diff --git a/src/liballoc/heap.rs b/src/liballoc/heap.rs
index 08a0b2a6d0080..056af13016cf2 100644
--- a/src/liballoc/heap.rs
+++ b/src/liballoc/heap.rs
@@ -16,7 +16,6 @@
             issue = "27700")]
 
 use core::{isize, usize};
-#[cfg(not(test))]
 use core::intrinsics::{min_align_of_val, size_of_val};
 
 #[allow(improper_ctypes)]
@@ -158,10 +157,9 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     }
 }
 
-#[cfg(not(test))]
-#[lang = "box_free"]
+#[cfg_attr(not(test), lang = "box_free")]
 #[inline]
-unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
+pub(crate) unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
     let size = size_of_val(&*ptr);
     let align = min_align_of_val(&*ptr);
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 0c01eabd593ff..c70d82392f914 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -87,6 +87,7 @@
 #![feature(needs_allocator)]
 #![feature(optin_builtin_traits)]
 #![feature(placement_in_syntax)]
+#![cfg_attr(stage0, feature(pub_restricted))]
 #![feature(shared)]
 #![feature(staged_api)]
 #![feature(unboxed_closures)]
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index fed718e9be4c6..69e5351cad53d 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -239,7 +239,7 @@ use core::ops::CoerceUnsized;
 use core::ptr::{self, Shared};
 use core::convert::From;
 
-use heap::deallocate;
+use heap::{allocate, deallocate, box_free};
 use raw_vec::RawVec;
 
 struct RcBox<T: ?Sized> {
@@ -248,7 +248,6 @@ struct RcBox<T: ?Sized> {
     value: T,
 }
 
-
 /// A single-threaded reference-counting pointer.
 ///
 /// See the [module-level documentation](./index.html) for more details.
@@ -438,6 +437,38 @@ impl Rc<str> {
     }
 }
 
+impl<T> Rc<[T]> {
+    /// Constructs a new `Rc<[T]>` from a `Box<[T]>`.
+    #[doc(hidden)]
+    #[unstable(feature = "rustc_private",
+               reason = "for internal use in rustc",
+               issue = "0")]
+    pub fn __from_array(value: Box<[T]>) -> Rc<[T]> {
+        unsafe {
+            let ptr: *mut RcBox<[T]> =
+                mem::transmute([mem::align_of::<RcBox<[T; 1]>>(), value.len()]);
+            // FIXME(custom-DST): creating this invalid &[T] is dubiously defined,
+            // we should have a better way of getting the size/align
+            // of a DST from its unsized part.
+            let ptr = allocate(size_of_val(&*ptr), align_of_val(&*ptr));
+            let ptr: *mut RcBox<[T]> = mem::transmute([ptr as usize, value.len()]);
+
+            // Initialize the new RcBox.
+            ptr::write(&mut (*ptr).strong, Cell::new(1));
+            ptr::write(&mut (*ptr).weak, Cell::new(1));
+            ptr::copy_nonoverlapping(
+                value.as_ptr(),
+                &mut (*ptr).value as *mut [T] as *mut T,
+                value.len());
+
+            // Free the original allocation without freeing its (moved) contents.
+            box_free(Box::into_raw(value));
+
+            Rc { ptr: Shared::new(ptr as *const _) }
+        }
+    }
+}
+
 impl<T: ?Sized> Rc<T> {
     /// Creates a new [`Weak`][weak] pointer to this value.
     ///
diff --git a/src/librustc/infer/freshen.rs b/src/librustc/infer/freshen.rs
index 697a1ecadc456..922842136dc9f 100644
--- a/src/librustc/infer/freshen.rs
+++ b/src/librustc/infer/freshen.rs
@@ -99,7 +99,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::ReEmpty |
             ty::ReErased => {
                 // replace all free regions with 'erased
-                self.tcx().mk_region(ty::ReErased)
+                self.tcx().types.re_erased
             }
         }
     }
diff --git a/src/librustc/infer/region_inference/mod.rs b/src/librustc/infer/region_inference/mod.rs
index 0bb9e2c7fa15c..fa6775737b57d 100644
--- a/src/librustc/infer/region_inference/mod.rs
+++ b/src/librustc/infer/region_inference/mod.rs
@@ -948,7 +948,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 } else {
                     // otherwise, we don't know what the free region is,
                     // so we must conservatively say the LUB is static:
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
 
@@ -971,7 +971,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
                 if a == b {
                     a
                 } else {
-                    self.tcx.mk_region(ReStatic)
+                    self.tcx.types.re_static
                 }
             }
         }
@@ -1018,7 +1018,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
 
     fn construct_var_data(&self) -> Vec<VarValue<'tcx>> {
         (0..self.num_vars() as usize)
-            .map(|_| Value(self.tcx.mk_region(ty::ReEmpty)))
+            .map(|_| Value(self.tcx.types.re_empty))
             .collect()
     }
 
