Auto merge of #94702 - b-naber:static-refs-mir, r=lcnr

Reinstate #93800

https://github.com/rust-lang/rust/pull/93800 caused a regression in an alt builder with parallel enabled. https://github.com/rust-lang/rust/pull/94205 reverted that PR because of the regression. For an unknown reason the regression has disappeared, so we reinstate the changes in https://github.com/rust-lang/rust/pull/93800 here.

r? `@Mark-Simulacrum`

compiler/rustc_middle/src/mir/mod.rs

@@ -2534,7 +2534,7 @@ pub enum ConstantKind<'tcx> {
 
 impl<'tcx> Constant<'tcx> {
     pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
-        match self.literal.const_for_ty()?.val().try_to_scalar() {
+        match self.literal.try_to_scalar() {
             Some(Scalar::Ptr(ptr, _size)) => match tcx.global_alloc(ptr.provenance) {
                 GlobalAlloc::Static(def_id) => {
                     assert!(!tcx.is_thread_local_static(def_id));

compiler/rustc_middle/src/mir/pretty.rs

@@ -18,9 +18,8 @@ use rustc_middle::mir::interpret::{
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::MirSource;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, TyCtxt, TypeFoldable, TypeVisitor};
+use rustc_middle::ty::{self, TyCtxt};
 use rustc_target::abi::Size;
-use std::ops::ControlFlow;
 
 const INDENT: &str = "    ";
 /// Alignment for lining up comments following MIR statements
@@ -672,16 +671,27 @@ pub fn write_allocations<'tcx>(
         }
     }
     struct CollectAllocIds(BTreeSet<AllocId>);
-    impl<'tcx> TypeVisitor<'tcx> for CollectAllocIds {
-        fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
+
+    impl<'tcx> Visitor<'tcx> for CollectAllocIds {
+        fn visit_const(&mut self, c: ty::Const<'tcx>, _loc: Location) {
             if let ty::ConstKind::Value(val) = c.val() {
                 self.0.extend(alloc_ids_from_const(val));
             }
-            c.super_visit_with(self)
+        }
+
+        fn visit_constant(&mut self, c: &Constant<'tcx>, loc: Location) {
+            match c.literal {
+                ConstantKind::Ty(c) => self.visit_const(c, loc),
+                ConstantKind::Val(val, _) => {
+                    self.0.extend(alloc_ids_from_const(val));
+                }
+            }
         }
     }
+
     let mut visitor = CollectAllocIds(Default::default());
-    body.visit_with(&mut visitor);
+    visitor.visit_body(body);
+
     // `seen` contains all seen allocations, including the ones we have *not* printed yet.
     // The protocol is to first `insert` into `seen`, and only if that returns `true`
     // then push to `todo`.

compiler/rustc_middle/src/thir.rs

@@ -17,6 +17,7 @@ use rustc_index::newtype_index;
 use rustc_index::vec::IndexVec;
 use rustc_middle::infer::canonical::Canonical;
 use rustc_middle::middle::region;
+use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{
     BinOp, BorrowKind, FakeReadCause, Field, Mutability, UnOp, UserTypeProjection,
 };
@@ -419,7 +420,8 @@ pub enum ExprKind<'tcx> {
     /// This is only distinguished from `Literal` so that we can register some
     /// info for diagnostics.
     StaticRef {
-        literal: Const<'tcx>,
+        alloc_id: AllocId,
+        ty: Ty<'tcx>,
         def_id: DefId,
     },
     /// Inline assembly, i.e. `asm!()`.

compiler/rustc_middle/src/thir/visit.rs

@@ -123,7 +123,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         }
         Closure { closure_id: _, substs: _, upvars: _, movability: _, fake_reads: _ } => {}
         Literal { literal, user_ty: _, const_id: _ } => visitor.visit_const(literal),
-        StaticRef { literal, def_id: _ } => visitor.visit_const(literal),
+        StaticRef { alloc_id: _, ty: _, def_id: _ } => {}
         InlineAsm { ref operands, template: _, options: _, line_spans: _ } => {
             for op in &**operands {
                 use InlineAsmOperand::*;

compiler/rustc_mir_build/src/build/expr/as_constant.rs

@@ -1,6 +1,7 @@
 //! See docs in build/expr/mod.rs
 
 use crate::build::Builder;
+use rustc_middle::mir::interpret::{ConstValue, Scalar};
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::CanonicalUserTypeAnnotation;
@@ -26,8 +27,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 assert_eq!(literal.ty(), ty);
                 Constant { span, user_ty, literal: literal.into() }
             }
-            ExprKind::StaticRef { literal, .. } => {
-                Constant { span, user_ty: None, literal: literal.into() }
+            ExprKind::StaticRef { alloc_id, ty, .. } => {
+                let const_val =
+                    ConstValue::Scalar(Scalar::from_pointer(alloc_id.into(), &this.tcx));
+                let literal = ConstantKind::Val(const_val, ty);
+
+                Constant { span, user_ty: None, literal }
             }
             ExprKind::ConstBlock { value } => {
                 Constant { span: span, user_ty: None, literal: value.into() }

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -8,7 +8,6 @@ use rustc_middle::hir::place::Place as HirPlace;
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
 use rustc_middle::middle::region;
-use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::{BinOp, BorrowKind, Field, UnOp};
 use rustc_middle::thir::*;
 use rustc_middle::ty::adjustment::{
@@ -941,15 +940,8 @@ impl<'tcx> Cx<'tcx> {
                 let kind = if self.tcx.is_thread_local_static(id) {
                     ExprKind::ThreadLocalRef(id)
                 } else {
-                    let ptr = self.tcx.create_static_alloc(id);
-                    ExprKind::StaticRef {
-                        literal: ty::Const::from_scalar(
-                            self.tcx,
-                            Scalar::from_pointer(ptr.into(), &self.tcx),
-                            ty,
-                        ),
-                        def_id: id,
-                    }
+                    let alloc_id = self.tcx.create_static_alloc(id);
+                    ExprKind::StaticRef { alloc_id, ty, def_id: id }
                 };
                 ExprKind::Deref {
                     arg: self.thir.exprs.push(Expr { ty, temp_lifetime, span: expr.span, kind }),