rustc_middle/ty/instance.rs
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use std::assert_matches::assert_matches;
use std::fmt;
use std::path::PathBuf;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::ErrorGuaranteed;
use rustc_hir as hir;
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::{Decodable, Encodable, HashStable, Lift, TyDecodable, TyEncodable};
use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
use rustc_span::def_id::LOCAL_CRATE;
use rustc_span::{DUMMY_SP, Span, Symbol};
use tracing::{debug, instrument};
use crate::error;
use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::ty::print::{FmtPrinter, Printer, shrunk_instance_name};
use crate::ty::{
self, EarlyBinder, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
TypeVisitable, TypeVisitableExt, TypeVisitor,
};
/// An `InstanceKind` along with the args that are needed to substitute the instance.
///
/// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
/// simply couples a potentially generic `InstanceKind` with some args, and codegen and const eval
/// will do all required instantiations 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: InstanceKind<'tcx>,
pub args: GenericArgsRef<'tcx>,
}
/// Describes why a `ReifyShim` was created. This is needed to distinguish a ReifyShim created to
/// adjust for things like `#[track_caller]` in a vtable from a `ReifyShim` created to produce a
/// function pointer from a vtable entry.
/// Currently, this is only used when KCFI is enabled, as only KCFI needs to treat those two
/// `ReifyShim`s differently.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
#[derive(TyEncodable, TyDecodable, HashStable)]
pub enum ReifyReason {
/// The `ReifyShim` was created to produce a function pointer. This happens when:
/// * A vtable entry is directly converted to a function call (e.g. creating a fn ptr from a
/// method on a `dyn` object).
/// * A function with `#[track_caller]` is converted to a function pointer
/// * If KCFI is enabled, creating a function pointer from a method on a dyn-compatible trait.
/// This includes the case of converting `::call`-like methods on closure-likes to function
/// pointers.
FnPtr,
/// This `ReifyShim` was created to populate a vtable. Currently, this happens when a
/// `#[track_caller]` mismatch occurs between the implementation of a method and the method.
/// This includes the case of `::call`-like methods in closure-likes' vtables.
Vtable,
}
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
#[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable, Lift)]
pub enum InstanceKind<'tcx> {
/// A user-defined callable item.
///
/// This includes:
/// - `fn` items
/// - closures
/// - coroutines
Item(DefId),
/// An intrinsic `fn` item (with `"rust-intrinsic"` ABI).
///
/// Alongside `Virtual`, this is the only `InstanceKind` 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 `InstanceKind::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).
///
/// The second field encodes *why* this shim was created. This allows distinguishing between
/// a `ReifyShim` that appears in a vtable vs one that appears as a function pointer.
///
/// This field will only be populated if we are compiling in a mode that needs these shims
/// to be separable, currently only when KCFI is enabled.
ReifyShim(DefId, Option<ReifyReason>),
/// `<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 `InstanceKind` 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/Fn closure] as FnOnce>::call_once`.
///
/// The `DefId` is the ID of the `call_once` method in `FnOnce`.
///
/// This generates a body that will just borrow the (owned) self type,
/// and dispatch to the `FnMut::call_mut` instance for the closure.
ClosureOnceShim { call_once: DefId, track_caller: bool },
/// `<[FnMut/Fn coroutine-closure] as FnOnce>::call_once`
///
/// The body generated here differs significantly from the `ClosureOnceShim`,
/// since we need to generate a distinct coroutine type that will move the
/// closure's upvars *out* of the closure.
ConstructCoroutineInClosureShim {
coroutine_closure_def_id: DefId,
// Whether the generated MIR body takes the coroutine by-ref. This is
// because the signature of `<{async fn} as FnMut>::call_mut` is:
// `fn(&mut self, args: A) -> <Self as FnOnce>::Output`, that is to say
// that it returns the `FnOnce`-flavored coroutine but takes the closure
// by mut ref (and similarly for `Fn::call`).
receiver_by_ref: 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>),
/// `core::future::async_drop::async_drop_in_place::<'_, T>`.
