1 use crate::hir::def::Namespace;
2 use crate::hir::def_id::DefId;
3 use crate::hir::CodegenFnAttrFlags;
4 use crate::middle::lang_items::DropInPlaceFnLangItem;
6 use crate::ty::print::{FmtPrinter, Printer};
7 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
8 use rustc_macros::HashStable;
9 use rustc_target::spec::abi::Abi;
13 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
14 #[derive(HashStable, Lift)]
15 pub struct Instance<'tcx> {
16 pub def: InstanceDef<'tcx>,
17 pub substs: SubstsRef<'tcx>,
20 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable, HashStable)]
21 pub enum InstanceDef<'tcx> {
25 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self`.
28 /// `fn()` pointer where the function itself cannot be turned into a pointer.
30 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
31 /// a virtual call, which codegen supports only via a direct call to the
32 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
34 /// Another example is functions annotated with `#[track_caller]`, which
35 /// must have their implicit caller location argument populated for a call.
36 /// Because this is a required part of the function's ABI but can't be tracked
37 /// as a property of the function pointer, we use a single "caller location"
38 /// (the definition of the function itself).
41 /// `<fn() as FnTrait>::call_*`
42 /// `DefId` is `FnTrait::call_*`.
43 FnPtrShim(DefId, Ty<'tcx>),
45 /// `<dyn Trait as Trait>::fn`, "direct calls" of which are implicitly
46 /// codegen'd as virtual calls.
48 /// NB: if this is reified to a `fn` pointer, a `ReifyShim` is used
49 /// (see `ReifyShim` above for more details on that).
50 Virtual(DefId, usize),
52 /// `<[mut closure] as FnOnce>::call_once`
57 /// `drop_in_place::<T>; None` for empty drop glue.
58 DropGlue(DefId, Option<Ty<'tcx>>),
60 ///`<T as Clone>::clone` shim.
61 CloneShim(DefId, Ty<'tcx>),
64 impl<'tcx> Instance<'tcx> {
65 pub fn ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
66 let ty = tcx.type_of(self.def.def_id());
67 tcx.subst_and_normalize_erasing_regions(self.substs, ty::ParamEnv::reveal_all(), &ty)
71 impl<'tcx> InstanceDef<'tcx> {
73 pub fn def_id(&self) -> DefId {
75 InstanceDef::Item(def_id)
76 | InstanceDef::VtableShim(def_id)
77 | InstanceDef::ReifyShim(def_id)
78 | InstanceDef::FnPtrShim(def_id, _)
79 | InstanceDef::Virtual(def_id, _)
80 | InstanceDef::Intrinsic(def_id)
81 | InstanceDef::ClosureOnceShim { call_once: def_id }
82 | InstanceDef::DropGlue(def_id, _)
83 | InstanceDef::CloneShim(def_id, _) => def_id,
88 pub fn attrs(&self, tcx: TyCtxt<'tcx>) -> ty::Attributes<'tcx> {
89 tcx.get_attrs(self.def_id())
92 pub fn is_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
93 use crate::hir::map::DefPathData;
94 let def_id = match *self {
95 ty::InstanceDef::Item(def_id) => def_id,
96 ty::InstanceDef::DropGlue(_, Some(_)) => return false,
99 match tcx.def_key(def_id).disambiguated_data.data {
100 DefPathData::Ctor | DefPathData::ClosureExpr => true,
105 pub fn requires_local(&self, tcx: TyCtxt<'tcx>) -> bool {
106 if self.is_inline(tcx) {
109 if let ty::InstanceDef::DropGlue(..) = *self {
110 // Drop glue wants to be instantiated at every codegen
111 // unit, but without an #[inline] hint. We should make this
112 // available to normal end-users.
