1 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
2 use crate::ty::print::{FmtPrinter, Printer};
3 use crate::ty::subst::{InternalSubsts, Subst};
4 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
5 use rustc_errors::ErrorReported;
6 use rustc_hir::def::Namespace;
7 use rustc_hir::def_id::{CrateNum, DefId};
8 use rustc_hir::lang_items::LangItem;
9 use rustc_macros::HashStable;
10
11 use std::fmt;
12
13 /// A monomorphized `InstanceDef`.
14 ///
15 /// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
16 /// simply couples a potentially generic `InstanceDef` with some substs, and codegen and const eval
17 /// will do all required substitution as they run.
18 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
19 #[derive(HashStable, Lift)]
20 pub struct Instance<'tcx> {
21 pub def: InstanceDef<'tcx>,
22 pub substs: SubstsRef<'tcx>,
23 }
24
25 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
26 #[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable)]
27 pub enum InstanceDef<'tcx> {
28 /// A user-defined callable item.
29 ///
30 /// This includes:
31 /// - `fn` items
32 /// - closures
33 /// - generators
34 Item(ty::WithOptConstParam<DefId>),
35
36 /// An intrinsic `fn` item (with `"rust-intrinsic"` or `"platform-intrinsic"` ABI).
37 ///
38 /// Alongside `Virtual`, this is the only `InstanceDef` that does not have its own callable MIR.
39 /// Instead, codegen and const eval "magically" evaluate calls to intrinsics purely in the
40 /// caller.
41 Intrinsic(DefId),
42
43 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self` (part of the
44 /// `unsized_locals` feature).
45 ///
46 /// The generated shim will take `Self` via `*mut Self` - conceptually this is `&owned Self` -
47 /// and dereference the argument to call the original function.
48 VtableShim(DefId),
49
50 /// `fn()` pointer where the function itself cannot be turned into a pointer.
51 ///
52 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
53 /// a virtual call, which codegen supports only via a direct call to the
54 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
55 ///
56 /// Another example is functions annotated with `#[track_caller]`, which
57 /// must have their implicit caller location argument populated for a call.
58 /// Because this is a required part of the function's ABI but can't be tracked
59 /// as a property of the function pointer, we use a single "caller location"
60 /// (the definition of the function itself).
61 ReifyShim(DefId),
62
63 /// `<fn() as FnTrait>::call_*` (generated `FnTrait` implementation for `fn()` pointers).
64 ///
65 /// `DefId` is `FnTrait::call_*`.
66 FnPtrShim(DefId, Ty<'tcx>),
67
68 /// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
69 ///
70 /// This `InstanceDef` does not have callable MIR. Calls to `Virtual` instances must be
71 /// codegen'd as virtual calls through the vtable.
72 ///
73 /// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
74 /// details on that).
75 Virtual(DefId, usize),
76
77 /// `<[FnMut closure] as FnOnce>::call_once`.
78 ///
79 /// The `DefId` is the ID of the `call_once` method in `FnOnce`.
80 ClosureOnceShim { call_once: DefId, track_caller: bool },
81
82 /// `core::ptr::drop_in_place::<T>`.
83 ///
84 /// The `DefId` is for `core::ptr::drop_in_place`.
85 /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
86 /// glue.
87 DropGlue(DefId, Option<Ty<'tcx>>),
88
89 /// Compiler-generated `<T as Clone>::clone` implementation.
90 ///
91 /// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
92 /// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
93 ///
94 /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
95 CloneShim(DefId, Ty<'tcx>),
96 }
97
98 impl<'tcx> Instance<'tcx> {
99 /// Returns the `Ty` corresponding to this `Instance`, with generic substitutions applied and
100 /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx>101 pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
102 let ty = tcx.type_of(self.def.def_id());
103 tcx.subst_and_normalize_erasing_regions(self.substs, param_env, &ty)
104 }
105
106 /// Finds a crate that contains a monomorphization of this instance that
107 /// can be linked to from the local crate. A return value of `None` means
108 /// no upstream crate provides such an exported monomorphization.
