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.

3 files changed, 3 insertions, 3 deletions

diff --git a/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs b/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
index f52a4524d78..edb6bc4fbea 100644
--- a/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
+++ b/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
@@ -64,7 +64,7 @@ impl<'tcx> MirPass<'tcx> for AbortUnwindingCalls {
                     let ty = func.ty(body, tcx);
                     let sig = ty.fn_sig(tcx);
                     let fn_def_id = match ty.kind() {
-                        ty::FnPtr(_) => None,
+                        ty::FnPtr(..) => None,
                         &ty::FnDef(def_id, _) => Some(def_id),
                         _ => span_bug!(span, "invalid callee of type {:?}", ty),
                     };
diff --git a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
index 4132e604f20..9a2cc057232 100644
--- a/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
+++ b/compiler/rustc_mir_transform/src/ffi_unwind_calls.rs
@@ -57,7 +57,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
         };
 
         let fn_def_id = match ty.kind() {
-            ty::FnPtr(_) => None,
+            ty::FnPtr(..) => None,
             &ty::FnDef(def_id, _) => {
                 // Rust calls cannot themselves create foreign unwinds (even if they use a non-Rust ABI).
                 // So the leak of the foreign unwind into Rust can only be elsewhere, not here.
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index f41f3ef656c..49d55166ec5 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -437,7 +437,7 @@ fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -
     let src = tcx.mk_place_deref(Place::from(Local::new(1 + 0)));
 
     match self_ty.kind() {
-        ty::FnDef(..) | ty::FnPtr(_) => builder.copy_shim(),
+        ty::FnDef(..) | ty::FnPtr(..) => builder.copy_shim(),
         ty::Closure(_, args) => builder.tuple_like_shim(dest, src, args.as_closure().upvar_tys()),
         ty::CoroutineClosure(_, args) => {
             builder.tuple_like_shim(dest, src, args.as_coroutine_closure().upvar_tys())