///
/// The `DefId` is for `core::future::async_drop::async_drop_in_place`, the `Ty`
/// is the type `T`.
AsyncDropGlueCtorShim(DefId, Option<Ty<'tcx>>),
}
impl<'tcx> Instance<'tcx> {
/// Returns the `Ty` corresponding to this `Instance`, with generic instantiations applied and
/// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
pub fn ty(&self, tcx: TyCtxt<'tcx>, typing_env: ty::TypingEnv<'tcx>) -> Ty<'tcx> {
let ty = tcx.type_of(self.def.def_id());
tcx.instantiate_and_normalize_erasing_regions(self.args, typing_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 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 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()
// However, if the def_id is marked inline(never), then it's fine to just reuse the
// upstream monomorphization.
&& tcx.codegen_fn_attrs(self.def_id()).inline != rustc_attr::InlineAttr::Never
{
return None;
}
// If this a non-generic instance, it cannot be a shared monomorphization.
self.args.non_erasable_generics().next()?;
// compiler_builtins cannot use upstream monomorphizations.
if tcx.is_compiler_builtins(LOCAL_CRATE) {
return None;
}
match self.def {
InstanceKind::Item(def) => tcx
.upstream_monomorphizations_for(def)
.and_then(|monos| monos.get(&self.args).cloned()),
InstanceKind::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.args),
InstanceKind::AsyncDropGlueCtorShim(_, Some(_)) => {
tcx.upstream_async_drop_glue_for(self.args)
}
_ => None,
}
}
}
impl<'tcx> InstanceKind<'tcx> {
#[inline]
pub fn def_id(self) -> DefId {
match self {
InstanceKind::Item(def_id)
| InstanceKind::VTableShim(def_id)
| InstanceKind::ReifyShim(def_id, _)
| InstanceKind::FnPtrShim(def_id, _)
| InstanceKind::Virtual(def_id, _)
| InstanceKind::Intrinsic(def_id)
| InstanceKind::ThreadLocalShim(def_id)
| InstanceKind::ClosureOnceShim { call_once: def_id, track_caller: _ }
| ty::InstanceKind::ConstructCoroutineInClosureShim {
coroutine_closure_def_id: def_id,
receiver_by_ref: _,
}
| InstanceKind::DropGlue(def_id, _)
| InstanceKind::CloneShim(def_id, _)
| InstanceKind::FnPtrAddrShim(def_id, _)
| InstanceKind::AsyncDropGlueCtorShim(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::InstanceKind::Item(def) => Some(def),
ty::InstanceKind::DropGlue(def_id, Some(_))
| InstanceKind::AsyncDropGlueCtorShim(def_id, Some(_))
| InstanceKind::ThreadLocalShim(def_id) => Some(def_id),
InstanceKind::VTableShim(..)
| InstanceKind::ReifyShim(..)
| InstanceKind::FnPtrShim(..)
| InstanceKind::Virtual(..)
| InstanceKind::Intrinsic(..)
| InstanceKind::ClosureOnceShim { .. }
| ty::InstanceKind::ConstructCoroutineInClosureShim { .. }
| InstanceKind::DropGlue(..)
| InstanceKind::AsyncDropGlueCtorShim(..)
| InstanceKind::CloneShim(..)