@@ -1493,7 +1493,7 @@ fn lookup<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                           -> &'tcx ty::Region {
     match values[rid.index as usize] {
         Value(r) => r,
-        ErrorValue => tcx.mk_region(ReStatic), // Previously reported error.
+        ErrorValue => tcx.types.re_static, // Previously reported error.
     }
 }
 
diff --git a/src/librustc/middle/cstore.rs b/src/librustc/middle/cstore.rs
index cbbfeacadb408..20ed2244e864c 100644
--- a/src/librustc/middle/cstore.rs
+++ b/src/librustc/middle/cstore.rs
@@ -188,14 +188,13 @@ pub trait CrateStore {
     fn visibility(&self, def: DefId) -> ty::Visibility;
     fn visible_parent_map<'a>(&'a self) -> ::std::cell::Ref<'a, DefIdMap<DefId>>;
     fn item_generics_cloned(&self, def: DefId) -> ty::Generics;
-    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;
+    fn item_attrs(&self, def_id: DefId) -> Rc<[ast::Attribute]>;
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name>;
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>;
 
     // impl info
-    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity;
     fn impl_parent(&self, impl_def_id: DefId) -> Option<DefId>;
 
     // trait/impl-item info
@@ -323,14 +322,13 @@ impl CrateStore for DummyCrateStore {
     }
     fn item_generics_cloned(&self, def: DefId) -> ty::Generics
         { bug!("item_generics_cloned") }
-    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute> { bug!("item_attrs") }
+    fn item_attrs(&self, def_id: DefId) -> Rc<[ast::Attribute]> { bug!("item_attrs") }
     fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name> { bug!("fn_arg_names") }
 
     // trait info
     fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId> { vec![] }
 
     // impl info
-    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity { bug!("impl_polarity") }
     fn impl_parent(&self, def: DefId) -> Option<DefId> { bug!("impl_parent") }
 
     // trait/impl-item info
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index a10f52e2d4cc0..8b26315915826 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -426,7 +426,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
 
             hir::ExprMatch(ref discr, ref arms, _) => {
                 let discr_cmt = return_if_err!(self.mc.cat_expr(&discr));
-                let r = self.tcx().mk_region(ty::ReEmpty);
+                let r = self.tcx().types.re_empty;
                 self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant);
 
                 // treatment of the discriminant is handled while walking the arms.
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 32dfb63d6150a..3b506d748ef7a 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -223,9 +223,10 @@ impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 
 pub fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
     for attribute in attrs {
-        match attribute.value_str() {
-            Some(value) if attribute.check_name("lang") => return Some(value),
-            _ => {}
+        if attribute.check_name("lang") {
+            if let Some(value) = attribute.value_str() {
+                return Some(value)
+            }
         }
     }
 
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 7d3c17a048917..188fcc9141492 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -871,8 +871,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         // we can promote to a constant, otherwise equal to enclosing temp
         // lifetime.
         let (re, old_re) = if promotable {
-            (self.tcx().mk_region(ty::ReStatic),
-             self.tcx().mk_region(ty::ReStatic))
+            (self.tcx().types.re_static,
+             self.tcx().types.re_static)
         } else {
             self.temporary_scope(id)
         };
diff --git a/src/librustc/traits/fulfill.rs b/src/librustc/traits/fulfill.rs
index d49affa3e872c..908bb337fa18e 100644
--- a/src/librustc/traits/fulfill.rs
+++ b/src/librustc/traits/fulfill.rs
@@ -443,7 +443,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
                         // Otherwise, we have something of the form
                         // `for<'a> T: 'a where 'a not in T`, which we can treat as `T: 'static`.
                         Some(t_a) => {
-                            let r_static = selcx.tcx().mk_region(ty::ReStatic);
+                            let r_static = selcx.tcx().types.re_static;
                             register_region_obligation(t_a, r_static,
                                                        obligation.cause.clone(),
                                                        region_obligations);
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 18f0a749f7018..281c1e253798c 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -629,7 +629,7 @@ pub fn get_vtable_methods<'a, 'tcx>(
             // the method may have some early-bound lifetimes, add
             // regions for those
             let substs = Substs::for_item(tcx, def_id,
-                                          |_, _| tcx.mk_region(ty::ReErased),
+                                          |_, _| tcx.types.re_erased,
                                           |def, _| trait_ref.substs().type_for_def(def));
 
             // the trait type may have higher-ranked lifetimes in it;
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 70ddcff5181be..6442487ead957 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -943,17 +943,17 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     debug!("Retaining candidate #{}/{}: {:?}",
                            i, candidates.len(), candidates[i]);
                     i += 1;
+
+                    // If there are *STILL* multiple candidates, give up
+                    // and report ambiguity.
+                    if i > 1 {
+                        debug!("multiple matches, ambig");
+                        return Ok(None);
+                    }
                 }
             }
         }
 
