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use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::ty::print::{FmtPrinter, Printer};
use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
use crate::ty::{EarlyBinder, GenericArgs, GenericArgsRef, TypeVisitableExt};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::Namespace;
use rustc_hir::def_id::{CrateNum, DefId};
use rustc_hir::lang_items::LangItem;
use rustc_index::bit_set::FiniteBitSet;
use rustc_macros::HashStable;
use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
use rustc_span::Symbol;
use std::fmt;
/// A monomorphized `InstanceDef`.
///
/// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
/// simply couples a potentially generic `InstanceDef` with some args, and codegen and const eval
/// will do all required substitution as they run.
///
/// Note: the `Lift` impl is currently not used by rustc, but is used by
/// rustc_codegen_cranelift when the `jit` feature is enabled.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
#[derive(HashStable, Lift, TypeFoldable, TypeVisitable)]
pub struct Instance<'tcx> {
pub def: InstanceDef<'tcx>,
pub args: GenericArgsRef<'tcx>,
}
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable, Lift)]
pub enum InstanceDef<'tcx> {
/// A user-defined callable item.
///
/// This includes:
/// - `fn` items
/// - closures
/// - generators
Item(DefId),
/// An intrinsic `fn` item (with `"rust-intrinsic"` or `"platform-intrinsic"` ABI).
///
/// Alongside `Virtual`, this is the only `InstanceDef` that does not have its own callable MIR.
/// Instead, codegen and const eval "magically" evaluate calls to intrinsics purely in the
/// caller.
Intrinsic(DefId),
/// `<T as Trait>::method` where `method` receives unsizeable `self: Self` (part of the
/// `unsized_locals` feature).
///
/// The generated shim will take `Self` via `*mut Self` - conceptually this is `&owned Self` -
/// and dereference the argument to call the original function.
VTableShim(DefId),
/// `fn()` pointer where the function itself cannot be turned into a pointer.
///
/// One example is `<dyn Trait as Trait>::fn`, where the shim contains
/// a virtual call, which codegen supports only via a direct call to the
/// `<dyn Trait as Trait>::fn` instance (an `InstanceDef::Virtual`).
///
/// Another example is functions annotated with `#[track_caller]`, which
/// must have their implicit caller location argument populated for a call.
/// Because this is a required part of the function's ABI but can't be tracked
/// as a property of the function pointer, we use a single "caller location"
/// (the definition of the function itself).
ReifyShim(DefId),
/// `<fn() as FnTrait>::call_*` (generated `FnTrait` implementation for `fn()` pointers).
///
/// `DefId` is `FnTrait::call_*`.
FnPtrShim(DefId, Ty<'tcx>),
/// Dynamic dispatch to `<dyn Trait as Trait>::fn`.
///
/// This `InstanceDef` does not have callable MIR. Calls to `Virtual` instances must be
/// codegen'd as virtual calls through the vtable.
///
/// If this is reified to a `fn` pointer, a `ReifyShim` is used (see `ReifyShim` above for more
/// details on that).
Virtual(DefId, usize),
/// `<[FnMut closure] as FnOnce>::call_once`.
///
/// The `DefId` is the ID of the `call_once` method in `FnOnce`.
ClosureOnceShim { call_once: DefId, track_caller: bool },
/// Compiler-generated accessor for thread locals which returns a reference to the thread local
/// the `DefId` defines. This is used to export thread locals from dylibs on platforms lacking
/// native support.
ThreadLocalShim(DefId),
/// `core::ptr::drop_in_place::<T>`.
///
/// The `DefId` is for `core::ptr::drop_in_place`.
/// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
/// glue.
DropGlue(DefId, Option<Ty<'tcx>>),
/// Compiler-generated `<T as Clone>::clone` implementation.
///
/// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
/// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
///
/// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
CloneShim(DefId, Ty<'tcx>),
/// Compiler-generated `<T as FnPtr>::addr` implementation.