115 tcx.codegen_fn_attrs(self.def_id()).requests_inline()
118 pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
119 tcx.codegen_fn_attrs(self.def_id()).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
123 impl<'tcx> fmt::Display for Instance<'tcx> {
124 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
125 ty::tls::with(|tcx| {
126 let substs = tcx.lift(&self.substs).expect("could not lift for printing");
127 FmtPrinter::new(tcx, &mut *f, Namespace::ValueNS)
128 .print_def_path(self.def_id(), substs)?;
133 InstanceDef::Item(_) => Ok(()),
134 InstanceDef::VtableShim(_) => write!(f, " - shim(vtable)"),
135 InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
136 InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
137 InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
138 InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({:?})", ty),
139 InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
140 InstanceDef::DropGlue(_, ty) => write!(f, " - shim({:?})", ty),
141 InstanceDef::CloneShim(_, ty) => write!(f, " - shim({:?})", ty),
146 impl<'tcx> Instance<'tcx> {
147 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
149 !substs.has_escaping_bound_vars(),
150 "substs of instance {:?} not normalized for codegen: {:?}",
154 Instance { def: InstanceDef::Item(def_id), substs: substs }
157 pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
158 Instance::new(def_id, tcx.empty_substs_for_def_id(def_id))
162 pub fn def_id(&self) -> DefId {
166 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
167 /// this is used to find the precise code that will run for a trait method invocation,
170 /// Returns `None` if we cannot resolve `Instance` to a specific instance.
171 /// For example, in a context like this,
174 /// fn foo<T: Debug>(t: T) { ... }
177 /// trying to resolve `Debug::fmt` applied to `T` will yield `None`, because we do not
178 /// know what code ought to run. (Note that this setting is also affected by the
179 /// `RevealMode` in the parameter environment.)
181 /// Presuming that coherence and type-check have succeeded, if this method is invoked
182 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
186 param_env: ty::ParamEnv<'tcx>,
188 substs: SubstsRef<'tcx>,
189 ) -> Option<Instance<'tcx>> {
190 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
191 let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
192 debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
193 let item = tcx.associated_item(def_id);
194 resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
196 let ty = tcx.type_of(def_id);
197 let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, &ty);
199 let def = match item_type.kind {
202 let f = item_type.fn_sig(tcx);
203 f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic
206 debug!(" => intrinsic");
207 ty::InstanceDef::Intrinsic(def_id)
210 if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
211 let ty = substs.type_at(0);
212 if ty.needs_drop(tcx, ty::ParamEnv::reveal_all()) {
213 debug!(" => nontrivial drop glue");
214 ty::InstanceDef::DropGlue(def_id, Some(ty))
216 debug!(" => trivial drop glue");
217 ty::InstanceDef::DropGlue(def_id, None)
220 debug!(" => free item");
221 ty::InstanceDef::Item(def_id)
225 Some(Instance { def: def, substs: substs })
227 debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result);
231 pub fn resolve_for_fn_ptr(
233 param_env: ty::ParamEnv<'tcx>,
235 substs: SubstsRef<'tcx>,
236 ) -> Option<Instance<'tcx>> {
237 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
238 Instance::resolve(tcx, param_env, def_id, substs).map(|mut resolved| {
240 InstanceDef::Item(def_id) if resolved.def.requires_caller_location(tcx) => {
241 debug!(" => fn pointer created for function with #[track_caller]");
242 resolved.def = InstanceDef::ReifyShim(def_id);
244 InstanceDef::Virtual(def_id, _) => {
245 debug!(" => fn pointer created for virtual call");
246 resolved.def = InstanceDef::ReifyShim(def_id);
255 pub fn resolve_for_vtable(
257 param_env: ty::ParamEnv<'tcx>,
259 substs: SubstsRef<'tcx>,
260 ) -> Option<Instance<'tcx>> {
261 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
262 let fn_sig = tcx.fn_sig(def_id);
263 let is_vtable_shim = fn_sig.inputs().skip_binder().len() > 0
264 && fn_sig.input(0).skip_binder().is_param(0)
265 && tcx.generics_of(def_id).has_self;
267 debug!(" => associated item with unsizeable self: Self");
268 Some(Instance { def: InstanceDef::VtableShim(def_id), substs })
270 Instance::resolve(tcx, param_env, def_id, substs)
274 pub fn resolve_closure(
277 substs: ty::SubstsRef<'tcx>,
278 requested_kind: ty::ClosureKind,
279 ) -> Instance<'tcx> {