-        // If there are *STILL* multiple candidates, give up and
-        // report ambiguity.
-        if candidates.len() > 1 {
-            debug!("multiple matches, ambig");
-            return Ok(None);
-        }
-
         // If there are *NO* candidates, then there are no impls --
         // that we know of, anyway. Note that in the case where there
         // are unbound type variables within the obligation, it might
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index e836bf23a5a81..b20ac8ddbfc8a 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -190,6 +190,10 @@ pub struct CommonTypes<'tcx> {
     pub f64: Ty<'tcx>,
     pub never: Ty<'tcx>,
     pub err: Ty<'tcx>,
+
+    pub re_empty: &'tcx Region,
+    pub re_static: &'tcx Region,
+    pub re_erased: &'tcx Region,
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
@@ -360,6 +364,14 @@ impl<'tcx> TypeckTables<'tcx> {
 impl<'tcx> CommonTypes<'tcx> {
     fn new(interners: &CtxtInterners<'tcx>) -> CommonTypes<'tcx> {
         let mk = |sty| interners.intern_ty(sty, None);
+        let mk_region = |r| {
+            if let Some(r) = interners.region.borrow().get(&r) {
+                return r.0;
+            }
+            let r = interners.arena.alloc(r);
+            interners.region.borrow_mut().insert(Interned(r));
+            &*r
+        };
         CommonTypes {
             bool: mk(TyBool),
             char: mk(TyChar),
@@ -379,6 +391,10 @@ impl<'tcx> CommonTypes<'tcx> {
             u128: mk(TyUint(ast::UintTy::U128)),
             f32: mk(TyFloat(ast::FloatTy::F32)),
             f64: mk(TyFloat(ast::FloatTy::F64)),
+
+            re_empty: mk_region(Region::ReEmpty),
+            re_static: mk_region(Region::ReStatic),
+            re_erased: mk_region(Region::ReErased),
         }
     }
 }
@@ -1232,7 +1248,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn mk_static_str(self) -> Ty<'tcx> {
-        self.mk_imm_ref(self.mk_region(ty::ReStatic), self.mk_str())
+        self.mk_imm_ref(self.types.re_static, self.mk_str())
     }
 
     pub fn mk_adt(self, def: &'tcx AdtDef, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
diff --git a/src/librustc/ty/fold.rs b/src/librustc/ty/fold.rs
index e29653c9e88a0..969d040e7a6e8 100644
--- a/src/librustc/ty/fold.rs
+++ b/src/librustc/ty/fold.rs
@@ -410,7 +410,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn erase_late_bound_regions<T>(self, value: &Binder<T>) -> T
         where T : TypeFoldable<'tcx>
     {
-        self.replace_late_bound_regions(value, |_| self.mk_region(ty::ReErased)).0
+        self.replace_late_bound_regions(value, |_| self.types.re_erased).0
     }
 
     /// Rewrite any late-bound regions so that they are anonymous.  Region numbers are
@@ -538,7 +538,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 // whenever a substitution occurs.
                 match *r {
                     ty::ReLateBound(..) => r,
-                    _ => self.tcx().mk_region(ty::ReErased)
+                    _ => self.tcx().types.re_erased
                 }
             }
         }
@@ -565,6 +565,22 @@ pub fn shift_region(region: ty::Region, amount: u32) -> ty::Region {
     }
 }
 
+pub fn shift_region_ref<'a, 'gcx, 'tcx>(
+    tcx: TyCtxt<'a, 'gcx, 'tcx>,
+    region: &'tcx ty::Region,
+    amount: u32)
+    -> &'tcx ty::Region
+{
+    match region {
+        &ty::ReLateBound(debruijn, br) if amount > 0 => {
+            tcx.mk_region(ty::ReLateBound(debruijn.shifted(amount), br))
+        }
+        _ => {
+            region
+        }
+    }
+}
+
 pub fn shift_regions<'a, 'gcx, 'tcx, T>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
                                         amount: u32, value: &T) -> T
     where T: TypeFoldable<'tcx>
@@ -573,7 +589,7 @@ pub fn shift_regions<'a, 'gcx, 'tcx, T>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
            value, amount);
 
     value.fold_with(&mut RegionFolder::new(tcx, &mut false, &mut |region, _current_depth| {
-        tcx.mk_region(shift_region(*region, amount))
+        shift_region_ref(tcx, region, amount)
     }))
 }
 
diff --git a/src/librustc/ty/instance.rs b/src/librustc/ty/instance.rs
index 67287f1b4ff72..cfff3d0e57360 100644
--- a/src/librustc/ty/instance.rs
+++ b/src/librustc/ty/instance.rs
@@ -13,10 +13,7 @@ use hir::def_id::DefId;
 use ty::{self, Ty, TypeFoldable, Substs};
 use util::ppaux;
 
-use std::borrow::Cow;
 use std::fmt;
-use syntax::ast;
-
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct Instance<'tcx> {
@@ -59,7 +56,7 @@ impl<'tcx> InstanceDef<'tcx> {
     }
 