///
/// Automatically generated for all potentially higher-ranked `fn(I) -> R` types.
///
/// The `DefId` is for `FnPtr::addr`, the `Ty` is the type `T`.
FnPtrAddrShim(DefId, Ty<'tcx>),
}
impl<'tcx> Instance<'tcx> {
/// Returns the `Ty` corresponding to this `Instance`, with generic substitutions applied and
/// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
let ty = tcx.type_of(self.def.def_id());
tcx.instantiate_and_normalize_erasing_regions(self.args, param_env, ty)
}
/// Finds a crate that contains a monomorphization of this instance that
/// can be linked to from the local crate. A return value of `None` means
/// no upstream crate provides such an exported monomorphization.
///
/// This method already takes into account the global `-Zshare-generics`
/// setting, always returning `None` if `share-generics` is off.
pub fn upstream_monomorphization(&self, tcx: TyCtxt<'tcx>) -> Option<CrateNum> {
// If we are not in share generics mode, we don't link to upstream
// monomorphizations but always instantiate our own internal versions
// instead.
if !tcx.sess.opts.share_generics() {
return None;
}
// If this is an item that is defined in the local crate, no upstream
// crate can know about it/provide a monomorphization.
if self.def_id().is_local() {
return None;
}
// If this a non-generic instance, it cannot be a shared monomorphization.
self.args.non_erasable_generics(tcx, self.def_id()).next()?;
match self.def {
InstanceDef::Item(def) => tcx
.upstream_monomorphizations_for(def)
.and_then(|monos| monos.get(&self.args).cloned()),
InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.args),
_ => None,
}
}
}
impl<'tcx> InstanceDef<'tcx> {
#[inline]
pub fn def_id(self) -> DefId {
match self {
InstanceDef::Item(def_id)
| InstanceDef::VTableShim(def_id)
| InstanceDef::ReifyShim(def_id)
| InstanceDef::FnPtrShim(def_id, _)
| InstanceDef::Virtual(def_id, _)
| InstanceDef::Intrinsic(def_id)
| InstanceDef::ThreadLocalShim(def_id)
| InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
| InstanceDef::DropGlue(def_id, _)
| InstanceDef::CloneShim(def_id, _)
| InstanceDef::FnPtrAddrShim(def_id, _) => def_id,
}
}
/// Returns the `DefId` of instances which might not require codegen locally.
pub fn def_id_if_not_guaranteed_local_codegen(self) -> Option<DefId> {
match self {
ty::InstanceDef::Item(def) => Some(def),
ty::InstanceDef::DropGlue(def_id, Some(_)) | InstanceDef::ThreadLocalShim(def_id) => {
Some(def_id)
}
InstanceDef::VTableShim(..)
| InstanceDef::ReifyShim(..)
| InstanceDef::FnPtrShim(..)
| InstanceDef::Virtual(..)
| InstanceDef::Intrinsic(..)
| InstanceDef::ClosureOnceShim { .. }
| InstanceDef::DropGlue(..)
| InstanceDef::CloneShim(..)
| InstanceDef::FnPtrAddrShim(..) => None,
}
}
#[inline]
pub fn get_attrs(
&self,
tcx: TyCtxt<'tcx>,
attr: Symbol,
) -> impl Iterator<Item = &'tcx rustc_ast::Attribute> {
tcx.get_attrs(self.def_id(), attr)
}
/// Returns `true` if the LLVM version of this instance is unconditionally
/// marked with `inline`. This implies that a copy of this instance is
/// generated in every codegen unit.
/// Note that this is only a hint. See the documentation for
/// `generates_cgu_internal_copy` for more information.
pub fn requires_inline(&self, tcx: TyCtxt<'tcx>) -> bool {
use rustc_hir::definitions::DefPathData;
let def_id = match *self {
ty::InstanceDef::Item(def) => def,
ty::InstanceDef::DropGlue(_, Some(_)) => return false,
ty::InstanceDef::ThreadLocalShim(_) => return false,
_ => return true,
};
matches!(
tcx.def_key(def_id).disambiguated_data.data,
DefPathData::Ctor | DefPathData::ClosureExpr
)
}
/// Returns `true` if the machine code for this instance is instantiated in
/// each codegen unit that references it.
