Erase query cache values

compiler/rustc_middle/src/lib.rs

@@ -33,6 +33,7 @@
 #![feature(generators)]
 #![feature(get_mut_unchecked)]
 #![feature(if_let_guard)]
+#![feature(inline_const)]
 #![feature(iter_from_generator)]
 #![feature(local_key_cell_methods)]
 #![feature(negative_impls)]

compiler/rustc_middle/src/query/erase.rs

@@ -0,0 +1,337 @@
+use crate::mir;
+use crate::traits;
+use crate::ty::{self, Ty};
+use std::mem::{size_of, transmute_copy, MaybeUninit};
+
+#[derive(Copy, Clone)]
+pub struct Erased<T: Copy> {
+    // We use `MaybeUninit` here so we can store any value
+    // in `data` since we aren't actually storing a `T`.
+    data: MaybeUninit<T>,
+}
+
+pub trait EraseType: Copy {
+    type Result: Copy;
+}
+
+// Allow `type_alias_bounds` since compilation will fail without `EraseType`.
+#[allow(type_alias_bounds)]
+pub type Erase<T: EraseType> = Erased<impl Copy>;
+
+#[inline(always)]
+pub fn erase<T: EraseType>(src: T) -> Erase<T> {
+    // Ensure the sizes match
+    const {
+        if std::mem::size_of::<T>() != std::mem::size_of::<T::Result>() {
+            panic!("size of T must match erased type T::Result")
+        }
+    };
+
+    Erased::<<T as EraseType>::Result> {
+        // SAFETY: Is it safe to transmute to MaybeUninit for types with the same sizes.
+        data: unsafe { transmute_copy(&src) },
+    }
+}
+
+/// Restores an erased value.
+#[inline(always)]
+pub fn restore<T: EraseType>(value: Erase<T>) -> T {
+    let value: Erased<<T as EraseType>::Result> = value;
+    // SAFETY: Due to the use of impl Trait in `Erase` the only way to safetly create an instance
+    // of `Erase` is to call `erase`, so we know that `value.data` is a valid instance of `T` of
+    // the right size.
+    unsafe { transmute_copy(&value.data) }
+}
+
+impl<T> EraseType for &'_ T {
+    type Result = [u8; size_of::<*const ()>()];
+}
+
+impl<T> EraseType for &'_ [T] {
+    type Result = [u8; size_of::<*const [()]>()];
+}
+
+impl<T> EraseType for &'_ ty::List<T> {
+    type Result = [u8; size_of::<*const ()>()];
+}
+
+impl<T> EraseType for Result<&'_ T, traits::query::NoSolution> {
+    type Result = [u8; size_of::<Result<&'static (), traits::query::NoSolution>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, rustc_errors::ErrorGuaranteed> {
+    type Result = [u8; size_of::<Result<&'static (), rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, traits::CodegenObligationError> {
+    type Result = [u8; size_of::<Result<&'static (), traits::CodegenObligationError>>()];
+}
+
+impl<T> EraseType for Result<&'_ T, ty::layout::FnAbiError<'_>> {
+    type Result = [u8; size_of::<Result<&'static (), ty::layout::FnAbiError<'static>>>()];
+}
+
+impl<T> EraseType for Result<(&'_ T, rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed> {
+    type Result = [u8; size_of::<
+        Result<(&'static (), rustc_middle::thir::ExprId), rustc_errors::ErrorGuaranteed>,
+    >()];
+}
+
+impl EraseType for Result<Option<ty::Instance<'_>>, rustc_errors::ErrorGuaranteed> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::Instance<'static>>, rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl EraseType for Result<Option<ty::Const<'_>>, rustc_errors::ErrorGuaranteed> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::Const<'static>>, rustc_errors::ErrorGuaranteed>>()];