     #[inline]
-    pub fn attrs<'a>(&self, tcx: ty::TyCtxt<'a, 'tcx, 'tcx>) -> Cow<'tcx, [ast::Attribute]> {
+    pub fn attrs<'a>(&self, tcx: ty::TyCtxt<'a, 'tcx, 'tcx>) -> ty::Attributes<'tcx> {
         tcx.get_attrs(self.def_id())
     }
 
diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 6a206640b3baa..49cc4e7c993a5 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -822,7 +822,7 @@ impl<'a, 'gcx, 'tcx> Struct {
             }
 
             (_, &ty::TyProjection(_)) | (_, &ty::TyAnon(..)) => {
-                let normalized = normalize_associated_type(infcx, ty);
+                let normalized = infcx.normalize_projections(ty);
                 if ty == normalized {
                     return Ok(None);
                 }
@@ -1067,28 +1067,6 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
     }
 }
 
-/// Helper function for normalizing associated types in an inference context.
-fn normalize_associated_type<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
-                                             ty: Ty<'gcx>)
-                                             -> Ty<'gcx> {
-    if !ty.has_projection_types() {
-        return ty;
-    }
-
-    let mut selcx = traits::SelectionContext::new(infcx);
-    let cause = traits::ObligationCause::dummy();
-    let traits::Normalized { value: result, obligations } =
-        traits::normalize(&mut selcx, cause, &ty);
-
-    let mut fulfill_cx = traits::FulfillmentContext::new();
-
-    for obligation in obligations {
-        fulfill_cx.register_predicate_obligation(infcx, obligation);
-    }
-
-    infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
-}
-
 impl<'a, 'gcx, 'tcx> Layout {
     pub fn compute_uncached(ty: Ty<'gcx>,
                             infcx: &InferCtxt<'a, 'gcx, 'tcx>)
@@ -1100,7 +1078,7 @@ impl<'a, 'gcx, 'tcx> Layout {
 
         let ptr_layout = |pointee: Ty<'gcx>| {
             let non_zero = !ty.is_unsafe_ptr();
-            let pointee = normalize_associated_type(infcx, pointee);
+            let pointee = infcx.normalize_projections(pointee);
             if pointee.is_sized(tcx, &infcx.parameter_environment, DUMMY_SP) {
                 Ok(Scalar { value: Pointer, non_zero: non_zero })
             } else {
@@ -1494,7 +1472,7 @@ impl<'a, 'gcx, 'tcx> Layout {
 
             // Types with no meaningful known layout.
             ty::TyProjection(_) | ty::TyAnon(..) => {
-                let normalized = normalize_associated_type(infcx, ty);
+                let normalized = infcx.normalize_projections(ty);
                 if ty == normalized {
                     return Err(LayoutError::Unknown(ty));
                 }
@@ -1812,7 +1790,7 @@ impl<'a, 'gcx, 'tcx> SizeSkeleton<'gcx> {
             }
 
             ty::TyProjection(_) | ty::TyAnon(..) => {
-                let normalized = normalize_associated_type(infcx, ty);
+                let normalized = infcx.normalize_projections(ty);
                 if ty == normalized {
                     Err(err)
                 } else {
@@ -1882,13 +1860,14 @@ pub trait LayoutTyper<'tcx>: HasTyCtxt<'tcx> {
     type TyLayout;
 
     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout;
+    fn normalize_projections(self, ty: Ty<'tcx>) -> Ty<'tcx>;
 }
 
 impl<'a, 'gcx, 'tcx> LayoutTyper<'gcx> for &'a InferCtxt<'a, 'gcx, 'tcx> {
     type TyLayout = Result<TyLayout<'gcx>, LayoutError<'gcx>>;
 
     fn layout_of(self, ty: Ty<'gcx>) -> Self::TyLayout {
-        let ty = normalize_associated_type(self, ty);
+        let ty = self.normalize_projections(ty);
 
         Ok(TyLayout {
             ty: ty,
@@ -1896,6 +1875,25 @@ impl<'a, 'gcx, 'tcx> LayoutTyper<'gcx> for &'a InferCtxt<'a, 'gcx, 'tcx> {
             variant_index: None
         })
     }
+
+    fn normalize_projections(self, ty: Ty<'gcx>) -> Ty<'gcx> {
+        if !ty.has_projection_types() {
+            return ty;
+        }
+
+        let mut selcx = traits::SelectionContext::new(self);
+        let cause = traits::ObligationCause::dummy();
+        let traits::Normalized { value: result, obligations } =
+            traits::normalize(&mut selcx, cause, &ty);
+
+        let mut fulfill_cx = traits::FulfillmentContext::new();
+
+        for obligation in obligations {
+            fulfill_cx.register_predicate_obligation(self, obligation);
+        }
+
+        self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
+    }
 }
 
 impl<'a, 'tcx> TyLayout<'tcx> {
@@ -2019,6 +2017,6 @@ impl<'a, 'tcx> TyLayout<'tcx> {
     }
 