| InstanceKind::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::InstanceKind::Item(def) => def,
ty::InstanceKind::DropGlue(_, Some(_)) => return false,
ty::InstanceKind::AsyncDropGlueCtorShim(_, Some(_)) => return false,
ty::InstanceKind::ThreadLocalShim(_) => return false,
_ => return true,
};
matches!(
tcx.def_key(def_id).disambiguated_data.data,
DefPathData::Ctor | DefPathData::Closure
)
}
/// 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::InstanceKind::DropGlue(.., Some(ty))
| ty::InstanceKind::AsyncDropGlueCtorShim(.., 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| {
match *self {
ty::InstanceKind::DropGlue(..) => adt_def.destructor(tcx).map(|dtor| dtor.did),
ty::InstanceKind::AsyncDropGlueCtorShim(..) => {
adt_def.async_destructor(tcx).map(|dtor| dtor.ctor)
}
_ => unreachable!(),
}
.map_or_else(|| adt_def.is_enum(), |did| tcx.cross_crate_inlinable(did))
});
}
if let ty::InstanceKind::ThreadLocalShim(..) = *self {
return false;
}
tcx.cross_crate_inlinable(self.def_id())
}
pub fn requires_caller_location(&self, tcx: TyCtxt<'_>) -> bool {
match *self {
InstanceKind::Item(def_id) | InstanceKind::Virtual(def_id, _) => {
tcx.body_codegen_attrs(def_id).flags.contains(CodegenFnAttrFlags::TRACK_CALLER)
}
InstanceKind::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 instantiating 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 instantiations.
pub fn has_polymorphic_mir_body(&self) -> bool {
match *self {
InstanceKind::CloneShim(..)
| InstanceKind::ThreadLocalShim(..)
| InstanceKind::FnPtrAddrShim(..)
| InstanceKind::FnPtrShim(..)
| InstanceKind::DropGlue(_, Some(_))
| InstanceKind::AsyncDropGlueCtorShim(_, Some(_)) => false,
InstanceKind::ClosureOnceShim { .. }
| InstanceKind::ConstructCoroutineInClosureShim { .. }
| InstanceKind::DropGlue(..)
| InstanceKind::AsyncDropGlueCtorShim(..)
| InstanceKind::Item(_)
| InstanceKind::Intrinsic(..)
| InstanceKind::ReifyShim(..)
| InstanceKind::Virtual(..)
| InstanceKind::VTableShim(..) => true,
}
}
}
fn type_length<'tcx>(item: impl TypeVisitable<TyCtxt<'tcx>>) -> usize {
struct Visitor<'tcx> {
type_length: usize,
cache: FxHashMap<Ty<'tcx>, usize>,
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for Visitor<'tcx> {
fn visit_ty(&mut self, t: Ty<'tcx>) {
if let Some(&value) = self.cache.get(&t) {
self.type_length += value;
return;
}
let prev = self.type_length;
self.type_length += 1;
t.super_visit_with(self);
// We don't try to use the cache if the type is fairly small.
if self.type_length > 16 {
self.cache.insert(t, self.type_length - prev);
}
}
fn visit_const(&mut self, ct: ty::Const<'tcx>) {
self.type_length += 1;
ct.super_visit_with(self);
}
}
let mut visitor = Visitor { type_length: 0, cache: Default::default() };
item.visit_with(&mut visitor);
visitor.type_length
}
pub fn fmt_instance(
f: &mut fmt::Formatter<'_>,
instance: Instance<'_>,
type_length: Option<rustc_session::Limit>,
) -> fmt::Result {
ty::tls::with(|tcx| {
let args = tcx.lift(instance.args).expect("could not lift for printing");
let mut cx = if let Some(type_length) = type_length {
FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
} else {
FmtPrinter::new(tcx, Namespace::ValueNS)
};
cx.print_def_path(instance.def_id(), args)?;
let s = cx.into_buffer();
f.write_str(&s)
})?;
match instance.def {
InstanceKind::Item(_) => Ok(()),
InstanceKind::VTableShim(_) => write!(f, " - shim(vtable)"),
InstanceKind::ReifyShim(_, None) => write!(f, " - shim(reify)"),
InstanceKind::ReifyShim(_, Some(ReifyReason::FnPtr)) => write!(f, " - shim(reify-fnptr)"),
