Auto merge of #119501 - cjgillot:clone-shim, r=<try>

Only generate a single shim for clone of copy types.

r? `@ghost`

Author: bors

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -544,6 +544,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             | ty::InstanceDef::FnPtrShim(..)
             | ty::InstanceDef::DropGlue(..)
             | ty::InstanceDef::CloneShim(..)
+            | ty::InstanceDef::CloneCopyShim(..)
             | ty::InstanceDef::FnPtrAddrShim(..)
             | ty::InstanceDef::ThreadLocalShim(..)
             | ty::InstanceDef::Item(_) => {

compiler/rustc_middle/src/mir/mono.rs

@@ -404,6 +404,7 @@ impl<'tcx> CodegenUnit<'tcx> {
                             | InstanceDef::ClosureOnceShim { .. }
                             | InstanceDef::DropGlue(..)
                             | InstanceDef::CloneShim(..)
+                            | InstanceDef::CloneCopyShim(..)
                             | InstanceDef::ThreadLocalShim(..)
                             | InstanceDef::FnPtrAddrShim(..) => None,
                         }

compiler/rustc_middle/src/mir/visit.rs

@@ -344,6 +344,7 @@ macro_rules! make_mir_visitor {
                         ty::InstanceDef::ReifyShim(_def_id) |
                         ty::InstanceDef::Virtual(_def_id, _) |
                         ty::InstanceDef::ThreadLocalShim(_def_id) |
+                        ty::InstanceDef::CloneCopyShim(_def_id) |
                         ty::InstanceDef::ClosureOnceShim { call_once: _def_id, track_caller: _ } |
                         ty::InstanceDef::DropGlue(_def_id, None) => {}
 

compiler/rustc_middle/src/ty/instance.rs

@@ -97,9 +97,13 @@ pub enum InstanceDef<'tcx> {
     /// glue.
     DropGlue(DefId, Option<Ty<'tcx>>),
 
+    /// Compiler-generated `<T as Clone>::clone` implementation where T is `Copy`.
+    ///
+    /// The `DefId` is for `Clone::clone`.
+    CloneCopyShim(DefId),
+
     /// Compiler-generated `<T as Clone>::clone` implementation.
     ///
-    /// For all types that automatically implement `Copy`, a trivial `Clone` impl is provided too.
     /// Additionally, arrays, tuples, and closures get a `Clone` shim even if they aren't `Copy`.
     ///
     /// The `DefId` is for `Clone::clone`, the `Ty` is the type `T` with the builtin `Clone` impl.
@@ -168,6 +172,7 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::ClosureOnceShim { call_once: def_id, track_caller: _ }
             | InstanceDef::DropGlue(def_id, _)
             | InstanceDef::CloneShim(def_id, _)
+            | InstanceDef::CloneCopyShim(def_id)
             | InstanceDef::FnPtrAddrShim(def_id, _) => def_id,
         }
     }
@@ -187,6 +192,7 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::ClosureOnceShim { .. }
             | InstanceDef::DropGlue(..)
             | InstanceDef::CloneShim(..)
+            | InstanceDef::CloneCopyShim(..)
             | InstanceDef::FnPtrAddrShim(..) => None,
         }
     }
@@ -280,6 +286,7 @@ impl<'tcx> InstanceDef<'tcx> {
             | InstanceDef::FnPtrShim(..)
             | InstanceDef::DropGlue(_, Some(_)) => false,
             InstanceDef::ClosureOnceShim { .. }
+            | InstanceDef::CloneCopyShim(..)
             | InstanceDef::DropGlue(..)
             | InstanceDef::Item(_)
             | InstanceDef::Intrinsic(..)
@@ -316,6 +323,7 @@ fn fmt_instance(
         InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
         InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({ty}))"),
         InstanceDef::CloneShim(_, ty) => write!(f, " - shim({ty})"),
+        InstanceDef::CloneCopyShim(_) => write!(f, " - shim(<Copy>)"),
         InstanceDef::FnPtrAddrShim(_, ty) => write!(f, " - shim({ty})"),
     }
 }

compiler/rustc_middle/src/ty/mod.rs

@@ -2334,6 +2334,7 @@ impl<'tcx> TyCtxt<'tcx> {
             | ty::InstanceDef::ClosureOnceShim { .. }
             | ty::InstanceDef::DropGlue(..)
             | ty::InstanceDef::CloneShim(..)
+            | ty::InstanceDef::CloneCopyShim(..)
             | ty::InstanceDef::ThreadLocalShim(..)
             | ty::InstanceDef::FnPtrAddrShim(..) => self.mir_shims(instance),
         }

compiler/rustc_mir_transform/src/inline.rs

@@ -319,6 +319,7 @@ impl<'tcx> Inliner<'tcx> {
             | InstanceDef::ClosureOnceShim { .. }
             | InstanceDef::DropGlue(..)
             | InstanceDef::CloneShim(..)
+            | InstanceDef::CloneCopyShim(..)
             | InstanceDef::ThreadLocalShim(..)
             | InstanceDef::FnPtrAddrShim(..) => return Ok(()),
         }

compiler/rustc_mir_transform/src/inline/cycle.rs

@@ -88,6 +88,7 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
                 | InstanceDef::FnPtrShim(..)
                 | InstanceDef::ClosureOnceShim { .. }
                 | InstanceDef::ThreadLocalShim { .. }
+                | InstanceDef::CloneCopyShim(..)
                 | InstanceDef::CloneShim(..) => {}
 