     pub fn field<C: LayoutTyper<'tcx>>(&self, cx: C, i: usize) -> C::TyLayout {
-        cx.layout_of(self.field_type(cx, i))
+        cx.layout_of(cx.normalize_projections(self.field_type(cx, i)))
     }
 }
diff --git a/src/librustc/ty/maps.rs b/src/librustc/ty/maps.rs
index 648923d6f04e5..add8db850e4f4 100644
--- a/src/librustc/ty/maps.rs
+++ b/src/librustc/ty/maps.rs
@@ -10,6 +10,7 @@
 
 use dep_graph::{DepGraph, DepNode, DepTrackingMap, DepTrackingMapConfig};
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
+use hir;
 use middle::const_val;
 use middle::privacy::AccessLevels;
 use mir;
@@ -394,6 +395,7 @@ define_maps! { <'tcx>
     pub associated_item: AssociatedItems(DefId) -> ty::AssociatedItem,
 
     pub impl_trait_ref: ItemSignature(DefId) -> Option<ty::TraitRef<'tcx>>,
+    pub impl_polarity: ItemSignature(DefId) -> hir::ImplPolarity,
 
     /// Maps a DefId of a type to a list of its inherent impls.
     /// Contains implementations of methods that are inherent to a type.
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 649298abed51a..1305b0d930378 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -34,7 +34,6 @@ use ty::walk::TypeWalker;
 use util::nodemap::{NodeSet, DefIdMap, FxHashMap};
 
 use serialize::{self, Encodable, Encoder};
-use std::borrow::Cow;
 use std::cell::{Cell, RefCell, Ref};
 use std::collections::BTreeMap;
 use std::cmp;
@@ -2036,6 +2035,23 @@ impl BorrowKind {
     }
 }
 
+#[derive(Debug, Clone)]
+pub enum Attributes<'gcx> {
+    Owned(Rc<[ast::Attribute]>),
+    Borrowed(&'gcx [ast::Attribute])
+}
+
+impl<'gcx> ::std::ops::Deref for Attributes<'gcx> {
+    type Target = [ast::Attribute];
+
+    fn deref(&self) -> &[ast::Attribute] {
+        match self {
+            &Attributes::Owned(ref data) => &data,
+            &Attributes::Borrowed(data) => data
+        }
+    }
+}
+
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn body_tables(self, body: hir::BodyId) -> &'gcx TypeckTables<'gcx> {
         self.item_tables(self.hir.body_owner_def_id(body))
@@ -2133,14 +2149,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn trait_impl_polarity(self, id: DefId) -> hir::ImplPolarity {
-        if let Some(id) = self.hir.as_local_node_id(id) {
-            match self.hir.expect_item(id).node {
-                hir::ItemImpl(_, polarity, ..) => polarity,
-                ref item => bug!("trait_impl_polarity: {:?} not an impl", item)
-            }
-        } else {
-            self.sess.cstore.impl_polarity(id)
-        }
+        queries::impl_polarity::get(self, DUMMY_SP, id)
     }
 
     pub fn trait_relevant_for_never(self, did: DefId) -> bool {
@@ -2389,11 +2398,11 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     /// Get the attributes of a definition.
-    pub fn get_attrs(self, did: DefId) -> Cow<'gcx, [ast::Attribute]> {
+    pub fn get_attrs(self, did: DefId) -> Attributes<'gcx> {
         if let Some(id) = self.hir.as_local_node_id(did) {
-            Cow::Borrowed(self.hir.attrs(id))
+            Attributes::Borrowed(self.hir.attrs(id))
         } else {
-            Cow::Owned(self.sess.cstore.item_attrs(did))
+            Attributes::Owned(self.sess.cstore.item_attrs(did))
         }
     }
 
@@ -2499,15 +2508,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// Construct a parameter environment suitable for static contexts or other contexts where there
     /// are no free type/lifetime parameters in scope.
     pub fn empty_parameter_environment(self) -> ParameterEnvironment<'tcx> {
-
-        // for an empty parameter environment, there ARE no free
-        // regions, so it shouldn't matter what we use for the free id
-        let free_id_outlive = self.region_maps.node_extent(ast::DUMMY_NODE_ID);
         ty::ParameterEnvironment {
             free_substs: self.intern_substs(&[]),
             caller_bounds: Vec::new(),
-            implicit_region_bound: self.mk_region(ty::ReEmpty),
-            free_id_outlive: free_id_outlive,
+            implicit_region_bound: self.types.re_empty,
+            // for an empty parameter environment, there ARE no free
+            // regions, so it shouldn't matter what we use for the free id
+            free_id_outlive: ROOT_CODE_EXTENT,
             is_copy_cache: RefCell::new(FxHashMap()),
             is_sized_cache: RefCell::new(FxHashMap()),
             is_freeze_cache: RefCell::new(FxHashMap()),
@@ -2760,4 +2767,3 @@ pub fn provide_extern(providers: &mut ty::maps::Providers) {
 pub struct CrateInherentImpls {
     pub inherent_impls: DefIdMap<Rc<Vec<DefId>>>,
 }
-
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
index 0a2cc1c30f40f..14aebdf8418fe 100644
--- a/src/librustc/ty/subst.rs
+++ b/src/librustc/ty/subst.rs
@@ -539,6 +539,9 @@ impl<'a, 'gcx, 'tcx> SubstFolder<'a, 'gcx, 'tcx> {
     }
 
