Querify MonoItem collection

compiler/rustc_middle/src/mir/mono.rs

@@ -46,7 +46,7 @@ pub enum InstantiationMode {
     LocalCopy,
 }
 
-#[derive(PartialEq, Eq, Clone, Copy, Debug, Hash, HashStable)]
+#[derive(PartialEq, Eq, Clone, Copy, Debug, Hash, HashStable, TyEncodable, TyDecodable)]
 pub enum MonoItem<'tcx> {
     Fn(Instance<'tcx>),
     Static(DefId),
@@ -66,20 +66,7 @@ impl<'tcx> MonoItem<'tcx> {
     // change NON_INCR_MIN_CGU_SIZE as well.
     pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
         match *self {
-            MonoItem::Fn(instance) => {
-                match instance.def {
-                    // "Normal" functions size estimate: the number of
-                    // statements, plus one for the terminator.
-                    InstanceKind::Item(..)
-                    | InstanceKind::DropGlue(..)
-                    | InstanceKind::AsyncDropGlueCtorShim(..) => {
-                        let mir = tcx.instance_mir(instance.def);
-                        mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
-                    }
-                    // Other compiler-generated shims size estimate: 1
-                    _ => 1,
-                }
-            }
+            MonoItem::Fn(instance) => tcx.size_estimate(instance),
             // Conservatively estimate the size of a static declaration or
             // assembly item to be 1.
             MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
@@ -556,3 +543,21 @@ impl<'tcx> CodegenUnitNameBuilder<'tcx> {
         Symbol::intern(&cgu_name)
     }
 }
+
+/// See module-level docs of `rustc_monomorphize::collector` on some context for "mentioned" items.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
+pub enum CollectionMode {
+    /// Collect items that are used, i.e., actually needed for codegen.
+    ///
+    /// Which items are used can depend on optimization levels, as MIR optimizations can remove
+    /// uses.
+    UsedItems,
+    /// Collect items that are mentioned. The goal of this mode is that it is independent of
+    /// optimizations: the set of "mentioned" items is computed before optimizations are run.
+    ///
+    /// The exact contents of this set are *not* a stable guarantee. (For instance, it is currently
+    /// computed after drop-elaboration. If we ever do some optimizations even in debug builds, we
+    /// might decide to run them before computing mentioned items.) The key property of this set is
+    /// that it is optimization-independent.
+    MentionedItems,
+}

compiler/rustc_middle/src/query/erase.rs

@@ -216,6 +216,10 @@ 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 [()])>()];
+}
+
 impl<T0> EraseType for (&'_ T0, Result<(), ErrorGuaranteed>) {
     type Result = [u8; size_of::<(&'static (), Result<(), ErrorGuaranteed>)>()];
 }

compiler/rustc_middle/src/query/keys.rs

@@ -7,6 +7,7 @@ use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{DUMMY_SP, Span};
 
 use crate::infer::canonical::CanonicalQueryInput;
+use crate::mir::mono::CollectionMode;
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::{TyAndLayout, ValidityRequirement};
 use crate::ty::{self, GenericArg, GenericArgsRef, Ty, TyCtxt};
@@ -590,3 +591,11 @@ impl<'tcx> Key for (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>) {
         }
     }
 }
+
+impl<'tcx> Key for (ty::Instance<'tcx>, CollectionMode) {
+    type Cache<V> = DefaultCache<Self, V>;
+
+    fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
+        self.0.default_span(tcx)
+    }
+}

compiler/rustc_middle/src/query/mod.rs

@@ -40,6 +40,7 @@ use rustc_session::cstore::{
 };
 use rustc_session::lint::LintExpectationId;
 use rustc_span::def_id::LOCAL_CRATE;
+use rustc_span::source_map::Spanned;
 use rustc_span::symbol::Symbol;
 use rustc_span::{DUMMY_SP, Span};
 use rustc_target::spec::PanicStrategy;
@@ -59,7 +60,7 @@ use crate::mir::interpret::{
     EvalStaticInitializerRawResult, EvalToAllocationRawResult, EvalToConstValueResult,
     EvalToValTreeResult, GlobalId, LitToConstError, LitToConstInput,
 };
-use crate::mir::mono::CodegenUnit;
+use crate::mir::mono::{CodegenUnit, CollectionMode, MonoItem};
 use crate::query::erase::{Erase, erase, restore};
 use crate::query::plumbing::{
     CyclePlaceholder, DynamicQuery, query_ensure, query_ensure_error_guaranteed, query_get_at,
@@ -2339,6 +2340,16 @@ rustc_queries! {
         arena_cache
         desc { "functions to skip for move-size check" }
     }
+
+    query items_of_instance(key: (ty::Instance<'tcx>, CollectionMode)) -> (&'tcx [Spanned<MonoItem<'tcx>>], &'tcx [Spanned<MonoItem<'tcx>>]) {
+        desc { "collecting items used by `{}`", key.0 }
+        cache_on_disk_if { true }
+    }
+
+    query size_estimate(key: ty::Instance<'tcx>) -> usize {
+        desc { "estimating codegen size of `{}`", key }
+        cache_on_disk_if { true }
+    }
 }
 
 rustc_query_append! { define_callbacks! }

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -12,6 +12,7 @@ use rustc_index::{Idx, IndexVec};
 use rustc_macros::{Decodable, Encodable};
 use rustc_middle::dep_graph::{DepNodeIndex, SerializedDepNodeIndex};
 use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
+use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::mir::{self, interpret};
 use rustc_middle::ty::codec::{RefDecodable, TyDecoder, TyEncoder};
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -22,7 +23,7 @@ use rustc_session::Session;
 use rustc_span::hygiene::{
     ExpnId, HygieneDecodeContext, HygieneEncodeContext, SyntaxContext, SyntaxContextData,
 };
-use rustc_span::source_map::SourceMap;
+use rustc_span::source_map::{SourceMap, Spanned};
 use rustc_span::{
     BytePos, CachingSourceMapView, ExpnData, ExpnHash, Pos, RelativeBytePos, SourceFile, Span,
     SpanDecoder, SpanEncoder, StableSourceFileId, Symbol,
@@ -773,6 +774,13 @@ impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [rustc_ast::InlineAsm
     }
 }
 
+impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>> for &'tcx [Spanned<MonoItem<'tcx>>] {
+    #[inline]
+    fn decode(d: &mut CacheDecoder<'a, 'tcx>) -> Self {
+        RefDecodable::decode(d)
+    }
+}
+
 impl<'a, 'tcx> Decodable<CacheDecoder<'a, 'tcx>>
     for &'tcx crate::traits::specialization_graph::Graph
 {

compiler/rustc_middle/src/ty/codec.rs

@@ -13,9 +13,11 @@ use std::marker::DiscriminantKind;
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::LocalDefId;
+use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::ty::TyCtxt;
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::Span;
+use rustc_span::source_map::Spanned;
 pub use rustc_type_ir::{TyDecoder, TyEncoder};
 
 use crate::arena::ArenaAllocatable;
@@ -397,6 +399,15 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     }
 }
 
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [Spanned<MonoItem<'tcx>>] {
+    fn decode(decoder: &mut D) -> &'tcx Self {
+        decoder
+            .interner()
+            .arena
+            .alloc_from_iter((0..decoder.read_usize()).map(|_| Decodable::decode(decoder)))
+    }
+}
+
 impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     for ty::List<ty::BoundVariableKind>
 {