109 ///
110 /// This method already takes into account the global `-Zshare-generics`
111 /// setting, always returning `None` if `share-generics` is off.
upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum>112 pub fn upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum> {
113 // If we are not in share generics mode, we don't link to upstream
114 // monomorphizations but always instantiate our own internal versions
115 // instead.
116 if !tcx.sess.opts.share_generics() {
117 return None;
118 }
119
120 // If this is an item that is defined in the local crate, no upstream
121 // crate can know about it/provide a monomorphization.
122 if self.def_id().is_local() {
123 return None;
124 }
125
126 // If this a non-generic instance, it cannot be a shared monomorphization.
127 self.substs.non_erasable_generics().next()?;
128
129 match self.def {
130 InstanceDef::Item(def) => tcx
131 .upstream_monomorphizations_for(def.did)
132 .and_then(|monos| monos.get(&self.substs).cloned()),
133 InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.substs),
134 _ => None,
135 }
136 }
137 }
138
139 impl<'tcx> InstanceDef<'tcx> {
140 #[inline]
def_id(self) -> DefId141 pub fn def_id(self) -> DefId {
142 match self {
143 InstanceDef::Item(def) => def.did,
144 InstanceDef::VtableShim(def_id)
145 | InstanceDef::ReifyShim(def_id)
146 | InstanceDef::FnPtrShim(def_id, _)
147 | InstanceDef::Virtual(def_id, _)
148 | InstanceDef::Intrinsic(def_id)
149 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
150 | InstanceDef::DropGlue(def_id, _)
151 | InstanceDef::CloneShim(def_id, _) => def_id,
152 }
153 }
154
155 /// Returns the `DefId` of instances which might not require codegen locally.
def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId>156 pub fn def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId> {
157 match self {
158 ty::InstanceDef::Item(def) => Some(def.did),
159 ty::InstanceDef::DropGlue(def_id, Some(_)) => Some(def_id),
160 InstanceDef::VtableShim(..)
161 | InstanceDef::ReifyShim(..)
162 | InstanceDef::FnPtrShim(..)
163 | InstanceDef::Virtual(..)
164 | InstanceDef::Intrinsic(..)
165 | InstanceDef::ClosureOnceShim { .. }
166 | InstanceDef::DropGlue(..)
167 | InstanceDef::CloneShim(..) => None,
168 }
169 }
170
171 #[inline]
with_opt_param(self) -> ty::WithOptConstParam<DefId>172 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
173 match self {
174 InstanceDef::Item(def) => def,
175 InstanceDef::VtableShim(def_id)
176 | InstanceDef::ReifyShim(def_id)
177 | InstanceDef::FnPtrShim(def_id, _)
178 | InstanceDef::Virtual(def_id, _)
179 | InstanceDef::Intrinsic(def_id)
180 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
181 | InstanceDef::DropGlue(def_id, _)
182 | InstanceDef::CloneShim(def_id, _) => ty::WithOptConstParam::unknown(def_id),
183 }
184 }
185
186 #[inline]
attrs(&self, tcx: TyCtxt<'tcx>) -> ty::Attributes<'tcx>187 pub fn attrs(&self, tcx: TyCtxt<'tcx>) -> ty::Attributes<'tcx> {
188 tcx.get_attrs(self.def_id())
189 }
190
191 /// Returns `true` if the LLVM version of this instance is unconditionally
192 /// marked with `inline`. This implies that a copy of this instance is
193 /// generated in every codegen unit.
194 /// Note that this is only a hint. See the documentation for
195 /// `generates_cgu_internal_copy` for more information.
requires_inline(&self, tcx: TyCtxt<'tcx>) -> bool196 pub fn requires_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
197 use rustc_hir::definitions::DefPathData;
198 let def_id = match *self {
199 ty::InstanceDef::Item(def) => def.did,
200 ty::InstanceDef::DropGlue(_, Some(_)) => return false,
201 _ => return true,
202 };
203 matches!(
204 tcx.def_key(def_id).disambiguated_data.data,
205 DefPathData::Ctor | DefPathData::ClosureExpr
206 )
207 }
208
209 /// Returns `true` if the machine code for this instance is instantiated in
210 /// each codegen unit that references it.
