Make TLS accesses explicit in MIR

Author: oli-obk

src/librustc_codegen_llvm/common.rs

@@ -259,6 +259,7 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     GlobalAlloc::Function(fn_instance) => self.get_fn_addr(fn_instance),
                     GlobalAlloc::Static(def_id) => {
                         assert!(self.tcx.is_static(def_id));
+                        assert!(!self.tcx.is_thread_local_static(def_id));
                         self.get_static(def_id)
                     }
                 };

src/librustc_codegen_ssa/mir/rvalue.rs

@@ -522,6 +522,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let operand = OperandRef { val: OperandValue::Immediate(val), layout: box_layout };
                 (bx, operand)
             }
+            mir::Rvalue::ThreadLocalRef(def_id) => {
+                assert!(bx.cx().tcx().is_static(def_id));
+                let static_ = bx.get_static(def_id);
+                let layout = bx.layout_of(bx.cx().tcx().static_ptr_ty(def_id));
+                let operand = OperandRef::from_immediate_or_packed_pair(&mut bx, static_, layout);
+                (bx, operand)
+            }
             mir::Rvalue::Use(ref operand) => {
                 let operand = self.codegen_operand(&mut bx, operand);
                 (bx, operand)
@@ -745,6 +752,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::Rvalue::UnaryOp(..) |
             mir::Rvalue::Discriminant(..) |
             mir::Rvalue::NullaryOp(..) |
+            mir::Rvalue::ThreadLocalRef(_) |
             mir::Rvalue::Use(..) => // (*)
                 true,
             mir::Rvalue::Repeat(..) |

src/librustc_middle/mir/interpret/error.rs

@@ -513,6 +513,8 @@ pub enum UnsupportedOpInfo {
     //
     /// Encountered raw bytes where we needed a pointer.
     ReadBytesAsPointer,
+    /// Accessing thread local statics
+    ThreadLocalStatic(DefId),
 }
 
 impl fmt::Display for UnsupportedOpInfo {
@@ -526,6 +528,7 @@ impl fmt::Display for UnsupportedOpInfo {
             NoMirFor(did) => write!(f, "no MIR body is available for {:?}", did),
             ReadPointerAsBytes => write!(f, "unable to turn pointer into raw bytes",),
             ReadBytesAsPointer => write!(f, "unable to turn bytes into a pointer"),
+            ThreadLocalStatic(did) => write!(f, "accessing thread local static {:?}", did),
         }
     }
 }

src/librustc_middle/mir/interpret/mod.rs

@@ -209,6 +209,7 @@ pub fn specialized_encode_alloc_id<'tcx, E: Encoder>(
             fn_instance.encode(encoder)?;
         }
         GlobalAlloc::Static(did) => {
+            assert!(!tcx.is_thread_local_static(did));
             // References to statics doesn't need to know about their allocations,
             // just about its `DefId`.
             AllocDiscriminant::Static.encode(encoder)?;

src/librustc_middle/mir/mod.rs

@@ -2209,6 +2209,11 @@ pub enum Rvalue<'tcx> {
     /// &x or &mut x
     Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
 
+    /// Accessing a thread local static. This is inherently a runtime operation, even if llvm
+    /// treats it as an access to a static. This `Rvalue` yields a reference to the thread local
+    /// static.
+    ThreadLocalRef(DefId),
+
     /// Create a raw pointer to the given place
     /// Can be generated by raw address of expressions (`&raw const x`),
     /// or when casting a reference to a raw pointer.
@@ -2348,6 +2353,10 @@ impl<'tcx> Debug for Rvalue<'tcx> {
             UnaryOp(ref op, ref a) => write!(fmt, "{:?}({:?})", op, a),
             Discriminant(ref place) => write!(fmt, "discriminant({:?})", place),
             NullaryOp(ref op, ref t) => write!(fmt, "{:?}({:?})", op, t),
+            ThreadLocalRef(did) => ty::tls::with(|tcx| {
+                let muta = tcx.static_mutability(did).unwrap().prefix_str();
+                write!(fmt, "&/*tls*/ {}{}", muta, tcx.def_path_str(did))
+            }),
             Ref(region, borrow_kind, ref place) => {
                 let kind_str = match borrow_kind {
                     BorrowKind::Shared => "",
@@ -2501,7 +2510,10 @@ impl Constant<'tcx> {
     pub fn check_static_ptr(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
         match self.literal.val.try_to_scalar() {
             Some(Scalar::Ptr(ptr)) => match tcx.global_alloc(ptr.alloc_id) {
-                GlobalAlloc::Static(def_id) => Some(def_id),
+                GlobalAlloc::Static(def_id) => {
+                    assert!(!tcx.is_thread_local_static(def_id));
+                    Some(def_id)
+                }
                 _ => None,
             },
             _ => None,

src/librustc_middle/mir/tcx.rs

@@ -152,6 +152,13 @@ impl<'tcx> Rvalue<'tcx> {
             Rvalue::Repeat(ref operand, count) => {
                 tcx.mk_ty(ty::Array(operand.ty(local_decls, tcx), count))
             }
+            Rvalue::ThreadLocalRef(did) => {
+                if tcx.is_mutable_static(did) {
+                    tcx.mk_mut_ptr(tcx.type_of(did))
+                } else {
+                    tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.type_of(did))
+                }
+            }
             Rvalue::Ref(reg, bk, ref place) => {
                 let place_ty = place.ty(local_decls, tcx).ty;
                 tcx.mk_ref(reg, ty::TypeAndMut { ty: place_ty, mutbl: bk.to_mutbl_lossy() })

src/librustc_middle/mir/type_foldable.rs

@@ -173,6 +173,7 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
         match *self {
             Use(ref op) => Use(op.fold_with(folder)),
             Repeat(ref op, len) => Repeat(op.fold_with(folder), len),
+            ThreadLocalRef(did) => ThreadLocalRef(did.fold_with(folder)),
             Ref(region, bk, ref place) => {
                 Ref(region.fold_with(folder), bk, place.fold_with(folder))
             }
@@ -216,6 +217,7 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
         match *self {
             Use(ref op) => op.visit_with(visitor),
             Repeat(ref op, _) => op.visit_with(visitor),
+            ThreadLocalRef(did) => did.visit_with(visitor),
             Ref(region, _, ref place) => region.visit_with(visitor) || place.visit_with(visitor),
             AddressOf(_, ref place) => place.visit_with(visitor),
             Len(ref place) => place.visit_with(visitor),

src/librustc_middle/mir/visit.rs

@@ -600,6 +600,8 @@ macro_rules! make_mir_visitor {
                         self.visit_operand(value, location);
                     }
 
+                    Rvalue::ThreadLocalRef(_) => {}
+
                     Rvalue::Ref(r, bk, path) => {
                         self.visit_region(r, location);
                         let ctx = match bk {

src/librustc_mir/borrow_check/invalidation.rs

@@ -295,6 +295,8 @@ impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> {
                 self.access_place(location, place, access_kind, LocalMutationIsAllowed::No);
             }
 
+            Rvalue::ThreadLocalRef(_) => {}
+
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)

src/librustc_mir/borrow_check/mod.rs

@@ -1290,6 +1290,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 );
             }
 
+            Rvalue::ThreadLocalRef(_) => {}
+
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)