InstanceKind::ReifyShim(_, Some(ReifyReason::Vtable)) => write!(f, " - shim(reify-vtable)"),
InstanceKind::ThreadLocalShim(_) => write!(f, " - shim(tls)"),
InstanceKind::Intrinsic(_) => write!(f, " - intrinsic"),
InstanceKind::Virtual(_, num) => write!(f, " - virtual#{num}"),
InstanceKind::FnPtrShim(_, ty) => write!(f, " - shim({ty})"),
InstanceKind::ClosureOnceShim { .. } => write!(f, " - shim"),
InstanceKind::ConstructCoroutineInClosureShim { .. } => write!(f, " - shim"),
InstanceKind::DropGlue(_, None) => write!(f, " - shim(None)"),
InstanceKind::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({ty}))"),
InstanceKind::CloneShim(_, ty) => write!(f, " - shim({ty})"),
InstanceKind::FnPtrAddrShim(_, ty) => write!(f, " - shim({ty})"),
InstanceKind::AsyncDropGlueCtorShim(_, None) => write!(f, " - shim(None)"),
InstanceKind::AsyncDropGlueCtorShim(_, Some(ty)) => write!(f, " - shim(Some({ty}))"),
}
}
pub struct ShortInstance<'tcx>(pub Instance<'tcx>, pub usize);
impl<'tcx> fmt::Display for ShortInstance<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt_instance(f, self.0, Some(rustc_session::Limit(self.1)))
}
}
impl<'tcx> fmt::Display for Instance<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt_instance(f, *self, None)
}
}
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:?} has escaping bound vars: {args:?}"
);
Instance { def: InstanceKind::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::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. This setting is also affected by the current `TypingMode`
/// of the 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))`, **except** for when the instance's inputs hit the type size limit,
/// in which case it may bail out and return `Ok(None)`.
///
/// 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 try_resolve(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
// Rust code can easily create exponentially-long types using only a
// polynomial recursion depth. Even with the default recursion
// depth, you can easily get cases that take >2^60 steps to run,
// which means that rustc basically hangs.
//
// Bail out in these cases to avoid that bad user experience.
if tcx.sess.opts.unstable_opts.enforce_type_length_limit
&& !tcx.type_length_limit().value_within_limit(type_length(args))
{
return Ok(None);
}
// All regions in the result of this query are erased, so it's
// fine to erase all of the input regions.
tcx.resolve_instance_raw(tcx.erase_regions(typing_env.as_query_input((def_id, args))))
}
pub fn expect_resolve(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
span: Span,
) -> Instance<'tcx> {
// We compute the span lazily, to avoid unnecessary query calls.
// If `span` is a DUMMY_SP, and the def id is local, then use the
// def span of the def id.
let span_or_local_def_span =
|| if span.is_dummy() && def_id.is_local() { tcx.def_span(def_id) } else { span };
match ty::Instance::try_resolve(tcx, typing_env, def_id, args) {
Ok(Some(instance)) => instance,
Ok(None) => {
let type_length = type_length(args);
if !tcx.type_length_limit().value_within_limit(type_length) {
let (shrunk, written_to_path) =
shrunk_instance_name(tcx, Instance::new(def_id, args));
let mut path = PathBuf::new();
let was_written = if let Some(path2) = written_to_path {
path = path2;
true
} else {
false
};
tcx.dcx().emit_fatal(error::TypeLengthLimit {
// We don't use `def_span(def_id)` so that diagnostics point
// to the crate root during mono instead of to foreign items.
