rust/src/declare.rs

use gccjit::{Function, FunctionType, GlobalKind, LValue, RValue, Type};
#[cfg(feature="master")]
use gccjit::{FnAttribute, ToRValue};
use rustc_codegen_ssa::traits::BaseTypeMethods;
use rustc_middle::ty::Ty;
use rustc_span::Symbol;
use rustc_target::abi::call::FnAbi;

use crate::abi::FnAbiGccExt;
use crate::context::CodegenCx;
use crate::intrinsic::llvm;

impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
    pub fn get_or_insert_global(&self, name: &str, ty: Type<'gcc>, is_tls: bool, link_section: Option<Symbol>) -> LValue<'gcc> {
        if self.globals.borrow().contains_key(name) {
            let typ = self.globals.borrow()[name].get_type();
            let global = self.context.new_global(None, GlobalKind::Imported, typ, name);
            if is_tls {
                global.set_tls_model(self.tls_model);
            }
            if let Some(link_section) = link_section {
                global.set_link_section(link_section.as_str());
            }
            global
        }
        else {
            self.declare_global(name, ty, GlobalKind::Exported, is_tls, link_section)
        }
    }

    pub fn declare_unnamed_global(&self, ty: Type<'gcc>) -> LValue<'gcc> {
        let name = self.generate_local_symbol_name("global");
        self.context.new_global(None, GlobalKind::Internal, ty, &name)
    }

    pub fn declare_global_with_linkage(&self, name: &str, ty: Type<'gcc>, linkage: GlobalKind) -> LValue<'gcc> {
        let global = self.context.new_global(None, linkage, ty, name);
        let global_address = global.get_address(None);
        self.globals.borrow_mut().insert(name.to_string(), global_address);
        global
    }

    pub fn declare_func(&self, name: &str, return_type: Type<'gcc>, params: &[Type<'gcc>], variadic: bool) -> Function<'gcc> {
        self.linkage.set(FunctionType::Extern);
        declare_raw_fn(self, name, () /*llvm::CCallConv*/, return_type, params, variadic)
    }

    pub fn declare_global(&self, name: &str, ty: Type<'gcc>, global_kind: GlobalKind, is_tls: bool, link_section: Option<Symbol>) -> LValue<'gcc> {
        let global = self.context.new_global(None, global_kind, ty, name);
        if is_tls {
            global.set_tls_model(self.tls_model);
        }
        if let Some(link_section) = link_section {
            global.set_link_section(link_section.as_str());
        }
        let global_address = global.get_address(None);
        self.globals.borrow_mut().insert(name.to_string(), global_address);
        global
    }

    pub fn declare_private_global(&self, name: &str, ty: Type<'gcc>) -> LValue<'gcc> {
        let global = self.context.new_global(None, GlobalKind::Internal, ty, name);
        let global_address = global.get_address(None);
        self.globals.borrow_mut().insert(name.to_string(), global_address);
        global
    }

    pub fn declare_entry_fn(&self, name: &str, _fn_type: Type<'gcc>, callconv: () /*llvm::CCallConv*/) -> RValue<'gcc> {
        // TODO(antoyo): use the fn_type parameter.
        let const_string = self.context.new_type::<u8>().make_pointer().make_pointer();
        let return_type = self.type_i32();
        let variadic = false;
        self.linkage.set(FunctionType::Exported);
        let func = declare_raw_fn(self, name, callconv, return_type, &[self.type_i32(), const_string], variadic);
        // NOTE: it is needed to set the current_func here as well, because get_fn() is not called
        // for the main function.
        *self.current_func.borrow_mut() = Some(func);
        // FIXME(antoyo): this is a wrong cast. That requires changing the compiler API.
        unsafe { std::mem::transmute(func) }
    }

    pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Function<'gcc> {
        let (return_type, params, variadic, on_stack_param_indices, fn_attrs) = fn_abi.gcc_type(self);
        let func = declare_raw_fn(self, name, () /*fn_abi.llvm_cconv()*/, return_type, &params, variadic);
        self.on_stack_function_params.borrow_mut().insert(func, on_stack_param_indices);
        // We need to handle `nonnull` here where we still have access to function args.
        for fn_attr in fn_attrs {
            func.add_attribute(fn_attr);
        }
        func
    }

