Auto merge of #94690 - nnethercote:clarify-Layout-interning, r=fee1-dead

Clarify `Layout` interning.

`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.

This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.

Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.

The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.

r? `@fee1-dead`

Author: bors

compiler/rustc_codegen_cranelift/src/abi/comments.rs

@@ -82,8 +82,14 @@ pub(super) fn add_local_place_comments<'tcx>(
         return;
     }
     let TyAndLayout { ty, layout } = place.layout();
-    let rustc_target::abi::Layout { size, align, abi: _, variants: _, fields: _, largest_niche: _ } =
-        layout;
+    let rustc_target::abi::LayoutS {
+        size,
+        align,
+        abi: _,
+        variants: _,
+        fields: _,
+        largest_niche: _,
+    } = layout.0.0;
 
     let (kind, extra) = match *place.inner() {
         CPlaceInner::Var(place_local, var) => {

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -1070,7 +1070,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         };
 
         raw_eq, (v lhs_ref, v rhs_ref) {
-            let size = fx.layout_of(substs.type_at(0)).layout.size;
+            let size = fx.layout_of(substs.type_at(0)).layout.size();
             // FIXME add and use emit_small_memcmp
             let is_eq_value =
                 if size == Size::ZERO {

compiler/rustc_codegen_gcc/src/intrinsic/mod.rs

@@ -272,20 +272,20 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                     use rustc_target::abi::Abi::*;
                     let tp_ty = substs.type_at(0);
                     let layout = self.layout_of(tp_ty).layout;
-                    let _use_integer_compare = match layout.abi {
+                    let _use_integer_compare = match layout.abi() {
                         Scalar(_) | ScalarPair(_, _) => true,
                         Uninhabited | Vector { .. } => false,
                         Aggregate { .. } => {
                             // For rusty ABIs, small aggregates are actually passed
                             // as `RegKind::Integer` (see `FnAbi::adjust_for_abi`),
                             // so we re-use that same threshold here.
-                            layout.size <= self.data_layout().pointer_size * 2
+                            layout.size() <= self.data_layout().pointer_size * 2
                         }
                     };
 
                     let a = args[0].immediate();
                     let b = args[1].immediate();
-                    if layout.size.bytes() == 0 {
+                    if layout.size().bytes() == 0 {
                         self.const_bool(true)
                     }
                     /*else if use_integer_compare {
@@ -301,7 +301,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                         let void_ptr_type = self.context.new_type::<*const ()>();
                         let a_ptr = self.bitcast(a, void_ptr_type);
                         let b_ptr = self.bitcast(b, void_ptr_type);
-                        let n = self.context.new_cast(None, self.const_usize(layout.size.bytes()), self.sizet_type);
+                        let n = self.context.new_cast(None, self.const_usize(layout.size().bytes()), self.sizet_type);
                         let builtin = self.context.get_builtin_function("memcmp");
                         let cmp = self.context.new_call(None, builtin, &[a_ptr, b_ptr, n]);
                         self.icmp(IntPredicate::IntEQ, cmp, self.const_i32(0))

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -300,34 +300,34 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 use abi::Abi::*;
                 let tp_ty = substs.type_at(0);
                 let layout = self.layout_of(tp_ty).layout;
-                let use_integer_compare = match layout.abi {
+                let use_integer_compare = match layout.abi() {
                     Scalar(_) | ScalarPair(_, _) => true,
                     Uninhabited | Vector { .. } => false,
                     Aggregate { .. } => {
                         // For rusty ABIs, small aggregates are actually passed
                         // as `RegKind::Integer` (see `FnAbi::adjust_for_abi`),
                         // so we re-use that same threshold here.
-                        layout.size <= self.data_layout().pointer_size * 2
+                        layout.size() <= self.data_layout().pointer_size * 2
                     }
                 };
 
                 let a = args[0].immediate();
                 let b = args[1].immediate();
-                if layout.size.bytes() == 0 {
+                if layout.size().bytes() == 0 {
                     self.const_bool(true)
                 } else if use_integer_compare {
-                    let integer_ty = self.type_ix(layout.size.bits());
+                    let integer_ty = self.type_ix(layout.size().bits());
                     let ptr_ty = self.type_ptr_to(integer_ty);
                     let a_ptr = self.bitcast(a, ptr_ty);
-                    let a_val = self.load(integer_ty, a_ptr, layout.align.abi);
+                    let a_val = self.load(integer_ty, a_ptr, layout.align().abi);
                     let b_ptr = self.bitcast(b, ptr_ty);
-                    let b_val = self.load(integer_ty, b_ptr, layout.align.abi);
+                    let b_val = self.load(integer_ty, b_ptr, layout.align().abi);
                     self.icmp(IntPredicate::IntEQ, a_val, b_val)
                 } else {
                     let i8p_ty = self.type_i8p();
                     let a_ptr = self.bitcast(a, i8p_ty);
                     let b_ptr = self.bitcast(b, i8p_ty);
-                    let n = self.const_usize(layout.size.bytes());
+                    let n = self.const_usize(layout.size().bytes());
                     let cmp = self.call_intrinsic("memcmp", &[a_ptr, b_ptr, n]);
                     self.icmp(IntPredicate::IntEQ, cmp, self.const_i32(0))
                 }