// This is arguably better.
span: span_or_local_def_span(),
shrunk,
was_written,
path,
type_length,
});
} else {
span_bug!(
span_or_local_def_span(),
"failed to resolve instance for {}",
tcx.def_path_str_with_args(def_id, args)
)
}
}
instance => span_bug!(
span_or_local_def_span(),
"failed to resolve instance for {}: {instance:#?}",
tcx.def_path_str_with_args(def_id, args)
),
}
}
pub fn resolve_for_fn_ptr(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'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_like(def_id), "Called `resolve_for_fn_ptr` on closure: {def_id:?}");
let reason = tcx.sess.is_sanitizer_kcfi_enabled().then_some(ReifyReason::FnPtr);
Instance::try_resolve(tcx, typing_env, def_id, args).ok().flatten().map(|mut resolved| {
match resolved.def {
InstanceKind::Item(def) if resolved.def.requires_caller_location(tcx) => {
debug!(" => fn pointer created for function with #[track_caller]");
resolved.def = InstanceKind::ReifyShim(def, reason);
}
InstanceKind::Virtual(def_id, _) => {
debug!(" => fn pointer created for virtual call");
resolved.def = InstanceKind::ReifyShim(def_id, reason);
}
// Reify `Trait::method` implementations if KCFI is enabled
// FIXME(maurer) only reify it if it is a vtable-safe function
_ if tcx.sess.is_sanitizer_kcfi_enabled()
&& tcx
.opt_associated_item(def_id)
.and_then(|assoc| assoc.trait_item_def_id)
.is_some() =>
{
// If this function could also go in a vtable, we need to `ReifyShim` it with
// KCFI because it can only attach one type per function.
resolved.def = InstanceKind::ReifyShim(resolved.def_id(), reason)
}
// Reify `::call`-like method implementations if KCFI is enabled
_ if tcx.sess.is_sanitizer_kcfi_enabled()
&& tcx.is_closure_like(resolved.def_id()) =>
{
// Reroute through a reify via the *unresolved* instance. The resolved one can't
// be directly reified because it's closure-like. The reify can handle the
// unresolved instance.
resolved = Instance { def: InstanceKind::ReifyShim(def_id, reason), args }
}
_ => {}
}
resolved
})
}
pub fn expect_resolve_for_vtable(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
def_id: DefId,
args: GenericArgsRef<'tcx>,
span: Span,
) -> 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");
return Instance { def: InstanceKind::VTableShim(def_id), args };
}
let mut resolved = Instance::expect_resolve(tcx, typing_env, def_id, args, span);
let reason = tcx.sess.is_sanitizer_kcfi_enabled().then_some(ReifyReason::Vtable);
match resolved.def {
InstanceKind::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
let needs_track_caller_shim = 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::Trait,
..
})
);
// We also need to generate a shim if this is an AFIT.
let needs_rpitit_shim =
tcx.return_position_impl_trait_in_trait_shim_data(def).is_some();
if needs_track_caller_shim || needs_rpitit_shim {
if tcx.is_closure_like(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: InstanceKind::ReifyShim(def_id, reason), args };
} else {
debug!(
" => vtable fn pointer created for function with #[track_caller]: {:?}",
def
);
resolved.def = InstanceKind::ReifyShim(def, reason);
}
}
}
InstanceKind::Virtual(def_id, _) => {
debug!(" => vtable fn pointer created for virtual call");
resolved.def = InstanceKind::ReifyShim(def_id, reason)
}
_ => {}
}
resolved
}
pub fn resolve_closure(
tcx: TyCtxt<'tcx>,
def_id: DefId,
args: ty::GenericArgsRef<'tcx>,
requested_kind: ty::ClosureKind,
) -> 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),
_ => 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::TypingEnv::fully_monomorphized(),
def_id,
args,
ty.ty_adt_def().and_then(|adt| tcx.hir().span_if_local(adt.did())).unwrap_or(DUMMY_SP),
)
}
pub fn resolve_async_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
let def_id = tcx.require_lang_item(LangItem::AsyncDropInPlace, None);
let args = tcx.mk_args(&[ty.into()]);
Instance::expect_resolve(
tcx,
ty::TypingEnv::fully_monomorphized(),
def_id,
args,
