1 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
2 use crate::ty::print::{FmtPrinter, Printer};
3 use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitable};
4 use crate::ty::{EarlyBinder, InternalSubsts, SubstsRef};
5 use rustc_errors::ErrorGuaranteed;
6 use rustc_hir::def::Namespace;
7 use rustc_hir::def_id::{CrateNum, DefId};
8 use rustc_hir::lang_items::LangItem;
9 use rustc_index::bit_set::FiniteBitSet;
10 use rustc_macros::HashStable;
11 use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
12 use rustc_span::Symbol;
16 /// A monomorphized `InstanceDef`.
18 /// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
19 /// simply couples a potentially generic `InstanceDef` with some substs, and codegen and const eval
20 /// will do all required substitution as they run.
21 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
22 #[derive(HashStable, Lift, TypeFoldable, TypeVisitable)]
23 pub struct Instance<'tcx> {
24 pub def: InstanceDef<'tcx>,
25 pub substs: SubstsRef<'tcx>,
28 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
29 #[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable, Lift)]
30 pub enum InstanceDef<'tcx> {
31 /// A user-defined callable item.
37 Item(ty::WithOptConstParam<DefId>),
39 /// An intrinsic `fn` item (with `"rust-intrinsic"` or `"platform-intrinsic"` ABI).
41 /// Alongside `Virtual`, this is the only `InstanceDef` that does not have its own callable MIR.
42 /// Instead, codegen and const eval "magically" evaluate calls to intrinsics purely in the
46 /// `<T as Trait>::method` where `method` receives unsizeable `self: Self` (part of the
47 /// `unsized_locals` feature).
49 /// The generated shim will take `Self` via `*mut Self` - conceptually this is `&owned Self` -
50 /// and dereference the argument to call the original function.
53 /// `fn()` pointer where the function itself cannot be turned into a pointer.
55 /// One example is `<dyn Trait as Trait>::fn`, where the shim contains
56 /// a virtual call, which codegen supports only via a direct call to the
57 /// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
59 /// Another example is functions annotated with `#[track_caller]`, which
60 /// must have their implicit caller location argument populated for a call.
61 /// Because this is a required part of the function's ABI but can't be tracked
62 /// as a property of the function pointer, we use a single "caller location"
63 /// (the definition of the function itself).
66 /// `<fn() as FnTrait>::call_*` (generated `FnTrait` implementation for `fn()` pointers).
68 /// `DefId` is `FnTrait::call_*`.
69 FnPtrShim(DefId, Ty<'tcx>),
71 /// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
73 /// This `InstanceDef` does not have callable MIR. Calls to `Virtual` instances must be
74 /// codegen'd as virtual calls through the vtable.
76 /// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
78 Virtual(DefId, usize),
80 /// `<[FnMut closure] as FnOnce>::call_once`.
82 /// The `DefId` is the ID of the `call_once` method in `FnOnce`.
83 ClosureOnceShim { call_once: DefId, track_caller: bool },
85 /// `core::ptr::drop_in_place::<T>`.
87 /// The `DefId` is for `core::ptr::drop_in_place`.
88 /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
90 DropGlue(DefId, Option<Ty<'tcx>>),
92 /// Compiler-generated `<T as Clone>::clone` implementation.
94 /// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
95 /// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
97 /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
98 CloneShim(DefId, Ty<'tcx>),
101 impl<'tcx> Instance<'tcx> {
102 /// Returns the `Ty` corresponding to this `Instance`, with generic substitutions applied and
103 /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
104 pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
105 let ty = tcx.type_of(self.def.def_id());
106 tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
109 /// Finds a crate that contains a monomorphization of this instance that
110 /// can be linked to from the local crate. A return value of `None` means
111 /// no upstream crate provides such an exported monomorphization.
113 /// This method already takes into account the global `-Zshare-generics`
114 /// setting, always returning `None` if `share-generics` is off.
115 pub fn upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum> {
116 // If we are not in share generics mode, we don't link to upstream
117 // monomorphizations but always instantiate our own internal versions
119 if !tcx.sess.opts.share_generics() {
123 // If this is an item that is defined in the local crate, no upstream
124 // crate can know about it/provide a monomorphization.