211 /// Note that this is only a hint! The compiler can globally decide to *not*
212 /// do this in order to speed up compilation. CGU-internal copies are
213 /// only exist to enable inlining. If inlining is not performed (e.g. at
214 /// `-Copt-level=0`) then the time for generating them is wasted and it's
215 /// better to create a single copy with external linkage.
generates_cgu_internal_copy(&self, tcx: TyCtxt<'tcx>) -> bool216 pub fn generates_cgu_internal_copy(&self, tcx: TyCtxt<'tcx>) -> bool {
217 if self.requires_inline(tcx) {
218 return true;
219 }
220 if let ty::InstanceDef::DropGlue(.., Some(ty)) = *self {
221 // Drop glue generally wants to be instantiated at every codegen
222 // unit, but without an #[inline] hint. We should make this
223 // available to normal end-users.
224 if tcx.sess.opts.incremental.is_none() {
225 return true;
226 }
227 // When compiling with incremental, we can generate a *lot* of
228 // codegen units. Including drop glue into all of them has a
229 // considerable compile time cost.
230 //
231 // We include enums without destructors to allow, say, optimizing
232 // drops of `Option::None` before LTO. We also respect the intent of
233 // `#[inline]` on `Drop::drop` implementations.
234 return ty.ty_adt_def().map_or(true, |adt_def| {
235 adt_def.destructor(tcx).map_or_else(
236 || adt_def.is_enum(),
237 |dtor| tcx.codegen_fn_attrs(dtor.did).requests_inline(),
238 )
239 });
240 }
241 tcx.codegen_fn_attrs(self.def_id()).requests_inline()
242 }
243
requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool244 pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
245 match *self {
246 InstanceDef::Item(ty::WithOptConstParam { did: def_id, .. })
247 | InstanceDef::Virtual(def_id, _) => {
248 tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
249 }
250 InstanceDef::ClosureOnceShim { call_once: _, track_caller } => track_caller,
251 _ => false,
252 }
253 }
254
255 /// Returns `true` when the MIR body associated with this instance should be monomorphized
256 /// by its users (e.g. codegen or miri) by substituting the `substs` from `Instance` (see
257 /// `Instance::substs_for_mir_body`).
258 ///
259 /// Otherwise, returns `false` only for some kinds of shims where the construction of the MIR
260 /// body should perform necessary substitutions.
has_polymorphic_mir_body(&self) -> bool261 pub fn has_polymorphic_mir_body(&self) -> bool {
262 match *self {
263 InstanceDef::CloneShim(..)
264 | InstanceDef::FnPtrShim(..)
265 | InstanceDef::DropGlue(_, Some(_)) => false,
266 InstanceDef::ClosureOnceShim { .. }
267 | InstanceDef::DropGlue(..)
268 | InstanceDef::Item(_)
269 | InstanceDef::Intrinsic(..)
270 | InstanceDef::ReifyShim(..)
271 | InstanceDef::Virtual(..)
272 | InstanceDef::VtableShim(..) => true,
273 }
274 }
275 }
276
277 impl<'tcx> fmt::Display for Instance<'tcx> {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result278 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
279 ty::tls::with(|tcx| {
280 let substs = tcx.lift(self.substs).expect("could not lift for printing");
281 FmtPrinter::new(tcx, &mut *f, Namespace::ValueNS)
282 .print_def_path(self.def_id(), substs)?;
283 Ok(())
284 })?;
285
286 match self.def {
287 InstanceDef::Item(_) => Ok(()),
288 InstanceDef::VtableShim(_) => write!(f, " - shim(vtable)"),
289 InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
290 InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
291 InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
292 InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
293 InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
294 InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
295 InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
296 InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
297 }
298 }
299 }
300
301 impl<'tcx> Instance<'tcx> {
new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx>302 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
303 assert!(
304 !substs.has_escaping_bound_vars(),
305 "substs of instance {:?} not normalized for codegen: {:?}",
306 def_id,
307 substs
308 );
309 Instance { def: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)), substs }
310 }
311
mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx>312 pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
313 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
314 ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
315 ty::GenericParamDefKind::Type { .. } => {
316 bug!("Instance::mono: {:?} has type parameters", def_id)
317 }
318 ty::GenericParamDefKind::Const { .. } => {
319 bug!("Instance::mono: {:?} has const parameters", def_id)
320 }
321 });
322
323 Instance::new(def_id, substs)
324 }
325
326 #[inline]
def_id(&self) -> DefId327 pub fn def_id(&self) -> DefId {
328 self.def.def_id()
329 }
330
331 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
332 /// this is used to find the precise code that will run for a trait method invocation,
333 /// if known.