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -427,7 +427,7 @@ fn push_debuginfo_type_name<'tcx>(
 
             // calculate the range of values for the dataful variant
             let dataful_discriminant_range =
-                dataful_variant_layout.largest_niche.unwrap().scalar.valid_range;
+                dataful_variant_layout.largest_niche().unwrap().scalar.valid_range;
 
             let min = dataful_discriminant_range.start;
             let min = tag.value.size(&tcx).truncate(min);

compiler/rustc_data_structures/src/intern.rs

@@ -1,3 +1,4 @@
+use crate::stable_hasher::{HashStable, StableHasher};
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
@@ -98,5 +99,14 @@ impl<'a, T> Hash for Interned<'a, T> {
     }
 }
 
+impl<T, CTX> HashStable<CTX> for Interned<'_, T>
+where
+    T: HashStable<CTX>,
+{
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        self.0.hash_stable(hcx, hasher);
+    }
+}
+
 #[cfg(test)]
 mod tests;

compiler/rustc_lint/src/builtin.rs

@@ -2861,8 +2861,8 @@ impl ClashingExternDeclarations {
 
                 let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
                     debug!("compare_layouts({:?}, {:?})", a, b);
-                    let a_layout = &cx.layout_of(a)?.layout.abi;
-                    let b_layout = &cx.layout_of(b)?.layout.abi;
+                    let a_layout = &cx.layout_of(a)?.layout.abi();
+                    let b_layout = &cx.layout_of(b)?.layout.abi();
                     debug!(
                         "comparing layouts: {:?} == {:?} = {}",
                         a_layout,

compiler/rustc_lint/src/types.rs

@@ -1349,7 +1349,7 @@ impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
             let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
                 .map(|(variant, variant_layout)| {
                     // Subtract the size of the enum tag.
-                    let bytes = variant_layout.size.bytes().saturating_sub(tag_size);
+                    let bytes = variant_layout.size().bytes().saturating_sub(tag_size);
 
                     debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
                     bytes

compiler/rustc_metadata/src/native_libs.rs

@@ -392,7 +392,7 @@ impl Collector<'_> {
                     .layout;
                 // In both stdcall and fastcall, we always round up the argument size to the
                 // nearest multiple of 4 bytes.
-                (layout.size.bytes_usize() + 3) & !3
+                (layout.size().bytes_usize() + 3) & !3
             })
             .sum()
     }

compiler/rustc_middle/src/arena.rs

@@ -6,7 +6,7 @@
 macro_rules! arena_types {
     ($macro:path) => (
         $macro!([
-            [] layout: rustc_target::abi::Layout,
+            [] layout: rustc_target::abi::LayoutS<'tcx>,
             [] fn_abi: rustc_target::abi::call::FnAbi<'tcx, rustc_middle::ty::Ty<'tcx>>,
             // AdtDef are interned and compared by address
             [decode] adt_def: rustc_middle::ty::AdtDef,

compiler/rustc_middle/src/ty/context.rs

@@ -56,7 +56,7 @@ use rustc_span::def_id::{DefPathHash, StableCrateId};
 use rustc_span::source_map::{MultiSpan, SourceMap};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
-use rustc_target::abi::{Layout, TargetDataLayout, VariantIdx};
+use rustc_target::abi::{Layout, LayoutS, TargetDataLayout, VariantIdx};
 use rustc_target::spec::abi;
 
 use rustc_type_ir::TypeFlags;
@@ -114,7 +114,7 @@ pub struct CtxtInterners<'tcx> {
     const_: InternedSet<'tcx, ConstS<'tcx>>,
     const_allocation: InternedSet<'tcx, Allocation>,
     bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
-    layout: InternedSet<'tcx, Layout>,
+    layout: InternedSet<'tcx, LayoutS<'tcx>>,
     adt_def: InternedSet<'tcx, AdtDef>,
 }
 
@@ -2146,6 +2146,7 @@ direct_interners! {
     region: mk_region(RegionKind): Region -> Region<'tcx>,
     const_: mk_const(ConstS<'tcx>): Const -> Const<'tcx>,
     const_allocation: intern_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
+    layout: intern_layout(LayoutS<'tcx>): Layout -> Layout<'tcx>,
 }
 
 macro_rules! direct_interners_old {
@@ -2186,7 +2187,6 @@ macro_rules! direct_interners_old {
 
 // FIXME: eventually these should all be converted to `direct_interners`.
 direct_interners_old! {
-    layout: intern_layout(Layout),
     adt_def: intern_adt_def(AdtDef),
 }