125 if self.def_id().is_local() {
129 // If this a non-generic instance, it cannot be a shared monomorphization.
130 self.substs.non_erasable_generics().next()?;
133 InstanceDef::Item(def) => tcx
134 .upstream_monomorphizations_for(def.did)
135 .and_then(|monos| monos.get(&self.substs).cloned()),
136 InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.substs),
142 impl<'tcx> InstanceDef<'tcx> {
144 pub fn def_id(self) -> DefId {
146 InstanceDef::Item(def) => def.did,
147 InstanceDef::VTableShim(def_id)
148 | InstanceDef::ReifyShim(def_id)
149 | InstanceDef::FnPtrShim(def_id, _)
150 | InstanceDef::Virtual(def_id, _)
151 | InstanceDef::Intrinsic(def_id)
152 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
153 | InstanceDef::DropGlue(def_id, _)
154 | InstanceDef::CloneShim(def_id, _) => def_id,
158 /// Returns the `DefId` of instances which might not require codegen locally.
159 pub fn def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId> {
161 ty::InstanceDef::Item(def) => Some(def.did),
162 ty::InstanceDef::DropGlue(def_id, Some(_)) => Some(def_id),
163 InstanceDef::VTableShim(..)
164 | InstanceDef::ReifyShim(..)
165 | InstanceDef::FnPtrShim(..)
166 | InstanceDef::Virtual(..)
167 | InstanceDef::Intrinsic(..)
168 | InstanceDef::ClosureOnceShim { .. }
169 | InstanceDef::DropGlue(..)
170 | InstanceDef::CloneShim(..) => None,
175 pub fn with_opt_param(self) -> ty::WithOptConstParam<DefId> {
177 InstanceDef::Item(def) => def,
178 InstanceDef::VTableShim(def_id)
179 | InstanceDef::ReifyShim(def_id)
180 | InstanceDef::FnPtrShim(def_id, _)
181 | InstanceDef::Virtual(def_id, _)
182 | InstanceDef::Intrinsic(def_id)
183 | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
184 | InstanceDef::DropGlue(def_id, _)
185 | InstanceDef::CloneShim(def_id, _) => ty::WithOptConstParam::unknown(def_id),
190 pub fn get_attrs(&self, tcx: TyCtxt<'tcx>, attr: Symbol) -> ty::Attributes<'tcx> {
191 tcx.get_attrs(self.def_id(), attr)
194 /// Returns `true` if the LLVM version of this instance is unconditionally
195 /// marked with `inline`. This implies that a copy of this instance is
196 /// generated in every codegen unit.
197 /// Note that this is only a hint. See the documentation for
198 /// `generates_cgu_internal_copy` for more information.
199 pub fn requires_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
200 use rustc_hir::definitions::DefPathData;
201 let def_id = match *self {
202 ty::InstanceDef::Item(def) => def.did,
203 ty::InstanceDef::DropGlue(_, Some(_)) => return false,
207 tcx.def_key(def_id).disambiguated_data.data,
208 DefPathData::Ctor | DefPathData::ClosureExpr
212 /// Returns `true` if the machine code for this instance is instantiated in
213 /// each codegen unit that references it.
214 /// Note that this is only a hint! The compiler can globally decide to *not*
215 /// do this in order to speed up compilation. CGU-internal copies are
216 /// only exist to enable inlining. If inlining is not performed (e.g. at
217 /// `-Copt-level=0`) then the time for generating them is wasted and it's
218 /// better to create a single copy with external linkage.
219 pub fn generates_cgu_internal_copy(&self, tcx: TyCtxt<'tcx>) -> bool {
220 if self.requires_inline(tcx) {
223 if let ty::InstanceDef::DropGlue(.., Some(ty)) = *self {
224 // Drop glue generally wants to be instantiated at every codegen
225 // unit, but without an #[inline] hint. We should make this
226 // available to normal end-users.
227 if tcx.sess.opts.incremental.is_none() {
230 // When compiling with incremental, we can generate a *lot* of
231 // codegen units. Including drop glue into all of them has a
232 // considerable compile time cost.
234 // We include enums without destructors to allow, say, optimizing
235 // drops of `Option::None` before LTO. We also respect the intent of
236 // `#[inline]` on `Drop::drop` implementations.