+}
+
+impl EraseType for Result<ty::GenericArg<'_>, traits::query::NoSolution> {
+    type Result = [u8; size_of::<Result<ty::GenericArg<'static>, traits::query::NoSolution>>()];
+}
+
+impl EraseType for Result<bool, ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<Result<bool, ty::layout::LayoutError<'static>>>()];
+}
+
+impl EraseType for Result<rustc_target::abi::TyAndLayout<'_, Ty<'_>>, ty::layout::LayoutError<'_>> {
+    type Result = [u8; size_of::<
+        Result<
+            rustc_target::abi::TyAndLayout<'static, Ty<'static>>,
+            ty::layout::LayoutError<'static>,
+        >,
+    >()];
+}
+
+impl EraseType for Result<ty::Const<'_>, mir::interpret::LitToConstError> {
+    type Result = [u8; size_of::<Result<ty::Const<'static>, mir::interpret::LitToConstError>>()];
+}
+
+impl EraseType for Result<mir::ConstantKind<'_>, mir::interpret::LitToConstError> {
+    type Result =
+        [u8; size_of::<Result<mir::ConstantKind<'static>, mir::interpret::LitToConstError>>()];
+}
+
+impl EraseType for Result<mir::interpret::ConstAlloc<'_>, mir::interpret::ErrorHandled> {
+    type Result = [u8; size_of::<
+        Result<mir::interpret::ConstAlloc<'static>, mir::interpret::ErrorHandled>,
+    >()];
+}
+
+impl EraseType for Result<mir::interpret::ConstValue<'_>, mir::interpret::ErrorHandled> {
+    type Result = [u8; size_of::<
+        Result<mir::interpret::ConstValue<'static>, mir::interpret::ErrorHandled>,
+    >()];
+}
+
+impl EraseType for Result<Option<ty::ValTree<'_>>, mir::interpret::ErrorHandled> {
+    type Result =
+        [u8; size_of::<Result<Option<ty::ValTree<'static>>, mir::interpret::ErrorHandled>>()];
+}
+
+impl EraseType for Result<&'_ ty::List<Ty<'_>>, ty::util::AlwaysRequiresDrop> {
+    type Result =
+        [u8; size_of::<Result<&'static ty::List<Ty<'static>>, ty::util::AlwaysRequiresDrop>>()];
+}
+
+impl<T> EraseType for Option<&'_ T> {
+    type Result = [u8; size_of::<Option<&'static ()>>()];
+}
+
+impl<T> EraseType for Option<&'_ [T]> {
+    type Result = [u8; size_of::<Option<&'static [()]>>()];
+}
+
+impl EraseType for Option<rustc_middle::hir::Owner<'_>> {
+    type Result = [u8; size_of::<Option<rustc_middle::hir::Owner<'static>>>()];
+}
+
+impl EraseType for Option<mir::DestructuredConstant<'_>> {
+    type Result = [u8; size_of::<Option<mir::DestructuredConstant<'static>>>()];
+}
+
+impl EraseType for Option<ty::EarlyBinder<ty::TraitRef<'_>>> {
+    type Result = [u8; size_of::<Option<ty::EarlyBinder<ty::TraitRef<'static>>>>()];
+}
+
+impl EraseType for Option<ty::EarlyBinder<Ty<'_>>> {
+    type Result = [u8; size_of::<Option<ty::EarlyBinder<Ty<'static>>>>()];
+}
+
+impl<T> EraseType for rustc_hir::MaybeOwner<&'_ T> {
+    type Result = [u8; size_of::<rustc_hir::MaybeOwner<&'static ()>>()];
+}
+
+impl<T: EraseType> EraseType for ty::EarlyBinder<T> {
+    type Result = T::Result;
+}
+
+impl EraseType for ty::Binder<'_, ty::FnSig<'_>> {