334 ///
335 /// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
336 /// For example, in a context like this,
337 ///
338 /// ```
339 /// fn foo<T: Debug>(t: T) { ... }
340 /// ```
341 ///
342 /// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
343 /// know what code ought to run. (Note that this setting is also affected by the
344 /// `RevealMode` in the parameter environment.)
345 ///
346 /// Presuming that coherence and type-check have succeeded, if this method is invoked
347 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
348 /// `Ok(Some(instance))`.
349 ///
350 /// Returns `Err(ErrorReported)` when the `Instance` resolution process
351 /// couldn't complete due to errors elsewhere - this is distinct
352 /// from `Ok(None)` to avoid misleading diagnostics when an error
353 /// has already been/will be emitted, for the original cause
resolve( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>, ) -> Result<Option<Instance<'tcx>>, ErrorReported>354 pub fn resolve(
355 tcx: TyCtxt<'tcx>,
356 param_env: ty::ParamEnv<'tcx>,
357 def_id: DefId,
358 substs: SubstsRef<'tcx>,
359 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
360 Instance::resolve_opt_const_arg(
361 tcx,
362 param_env,
363 ty::WithOptConstParam::unknown(def_id),
364 substs,
365 )
366 }
367
368 // This should be kept up to date with `resolve`.
369 #[instrument(level = "debug", skip(tcx))]
resolve_opt_const_arg( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, def: ty::WithOptConstParam<DefId>, substs: SubstsRef<'tcx>, ) -> Result<Option<Instance<'tcx>>, ErrorReported>370 pub fn resolve_opt_const_arg(
371 tcx: TyCtxt<'tcx>,
372 param_env: ty::ParamEnv<'tcx>,
373 def: ty::WithOptConstParam<DefId>,
374 substs: SubstsRef<'tcx>,
375 ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
376 // All regions in the result of this query are erased, so it's
377 // fine to erase all of the input regions.
378
379 // HACK(eddyb) erase regions in `substs` first, so that `param_env.and(...)`
380 // below is more likely to ignore the bounds in scope (e.g. if the only
381 // generic parameters mentioned by `substs` were lifetime ones).
382 let substs = tcx.erase_regions(substs);
383
384 // FIXME(eddyb) should this always use `param_env.with_reveal_all()`?
