Remove statics from HAIR by lowering them to a pointer constant

Author: oli-obk

src/librustc_mir/build/expr/as_place.rs

@@ -197,13 +197,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 };
                 block.and(place_builder)
             }
-            ExprKind::StaticRef { id } => block.and(PlaceBuilder::from(
-                PlaceBase::Static(Box::new(Static {
-                    ty: expr.ty,
-                    kind: StaticKind::Static,
-                    def_id: id,
-                }))
-            )),
 
             ExprKind::PlaceTypeAscription { source, user_ty } => {
                 let source = this.hir.mirror(source);

src/librustc_mir/build/expr/as_rvalue.rs

@@ -288,7 +288,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::Continue { .. }
             | ExprKind::Return { .. }
             | ExprKind::InlineAsm { .. }
-            | ExprKind::StaticRef { .. }
             | ExprKind::PlaceTypeAscription { .. }
             | ExprKind::ValueTypeAscription { .. } => {
                 // these do not have corresponding `Rvalue` variants,

src/librustc_mir/build/expr/category.rs

@@ -40,7 +40,6 @@ impl Category {
             | ExprKind::Index { .. }
             | ExprKind::SelfRef
             | ExprKind::VarRef { .. }
-            | ExprKind::StaticRef { .. }
             | ExprKind::PlaceTypeAscription { .. }
             | ExprKind::ValueTypeAscription { .. } => Some(Category::Place),
 

src/librustc_mir/build/expr/into.rs

@@ -384,7 +384,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             // Avoid creating a temporary
             ExprKind::VarRef { .. } |
             ExprKind::SelfRef |
-            ExprKind::StaticRef { .. } |
             ExprKind::PlaceTypeAscription { .. } |
             ExprKind::ValueTypeAscription { .. } => {
                 debug_assert!(Category::of(&expr.kind) == Some(Category::Place));

src/librustc_mir/hair/cx/expr.rs

@@ -5,7 +5,7 @@ use crate::hair::cx::to_ref::ToRef;
 use crate::hair::util::UserAnnotatedTyHelpers;
 use rustc_index::vec::Idx;
 use rustc::hir::def::{CtorOf, Res, DefKind, CtorKind};
-use rustc::mir::interpret::{GlobalId, ErrorHandled};
+use rustc::mir::interpret::{GlobalId, ErrorHandled, ConstValue, Scalar};
 use rustc::ty::{self, AdtKind, Ty};
 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability, PointerCast};
 use rustc::ty::subst::{InternalSubsts, SubstsRef};
@@ -961,7 +961,31 @@ fn convert_path_expr<'a, 'tcx>(
             }
         }
 
-        Res::Def(DefKind::Static, id) => ExprKind::StaticRef { id },
+        // We encode uses of statics as a `*&STATIC` where the `&STATIC` part is
+        // a constant reference (or constant raw pointer for `static mut`) in MIR
+        Res::Def(DefKind::Static, id) => {
+            let ty = cx.tcx.type_of(id);
+            let ty = if cx.tcx.is_mutable_static(id) {
+                cx.tcx.mk_mut_ptr(ty)
+            } else if cx.tcx.is_foreign_item(id) {
+                cx.tcx.mk_imm_ptr(ty)
+            } else {
+                cx.tcx.mk_imm_ref(cx.tcx.lifetimes.re_static, ty)
+            };
+            let ptr = cx.tcx.alloc_map.lock().create_static_alloc(id);
+            let temp_lifetime = cx.region_scope_tree.temporary_scope(expr.hir_id.local_id);
+            ExprKind::Deref { arg: Expr {
+                ty,
+                temp_lifetime,
+                span: expr.span,
+                kind: ExprKind::Literal {
+                    literal: cx.tcx.mk_const(ty::Const {
+                        ty, val: ConstValue::Scalar(Scalar::Ptr(ptr.into())),
+                    }),
+                    user_ty: None,
+                }
+            }.to_ref() }
+        },
 
         Res::Local(var_hir_id) => convert_var(cx, expr, var_hir_id),
 

src/librustc_mir/hair/mod.rs

@@ -208,9 +208,6 @@ pub enum ExprKind<'tcx> {
     },
     /// first argument, used for self in a closure
     SelfRef,
-    StaticRef {
-        id: DefId,
-    },
     Borrow {
         borrow_kind: BorrowKind,
         arg: ExprRef<'tcx>,