+    type Result = [u8; size_of::<ty::Binder<'static, ty::FnSig<'static>>>()];
+}
+
+impl<T0, T1> EraseType for (&'_ T0, &'_ T1) {
+    type Result = [u8; size_of::<(&'static (), &'static ())>()];
+}
+
+impl<T0, T1> EraseType for (&'_ T0, &'_ [T1]) {
+    type Result = [u8; size_of::<(&'static (), &'static [()])>()];
+}
+
+macro_rules! trivial {
+    ($($ty:ty),+ $(,)?) => {
+        $(
+            impl EraseType for $ty {
+                type Result = [u8; size_of::<$ty>()];
+            }
+        )*
+    }
+}
+
+trivial! {
+    (),
+    bool,
+    Option<(rustc_span::def_id::DefId, rustc_session::config::EntryFnType)>,
+    Option<rustc_ast::expand::allocator::AllocatorKind>,
+    Option<rustc_attr::ConstStability>,
+    Option<rustc_attr::DefaultBodyStability>,
+    Option<rustc_attr::Stability>,
+    Option<rustc_data_structures::svh::Svh>,
+    Option<rustc_hir::def::DefKind>,
+    Option<rustc_hir::GeneratorKind>,
+    Option<rustc_hir::HirId>,
+    Option<rustc_middle::middle::stability::DeprecationEntry>,
+    Option<rustc_middle::ty::Destructor>,
+    Option<rustc_middle::ty::ImplTraitInTraitData>,
+    Option<rustc_span::def_id::CrateNum>,
+    Option<rustc_span::def_id::DefId>,
+    Option<rustc_span::def_id::LocalDefId>,
+    Option<rustc_span::Span>,
+    Option<rustc_target::spec::PanicStrategy>,
+    Option<usize>,
+    Result<(), rustc_errors::ErrorGuaranteed>,
+    Result<(), rustc_middle::traits::query::NoSolution>,
+    Result<rustc_middle::traits::EvaluationResult, rustc_middle::traits::OverflowError>,
+    rustc_ast::expand::allocator::AllocatorKind,
+    rustc_attr::ConstStability,
+    rustc_attr::DefaultBodyStability,
+    rustc_attr::Deprecation,
+    rustc_attr::Stability,
+    rustc_data_structures::svh::Svh,
+    rustc_errors::ErrorGuaranteed,
+    rustc_hir::Constness,
+    rustc_hir::def_id::DefId,
+    rustc_hir::def_id::DefIndex,
+    rustc_hir::def_id::LocalDefId,
+    rustc_hir::def::DefKind,
+    rustc_hir::Defaultness,
+    rustc_hir::definitions::DefKey,
+    rustc_hir::GeneratorKind,
+    rustc_hir::HirId,
+    rustc_hir::IsAsync,
+    rustc_hir::ItemLocalId,
+    rustc_hir::LangItem,
+    rustc_hir::OwnerId,
+    rustc_hir::Upvar,
+    rustc_index::bit_set::FiniteBitSet<u32>,
+    rustc_middle::metadata::ModChild,
+    rustc_middle::middle::dependency_format::Linkage,
+    rustc_middle::middle::exported_symbols::SymbolExportInfo,
+    rustc_middle::middle::resolve_bound_vars::ObjectLifetimeDefault,
+    rustc_middle::middle::resolve_bound_vars::ResolvedArg,
+    rustc_middle::middle::stability::DeprecationEntry,
+    rustc_middle::mir::ConstQualifs,
+    rustc_middle::mir::interpret::AllocId,
+    rustc_middle::mir::interpret::ErrorHandled,
+    rustc_middle::mir::interpret::LitToConstError,
+    rustc_middle::thir::ExprId,
+    rustc_middle::traits::CodegenObligationError,
+    rustc_middle::traits::EvaluationResult,
+    rustc_middle::traits::OverflowError,
+    rustc_middle::traits::query::NoSolution,
+    rustc_middle::traits::WellFormedLoc,
+    rustc_middle::ty::adjustment::CoerceUnsizedInfo,
+    rustc_middle::ty::AssocItem,
+    rustc_middle::ty::AssocItemContainer,