/// Note that this is only a hint! The compiler can globally decide to *not*
/// do this in order to speed up compilation. CGU-internal copies are
/// only exist to enable inlining. If inlining is not performed (e.g. at
/// `-Copt-level=0`) then the time for generating them is wasted and it's
/// better to create a single copy with external linkage.
pub fn generates_cgu_internal_copy(&self, tcx: TyCtxt<'tcx>) -> bool {
if self.requires_inline(tcx) {
return true;
}
if let ty::InstanceDef::DropGlue(.., Some(ty)) = *self {
// Drop glue generally wants to be instantiated at every codegen
// unit, but without an #[inline] hint. We should make this
// available to normal end-users.
if tcx.sess.opts.incremental.is_none() {
return true;
}
// When compiling with incremental, we can generate a *lot* of
// codegen units. Including drop glue into all of them has a
// considerable compile time cost.
//
// We include enums without destructors to allow, say, optimizing
// drops of `Option::None` before LTO. We also respect the intent of
// `#[inline]` on `Drop::drop` implementations.
return ty.ty_adt_def().map_or(true, |adt_def| {
adt_def.destructor(tcx).map_or_else(
|| adt_def.is_enum(),
|dtor| tcx.codegen_fn_attrs(dtor.did).requests_inline(),
)
});
}
if let ty::InstanceDef::ThreadLocalShim(..) = *self {
return false;
}
tcx.codegen_fn_attrs(self.def_id()).requests_inline()
}
pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
match *self {
InstanceDef::Item(def_id) | InstanceDef::Virtual(def_id, _) => {
tcx.body_codegen_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
}
InstanceDef::ClosureOnceShim { call_once: _, track_caller } => track_caller,
_ => false,
}
}
/// Returns `true` when the MIR body associated with this instance should be monomorphized
/// by its users (e.g. codegen or miri) by substituting the `args` from `Instance` (see
/// `Instance::args_for_mir_body`).
///
/// Otherwise, returns `false` only for some kinds of shims where the construction of the MIR
/// body should perform necessary substitutions.
pub fn has_polymorphic_mir_body(&self) -> bool {
match *self {
InstanceDef::CloneShim(..)
| InstanceDef::ThreadLocalShim(..)
| InstanceDef::FnPtrAddrShim(..)
| InstanceDef::FnPtrShim(..)
| InstanceDef::DropGlue(_, Some(_)) => false,
InstanceDef::ClosureOnceShim { .. }
| InstanceDef::DropGlue(..)
| InstanceDef::Item(_)
| InstanceDef::Intrinsic(..)
| InstanceDef::ReifyShim(..)
| InstanceDef::Virtual(..)
| InstanceDef::VTableShim(..) => true,
}
}
}
fn fmt_instance(
f: &mut fmt::Formatter<'_>,
instance: &Instance<'_>,
type_length: rustc_session::Limit,
) -> fmt::Result {
ty::tls::with(|tcx| {
let args = tcx.lift(instance.args).expect("could not lift for printing");
let s = FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
.print_def_path(instance.def_id(), args)?
