Auto merge of #115326 - matthiaskrgr:rollup-qsoa8ar, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #115164 (MIR validation: reject in-place argument/return for packed fields)
 - #115240 (codegen_llvm/llvm_type: avoid matching on the Rust type)
 - #115294 (More precisely detect cycle errors from type_of on opaque)
 - #115310 (Document panic behavior across editions, and improve xrefs)
 - #115311 (Revert "Suggest using `Arc` on `!Send`/`!Sync` types")
 - #115317 (Devacationize oli-obk)
 - #115319 (don't use SnapshotVec in Graph implementation, as it looks unused; use Vec instead)
 - #115322 (Tweak output of `to_pretty_impl_header` involving only anon lifetimes)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_codegen_gcc/src/abi.rs

@@ -125,8 +125,8 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 PassMode::Ignore => continue,
                 PassMode::Direct(_) => arg.layout.immediate_gcc_type(cx),
                 PassMode::Pair(..) => {
-                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 0, true));
-                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 1, true));
+                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 0));
+                    argument_tys.push(arg.layout.scalar_pair_element_gcc_type(cx, 1));
                     continue;
                 }
                 PassMode::Indirect { extra_attrs: Some(_), .. } => {

compiler/rustc_codegen_gcc/src/builder.rs

@@ -821,7 +821,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
 
                 let mut load = |i, scalar: &abi::Scalar, align| {
                     let llptr = self.struct_gep(pair_type, place.llval, i as u64);
-                    let llty = place.layout.scalar_pair_element_gcc_type(self, i, false);
+                    let llty = place.layout.scalar_pair_element_gcc_type(self, i);
                     let load = self.load(llty, llptr, align);
                     scalar_load_metadata(self, load, scalar);
                     if scalar.is_bool() { self.trunc(load, self.type_i1()) } else { load }

compiler/rustc_codegen_gcc/src/type_of.rs

@@ -4,7 +4,7 @@ use gccjit::{Struct, Type};
 use crate::rustc_codegen_ssa::traits::{BaseTypeMethods, DerivedTypeMethods, LayoutTypeMethods};
 use rustc_middle::bug;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
-use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_target::abi::{self, Abi, Align, F32, F64, FieldsShape, Int, Integer, Pointer, PointeeInfo, Size, TyAbiInterface, Variants};
 use rustc_target::abi::call::{CastTarget, FnAbi, Reg};
@@ -74,8 +74,8 @@ fn uncached_gcc_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, layout: TyAndLayout
         Abi::ScalarPair(..) => {
             return cx.type_struct(
                 &[
-                    layout.scalar_pair_element_gcc_type(cx, 0, false),
-                    layout.scalar_pair_element_gcc_type(cx, 1, false),
+                    layout.scalar_pair_element_gcc_type(cx, 0),
+                    layout.scalar_pair_element_gcc_type(cx, 1),
                 ],
                 false,
             );
@@ -150,7 +150,7 @@ pub trait LayoutGccExt<'tcx> {
     fn gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc>;
     fn immediate_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc>;
     fn scalar_gcc_type_at<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, scalar: &abi::Scalar, offset: Size) -> Type<'gcc>;
-    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize, immediate: bool) -> Type<'gcc>;
+    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize) -> Type<'gcc>;
     fn gcc_field_index(&self, index: usize) -> u64;
     fn pointee_info_at<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, offset: Size) -> Option<PointeeInfo>;
 }
@@ -182,23 +182,16 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
     /// of that field's type - this is useful for taking the address of
     /// that field and ensuring the struct has the right alignment.
     fn gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>) -> Type<'gcc> {
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         if let Abi::Scalar(ref scalar) = self.abi {
             // Use a different cache for scalars because pointers to DSTs
             // can be either fat or thin (data pointers of fat pointers).
             if let Some(&ty) = cx.scalar_types.borrow().get(&self.ty) {
                 return ty;
             }
-            let ty =
-                match *self.ty.kind() {
-                    ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
-                        cx.type_ptr_to(cx.layout_of(ty).gcc_type(cx))
-                    }
-                    ty::Adt(def, _) if def.is_box() => {
-                        cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).gcc_type(cx))
-                    }
-                    ty::FnPtr(sig) => cx.fn_ptr_backend_type(&cx.fn_abi_of_fn_ptr(sig, ty::List::empty())),
-                    _ => self.scalar_gcc_type_at(cx, scalar, Size::ZERO),
-                };
+            let ty = self.scalar_gcc_type_at(cx, scalar, Size::ZERO);
             cx.scalar_types.borrow_mut().insert(self.ty, ty);
             return ty;
         }
@@ -272,23 +265,10 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
         }
     }
 