ty.ty_adt_def().and_then(|adt| tcx.hir().span_if_local(adt.did())).unwrap_or(DUMMY_SP),
)
}
#[instrument(level = "debug", skip(tcx), ret)]
pub fn fn_once_adapter_instance(
tcx: TyCtxt<'tcx>,
closure_did: DefId,
args: ty::GenericArgsRef<'tcx>,
) -> 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::InstanceKind::ClosureOnceShim { call_once, track_caller };
let self_ty = Ty::new_closure(tcx, closure_did, args);
let tupled_inputs_ty = args.as_closure().sig().map_bound(|sig| sig.inputs()[0]);
let tupled_inputs_ty = tcx.instantiate_bound_regions_with_erased(tupled_inputs_ty);
let args = tcx.mk_args_trait(self_ty, [tupled_inputs_ty.into()]);
debug!(?self_ty, args=?tupled_inputs_ty.tuple_fields());
Instance { def, args }
}
pub fn try_resolve_item_for_coroutine(
tcx: TyCtxt<'tcx>,
trait_item_id: DefId,
trait_id: DefId,
rcvr_args: ty::GenericArgsRef<'tcx>,
) -> Option<Instance<'tcx>> {
let ty::Coroutine(coroutine_def_id, args) = *rcvr_args.type_at(0).kind() else {
return None;
};
let coroutine_kind = tcx.coroutine_kind(coroutine_def_id).unwrap();
let coroutine_callable_item = if tcx.is_lang_item(trait_id, LangItem::Future) {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)
);
hir::LangItem::FuturePoll
} else if tcx.is_lang_item(trait_id, LangItem::Iterator) {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
);
hir::LangItem::IteratorNext
} else if tcx.is_lang_item(trait_id, LangItem::AsyncIterator) {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)
);
hir::LangItem::AsyncIteratorPollNext
} else if tcx.is_lang_item(trait_id, LangItem::Coroutine) {
assert_matches!(coroutine_kind, hir::CoroutineKind::Coroutine(_));
hir::LangItem::CoroutineResume
} else {
return None;
};
if tcx.is_lang_item(trait_item_id, coroutine_callable_item) {
let ty::Coroutine(_, id_args) = *tcx.type_of(coroutine_def_id).skip_binder().kind()
else {
bug!()
};
// If the closure's kind ty disagrees with the identity closure's kind ty,
// then this must be a coroutine generated by one of the `ConstructCoroutineInClosureShim`s.
if args.as_coroutine().kind_ty() == id_args.as_coroutine().kind_ty() {
Some(Instance { def: ty::InstanceKind::Item(coroutine_def_id), args })
} else {
Some(Instance {
def: ty::InstanceKind::Item(
tcx.coroutine_by_move_body_def_id(coroutine_def_id),
),
args,
})
}
} else {
// All other methods should be defaulted methods of the built-in trait.
// This is important for `Iterator`'s combinators, but also useful for
// adding future default methods to `Future`, for instance.
debug_assert!(tcx.defaultness(trait_item_id).has_value());
Some(Instance::new(trait_item_id, rcvr_args))
}
}
/// Depending on the kind of `InstanceKind`, 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 generic parameter array.
/// In the former case, we want to instantiate 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 instantiation, 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 instantiation 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<'tcx, &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)]
// Keep me in sync with try_instantiate_mir_and_normalize_erasing_regions
pub fn instantiate_mir_and_normalize_erasing_regions<T>(
&self,
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
v: EarlyBinder<'tcx, T>,
) -> T
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if let Some(args) = self.args_for_mir_body() {
tcx.instantiate_and_normalize_erasing_regions(args, typing_env, v)
} else {
tcx.normalize_erasing_regions(typing_env, v.instantiate_identity())
}
}
#[inline(always)]
// Keep me in sync with instantiate_mir_and_normalize_erasing_regions
pub fn try_instantiate_mir_and_normalize_erasing_regions<T>(
&self,
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
v: EarlyBinder<'tcx, 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, typing_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(typing_env, v.instantiate_identity())
}
}
}
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))
}
}