Rollup merge of #124251 - scottmcm:unop-ptr-metadata, r=oli-obk

Add an intrinsic for `ptr::metadata`

The follow-up to #123840, so we can remove `PtrComponents` and `PtrRepr` from libcore entirely (well, after a bootstrap update).

As discussed in <https://rust-lang.zulipchat.com/#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/.60ptr_metadata.60.20in.20MIR/near/435637808>, this introduces `UnOp::PtrMetadata` taking a raw pointer and returning the associated metadata value.

By no longer going through a `union`, this should also help future PRs better optimize pointer operations.

r? ``@oli-obk``

Author: jieyouxu

compiler/rustc_mir_transform/src/validate.rs

@@ -1109,6 +1109,16 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             ty::Int(..) | ty::Uint(..) | ty::Bool
                         );
                     }
+                    UnOp::PtrMetadata => {
+                        if !matches!(self.mir_phase, MirPhase::Runtime(_)) {
+                            // It would probably be fine to support this in earlier phases,
+                            // but at the time of writing it's only ever introduced from intrinsic lowering,
+                            // so earlier things can just `bug!` on it.
+                            self.fail(location, "PtrMetadata should be in runtime MIR only");
+                        }
+
+                        check_kinds!(a, "Cannot PtrMetadata non-pointer type {:?}", ty::RawPtr(..));
+                    }
                 }
             }
             Rvalue::ShallowInitBox(operand, _) => {

compiler/rustc_smir/src/rustc_internal/internal.rs

@@ -10,7 +10,7 @@ use rustc_span::Symbol;
 use stable_mir::abi::Layout;
 use stable_mir::mir::alloc::AllocId;
 use stable_mir::mir::mono::{Instance, MonoItem, StaticDef};
-use stable_mir::mir::{BinOp, Mutability, Place, ProjectionElem, Safety};
+use stable_mir::mir::{BinOp, Mutability, Place, ProjectionElem, Safety, UnOp};
 use stable_mir::ty::{
     Abi, AdtDef, Binder, BoundRegionKind, BoundTyKind, BoundVariableKind, ClosureKind, Const,
     DynKind, ExistentialPredicate, ExistentialProjection, ExistentialTraitRef, FloatTy, FnSig,
@@ -582,6 +582,18 @@ impl RustcInternal for BinOp {
     }
 }
 
+impl RustcInternal for UnOp {
+    type T<'tcx> = rustc_middle::mir::UnOp;
+
+    fn internal<'tcx>(&self, _tables: &mut Tables<'_>, _tcx: TyCtxt<'tcx>) -> Self::T<'tcx> {
+        match self {
+            UnOp::Not => rustc_middle::mir::UnOp::Not,
+            UnOp::Neg => rustc_middle::mir::UnOp::Neg,
+            UnOp::PtrMetadata => rustc_middle::mir::UnOp::PtrMetadata,
+        }
+    }
+}
+
 impl<T> RustcInternal for &T
 where
     T: RustcInternal,