385 if let Some((did, param_did)) = def.as_const_arg() {
386 tcx.resolve_instance_of_const_arg(
387 tcx.erase_regions(param_env.and((did, param_did, substs))),
388 )
389 } else {
390 tcx.resolve_instance(tcx.erase_regions(param_env.and((def.did, substs))))
391 }
392 }
393
resolve_for_fn_ptr( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>, ) -> Option<Instance<'tcx>>394 pub fn resolve_for_fn_ptr(
395 tcx: TyCtxt<'tcx>,
396 param_env: ty::ParamEnv<'tcx>,
397 def_id: DefId,
398 substs: SubstsRef<'tcx>,
399 ) -> Option<Instance<'tcx>> {
400 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
401 // Use either `resolve_closure` or `resolve_for_vtable`
402 assert!(!tcx.is_closure(def_id), "Called `resolve_for_fn_ptr` on closure: {:?}", def_id);
403 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
404 match resolved.def {
405 InstanceDef::Item(def) if resolved.def.requires_caller_location(tcx) => {
406 debug!(" => fn pointer created for function with #[track_caller]");
407 resolved.def = InstanceDef::ReifyShim(def.did);
408 }
409 InstanceDef::Virtual(def_id, _) => {
410 debug!(" => fn pointer created for virtual call");
411 resolved.def = InstanceDef::ReifyShim(def_id);
412 }
413 _ => {}
414 }
415
416 resolved
417 })
418 }
419
resolve_for_vtable( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>, ) -> Option<Instance<'tcx>>420 pub fn resolve_for_vtable(
421 tcx: TyCtxt<'tcx>,
422 param_env: ty::ParamEnv<'tcx>,
423 def_id: DefId,
424 substs: SubstsRef<'tcx>,
425 ) -> Option<Instance<'tcx>> {
426 debug!("resolve_for_vtable(def_id={:?}, substs={:?})", def_id, substs);
427 let fn_sig = tcx.fn_sig(def_id);
428 let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
429 && fn_sig.input(0).skip_binder().is_param(0)
430 && tcx.generics_of(def_id).has_self;
431 if is_vtable_shim {
432 debug!(" => associated item with unsizeable self: Self");
433 Some(Instance { def: InstanceDef::VtableShim(def_id), substs })
434 } else {
435 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
436 match resolved.def {
437 InstanceDef::Item(def) => {
438 // We need to generate a shim when we cannot guarantee that
439 // the caller of a trait object method will be aware of
440 // `#[track_caller]` - this ensures that the caller
441 // and callee ABI will always match.
442 //
443 // The shim is generated when all of these conditions are met:
444 //
445 // 1) The underlying method expects a caller location parameter
446 // in the ABI
447 if resolved.def.requires_caller_location(tcx)
448 // 2) The caller location parameter comes from having `#[track_caller]`
449 // on the implementation, and *not* on the trait method.
450 && !tcx.should_inherit_track_caller(def.did)
451 // If the method implementation comes from the trait definition itself
452 // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
453 // then we don't need to generate a shim. This check is needed because
454 // `should_inherit_track_caller` returns `false` if our method
455 // implementation comes from the trait block, and not an impl block
456 && !matches!(
457 tcx.opt_associated_item(def.did),
458 Some(ty::AssocItem {
459 container: ty::AssocItemContainer::TraitContainer(_),
460 ..
461 })
462 )
463 {
464 if tcx.is_closure(def.did) {
465 debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
466 def.did, def_id, substs);
467
468 // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
469 // - unlike functions, invoking a closure always goes through a
470 // trait.
471 resolved = Instance { def: InstanceDef::ReifyShim(def_id), substs };
472 } else {
473 debug!(
474 " => vtable fn pointer created for function with #[track_caller]: {:?}", def.did
475 );
476 resolved.def = InstanceDef::ReifyShim(def.did);
477 }
478 }
479 }
480 InstanceDef::Virtual(def_id, _) => {
481 debug!(" => vtable fn pointer created for virtual call");
482 resolved.def = InstanceDef::ReifyShim(def_id);
483 }
484 _ => {}
485 }
486
487 resolved
488 })
489 }
490 }
491
resolve_closure( tcx: TyCtxt<'tcx>, def_id: DefId, substs: ty::SubstsRef<'tcx>, requested_kind: ty::ClosureKind, ) -> Instance<'tcx>492 pub fn resolve_closure(
493 tcx: TyCtxt<'tcx>,
494 def_id: DefId,
495 substs: ty::SubstsRef<'tcx>,
496 requested_kind: ty::ClosureKind,
497 ) -> Instance<'tcx> {
498 let actual_kind = substs.as_closure().kind();
499
500 match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
501 Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
502 _ => Instance::new(def_id, substs),
503 }
504 }
505
resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx>506 pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
507 let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
508 let substs = tcx.intern_substs(&[ty.into()]);
509 Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap().unwrap()
510 }
511
fn_once_adapter_instance( tcx: TyCtxt<'tcx>, closure_did: DefId, substs: ty::SubstsRef<'tcx>, ) -> Instance<'tcx>512 pub fn fn_once_adapter_instance(
513 tcx: TyCtxt<'tcx>,
514 closure_did: DefId,
515 substs: ty::SubstsRef<'tcx>,
516 ) -> Instance<'tcx> {
517 debug!("fn_once_adapter_shim({:?}, {:?})", closure_did, substs);
518 let fn_once = tcx.require_lang_item(LangItem::FnOnce, None);
519 let call_once = tcx
520 .associated_items(fn_once)
521 .in_definition_order()
522 .find(|it| it.kind == ty::AssocKind::Fn)
523 .unwrap()
524 .def_id;
525 let track_caller =
526 tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
527 let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
528
529 let self_ty = tcx.mk_closure(closure_did, substs);
530
531 let sig = substs.as_closure().sig();
532 let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig);
533 assert_eq!(sig.inputs().len(), 1);
534 let substs = tcx.mk_substs_trait(self_ty, &[sig.inputs()[0].into()]);
535
536 debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
537 Instance { def, substs }
538 }
539
540 /// Depending on the kind of `InstanceDef`, the MIR body associated with an
541 /// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
542 /// cases the MIR body is expressed in terms of the types found in the substitution array.