     fn shift_region_through_binders(&self, region: &'tcx ty::Region) -> &'tcx ty::Region {
+        if self.region_binders_passed == 0 || !region.has_escaping_regions() {
+            return region;
+        }
         self.tcx().mk_region(ty::fold::shift_region(*region, self.region_binders_passed))
     }
 }
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index 49d79f6545e2d..cdf3cf00b24ee 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -412,7 +412,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// a suitable "empty substs" for it.
     pub fn empty_substs_for_def_id(self, item_def_id: DefId) -> &'tcx ty::Substs<'tcx> {
         ty::Substs::for_item(self, item_def_id,
-                             |_, _| self.mk_region(ty::ReErased),
+                             |_, _| self.types.re_erased,
                              |_, _| {
             bug!("empty_substs_for_def_id: {:?} has type parameters", item_def_id)
         })
diff --git a/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs b/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
index bbfb7e5874ea0..b921678b495c2 100644
--- a/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
+++ b/src/librustc_borrowck/borrowck/gather_loans/lifetime.rs
@@ -120,7 +120,7 @@ impl<'a, 'tcx> GuaranteeLifetimeContext<'a, 'tcx> {
             }
             Categorization::StaticItem |
             Categorization::Deref(.., mc::UnsafePtr(..)) => {
-                self.bccx.tcx.mk_region(ty::ReStatic)
+                self.bccx.tcx.types.re_static
             }
             Categorization::Deref(.., mc::BorrowedPtr(_, r)) |
             Categorization::Deref(.., mc::Implicit(_, r)) => {
diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index ac4e2bd5c1038..438f482fa55c7 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -225,6 +225,8 @@ pub fn compile_input(sess: &Session,
         sess.code_stats.borrow().print_type_sizes();
     }
 
+    if ::std::env::var("SKIP_LLVM").is_ok() { ::std::process::exit(0); }
+
     let phase5_result = phase_5_run_llvm_passes(sess, &trans, &outputs);
 
     controller_entry_point!(after_llvm,
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index 7447fba3038ea..147d6558e19cc 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -343,12 +343,12 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
     }
 
     pub fn t_rptr_static(&self) -> Ty<'tcx> {
-        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.mk_region(ty::ReStatic),
+        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.types.re_static,
                                   self.tcx().types.isize)
     }
 
     pub fn t_rptr_empty(&self) -> Ty<'tcx> {
-        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.mk_region(ty::ReEmpty),
+        self.infcx.tcx.mk_imm_ref(self.infcx.tcx.types.re_empty,
                                   self.tcx().types.isize)
     }
 
diff --git a/src/librustc_metadata/creader.rs b/src/librustc_metadata/creader.rs
index a8ee999505e20..7bc0e8a512be0 100644
--- a/src/librustc_metadata/creader.rs
+++ b/src/librustc_metadata/creader.rs
@@ -326,6 +326,7 @@ impl<'a> CrateLoader<'a> {
             cnum_map: RefCell::new(cnum_map),
             cnum: cnum,
             codemap_import_info: RefCell::new(vec![]),
+            attribute_cache: RefCell::new([Vec::new(), Vec::new()]),
             dep_kind: Cell::new(dep_kind),
             source: cstore::CrateSource {
                 dylib: dylib,
diff --git a/src/librustc_metadata/cstore.rs b/src/librustc_metadata/cstore.rs
index 17a6a706e0aaa..72ad1d75a5615 100644
--- a/src/librustc_metadata/cstore.rs
+++ b/src/librustc_metadata/cstore.rs
@@ -72,6 +72,7 @@ pub struct CrateMetadata {
     pub cnum_map: RefCell<CrateNumMap>,
     pub cnum: CrateNum,
     pub codemap_import_info: RefCell<Vec<ImportedFileMap>>,
+    pub attribute_cache: RefCell<[Vec<Option<Rc<[ast::Attribute]>>>; 2]>,
 
