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use gccjit::{FunctionType, RValue};
use rustc_codegen_ssa::traits::BaseTypeMethods;
use rustc_middle::ty::{self, Instance, TypeVisitableExt};
use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
use crate::abi::FnAbiGccExt;
use crate::context::CodegenCx;
/// Codegens a reference to a fn/method item, monomorphizing and
/// inlining as it goes.
///
/// # Parameters
///
/// - `cx`: the crate context
/// - `instance`: the instance to be instantiated
pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>) -> RValue<'gcc> {
let tcx = cx.tcx();
assert!(!instance.substs.needs_infer());
assert!(!instance.substs.has_escaping_bound_vars());
if let Some(&func) = cx.function_instances.borrow().get(&instance) {
return func;
}
let sym = tcx.symbol_name(instance).name;
let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
let func =
if let Some(func) = cx.get_declared_value(&sym) {
// Create a fn pointer with the new signature.
let ptrty = fn_abi.ptr_to_gcc_type(cx);
// This is subtle and surprising, but sometimes we have to bitcast
// the resulting fn pointer. The reason has to do with external
// functions. If you have two crates that both bind the same C
// library, they may not use precisely the same types: for
// example, they will probably each declare their own structs,
// which are distinct types from LLVM's point of view (nominal
// types).
//
// Now, if those two crates are linked into an application, and
// they contain inlined code, you can wind up with a situation
// where both of those functions wind up being loaded into this
// application simultaneously. In that case, the same function
// (from LLVM's point of view) requires two types. But of course
// LLVM won't allow one function to have two types.
//
// What we currently do, therefore, is declare the function with
// one of the two types (whichever happens to come first) and then
// bitcast as needed when the function is referenced to make sure
// it has the type we expect.
//
// This can occur on either a crate-local or crate-external
// reference. It also occurs when testing libcore and in some
// other weird situations. Annoying.
if cx.val_ty(func) != ptrty {
// TODO(antoyo): cast the pointer.
func
}
else {
func
}
}
else {
cx.linkage.set(FunctionType::Extern);
let func = cx.declare_fn(&sym, &fn_abi);
// TODO(antoyo): set linkage and attributes.
func
};
cx.function_instances.borrow_mut().insert(instance, func);
func
}
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