-    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize, immediate: bool) -> Type<'gcc> {
-        // TODO(antoyo): remove llvm hack:
-        // HACK(eddyb) special-case fat pointers until LLVM removes
-        // pointee types, to avoid bitcasting every `OperandRef::deref`.
-        match self.ty.kind() {
-            ty::Ref(..) | ty::RawPtr(_) => {
-                return self.field(cx, index).gcc_type(cx);
-            }
-            // only wide pointer boxes are handled as pointers
-            // thin pointer boxes with scalar allocators are handled by the general logic below
-            ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
-                let ptr_ty = Ty::new_mut_ptr(cx.tcx,self.ty.boxed_ty());
-                return cx.layout_of(ptr_ty).scalar_pair_element_gcc_type(cx, index, immediate);
-            }
-            _ => {}
-        }
-
+    fn scalar_pair_element_gcc_type<'gcc>(&self, cx: &CodegenCx<'gcc, 'tcx>, index: usize) -> Type<'gcc> {
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         let (a, b) = match self.abi {
             Abi::ScalarPair(ref a, ref b) => (a, b),
             _ => bug!("TyAndLayout::scalar_pair_element_llty({:?}): not applicable", self),
@@ -367,8 +347,8 @@ impl<'gcc, 'tcx> LayoutTypeMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         layout.gcc_field_index(index)
     }
 
-    fn scalar_pair_element_backend_type(&self, layout: TyAndLayout<'tcx>, index: usize, immediate: bool) -> Type<'gcc> {
-        layout.scalar_pair_element_gcc_type(self, index, immediate)
+    fn scalar_pair_element_backend_type(&self, layout: TyAndLayout<'tcx>, index: usize, _immediate: bool) -> Type<'gcc> {
+        layout.scalar_pair_element_gcc_type(self, index)
     }
 
     fn cast_backend_type(&self, ty: &CastTarget) -> Type<'gcc> {

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -3,7 +3,7 @@ use crate::context::TypeLowering;
 use crate::type_::Type;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
-use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, TyAndLayout};
+use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 use rustc_target::abi::HasDataLayout;
@@ -215,20 +215,16 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
     /// of that field's type - this is useful for taking the address of
     /// that field and ensuring the struct has the right alignment.
     fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         if let Abi::Scalar(scalar) = self.abi {
             // Use a different cache for scalars because pointers to DSTs
             // can be either fat or thin (data pointers of fat pointers).
             if let Some(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
                 return llty;
             }
-            let llty = match *self.ty.kind() {
-                ty::Ref(..) | ty::RawPtr(_) => cx.type_ptr(),
-                ty::Adt(def, _) if def.is_box() => cx.type_ptr(),
-                ty::FnPtr(sig) => {
-                    cx.fn_ptr_backend_type(cx.fn_abi_of_fn_ptr(sig, ty::List::empty()))
-                }
-                _ => self.scalar_llvm_type_at(cx, scalar),
-            };
+            let llty = self.scalar_llvm_type_at(cx, scalar);
             cx.scalar_lltypes.borrow_mut().insert(self.ty, llty);
             return llty;
         }
@@ -303,27 +299,9 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
         index: usize,
         immediate: bool,
     ) -> &'a Type {
-        // HACK(eddyb) special-case fat pointers until LLVM removes
-        // pointee types, to avoid bitcasting every `OperandRef::deref`.
-        match *self.ty.kind() {
-            ty::Ref(..) | ty::RawPtr(_) => {
-                return self.field(cx, index).llvm_type(cx);
-            }
-            // only wide pointer boxes are handled as pointers
-            // thin pointer boxes with scalar allocators are handled by the general logic below
-            ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
-                let ptr_ty = Ty::new_mut_ptr(cx.tcx, self.ty.boxed_ty());
-                return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
-            }
-            // `dyn* Trait` has the same ABI as `*mut dyn Trait`
-            ty::Dynamic(bounds, region, ty::DynStar) => {
-                let ptr_ty =
-                    Ty::new_mut_ptr(cx.tcx, Ty::new_dynamic(cx.tcx, bounds, region, ty::Dyn));
-                return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
-            }
-            _ => {}
-        }
-
+        // This must produce the same result for `repr(transparent)` wrappers as for the inner type!
+        // In other words, this should generally not look at the type at all, but only at the
+        // layout.
         let Abi::ScalarPair(a, b) = self.abi else {
             bug!("TyAndLayout::scalar_pair_element_llty({:?}): not applicable", self);
         };

compiler/rustc_const_eval/src/transform/validate.rs

@@ -20,6 +20,8 @@ use rustc_mir_dataflow::{Analysis, ResultsCursor};
 use rustc_target::abi::{Size, FIRST_VARIANT};
 use rustc_target::spec::abi::Abi;
 
+use crate::util::is_within_packed;
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 enum EdgeKind {
     Unwind,
@@ -93,6 +95,7 @@ impl<'tcx> MirPass<'tcx> for Validator {
         cfg_checker.visit_body(body);
         cfg_checker.check_cleanup_control_flow();
 