280 let actual_kind = substs.as_closure().kind(def_id, tcx);
282 match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
283 Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
284 _ => Instance::new(def_id, substs),
288 pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
289 let def_id = tcx.require_lang_item(DropInPlaceFnLangItem, None);
290 let substs = tcx.intern_substs(&[ty.into()]);
291 Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap()
294 pub fn fn_once_adapter_instance(
297 substs: ty::SubstsRef<'tcx>,
298 ) -> Instance<'tcx> {
299 debug!("fn_once_adapter_shim({:?}, {:?})", closure_did, substs);
300 let fn_once = tcx.lang_items().fn_once_trait().unwrap();
302 .associated_items(fn_once)
303 .find(|it| it.kind == ty::AssocKind::Method)
306 let def = ty::InstanceDef::ClosureOnceShim { call_once };
308 let self_ty = tcx.mk_closure(closure_did, substs);
310 let sig = substs.as_closure().sig(closure_did, tcx);
311 let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
312 assert_eq!(sig.inputs().len(), 1);
313 let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
315 debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
316 Instance { def, substs }
319 pub fn is_vtable_shim(&self) -> bool {
320 if let InstanceDef::VtableShim(..) = self.def { true } else { false }
324 fn resolve_associated_item<'tcx>(
326 trait_item: &ty::AssocItem,
327 param_env: ty::ParamEnv<'tcx>,
329 rcvr_substs: SubstsRef<'tcx>,
330 ) -> Option<Instance<'tcx>> {
331 let def_id = trait_item.def_id;
333 "resolve_associated_item(trait_item={:?}, \
337 def_id, param_env, trait_id, rcvr_substs
340 let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
341 let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref)));
343 // Now that we know which impl is being used, we can dispatch to
344 // the actual function:
346 traits::VtableImpl(impl_data) => {
347 let (def_id, substs) =
348 traits::find_associated_item(tcx, param_env, trait_item, rcvr_substs, &impl_data);
350 let resolved_item = tcx.associated_item(def_id);
352 // Since this is a trait item, we need to see if the item is either a trait default item
353 // or a specialization because we can't resolve those unless we can `Reveal::All`.
354 // NOTE: This should be kept in sync with the similar code in
355 // `rustc::traits::project::assemble_candidates_from_impls()`.
356 let eligible = if !resolved_item.defaultness.is_default() {
358 } else if param_env.reveal == traits::Reveal::All {
359 !trait_ref.needs_subst()
368 let substs = tcx.erase_regions(&substs);
369 Some(ty::Instance::new(def_id, substs))
371 traits::VtableGenerator(generator_data) => Some(Instance {
372 def: ty::InstanceDef::Item(generator_data.generator_def_id),
373 substs: generator_data.substs,
375 traits::VtableClosure(closure_data) => {
376 let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
377 Some(Instance::resolve_closure(
379 closure_data.closure_def_id,
384 traits::VtableFnPointer(ref data) => Some(Instance {
385 def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
388 traits::VtableObject(ref data) => {
389 let index = tcx.get_vtable_index_of_object_method(data, def_id);
390 Some(Instance { def: ty::InstanceDef::Virtual(def_id, index), substs: rcvr_substs })
392 traits::VtableBuiltin(..) => {
393 if tcx.lang_items().clone_trait().is_some() {
395 def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
402 traits::VtableAutoImpl(..) | traits::VtableParam(..) | traits::VtableTraitAlias(..) => None,
406 fn needs_fn_once_adapter_shim(
407 actual_closure_kind: ty::ClosureKind,
408 trait_closure_kind: ty::ClosureKind,
409 ) -> Result<bool, ()> {
410 match (actual_closure_kind, trait_closure_kind) {
411 (ty::ClosureKind::Fn, ty::ClosureKind::Fn)
412 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
413 | (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
414 // No adapter needed.
417 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
418 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
419 // `fn(&mut self, ...)`. In fact, at codegen time, these are
420 // basically the same thing, so we can just return llfn.
423 (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce)
424 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
425 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
426 // self, ...)`. We want a `fn(self, ...)`. We can produce
427 // this by doing something like:
429 // fn call_once(self, ...) { call_mut(&self, ...) }
430 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
432 // These are both the same at codegen time.
435 (ty::ClosureKind::FnMut, _) | (ty::ClosureKind::FnOnce, _) => Err(()),