237 return ty.ty_adt_def().map_or(true, |adt_def| {
238 adt_def.destructor(tcx).map_or_else(
239 || adt_def.is_enum(),
240 |dtor| tcx.codegen_fn_attrs(dtor.did).requests_inline(),
244 tcx.codegen_fn_attrs(self.def_id()).requests_inline()
247 pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
249 InstanceDef::Item(ty::WithOptConstParam { did: def_id, .. })
250 | InstanceDef::Virtual(def_id, _) => {
251 tcx.body_codegen_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
253 InstanceDef::ClosureOnceShim { call_once: _, track_caller } => track_caller,
258 /// Returns `true` when the MIR body associated with this instance should be monomorphized
259 /// by its users (e.g. codegen or miri) by substituting the `substs` from `Instance` (see
260 /// `Instance::substs_for_mir_body`).
262 /// Otherwise, returns `false` only for some kinds of shims where the construction of the MIR
263 /// body should perform necessary substitutions.
264 pub fn has_polymorphic_mir_body(&self) -> bool {
266 InstanceDef::CloneShim(..)
267 | InstanceDef::FnPtrShim(..)
268 | InstanceDef::DropGlue(_, Some(_)) => false,
269 InstanceDef::ClosureOnceShim { .. }
270 | InstanceDef::DropGlue(..)
271 | InstanceDef::Item(_)
272 | InstanceDef::Intrinsic(..)
273 | InstanceDef::ReifyShim(..)
274 | InstanceDef::Virtual(..)
275 | InstanceDef::VTableShim(..) => true,
281 f: &mut fmt::Formatter<'_>,
282 instance: &Instance<'_>,
283 type_length: rustc_session::Limit,
285 ty::tls::with(|tcx| {
286 let substs = tcx.lift(instance.substs).expect("could not lift for printing");
288 let s = FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
289 .print_def_path(instance.def_id(), substs)?
295 InstanceDef::Item(_) => Ok(()),
296 InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
297 InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
298 InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
299 InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
300 InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
301 InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
302 InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
303 InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
304 InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
308 pub struct ShortInstance<'a, 'tcx>(pub &'a Instance<'tcx>, pub usize);
310 impl<'a, 'tcx> fmt::Display for ShortInstance<'a, 'tcx> {
311 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
312 fmt_instance(f, self.0, rustc_session::Limit(self.1))
316 impl<'tcx> fmt::Display for Instance<'tcx> {
317 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
318 ty::tls::with(|tcx| fmt_instance(f, self, tcx.type_length_limit()))
322 impl<'tcx> Instance<'tcx> {
323 pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
325 !substs.has_escaping_bound_vars(),
326 "substs of instance {:?} not normalized for codegen: {:?}",
330 Instance { def: InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)), substs }
333 pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
334 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
335 ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
336 ty::GenericParamDefKind::Type { .. } => {
337 bug!("Instance::mono: {:?} has type parameters", def_id)
339 ty::GenericParamDefKind::Const { .. } => {
340 bug!("Instance::mono: {:?} has const parameters", def_id)
344 Instance::new(def_id, substs)
348 pub fn def_id(&self) -> DefId {
352 /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
353 /// this is used to find the precise code that will run for a trait method invocation,
356 /// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
357 /// For example, in a context like this,
359 /// ```ignore (illustrative)
360 /// fn foo<T: Debug>(t: T) { ... }
363 /// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
364 /// know what code ought to run. (Note that this setting is also affected by the
365 /// `RevealMode` in the parameter environment.)
367 /// Presuming that coherence and type-check have succeeded, if this method is invoked
368 /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
369 /// `Ok(Some(instance))`.
371 /// Returns `Err(ErrorGuaranteed)` when the `Instance` resolution process
372 /// couldn't complete due to errors elsewhere - this is distinct
373 /// from `Ok(None)` to avoid misleading diagnostics when an error
374 /// has already been/will be emitted, for the original cause
377 param_env: ty::ParamEnv<'tcx>,
379 substs: SubstsRef<'tcx>,
380 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
381 Instance::resolve_opt_const_arg(
384 ty::WithOptConstParam::unknown(def_id),
389 pub fn expect_resolve(
391 param_env: ty::ParamEnv<'tcx>,
393 substs: SubstsRef<'tcx>,
394 ) -> Instance<'tcx> {
395 match ty::Instance::resolve(tcx, param_env, def_id, substs) {
396 Ok(Some(instance)) => instance,
398 "failed to resolve instance for {}",
399 tcx.def_path_str_with_substs(def_id, substs)
404 // This should be kept up to date with `resolve`.
