size = (unwind.get_unwind_info_size(block_size) + (K_CODE_ALIGNMENT - 1))
            & !(K_CODE_ALIGNMENT - 1);

        CODEGEN_ASSERT!(block_size >= unwind_size);

        unwind.finalize(block.cast(), unwind_size, block.cast(), block_size);

        (unwind.get_begin_offset(), unwind_size)
    };

    #[cfg(target_os = "windows")]
    {
        if RtlAddFunctionTable(block.cast(), function_count as u32, block as usize) == 0 {
            CODEGEN_ASSERT!(false);
            return core::ptr::null_mut();
        }
    }

    #[cfg(not(target_os = "windows"))]
    {
        visit_fde_entries(block.cast(), __register_frame);
    }

    #[cfg(all(target_os = "macos", target_arch = "aarch64"))]
    register_macos_a64_unwind_sections();

    *begin_offset = unwind_size + builder_begin_offset;
    block.cast()
}

#[cfg(all(target_os = "macos", target_arch = "aarch64"))]
fn register_macos_a64_unwind_sections() {
    use crate::functions::find_dynamic_unwind_sections::find_dynamic_unwind_sections;
    use crate::records::unw_dynamic_unwind_sections_t::unw_dynamic_unwind_sections_t;
    use crate::type_aliases::unw_add_find_dynamic_unwind_sections_t::unw_add_find_dynamic_unwind_sections_t;
    use std::sync::OnceLock;

    unsafe extern "C" fn find_dynamic_unwind_sections_thunk(
        addr: usize,
        info: *mut unw_dynamic_unwind_sections_t,
    ) -> core::ffi::c_int {
        if info.is_null() {
            return 0;
        }

        find_dynamic_unwind_sections(addr, unsafe { &mut *info })
    }

    static REGISTER_RESULT: OnceLock<i32> = OnceLock::new();

    let result = REGISTER_RESULT.get_or_init(|| unsafe {
        const RTLD_DEFAULT: *mut core::ffi::c_void = -2_isize as *mut core::ffi::c_void;
        let symbol = c"__unw_add_find_dynamic_unwind_sections";
        let add_find_dynamic_unwind_sections: unw_add_find_dynamic_unwind_sections_t =
            core::mem::transmute(dlsym(RTLD_DEFAULT, symbol.as_ptr()));

        match add_find_dynamic_unwind_sections {
            Some(register) => register(Some(find_dynamic_unwind_sections_thunk)),
            None => 0,
        }
    });

    CODEGEN_ASSERT!(*result == 0);
}