    pub fn define_global(&self, name: &str, ty: Type<'gcc>, is_tls: bool, link_section: Option<Symbol>) -> LValue<'gcc> {
        self.get_or_insert_global(name, ty, is_tls, link_section)
    }

    pub fn get_declared_value(&self, name: &str) -> Option<RValue<'gcc>> {
        // TODO(antoyo): use a different field than globals, because this seems to return a function?
        self.globals.borrow().get(name).cloned()
    }
}

/// Declare a function.
///
/// If there’s a value with the same name already declared, the function will
/// update the declaration and return existing Value instead.
fn declare_raw_fn<'gcc>(cx: &CodegenCx<'gcc, '_>, name: &str, _callconv: () /*llvm::CallConv*/, return_type: Type<'gcc>, param_types: &[Type<'gcc>], variadic: bool) -> Function<'gcc> {
    if name.starts_with("llvm.") {
        let intrinsic = llvm::intrinsic(name, cx);
        cx.intrinsics.borrow_mut().insert(name.to_string(), intrinsic);
        return intrinsic;
    }
    let func =
        if cx.functions.borrow().contains_key(name) {
            cx.functions.borrow()[name]
        }
        else {
            let params: Vec<_> = param_types.into_iter().enumerate()
                .map(|(index, param)| cx.context.new_parameter(None, *param, &format!("param{}", index))) // TODO(antoyo): set name.
                .collect();
            let func = cx.context.new_function(None, cx.linkage.get(), return_type, &params, mangle_name(name), variadic);
            cx.functions.borrow_mut().insert(name.to_string(), func);

            #[cfg(feature="master")]
            if name == "rust_eh_personality" {
                // NOTE: GCC will sometimes change the personality function set on a function from
                // rust_eh_personality to __gcc_personality_v0 as an optimization.
                // As such, we need to create a weak alias from __gcc_personality_v0 to
                // rust_eh_personality in order to avoid a linker error.
                // This needs to be weak in order to still allow using the standard
                // __gcc_personality_v0 when the linking to it.
                // Since aliases don't work (maybe because of a bug in LTO partitioning?), we
                // create a wrapper function that calls rust_eh_personality.

                let params: Vec<_> = param_types.into_iter().enumerate()
                    .map(|(index, param)| cx.context.new_parameter(None, *param, &format!("param{}", index))) // TODO(antoyo): set name.
                    .collect();
                let gcc_func = cx.context.new_function(None, FunctionType::Exported, return_type, &params, "__gcc_personality_v0", variadic);

                // We need a normal extern function for the crates that access rust_eh_personality
                // without defining it, otherwise we'll get a compiler error.
                //
                // For the crate defining it, that needs to be a weak alias instead.
                gcc_func.add_attribute(FnAttribute::Weak);

                let block = gcc_func.new_block("start");
                let mut args = vec![];
                for param in &params {
                    args.push(param.to_rvalue());
                }
                let call = cx.context.new_call(None, func, &args);
                if return_type == cx.type_void() {
                    block.add_eval(None, call);
                    block.end_with_void_return(None);
                }
                else {
                    block.end_with_return(None, call);
                }
            }

            func
        };

    // TODO(antoyo): set function calling convention.
    // TODO(antoyo): set unnamed address.
    // TODO(antoyo): set no red zone function attribute.
    // TODO(antoyo): set attributes for optimisation.
    // TODO(antoyo): set attributes for non lazy bind.

    // FIXME(antoyo): invalid cast.
    func
}

// FIXME(antoyo): this is a hack because libgccjit currently only supports alpha, num and _.
// Unsupported characters: `$` and `.`.
pub fn mangle_name(name: &str) -> String {
    name.replace(|char: char| {
        if !char.is_alphanumeric() && char != '_' {
            debug_assert!("$.*".contains(char), "Unsupported char in function name {}: {}", name, char);
            true
        }
        else {
            false
        }
    }, "_")
}