405 pub fn resolve_opt_const_arg(
407 param_env: ty::ParamEnv<'tcx>,
408 def: ty::WithOptConstParam<DefId>,
409 substs: SubstsRef<'tcx>,
410 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
411 // All regions in the result of this query are erased, so it's
412 // fine to erase all of the input regions.
414 // HACK(eddyb) erase regions in `substs` first, so that `param_env.and(...)`
415 // below is more likely to ignore the bounds in scope (e.g. if the only
416 // generic parameters mentioned by `substs` were lifetime ones).
417 let substs = tcx.erase_regions(substs);
419 // FIXME(eddyb) should this always use `param_env.with_reveal_all()`?
420 if let Some((did, param_did)) = def.as_const_arg() {
421 tcx.resolve_instance_of_const_arg(
422 tcx.erase_regions(param_env.and((did, param_did, substs))),
425 tcx.resolve_instance(tcx.erase_regions(param_env.and((def.did, substs))))
429 pub fn resolve_for_fn_ptr(
431 param_env: ty::ParamEnv<'tcx>,
433 substs: SubstsRef<'tcx>,
434 ) -> Option<Instance<'tcx>> {
435 debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
436 // Use either `resolve_closure` or `resolve_for_vtable`
437 assert!(!tcx.is_closure(def_id), "Called `resolve_for_fn_ptr` on closure: {:?}", def_id);
438 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
440 InstanceDef::Item(def) if resolved.def.requires_caller_location(tcx) => {
441 debug!(" => fn pointer created for function with #[track_caller]");
442 resolved.def = InstanceDef::ReifyShim(def.did);
444 InstanceDef::Virtual(def_id, _) => {
445 debug!(" => fn pointer created for virtual call");
446 resolved.def = InstanceDef::ReifyShim(def_id);
455 pub fn resolve_for_vtable(
457 param_env: ty::ParamEnv<'tcx>,
459 substs: SubstsRef<'tcx>,
460 ) -> Option<Instance<'tcx>> {
461 debug!("resolve_for_vtable(def_id={:?}, substs={:?})", def_id, substs);
462 let fn_sig = tcx.fn_sig(def_id).subst_identity();
463 let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
464 && fn_sig.input(0).skip_binder().is_param(0)
465 && tcx.generics_of(def_id).has_self;
467 debug!(" => associated item with unsizeable self: Self");
468 Some(Instance { def: InstanceDef::VTableShim(def_id), substs })
470 Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
472 InstanceDef::Item(def) => {
473 // We need to generate a shim when we cannot guarantee that
474 // the caller of a trait object method will be aware of
475 // `#[track_caller]` - this ensures that the caller
476 // and callee ABI will always match.
478 // The shim is generated when all of these conditions are met:
480 // 1) The underlying method expects a caller location parameter
482 if resolved.def.requires_caller_location(tcx)
483 // 2) The caller location parameter comes from having `#[track_caller]`
484 // on the implementation, and *not* on the trait method.