543 /// In the former case, we want to substitute those generic types and replace them with the
544 /// values from the substs when monomorphizing the function body. But in the latter case, we
545 /// don't want to do that substitution, since it has already been done effectively.
546 ///
547 /// This function returns `Some(substs)` in the former case and `None` otherwise -- i.e., if
548 /// this function returns `None`, then the MIR body does not require substitution during
549 /// codegen.
substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>>550 fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
551 if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
552 }
553
subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T where T: TypeFoldable<'tcx> + Copy,554 pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
555 where
556 T: TypeFoldable<'tcx> + Copy,
557 {
558 if let Some(substs) = self.substs_for_mir_body() { v.subst(tcx, substs) } else { *v }
559 }
560
561 #[inline(always)]
subst_mir_and_normalize_erasing_regions<T>( &self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, v: T, ) -> T where T: TypeFoldable<'tcx> + Clone,562 pub fn subst_mir_and_normalize_erasing_regions<T>(
563 &self,
564 tcx: TyCtxt<'tcx>,
565 param_env: ty::ParamEnv<'tcx>,
566 v: T,
567 ) -> T
568 where
569 T: TypeFoldable<'tcx> + Clone,
570 {
571 if let Some(substs) = self.substs_for_mir_body() {
572 tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
573 } else {
574 tcx.normalize_erasing_regions(param_env, v)
575 }
576 }
577
578 /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
579 /// identity parameters if they are determined to be unused in `instance.def`.
polymorphize(self, tcx: TyCtxt<'tcx>) -> Self580 pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {
581 debug!("polymorphize: running polymorphization analysis");
582 if !tcx.sess.opts.debugging_opts.polymorphize {
583 return self;
584 }
585
586 let polymorphized_substs = polymorphize(tcx, self.def, self.substs);
587 debug!("polymorphize: self={:?} polymorphized_substs={:?}", self, polymorphized_substs);
588 Self { def: self.def, substs: polymorphized_substs }
589 }
590 }
591
polymorphize<'tcx>( tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>, substs: SubstsRef<'tcx>, ) -> SubstsRef<'tcx>592 fn polymorphize<'tcx>(
593 tcx: TyCtxt<'tcx>,
594 instance: ty::InstanceDef<'tcx>,
595 substs: SubstsRef<'tcx>,
596 ) -> SubstsRef<'tcx> {
597 debug!("polymorphize({:?}, {:?})", instance, substs);
598 let unused = tcx.unused_generic_params(instance);
599 debug!("polymorphize: unused={:?}", unused);
600
601 // If this is a closure or generator then we need to handle the case where another closure
602 // from the function is captured as an upvar and hasn't been polymorphized. In this case,
603 // the unpolymorphized upvar closure would result in a polymorphized closure producing
604 // multiple mono items (and eventually symbol clashes).