     pub root: schema::CrateRoot,
 
@@ -269,7 +270,7 @@ impl CrateMetadata {
     }
 
     pub fn is_staged_api(&self) -> bool {
-        for attr in self.get_item_attrs(CRATE_DEF_INDEX) {
+        for attr in self.get_item_attrs(CRATE_DEF_INDEX).iter() {
             if attr.path == "stable" || attr.path == "unstable" {
                 return true;
             }
diff --git a/src/librustc_metadata/cstore_impl.rs b/src/librustc_metadata/cstore_impl.rs
index 3cff063a8f568..cb1b0c4c0b78b 100644
--- a/src/librustc_metadata/cstore_impl.rs
+++ b/src/librustc_metadata/cstore_impl.rs
@@ -89,6 +89,7 @@ provide! { <'tcx> tcx, def_id, cdata
     }
     associated_item => { cdata.get_associated_item(def_id.index) }
     impl_trait_ref => { cdata.get_impl_trait(def_id.index, tcx) }
+    impl_polarity => { cdata.get_impl_polarity(def_id.index) }
     coerce_unsized_info => {
         cdata.get_coerce_unsized_info(def_id.index).unwrap_or_else(|| {
             bug!("coerce_unsized_info: `{:?}` is missing its info", def_id);
@@ -149,7 +150,7 @@ impl CrateStore for cstore::CStore {
         self.get_crate_data(def.krate).get_generics(def.index)
     }
 
-    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>
+    fn item_attrs(&self, def_id: DefId) -> Rc<[ast::Attribute]>
     {
         self.dep_graph.read(DepNode::MetaData(def_id));
         self.get_crate_data(def_id.krate).get_item_attrs(def_id.index)
@@ -177,12 +178,6 @@ impl CrateStore for cstore::CStore {
         result
     }
 
-    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity
-    {
-        self.dep_graph.read(DepNode::MetaData(def));
-        self.get_crate_data(def.krate).get_impl_polarity(def.index)
-    }
-
     fn impl_parent(&self, impl_def: DefId) -> Option<DefId> {
         self.dep_graph.read(DepNode::MetaData(impl_def));
         self.get_crate_data(impl_def.krate).get_parent_impl(impl_def.index)
@@ -406,7 +401,7 @@ impl CrateStore for cstore::CStore {
 
         // Mark the attrs as used
         let attrs = data.get_item_attrs(id.index);
-        for attr in &attrs {
+        for attr in attrs.iter() {
             attr::mark_used(attr);
         }
 
@@ -419,7 +414,7 @@ impl CrateStore for cstore::CStore {
             ident: ast::Ident::with_empty_ctxt(name),
             id: ast::DUMMY_NODE_ID,
             span: local_span,
-            attrs: attrs,
+            attrs: attrs.iter().cloned().collect(),
             node: ast::ItemKind::MacroDef(body.into()),
             vis: ast::Visibility::Inherited,
         })
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index fac6079529e30..2d562aceb65cd 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -31,6 +31,7 @@ use std::cell::Ref;
 use std::collections::BTreeMap;
 use std::io;
 use std::mem;
+use std::rc::Rc;
 use std::str;
 use std::u32;
 
@@ -859,10 +860,18 @@ impl<'a, 'tcx> CrateMetadata {
         }
     }
 
-    pub fn get_item_attrs(&self, node_id: DefIndex) -> Vec<ast::Attribute> {
+    pub fn get_item_attrs(&self, node_id: DefIndex) -> Rc<[ast::Attribute]> {
+        let (node_as, node_index) =
+            (node_id.address_space().index(), node_id.as_array_index());
         if self.is_proc_macro(node_id) {
-            return Vec::new();
+            return Rc::new([]);
         }
+
+        if let Some(&Some(ref val)) =
+            self.attribute_cache.borrow()[node_as].get(node_index) {
+            return val.clone();
+        }
+
         // The attributes for a tuple struct are attached to the definition, not the ctor;
         // we assume that someone passing in a tuple struct ctor is actually wanting to
         // look at the definition
@@ -871,7 +880,13 @@ impl<'a, 'tcx> CrateMetadata {
         if def_key.disambiguated_data.data == DefPathData::StructCtor {
             item = self.entry(def_key.parent.unwrap());
         }
-        self.get_attributes(&item)
+        let result = Rc::__from_array(self.get_attributes(&item).into_boxed_slice());
+        let vec_ = &mut self.attribute_cache.borrow_mut()[node_as];
+        if vec_.len() < node_index + 1 {
+            vec_.resize(node_index + 1, None);
+        }
+        vec_[node_index] = Some(result.clone());
+        result
     }
 
     pub fn get_struct_field_names(&self, id: DefIndex) -> Vec<ast::Name> {
diff --git a/src/librustc_mir/build/matches/test.rs b/src/librustc_mir/build/matches/test.rs
index 5fece4d6a5d23..0833342927fec 100644
--- a/src/librustc_mir/build/matches/test.rs
+++ b/src/librustc_mir/build/matches/test.rs
@@ -280,7 +280,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     assert!(ty.is_slice());
 