.into_buffer();
f.write_str(&s)
})?;
match instance.def {
InstanceDef::Item(_) => Ok(()),
InstanceDef::VTableShim(_) => write!(f, " - shim(vtable)"),
InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
InstanceDef::ThreadLocalShim(_) => write!(f, " - shim(tls)"),
InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
InstanceDef::Virtual(_, num) => write!(f, " - virtual#{num}"),
InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({ty})"),
InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({ty}))"),
InstanceDef::CloneShim(_, ty) => write!(f, " - shim({ty})"),
InstanceDef::FnPtrAddrShim(_, ty) => write!(f, " - shim({ty})"),
}
}
pub struct ShortInstance<'a, 'tcx>(pub &'a Instance<'tcx>, pub usize);
impl<'a, 'tcx> fmt::Display for ShortInstance<'a, 'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt_instance(f, self.0, rustc_session::Limit(self.1))
}
}
impl<'tcx> fmt::Display for Instance<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
ty::tls::with(|tcx| fmt_instance(f, self, tcx.type_length_limit()))
}
}
impl<'tcx> Instance<'tcx> {
pub fn new(def_id: DefId, args: GenericArgsRef<'tcx>) -> Instance<'tcx> {
assert!(
!args.has_escaping_bound_vars(),
"args of instance {def_id:?} not normalized for codegen: {args:?}"
);
Instance { def: InstanceDef::Item(def_id), args }
}
pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
let args = GenericArgs::for_item(tcx, def_id, |param, _| match param.kind {
ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
ty::GenericParamDefKind::Const { is_host_effect: true, .. } => tcx.consts.true_.into(),
ty::GenericParamDefKind::Type { .. } => {
bug!("Instance::mono: {:?} has type parameters", def_id)
}
ty::GenericParamDefKind::Const { .. } => {
bug!("Instance::mono: {:?} has const parameters", def_id)
}
});
Instance::new(def_id, args)
}
#[inline]
pub fn def_id(&self) -> DefId {
self.def.def_id()
}
/// Resolves a `(def_id, args)` pair to an (optional) instance -- most commonly,
/// this is used to find the precise code that will run for a trait method invocation,
/// if known.
///
/// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
/// For example, in a context like this,
///
/// ```ignore (illustrative)
/// fn foo<T: Debug>(t: T) { ... }
/// ```
///
/// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
/// know what code ought to run. (Note that this setting is also affected by the
/// `RevealMode` in the parameter environment.)
///
/// Presuming that coherence and type-check have succeeded, if this method is invoked
/// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
/// `Ok(Some(instance))`.
///
/// Returns `Err(ErrorGuaranteed)` when the `Instance` resolution process
/// couldn't complete due to errors elsewhere - this is distinct
/// from `Ok(None)` to avoid misleading diagnostics when an error
/// has already been/will be emitted, for the original cause
#[instrument(level = "debug", skip(tcx), ret)]
pub fn resolve(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
// All regions in the result of this query are erased, so it's
// fine to erase all of the input regions.
// HACK(eddyb) erase regions in `args` first, so that `param_env.and(...)`
// below is more likely to ignore the bounds in scope (e.g. if the only
// generic parameters mentioned by `args` were lifetime ones).
let args = tcx.erase_regions(args);
tcx.resolve_instance(tcx.erase_regions(param_env.and((def_id, args))))
}
pub fn expect_resolve(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Instance<'tcx> {
match ty::Instance::resolve(tcx, param_env, def_id, args) {
Ok(Some(instance)) => instance,
instance => bug!(
"failed to resolve instance for {}: {instance:#?}",
tcx.def_path_str_with_args(def_id, args)
),
}
}
pub fn resolve_for_fn_ptr(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Option<Instance<'tcx>> {
debug!("resolve(def_id={:?}, args={:?})", def_id, args);
// Use either `resolve_closure` or `resolve_for_vtable`
assert!(!tcx.is_closure(def_id), "Called `resolve_for_fn_ptr` on closure: {def_id:?}");
Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
match resolved.def {
InstanceDef::Item(def) if resolved.def.requires_caller_location(tcx) => {
debug!(" => fn pointer created for function with #[track_caller]");
resolved.def = InstanceDef::ReifyShim(def);
}
InstanceDef::Virtual(def_id, _) => {
debug!(" => fn pointer created for virtual call");
resolved.def = InstanceDef::ReifyShim(def_id);
}
_ => {}
}
resolved
})
}
pub fn resolve_for_vtable(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Option<Instance<'tcx>> {
debug!("resolve_for_vtable(def_id={:?}, args={:?})", def_id, args);
let fn_sig = tcx.fn_sig(def_id).instantiate_identity();
let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
&& fn_sig.input(0).skip_binder().is_param(0)
&& tcx.generics_of(def_id).has_self;
if is_vtable_shim {
debug!(" => associated item with unsizeable self: Self");
Some(Instance { def: InstanceDef::VTableShim(def_id), args })
} else {
Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
match resolved.def {
InstanceDef::Item(def) => {
// We need to generate a shim when we cannot guarantee that
// the caller of a trait object method will be aware of
// `#[track_caller]` - this ensures that the caller
// and callee ABI will always match.
