Introduce -Zprofile-closures to evaluate the impact of 2229

This creates a CSV with name "closure_profile_XXXXX.csv", where the
variable part is the process id of the compiler.

To profile a cargo project you can run one of the following depending on
if you're compiling a library or a binary:

```
cargo +stage1 rustc --lib -- -Zprofile-closures
cargo +stage1 rustc --bin -- -Zprofile-closures
```

2 files changed, 32 insertions, 5 deletions

diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 77f955e93b9..6e910d0087f 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -19,11 +19,12 @@ use crate::ty::query::{self, OnDiskCache, TyCtxtAt};
 use crate::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, Subst, SubstsRef, UserSubsts};
 use crate::ty::TyKind::*;
 use crate::ty::{
-    self, AdtDef, AdtKind, Binder, BindingMode, BoundVar, CanonicalPolyFnSig, Const, ConstVid,
-    DefIdTree, ExistentialPredicate, FloatTy, FloatVar, FloatVid, GenericParamDefKind, InferConst,
-    InferTy, IntTy, IntVar, IntVid, List, MainDefinition, ParamConst, ParamTy, PolyFnSig,
-    Predicate, PredicateInner, PredicateKind, ProjectionTy, Region, RegionKind, ReprOptions,
-    TraitObjectVisitor, Ty, TyKind, TyS, TyVar, TyVid, TypeAndMut, UintTy, Visibility,
+    self, AdtDef, AdtKind, Binder, BindingMode, BoundVar, CanonicalPolyFnSig,
+    ClosureSizeProfileData, Const, ConstVid, DefIdTree, ExistentialPredicate, FloatTy, FloatVar,
+    FloatVid, GenericParamDefKind, InferConst, InferTy, IntTy, IntVar, IntVid, List,
+    MainDefinition, ParamConst, ParamTy, PolyFnSig, Predicate, PredicateInner, PredicateKind,
+    ProjectionTy, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty, TyKind, TyS, TyVar,
+    TyVid, TypeAndMut, UintTy, Visibility,
 };
 use rustc_ast as ast;
 use rustc_ast::expand::allocator::AllocatorKind;
@@ -484,6 +485,10 @@ pub struct TypeckResults<'tcx> {
     /// This hashset records all instances where we behave
     /// like this to allow `const_to_pat` to reliably handle this situation.
     pub treat_byte_string_as_slice: ItemLocalSet,
+
+    /// Contains the data for evaluating the effect of feature `capture_disjoint_fields`
+    /// on closure size.
+    pub closure_size_eval: FxHashMap<DefId, ClosureSizeProfileData<'tcx>>,
 }
 
 impl<'tcx> TypeckResults<'tcx> {
@@ -510,6 +515,7 @@ impl<'tcx> TypeckResults<'tcx> {
             closure_fake_reads: Default::default(),
             generator_interior_types: ty::Binder::dummy(Default::default()),
             treat_byte_string_as_slice: Default::default(),
+            closure_size_eval: Default::default(),
         }
     }
 
@@ -754,6 +760,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TypeckResults<'tcx> {
             ref closure_fake_reads,
             ref generator_interior_types,
             ref treat_byte_string_as_slice,
+            ref closure_size_eval,
         } = *self;
 
         hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
@@ -780,6 +787,7 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TypeckResults<'tcx> {
             closure_fake_reads.hash_stable(hcx, hasher);
             generator_interior_types.hash_stable(hcx, hasher);
             treat_byte_string_as_slice.hash_stable(hcx, hasher);
+            closure_size_eval.hash_stable(hcx, hasher);
         })
     }
 }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index a2abbec7492..dc5687de896 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -173,6 +173,25 @@ pub enum Visibility {
     Invisible,
 }
 
+#[derive(
+    Clone,
+    Debug,
+    PartialEq,
+    Eq,
+    Copy,
+    Hash,
+    TyEncodable,
+    TyDecodable,
+    HashStable,
+    TypeFoldable
+)]
+pub struct ClosureSizeProfileData<'tcx> {
+    /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
+    pub before_feature_tys: Ty<'tcx>,
+    /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
+    pub after_feature_tys: Ty<'tcx>,
+}
+
 pub trait DefIdTree: Copy {
     fn parent(self, id: DefId) -> Option<DefId>;