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