//
// The shim is generated when all of these conditions are met:
//
// 1) The underlying method expects a caller location parameter
// in the ABI
if resolved.def.requires_caller_location(tcx)
// 2) The caller location parameter comes from having `#[track_caller]`
// on the implementation, and *not* on the trait method.
&& !tcx.should_inherit_track_caller(def)
// If the method implementation comes from the trait definition itself
// (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`),
// then we don't need to generate a shim. This check is needed because
// `should_inherit_track_caller` returns `false` if our method
// implementation comes from the trait block, and not an impl block
&& !matches!(
tcx.opt_associated_item(def),
Some(ty::AssocItem {
container: ty::AssocItemContainer::TraitContainer,
..
})
)
{
if tcx.is_closure(def) {
debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
def, def_id, args);
// Create a shim for the `FnOnce/FnMut/Fn` method we are calling
// - unlike functions, invoking a closure always goes through a
// trait.
resolved = Instance { def: InstanceDef::ReifyShim(def_id), args };
} else {
debug!(
" => vtable fn pointer created for function with #[track_caller]: {:?}", def
);
resolved.def = InstanceDef::ReifyShim(def);
}
}
}
InstanceDef::Virtual(def_id, _) => {
debug!(" => vtable fn pointer created for virtual call");
resolved.def = InstanceDef::ReifyShim(def_id);
}
_ => {}
}
resolved
})
}
}
pub fn resolve_closure(
tcx: TyCtxt<'tcx>,
def_id: DefId,
args: ty::GenericArgsRef<'tcx>,
requested_kind: ty::ClosureKind,
) -> Option<Instance<'tcx>> {
let actual_kind = args.as_closure().kind();
match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, args),
_ => Some(Instance::new(def_id, args)),
}
}
pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
let args = tcx.mk_args(&[ty.into()]);
Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
}
#[instrument(level = "debug", skip(tcx), ret)]
pub fn fn_once_adapter_instance(
tcx: TyCtxt<'tcx>,
closure_did: DefId,
args: ty::GenericArgsRef<'tcx>,
) -> Option<Instance<'tcx>> {
let fn_once = tcx.require_lang_item(LangItem::FnOnce, None);
let call_once = tcx
.associated_items(fn_once)
.in_definition_order()
.find(|it| it.kind == ty::AssocKind::Fn)
.unwrap()
.def_id;
let track_caller =
tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
let self_ty = Ty::new_closure(tcx, closure_did, args);
let sig = args.as_closure().sig();
let sig =
tcx.try_normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig).ok()?;
assert_eq!(sig.inputs().len(), 1);
let args = tcx.mk_args_trait(self_ty, [sig.inputs()[0].into()]);
debug!(?self_ty, ?sig);
Some(Instance { def, args })
}
/// Depending on the kind of `InstanceDef`, the MIR body associated with an
/// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
/// cases the MIR body is expressed in terms of the types found in the substitution array.
/// In the former case, we want to substitute those generic types and replace them with the
/// values from the args when monomorphizing the function body. But in the latter case, we
/// don't want to do that substitution, since it has already been done effectively.