485 && !tcx.should_inherit_track_caller(def.did)
486 // If the method implementation comes from the trait definition itself
487 // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
488 // then we don't need to generate a shim. This check is needed because
489 // `should_inherit_track_caller` returns `false` if our method
490 // implementation comes from the trait block, and not an impl block
492 tcx.opt_associated_item(def.did),
494 container: ty::AssocItemContainer::TraitContainer,
499 if tcx.is_closure(def.did) {
500 debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
501 def.did, def_id, substs);
503 // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
504 // - unlike functions, invoking a closure always goes through a
506 resolved = Instance { def: InstanceDef::ReifyShim(def_id), substs };
509 " => vtable fn pointer created for function with #[track_caller]: {:?}", def.did
511 resolved.def = InstanceDef::ReifyShim(def.did);
515 InstanceDef::Virtual(def_id, _) => {
516 debug!(" => vtable fn pointer created for virtual call");
517 resolved.def = InstanceDef::ReifyShim(def_id);
527 pub fn resolve_closure(
530 substs: ty::SubstsRef<'tcx>,
531 requested_kind: ty::ClosureKind,
532 ) -> Option<Instance<'tcx>> {
533 let actual_kind = substs.as_closure().kind();
535 match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
536 Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
537 _ => Some(Instance::new(def_id, substs)),
541 pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
542 let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
543 let substs = tcx.intern_substs(&[ty.into()]);
544 Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
547 #[instrument(level = "debug", skip(tcx), ret)]
548 pub fn fn_once_adapter_instance(
551 substs: ty::SubstsRef<'tcx>,
552 ) -> Option<Instance<'tcx>> {
553 let fn_once = tcx.require_lang_item(LangItem::FnOnce, None);
555 .associated_items(fn_once)
556 .in_definition_order()
557 .find(|it| it.kind == ty::AssocKind::Fn)
561 tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
562 let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
564 let self_ty = tcx.mk_closure(closure_did, substs);
566 let sig = substs.as_closure().sig();
568 tcx.try_normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig).ok()?;
569 assert_eq!(sig.inputs().len(), 1);
570 let substs = tcx.mk_substs_trait(self_ty, [sig.inputs()[0].into()]);
572 debug!(?self_ty, ?sig);
573 Some(Instance { def, substs })
576 /// Depending on the kind of `InstanceDef`, the MIR body associated with an
577 /// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
578 /// cases the MIR body is expressed in terms of the types found in the substitution array.
579 /// In the former case, we want to substitute those generic types and replace them with the
580 /// values from the substs when monomorphizing the function body. But in the latter case, we
581 /// don't want to do that substitution, since it has already been done effectively.
583 /// This function returns `Some(substs)` in the former case and `None` otherwise -- i.e., if
584 /// this function returns `None`, then the MIR body does not require substitution during
586 fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
587 if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
590 pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
592 T: TypeFoldable<'tcx> + Copy,
594 if let Some(substs) = self.substs_for_mir_body() {
595 EarlyBinder(*v).subst(tcx, substs)
602 pub fn subst_mir_and_normalize_erasing_regions<T>(
605 param_env: ty::ParamEnv<'tcx>,
609 T: TypeFoldable<'tcx> + Clone,
611 if let Some(substs) = self.substs_for_mir_body() {
612 tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
614 tcx.normalize_erasing_regions(param_env, v)
619 pub fn try_subst_mir_and_normalize_erasing_regions<T>(
622 param_env: ty::ParamEnv<'tcx>,
624 ) -> Result<T, NormalizationError<'tcx>>
626 T: TypeFoldable<'tcx> + Clone,
628 if let Some(substs) = self.substs_for_mir_body() {
629 tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
631 tcx.try_normalize_erasing_regions(param_env, v)
635 /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
636 /// identity parameters if they are determined to be unused in `instance.def`.
637 pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {
638 debug!("polymorphize: running polymorphization analysis");
639 if !tcx.sess.opts.unstable_opts.polymorphize {
643 let polymorphized_substs = polymorphize(tcx, self.def, self.substs);
644 debug!("polymorphize: self={:?} polymorphized_substs={:?}", self, polymorphized_substs);
645 Self { def: self.def, substs: polymorphized_substs }
649 fn polymorphize<'tcx>(
651 instance: ty::InstanceDef<'tcx>,
652 substs: SubstsRef<'tcx>,
653 ) -> SubstsRef<'tcx> {
654 debug!("polymorphize({:?}, {:?})", instance, substs);
655 let unused = tcx.unused_generic_params(instance);
656 debug!("polymorphize: unused={:?}", unused);
658 // If this is a closure or generator then we need to handle the case where another closure
659 // from the function is captured as an upvar and hasn't been polymorphized. In this case,
660 // the unpolymorphized upvar closure would result in a polymorphized closure producing
661 // multiple mono items (and eventually symbol clashes).
