rust/compiler/rustc_codegen_gcc/src/allocator.rs

#[cfg(feature = "master")]
use gccjit::FnAttribute;
use gccjit::{Context, FunctionType, ToRValue, Type};
use rustc_ast::expand::allocator::{
    AllocatorMethod, AllocatorTy, NO_ALLOC_SHIM_IS_UNSTABLE, default_fn_name, global_fn_name,
};
use rustc_middle::bug;
use rustc_middle::ty::TyCtxt;
use rustc_symbol_mangling::mangle_internal_symbol;

use crate::GccContext;
#[cfg(feature = "master")]
use crate::base::symbol_visibility_to_gcc;

pub(crate) unsafe fn codegen(
    tcx: TyCtxt<'_>,
    mods: &mut GccContext,
    _module_name: &str,
    methods: &[AllocatorMethod],
) {
    let context = &mods.context;
    let usize = match tcx.sess.target.pointer_width {
        16 => context.new_type::<u16>(),
        32 => context.new_type::<u32>(),
        64 => context.new_type::<u64>(),
        tws => bug!("Unsupported target word size for int: {}", tws),
    };
    let i8 = context.new_type::<i8>();
    let i8p = i8.make_pointer();

    for method in methods {
        let mut types = Vec::with_capacity(method.inputs.len());
        for input in method.inputs.iter() {
            match input.ty {
                AllocatorTy::Layout => {
                    types.push(usize);
                    types.push(usize);
                }
                AllocatorTy::Ptr => types.push(i8p),
                AllocatorTy::Usize => types.push(usize),

                AllocatorTy::Never | AllocatorTy::ResultPtr | AllocatorTy::Unit => {
                    panic!("invalid allocator arg")
                }
            }
        }
        let output = match method.output {
            AllocatorTy::ResultPtr => Some(i8p),
            AllocatorTy::Never | AllocatorTy::Unit => None,

            AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
                panic!("invalid allocator output")
            }
        };
        let from_name = mangle_internal_symbol(tcx, &global_fn_name(method.name));
        let to_name = mangle_internal_symbol(tcx, &default_fn_name(method.name));

        create_wrapper_function(tcx, context, &from_name, Some(&to_name), &types, output);
    }

    create_wrapper_function(
        tcx,
        context,
        &mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
        None,
        &[],
        None,
    );
}

fn create_wrapper_function(
    tcx: TyCtxt<'_>,
    context: &Context<'_>,
    from_name: &str,
    to_name: Option<&str>,
    types: &[Type<'_>],
    output: Option<Type<'_>>,
) {
    let void = context.new_type::<()>();

    let args: Vec<_> = types
        .iter()
        .enumerate()
        .map(|(index, typ)| context.new_parameter(None, *typ, format!("param{}", index)))
        .collect();
    let func = context.new_function(
        None,
        FunctionType::Exported,
        output.unwrap_or(void),
        &args,
        from_name,
        false,
    );

    #[cfg(feature = "master")]
    func.add_attribute(FnAttribute::Visibility(symbol_visibility_to_gcc(
        tcx.sess.default_visibility(),
    )));

    if tcx.sess.must_emit_unwind_tables() {
        // TODO(antoyo): emit unwind tables.
    }

    let block = func.new_block("entry");

    if let Some(to_name) = to_name {
        let args: Vec<_> = types
            .iter()
            .enumerate()
            .map(|(index, typ)| context.new_parameter(None, *typ, format!("param{}", index)))
            .collect();
        let callee = context.new_function(
            None,
            FunctionType::Extern,
            output.unwrap_or(void),
            &args,
            to_name,
            false,
        );
        #[cfg(feature = "master")]
        callee.add_attribute(FnAttribute::Visibility(gccjit::Visibility::Hidden));

        let args = args
            .iter()
            .enumerate()
            .map(|(i, _)| func.get_param(i as i32).to_rvalue())
            .collect::<Vec<_>>();
        let ret = context.new_call(None, callee, &args);
        //llvm::LLVMSetTailCall(ret, True);
        if output.is_some() {
            block.end_with_return(None, ret);
        } else {
            block.add_eval(None, ret);
            block.end_with_void_return(None);
        }
    } else {
        assert!(output.is_none());
        block.end_with_void_return(None);
    }

    // TODO(@Commeownist): Check if we need to emit some extra debugging info in certain circumstances
    // as described in https://github.com/rust-lang/rust/commit/77a96ed5646f7c3ee8897693decc4626fe380643
}