///
/// This function returns `Some(args)` in the former case and `None` otherwise -- i.e., if
/// this function returns `None`, then the MIR body does not require substitution during
/// codegen.
fn args_for_mir_body(&self) -> Option<GenericArgsRef<'tcx>> {
self.def.has_polymorphic_mir_body().then_some(self.args)
}
pub fn instantiate_mir<T>(&self, tcx: TyCtxt<'tcx>, v: EarlyBinder<&T>) -> T
where
T: TypeFoldable<TyCtxt<'tcx>> + Copy,
{
let v = v.map_bound(|v| *v);
if let Some(args) = self.args_for_mir_body() {
v.instantiate(tcx, args)
} else {
v.instantiate_identity()
}
}
#[inline(always)]
pub fn instantiate_mir_and_normalize_erasing_regions<T>(
&self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
v: EarlyBinder<T>,
) -> T
where
T: TypeFoldable<TyCtxt<'tcx>> + Clone,
{
if let Some(args) = self.args_for_mir_body() {
tcx.instantiate_and_normalize_erasing_regions(args, param_env, v)
} else {
tcx.normalize_erasing_regions(param_env, v.skip_binder())
}
}
#[inline(always)]
pub fn try_instantiate_mir_and_normalize_erasing_regions<T>(
&self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
v: EarlyBinder<T>,
) -> Result<T, NormalizationError<'tcx>>
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if let Some(args) = self.args_for_mir_body() {
tcx.try_instantiate_and_normalize_erasing_regions(args, param_env, v)
} else {
// We're using `instantiate_identity` as e.g.
// `FnPtrShim` is separately generated for every
// instantiation of the `FnDef`, so the MIR body
// is already instantiated. Any generic parameters it
// contains are generic parameters from the caller.
tcx.try_normalize_erasing_regions(param_env, v.instantiate_identity())
}
}
/// Returns a new `Instance` where generic parameters in `instance.args` are replaced by
/// identity parameters if they are determined to be unused in `instance.def`.
pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {
debug!("polymorphize: running polymorphization analysis");
if !tcx.sess.opts.unstable_opts.polymorphize {
return self;
}
let polymorphized_args = polymorphize(tcx, self.def, self.args);
debug!("polymorphize: self={:?} polymorphized_args={:?}", self, polymorphized_args);
Self { def: self.def, args: polymorphized_args }
}
}
fn polymorphize<'tcx>(
tcx: TyCtxt<'tcx>,
instance: ty::InstanceDef<'tcx>,
args: GenericArgsRef<'tcx>,
) -> GenericArgsRef<'tcx> {
debug!("polymorphize({:?}, {:?})", instance, args);
let unused = tcx.unused_generic_params(instance);
debug!("polymorphize: unused={:?}", unused);
// If this is a closure or generator then we need to handle the case where another closure
// from the function is captured as an upvar and hasn't been polymorphized. In this case,
// the unpolymorphized upvar closure would result in a polymorphized closure producing
// multiple mono items (and eventually symbol clashes).
let def_id = instance.def_id();
let upvars_ty = if tcx.is_closure(def_id) {
Some(args.as_closure().tupled_upvars_ty())
} else if tcx.type_of(def_id).skip_binder().is_generator() {
Some(args.as_generator().tupled_upvars_ty())
} else {
None
};
let has_upvars = upvars_ty.is_some_and(|ty| !ty.tuple_fields().is_empty());
debug!("polymorphize: upvars_ty={:?} has_upvars={:?}", upvars_ty, has_upvars);
struct PolymorphizationFolder<'tcx> {
tcx: TyCtxt<'tcx>,
}
impl<'tcx> ty::TypeFolder<TyCtxt<'tcx>> for PolymorphizationFolder<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
debug!("fold_ty: ty={:?}", ty);
match *ty.kind() {
ty::Closure(def_id, args) => {
let polymorphized_args =
polymorphize(self.tcx, ty::InstanceDef::Item(def_id), args);
if args == polymorphized_args {
ty
} else {
Ty::new_closure(self.tcx, def_id, polymorphized_args)
}
}
ty::Generator(def_id, args, movability) => {
let polymorphized_args =
polymorphize(self.tcx, ty::InstanceDef::Item(def_id), args);
if args == polymorphized_args {
ty
} else {
Ty::new_generator(self.tcx, def_id, polymorphized_args, movability)
}
}
_ => ty.super_fold_with(self),
}
}
}
GenericArgs::for_item(tcx, def_id, |param, _| {
let is_unused = unused.is_unused(param.index);
debug!("polymorphize: param={:?} is_unused={:?}", param, is_unused);
match param.kind {
// Upvar case: If parameter is a type parameter..