662 let def_id = instance.def_id();
663 let upvars_ty = if tcx.is_closure(def_id) {
664 Some(substs.as_closure().tupled_upvars_ty())
665 } else if tcx.type_of(def_id).is_generator() {
666 Some(substs.as_generator().tupled_upvars_ty())
670 let has_upvars = upvars_ty.map_or(false, |ty| !ty.tuple_fields().is_empty());
671 debug!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty, has_upvars);
673 struct PolymorphizationFolder<'tcx> {
677 impl<'tcx> ty::TypeFolder<'tcx> for PolymorphizationFolder<'tcx> {
678 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
682 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
683 debug!("fold_ty: ty={:?}", ty);
685 ty::Closure(def_id, substs) => {
686 let polymorphized_substs = polymorphize(
688 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
691 if substs == polymorphized_substs {
694 self.tcx.mk_closure(def_id, polymorphized_substs)
697 ty::Generator(def_id, substs, movability) => {
698 let polymorphized_substs = polymorphize(
700 ty::InstanceDef::Item(ty::WithOptConstParam::unknown(def_id)),
703 if substs == polymorphized_substs {
706 self.tcx.mk_generator(def_id, polymorphized_substs, movability)
709 _ => ty.super_fold_with(self),
714 InternalSubsts::for_item(tcx, def_id, |param, _| {
715 let is_unused = unused.is_unused(param.index);
716 debug!("polymorphize: param={:?} is_unused={:?}", param, is_unused);
718 // Upvar case: If parameter is a type parameter..
719 ty::GenericParamDefKind::Type { .. } if
720 // ..and has upvars..
722 // ..and this param has the same type as the tupled upvars..
723 upvars_ty == Some(substs[param.index as usize].expect_ty()) => {
724 // ..then double-check that polymorphization marked it used..
725 debug_assert!(!is_unused);
726 // ..and polymorphize any closures/generators captured as upvars.
727 let upvars_ty = upvars_ty.unwrap();
728 let polymorphized_upvars_ty = upvars_ty.fold_with(
729 &mut PolymorphizationFolder { tcx });
730 debug!("polymorphize: polymorphized_upvars_ty={:?}", polymorphized_upvars_ty);
731 ty::GenericArg::from(polymorphized_upvars_ty)
734 // Simple case: If parameter is a const or type parameter..
735 ty::GenericParamDefKind::Const { .. } | ty::GenericParamDefKind::Type { .. } if
736 // ..and is within range and unused..
737 unused.is_unused(param.index) =>
738 // ..then use the identity for this parameter.
739 tcx.mk_param_from_def(param),
741 // Otherwise, use the parameter as before.
742 _ => substs[param.index as usize],
747 fn needs_fn_once_adapter_shim(
748 actual_closure_kind: ty::ClosureKind,
749 trait_closure_kind: ty::ClosureKind,
750 ) -> Result<bool, ()> {
751 match (actual_closure_kind, trait_closure_kind) {
752 (ty::ClosureKind::Fn, ty::ClosureKind::Fn)
753 | (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
754 | (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
755 // No adapter needed.
758 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
759 // The closure fn `llfn` is a `fn(&self, ...)`. We want a
760 // `fn(&mut self, ...)`. In fact, at codegen time, these are
761 // basically the same thing, so we can just return llfn.
764 (ty::ClosureKind::Fn | ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
765 // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
766 // self, ...)`. We want a `fn(self, ...)`. We can produce
767 // this by doing something like:
769 // fn call_once(self, ...) { call_mut(&self, ...) }
770 // fn call_once(mut self, ...) { call_mut(&mut self, ...) }
772 // These are both the same at codegen time.
775 (ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce, _) => Err(()),
779 // Set bits represent unused generic parameters.
780 // An empty set indicates that all parameters are used.
781 #[derive(Debug, Copy, Clone, Eq, PartialEq, Decodable, Encodable, HashStable)]
782 pub struct UnusedGenericParams(FiniteBitSet<u32>);
784 impl UnusedGenericParams {
785 pub fn new_all_unused(amount: u32) -> Self {
786 let mut bitset = FiniteBitSet::new_empty();
787 bitset.set_range(0..amount);
791 pub fn new_all_used() -> Self {
792 Self(FiniteBitSet::new_empty())
795 pub fn mark_used(&mut self, idx: u32) {
799 pub fn is_unused(&self, idx: u32) -> bool {
800 self.0.contains(idx).unwrap_or(false)
803 pub fn is_used(&self, idx: u32) -> bool {
807 pub fn all_used(&self) -> bool {