                 // This shim does not call any other functions, thus there can be no recursion.

compiler/rustc_mir_transform/src/shim.rs

@@ -1,15 +1,14 @@
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, CoroutineArgs, EarlyBinder, Ty, TyCtxt};
-use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
-
-use rustc_index::{Idx, IndexVec};
-
+use rustc_span::symbol::kw;
 use rustc_span::Span;
+use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 use rustc_target::spec::abi::Abi;
 
 use std::fmt;
@@ -90,7 +89,18 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
             build_drop_shim(tcx, def_id, ty)
         }
         ty::InstanceDef::ThreadLocalShim(..) => build_thread_local_shim(tcx, instance),
-        ty::InstanceDef::CloneShim(def_id, ty) => build_clone_shim(tcx, def_id, ty),
+        ty::InstanceDef::CloneCopyShim(def_id) => {
+            let self_ty = Ty::new_param(tcx, 0, kw::SelfUpper);
+            let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
+            builder.copy_shim();
+            let mut result = builder.into_mir(instance);
+            // Mark as runtime MIR to bypass MIR validation checking `Operand::Copy`.
+            result.phase = MirPhase::Runtime(RuntimePhase::Initial);
+            result
+        }
+        ty::InstanceDef::CloneShim(def_id, ty) => {
+            build_clone_shim(tcx, def_id, ty).into_mir(instance)
+        }
         ty::InstanceDef::FnPtrAddrShim(def_id, ty) => build_fn_ptr_addr_shim(tcx, def_id, ty),
         ty::InstanceDef::Virtual(..) => {
             bug!("InstanceDef::Virtual ({:?}) is for direct calls only", instance)
@@ -379,19 +389,18 @@ fn build_thread_local_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'t
 }
 
 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
-fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
-    debug!("build_clone_shim(def_id={:?})", def_id);
-
-    let param_env = tcx.param_env_reveal_all_normalized(def_id);
-
+#[instrument(level = "trace", skip(tcx))]
+fn build_clone_shim<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    def_id: DefId,
+    self_ty: Ty<'tcx>,
+) -> CloneShimBuilder<'tcx> {
     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
-    let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env);
 
     let dest = Place::return_place();
     let src = tcx.mk_place_deref(Place::from(Local::new(1 + 0)));
 
     match self_ty.kind() {
-        _ if is_copy => builder.copy_shim(),
         ty::Closure(_, args) => builder.tuple_like_shim(dest, src, args.as_closure().upvar_tys()),
         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
         ty::Coroutine(coroutine_def_id, args) => {
@@ -401,7 +410,7 @@ fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -
         _ => bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty),
     };
 
-    builder.into_mir()
+    builder
 }
 
 struct CloneShimBuilder<'tcx> {
@@ -432,11 +441,8 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         }
     }
 
-    fn into_mir(self) -> Body<'tcx> {
-        let source = MirSource::from_instance(ty::InstanceDef::CloneShim(
-            self.def_id,
-            self.sig.inputs_and_output[0],
-        ));
+    fn into_mir(self, def: ty::InstanceDef<'tcx>) -> Body<'tcx> {
+        let source = MirSource::from_instance(def);
         new_body(source, self.blocks, self.local_decls, self.sig.inputs().len(), self.span)
     }
 

compiler/rustc_monomorphize/src/collector.rs

@@ -961,6 +961,7 @@ fn visit_instance_use<'tcx>(
         | ty::InstanceDef::Item(..)
         | ty::InstanceDef::FnPtrShim(..)
         | ty::InstanceDef::CloneShim(..)
+        | ty::InstanceDef::CloneCopyShim(..)
         | ty::InstanceDef::FnPtrAddrShim(..) => {
             output.push(create_fn_mono_item(tcx, instance, source));
         }

compiler/rustc_monomorphize/src/partitioning.rs

@@ -624,6 +624,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
                 | ty::InstanceDef::DropGlue(..)
                 | ty::InstanceDef::Virtual(..)
                 | ty::InstanceDef::CloneShim(..)
+                | ty::InstanceDef::CloneCopyShim(..)
                 | ty::InstanceDef::ThreadLocalShim(..)
                 | ty::InstanceDef::FnPtrAddrShim(..) => return None,
             };
@@ -785,6 +786,7 @@ fn mono_item_visibility<'tcx>(
         | InstanceDef::ClosureOnceShim { .. }
         | InstanceDef::DropGlue(..)
         | InstanceDef::CloneShim(..)
+        | InstanceDef::CloneCopyShim(..)
         | InstanceDef::FnPtrAddrShim(..) => return Visibility::Hidden,
     };