+        // Also run the TypeChecker.
         for (location, msg) in validate_types(tcx, self.mir_phase, param_env, body) {
             cfg_checker.fail(location, msg);
         }
@@ -427,22 +430,42 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
                 self.check_unwind_edge(location, *unwind);
 
                 // The call destination place and Operand::Move place used as an argument might be
-                // passed by a reference to the callee. Consequently they must be non-overlapping.
-                // Currently this simply checks for duplicate places.
+                // passed by a reference to the callee. Consequently they must be non-overlapping
+                // and cannot be packed. Currently this simply checks for duplicate places.
                 self.place_cache.clear();
                 self.place_cache.insert(destination.as_ref());
+                if is_within_packed(self.tcx, &self.body.local_decls, *destination).is_some() {
+                    // This is bad! The callee will expect the memory to be aligned.
+                    self.fail(
+                        location,
+                        format!(
+                            "encountered packed place in `Call` terminator destination: {:?}",
+                            terminator.kind,
+                        ),
+                    );
+                }
                 let mut has_duplicates = false;
                 for arg in args {
                     if let Operand::Move(place) = arg {
                         has_duplicates |= !self.place_cache.insert(place.as_ref());
+                        if is_within_packed(self.tcx, &self.body.local_decls, *place).is_some() {
+                            // This is bad! The callee will expect the memory to be aligned.
+                            self.fail(
+                                location,
+                                format!(
+                                    "encountered `Move` of a packed place in `Call` terminator: {:?}",
+                                    terminator.kind,
+                                ),
+                            );
+                        }
                     }
                 }
 
                 if has_duplicates {
                     self.fail(
                         location,
                         format!(
-                            "encountered overlapping memory in `Call` terminator: {:?}",
+                            "encountered overlapping memory in `Move` arguments to `Call` terminator: {:?}",
                             terminator.kind,
                         ),
                     );
@@ -541,6 +564,8 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
     }
 }
 
+/// A faster version of the validation pass that only checks those things which may break when apply
+/// generic substitutions.
 pub fn validate_types<'tcx>(
     tcx: TyCtxt<'tcx>,
     mir_phase: MirPhase,

compiler/rustc_const_eval/src/util/alignment.rs

@@ -34,6 +34,7 @@ where
             false
         }
         _ => {
+            // We cannot figure out the layout. Conservatively assume that this is disaligned.
             debug!("is_disaligned({:?}) - true", place);
             true
         }

compiler/rustc_data_structures/src/graph/implementation/mod.rs

@@ -20,16 +20,15 @@
 //! the field `next_edge`). Each of those fields is an array that should
 //! be indexed by the direction (see the type `Direction`).
 
-use crate::snapshot_vec::{SnapshotVec, SnapshotVecDelegate};
 use rustc_index::bit_set::BitSet;
 use std::fmt::Debug;
 
 #[cfg(test)]
 mod tests;
 
 pub struct Graph<N, E> {
-    nodes: SnapshotVec<Node<N>>,
-    edges: SnapshotVec<Edge<E>>,
+    nodes: Vec<Node<N>>,
+    edges: Vec<Edge<E>>,
 }
 
 pub struct Node<N> {
@@ -45,20 +44,6 @@ pub struct Edge<E> {
     pub data: E,
 }
 
-impl<N> SnapshotVecDelegate for Node<N> {
-    type Value = Node<N>;
-    type Undo = ();
-
-    fn reverse(_: &mut Vec<Node<N>>, _: ()) {}
-}
-
-impl<N> SnapshotVecDelegate for Edge<N> {
-    type Value = Edge<N>;
-    type Undo = ();
-
-    fn reverse(_: &mut Vec<Edge<N>>, _: ()) {}
-}
-
 #[derive(Copy, Clone, PartialEq, Debug)]
 pub struct NodeIndex(pub usize);
 
@@ -86,11 +71,11 @@ impl NodeIndex {
 
 impl<N: Debug, E: Debug> Graph<N, E> {
     pub fn new() -> Graph<N, E> {
-        Graph { nodes: SnapshotVec::new(), edges: SnapshotVec::new() }
+        Graph { nodes: Vec::new(), edges: Vec::new() }
     }
 
     pub fn with_capacity(nodes: usize, edges: usize) -> Graph<N, E> {
-        Graph { nodes: SnapshotVec::with_capacity(nodes), edges: SnapshotVec::with_capacity(edges) }
+        Graph { nodes: Vec::with_capacity(nodes), edges: Vec::with_capacity(edges) }
     }
 
     // # Simple accessors

compiler/rustc_hir_analysis/src/collect.rs

@@ -56,6 +56,7 @@ pub fn provide(providers: &mut Providers) {
     resolve_bound_vars::provide(providers);
     *providers = Providers {
         type_of: type_of::type_of,
+        type_of_opaque: type_of::type_of_opaque,
         item_bounds: item_bounds::item_bounds,
         explicit_item_bounds: item_bounds::explicit_item_bounds,
         generics_of: generics_of::generics_of,