+    rustc_middle::ty::BoundVariableKind,
+    rustc_middle::ty::DeducedParamAttrs,
+    rustc_middle::ty::Destructor,
+    rustc_middle::ty::fast_reject::SimplifiedType,
+    rustc_middle::ty::ImplPolarity,
+    rustc_middle::ty::Representability,
+    rustc_middle::ty::ReprOptions,
+    rustc_middle::ty::UnusedGenericParams,
+    rustc_middle::ty::util::AlwaysRequiresDrop,
+    rustc_middle::ty::Visibility<rustc_span::def_id::DefId>,
+    rustc_session::config::CrateType,
+    rustc_session::config::EntryFnType,
+    rustc_session::config::OptLevel,
+    rustc_session::config::SymbolManglingVersion,
+    rustc_session::cstore::CrateDepKind,
+    rustc_session::cstore::ExternCrate,
+    rustc_session::cstore::LinkagePreference,
+    rustc_session::Limits,
+    rustc_session::lint::LintExpectationId,
+    rustc_span::def_id::CrateNum,
+    rustc_span::def_id::DefPathHash,
+    rustc_span::ExpnHash,
+    rustc_span::ExpnId,
+    rustc_span::Span,
+    rustc_span::Symbol,
+    rustc_span::symbol::Ident,
+    rustc_target::spec::PanicStrategy,
+    rustc_type_ir::Variance,
+    u32,
+    usize,
+}
+
+macro_rules! tcx_lifetime {
+    ($($($fake_path:ident)::+),+ $(,)?) => {
+        $(
+            impl<'tcx> EraseType for $($fake_path)::+<'tcx> {
+                type Result = [u8; size_of::<$($fake_path)::+<'static>>()];
+            }
+        )*
+    }
+}
+
+tcx_lifetime! {
+    rustc_middle::hir::Owner,
+    rustc_middle::middle::exported_symbols::ExportedSymbol,
+    rustc_middle::mir::ConstantKind,
+    rustc_middle::mir::DestructuredConstant,
+    rustc_middle::mir::interpret::ConstAlloc,
+    rustc_middle::mir::interpret::ConstValue,
+    rustc_middle::mir::interpret::GlobalId,
+    rustc_middle::mir::interpret::LitToConstInput,
+    rustc_middle::traits::ChalkEnvironmentAndGoal,
+    rustc_middle::traits::query::MethodAutoderefStepsResult,
+    rustc_middle::traits::query::type_op::AscribeUserType,
+    rustc_middle::traits::query::type_op::Eq,
+    rustc_middle::traits::query::type_op::ProvePredicate,
+    rustc_middle::traits::query::type_op::Subtype,
+    rustc_middle::ty::AdtDef,
+    rustc_middle::ty::AliasTy,
+    rustc_middle::ty::Clause,
+    rustc_middle::ty::ClosureTypeInfo,
+    rustc_middle::ty::Const,
+    rustc_middle::ty::DestructuredConst,
+    rustc_middle::ty::ExistentialTraitRef,
+    rustc_middle::ty::FnSig,
+    rustc_middle::ty::GenericArg,
+    rustc_middle::ty::GenericPredicates,
+    rustc_middle::ty::inhabitedness::InhabitedPredicate,
+    rustc_middle::ty::Instance,
+    rustc_middle::ty::InstanceDef,
+    rustc_middle::ty::layout::FnAbiError,
+    rustc_middle::ty::layout::LayoutError,
+    rustc_middle::ty::ParamEnv,
+    rustc_middle::ty::Predicate,
+    rustc_middle::ty::SymbolName,
+    rustc_middle::ty::TraitRef,
+    rustc_middle::ty::Ty,
+    rustc_middle::ty::UnevaluatedConst,
+    rustc_middle::ty::ValTree,
+    rustc_middle::ty::VtblEntry,
+}

compiler/rustc_middle/src/query/mod.rs

@@ -7,6 +7,7 @@
 use crate::ty::{self, print::describe_as_module, TyCtxt};
 use rustc_span::def_id::LOCAL_CRATE;
 
+pub mod erase;
 mod keys;
 pub use keys::{AsLocalKey, Key, LocalCrate};