Auto merge of #128812 - nnethercote:shrink-TyKind-FnPtr, r=compiler-errors

Shrink `TyKind::FnPtr`.

By splitting the `FnSig` within `TyKind::FnPtr` into `FnSigTys` and `FnHeader`, which can be packed more efficiently. This reduces the size of the hot `TyKind` type from 32 bytes to 24 bytes on 64-bit platforms. This reduces peak memory usage by a few percent on some benchmarks. It also reduces cache misses and page faults similarly, though this doesn't translate to clear cycles or wall-time improvements on CI.

r? `@compiler-errors`

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1636,7 +1636,7 @@ fn confirm_fn_pointer_candidate<'cx, 'tcx>(
             .generics_of(def_id)
             .host_effect_index
             .map_or(tcx.consts.true_, |idx| args.const_at(idx)),
-        ty::FnPtr(_) => tcx.consts.true_,
+        ty::FnPtr(..) => tcx.consts.true_,
         _ => unreachable!("only expected FnPtr or FnDef in `confirm_fn_pointer_candidate`"),
     };
 

compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs

@@ -33,7 +33,7 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
         | ty::Float(_)
         | ty::Never
         | ty::FnDef(..)
-        | ty::FnPtr(_)
+        | ty::FnPtr(..)
         | ty::Char
         | ty::CoroutineWitness(..)
         | ty::RawPtr(_, _)
@@ -224,7 +224,7 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
         | ty::RawPtr(..)
         | ty::Ref(..)
         | ty::FnDef(..)
-        | ty::FnPtr(_)
+        | ty::FnPtr(..)
         | ty::CoroutineWitness(..) => {
             // these types never have a destructor
         }

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -468,8 +468,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 candidates.vec.push(AsyncClosureCandidate);
             }
             // Provide an impl, but only for suitable `fn` pointers.
-            ty::FnPtr(sig) => {
-                if sig.is_fn_trait_compatible() {
+            ty::FnPtr(sig_tys, hdr) => {
+                if sig_tys.with(hdr).is_fn_trait_compatible() {
                     candidates.vec.push(AsyncClosureCandidate);
                 }
             }
@@ -535,8 +535,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 candidates.ambiguous = true; // Could wind up being a fn() type.
             }
             // Provide an impl, but only for suitable `fn` pointers.
-            ty::FnPtr(sig) => {
-                if sig.is_fn_trait_compatible() {
+            ty::FnPtr(sig_tys, hdr) => {
+                if sig_tys.with(hdr).is_fn_trait_compatible() {
                     candidates
                         .vec
                         .push(FnPointerCandidate { fn_host_effect: self.tcx().consts.true_ });
@@ -819,7 +819,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 | ty::RawPtr(_, _)
                 | ty::Ref(..)
                 | ty::FnDef(..)
-                | ty::FnPtr(_)
+                | ty::FnPtr(..)
                 | ty::Closure(..)
                 | ty::CoroutineClosure(..)
                 | ty::Coroutine(..)
@@ -1207,7 +1207,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             | ty::RawPtr(_, _)
             | ty::Ref(..)
             | ty::FnDef(..)
-            | ty::FnPtr(_)
+            | ty::FnPtr(..)
             | ty::Never
             | ty::Foreign(_)
             | ty::Array(..)
@@ -1290,7 +1290,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             | ty::Ref(_, _, _)
             | ty::FnDef(_, _)
             | ty::Pat(_, _)
-            | ty::FnPtr(_)
+            | ty::FnPtr(..)
             | ty::Dynamic(_, _, _)
             | ty::Closure(..)
             | ty::CoroutineClosure(..)
@@ -1339,7 +1339,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let self_ty = self.infcx.resolve_vars_if_possible(obligation.self_ty());
 
         match self_ty.skip_binder().kind() {
-            ty::FnPtr(_) => candidates.vec.push(BuiltinCandidate { has_nested: false }),
+            ty::FnPtr(..) => candidates.vec.push(BuiltinCandidate { has_nested: false }),
             ty::Bool
             | ty::Char
             | ty::Int(_)

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -1398,7 +1398,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 | ty::RawPtr(_, _)
                 | ty::Ref(..)
                 | ty::FnDef(..)
-                | ty::FnPtr(_)
+                | ty::FnPtr(..)
                 | ty::Never
                 | ty::Foreign(_) => {}
 

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2113,7 +2113,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             | ty::Bool
             | ty::Float(_)
             | ty::FnDef(..)
-            | ty::FnPtr(_)
+            | ty::FnPtr(..)
             | ty::RawPtr(..)
             | ty::Char
             | ty::Ref(..)
@@ -2170,7 +2170,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         use self::BuiltinImplConditions::{Ambiguous, None, Where};
 
         match *self_ty.kind() {
-            ty::FnDef(..) | ty::FnPtr(_) | ty::Error(_) => Where(ty::Binder::dummy(Vec::new())),
+            ty::FnDef(..) | ty::FnPtr(..) | ty::Error(_) => Where(ty::Binder::dummy(Vec::new())),
 
             ty::Uint(_)
             | ty::Int(_)
@@ -2332,7 +2332,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             | ty::Bool
             | ty::Float(_)
             | ty::FnDef(..)
-            | ty::FnPtr(_)
+            | ty::FnPtr(..)
             | ty::Error(_)
             | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
             | ty::Never

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -812,7 +812,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                 return upvars.visit_with(self);
             }
 
-            ty::FnPtr(_) => {
+            ty::FnPtr(..) => {
                 // Let the visitor iterate into the argument/return
                 // types appearing in the fn signature.
             }