ty::GenericParamDefKind::Type { .. } if
// ..and has upvars..
has_upvars &&
// ..and this param has the same type as the tupled upvars..
upvars_ty == Some(args[param.index as usize].expect_ty()) => {
// ..then double-check that polymorphization marked it used..
debug_assert!(!is_unused);
// ..and polymorphize any closures/generators captured as upvars.
let upvars_ty = upvars_ty.unwrap();
let polymorphized_upvars_ty = upvars_ty.fold_with(
&mut PolymorphizationFolder { tcx });
debug!("polymorphize: polymorphized_upvars_ty={:?}", polymorphized_upvars_ty);
ty::GenericArg::from(polymorphized_upvars_ty)
},
// Simple case: If parameter is a const or type parameter..
ty::GenericParamDefKind::Const { .. } | ty::GenericParamDefKind::Type { .. } if
// ..and is within range and unused..
unused.is_unused(param.index) =>
// ..then use the identity for this parameter.
tcx.mk_param_from_def(param),
// Otherwise, use the parameter as before.
_ => args[param.index as usize],
}
})
}
fn needs_fn_once_adapter_shim(
actual_closure_kind: ty::ClosureKind,
trait_closure_kind: ty::ClosureKind,
) -> Result<bool, ()> {
match (actual_closure_kind, trait_closure_kind) {
(ty::ClosureKind::Fn, ty::ClosureKind::Fn)
| (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut)
| (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
// No adapter needed.
Ok(false)
}
(ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
// The closure fn `llfn` is a `fn(&self, ...)`. We want a
// `fn(&mut self, ...)`. In fact, at codegen time, these are
// basically the same thing, so we can just return llfn.
Ok(false)
}
(ty::ClosureKind::Fn | ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
// The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
// self, ...)`. We want a `fn(self, ...)`. We can produce
// this by doing something like:
//
// fn call_once(self, ...) { call_mut(&self, ...) }
// fn call_once(mut self, ...) { call_mut(&mut self, ...) }
//
// These are both the same at codegen time.
Ok(true)
}
(ty::ClosureKind::FnMut | ty::ClosureKind::FnOnce, _) => Err(()),
}
}
// Set bits represent unused generic parameters.
// An empty set indicates that all parameters are used.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Decodable, Encodable, HashStable)]
pub struct UnusedGenericParams(FiniteBitSet<u32>);
impl Default for UnusedGenericParams {
fn default() -> Self {
UnusedGenericParams::new_all_used()
}
}
impl UnusedGenericParams {
pub fn new_all_unused(amount: u32) -> Self {
let mut bitset = FiniteBitSet::new_empty();
bitset.set_range(0..amount);
Self(bitset)
}
pub fn new_all_used() -> Self {
Self(FiniteBitSet::new_empty())
}
pub fn mark_used(&mut self, idx: u32) {
self.0.clear(idx);
}
pub fn is_unused(&self, idx: u32) -> bool {
self.0.contains(idx).unwrap_or(false)
}
pub fn is_used(&self, idx: u32) -> bool {
!self.is_unused(idx)
}
pub fn all_used(&self) -> bool {
self.0.is_empty()
}
pub fn bits(&self) -> u32 {
self.0.0
}
pub fn from_bits(bits: u32) -> UnusedGenericParams {
UnusedGenericParams(FiniteBitSet(bits))
}
}