605 let def_id = instance.def_id();
606 let upvars_ty = if tcx.is_closure(def_id) {
607 Some(substs.as_closure().tupled_upvars_ty())
608 } else if tcx.type_of(def_id).is_generator() {
609 Some(substs.as_generator().tupled_upvars_ty())
610 } else {
611 None
612 };
613 let has_upvars = upvars_ty.map_or(false, |ty| ty.tuple_fields().count() > 0);
614 debug!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty, has_upvars);
615
616 struct PolymorphizationFolder<'tcx> {
617 tcx: TyCtxt<'tcx>,
618 }
619
620 impl ty::TypeFolder<'tcx> for PolymorphizationFolder<'tcx> {
621 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
622 self.tcx
623 }
624
625 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
626 debug!("fold_ty: ty={:?}", ty);
627 match ty.kind {
628 ty::Closure(def_id, substs) => {
629 let polymorphized_substs = polymorphize(
630 self.tcx,
631 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
632 substs,
633 );
634 if substs == polymorphized_substs {
635 ty
636 } else {
637 self.tcx.mk_closure(def_id, polymorphized_substs)
638 }
639 }
640 ty::Generator(def_id, substs, movability) => {
641 let polymorphized_substs = polymorphize(
642 self.tcx,
643 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
644 substs,
645 );
646 if substs == polymorphized_substs {
647 ty
648 } else {
649 self.tcx.mk_generator(def_id, polymorphized_substs, movability)
650 }
651 }
652 _ => ty.super_fold_with(self),
653 }
654 }
655 }
656
657 InternalSubsts::for_item(tcx, def_id, |param, _| {
658 let is_unused = unused.contains(param.index).unwrap_or(false);
659 debug!("polymorphize: param={:?} is_unused={:?}", param, is_unused);
660 match param.kind {
661 // Upvar case: If parameter is a type parameter..
662 ty::GenericParamDefKind::Type { .. } if
663 // ..and has upvars..
664 has_upvars &&
665 // ..and this param has the same type as the tupled upvars..
666 upvars_ty == Some(substs[param.index as usize].expect_ty()) => {
667 // ..then double-check that polymorphization marked it used..
668 debug_assert!(!is_unused);
669 // ..and polymorphize any closures/generators captured as upvars.
670 let upvars_ty = upvars_ty.unwrap();
671 let polymorphized_upvars_ty = upvars_ty.fold_with(
672 &mut PolymorphizationFolder { tcx });
673 debug!("polymorphize: polymorphized_upvars_ty={:?}", polymorphized_upvars_ty);
674 ty::GenericArg::from(polymorphized_upvars_ty)
675 },
676
677 // Simple case: If parameter is a const or type parameter..
678 ty::GenericParamDefKind::Const { .. } | ty::GenericParamDefKind::Type { .. } if
679 // ..and is within range and unused..
680 unused.contains(param.index).unwrap_or(false) =>
681 // ..then use the identity for this parameter.
682 tcx.mk_param_from_def(param),
683
684 // Otherwise, use the parameter as before.
685 _ => substs[param.index as usize],
686 }
687 })
688 }
689
needs_fn_once_adapter_shim( actual_closure_kind: ty::ClosureKind, trait_closure_kind: ty::ClosureKind, ) -> Result<bool, ()>690 fn needs_fn_once_adapter_shim(
691 actual_closure_kind: ty::ClosureKind,
692 trait_closure_kind: ty::ClosureKind,
693 ) -> Result<bool, ()> {
694 match (actual_closure_kind, trait_closure_kind) {
695 (ty::ClosureKind::Fn, ty::ClosureKind::Fn)
696 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
697 | (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
698 // No adapter needed.
699 Ok(false)
700 }
701 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
702 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
703 // `fn(&mut self, ...)`. In fact, at codegen time, these are
704 // basically the same thing, so we can just return llfn.
705 Ok(false)
706 }
707 (ty::ClosureKind::Fn | ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
708 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
709 // self, ...)`. We want a `fn(self, ...)`. We can produce
710 // this by doing something like:
711 //
712 // fn call_once(self, ...) { call_mut(&self, ...) }
713 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
714 //
715 // These are both the same at codegen time.
716 Ok(true)
717 }
718 (ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce, _) => Err(()),
719 }
720 }
721