                     let array_ty = tcx.mk_array(tcx.types.u8, bytes.len());
-                    let array_ref = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic), array_ty);
+                    let array_ref = tcx.mk_imm_ref(tcx.types.re_static, array_ty);
                     let array = self.literal_operand(test.span, array_ref, Literal::Value {
                         value: value.clone()
                     });
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index 4d70540a7c688..7f7377e5ffe3f 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -308,10 +308,9 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
         Adjustment::Deref => Operand::Consume(rcvr_l.deref()),
         Adjustment::RefMut => {
             // let rcvr = &mut rcvr;
-            let re_erased = tcx.mk_region(ty::ReErased);
             let ref_rcvr = local_decls.push(temp_decl(
                 Mutability::Not,
-                tcx.mk_ref(re_erased, ty::TypeAndMut {
+                tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
                     ty: sig.inputs()[0],
                     mutbl: hir::Mutability::MutMutable
                 }),
@@ -321,7 +320,7 @@ fn build_call_shim<'a, 'tcx>(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
                 source_info: source_info,
                 kind: StatementKind::Assign(
                     Lvalue::Local(ref_rcvr),
-                    Rvalue::Ref(re_erased, BorrowKind::Mut, rcvr_l)
+                    Rvalue::Ref(tcx.types.re_erased, BorrowKind::Mut, rcvr_l)
                 )
             });
             Operand::Consume(Lvalue::Local(ref_rcvr))
diff --git a/src/librustc_mir/transform/erase_regions.rs b/src/librustc_mir/transform/erase_regions.rs
index 0f869e7ed02ff..5cc5cf297936d 100644
--- a/src/librustc_mir/transform/erase_regions.rs
+++ b/src/librustc_mir/transform/erase_regions.rs
@@ -13,7 +13,7 @@
 //! care erasing regions all over the place.
 
 use rustc::ty::subst::Substs;
-use rustc::ty::{Ty, TyCtxt, ReErased, ClosureSubsts};
+use rustc::ty::{Ty, TyCtxt, ClosureSubsts};
 use rustc::mir::*;
 use rustc::mir::visit::MutVisitor;
 use rustc::mir::transform::{MirPass, MirSource, Pass};
@@ -43,7 +43,7 @@ impl<'a, 'tcx> MutVisitor<'tcx> for EraseRegionsVisitor<'a, 'tcx> {
     fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
         match *rvalue {
             Rvalue::Ref(ref mut r, _, _) => {
-                *r = self.tcx.mk_region(ReErased);
+                *r = self.tcx.types.re_erased;
             }
             Rvalue::Use(..) |
             Rvalue::Repeat(..) |
diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
index 892d67ac23725..45bdff9195c4f 100644
--- a/src/librustc_mir/transform/inline.rs
+++ b/src/librustc_mir/transform/inline.rs
@@ -497,7 +497,7 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
                 let dest = if dest_needs_borrow(&destination.0) {
                     debug!("Creating temp for return destination");
                     let dest = Rvalue::Ref(
-                        self.tcx.mk_region(ty::ReErased),
+                        self.tcx.types.re_erased,
                         BorrowKind::Mut,
                         destination.0);
 
@@ -582,7 +582,7 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
     fn cast_box_free_arg(&self, arg: Lvalue<'tcx>, ptr_ty: Ty<'tcx>,
                          callsite: &CallSite<'tcx>, caller_mir: &mut Mir<'tcx>) -> Operand<'tcx> {
         let arg = Rvalue::Ref(
-            self.tcx.mk_region(ty::ReErased),
+            self.tcx.types.re_erased,
             BorrowKind::Mut,
             arg.deref());
 
diff --git a/src/librustc_mir/transform/simplify.rs b/src/librustc_mir/transform/simplify.rs
index 0a8f147b21410..ef7990653ba98 100644
--- a/src/librustc_mir/transform/simplify.rs
+++ b/src/librustc_mir/transform/simplify.rs
@@ -124,6 +124,8 @@ impl<'a, 'tcx: 'a> CfgSimplifier<'a, 'tcx> {
                     self.collapse_goto_chain(successor, &mut changed);
                 }
 
+                changed |= self.simplify_unwind(&mut terminator);
+
                 let mut new_stmts = vec![];
                 let mut inner_changed = true;
                 while inner_changed {
@@ -238,6 +240,38 @@ impl<'a, 'tcx: 'a> CfgSimplifier<'a, 'tcx> {
         true
     }
 
+    // turn an unwind branch to a resume block into a None
+    fn simplify_unwind(&mut self, terminator: &mut Terminator<'tcx>) -> bool {
+        let unwind = match terminator.kind {
+            TerminatorKind::Drop { ref mut unwind, .. } |
+            TerminatorKind::DropAndReplace { ref mut unwind, .. } |
+            TerminatorKind::Call { cleanup: ref mut unwind, .. } |
+            TerminatorKind::Assert { cleanup: ref mut unwind, .. } =>
+                unwind,
+            _ => return false
+        };
+
+        if let &mut Some(unwind_block) = unwind {
+            let is_resume_block = match self.basic_blocks[unwind_block] {
+                BasicBlockData {
+                    ref statements,
+                    terminator: Some(Terminator {
+                        kind: TerminatorKind::Resume, ..
+                    }), ..
+                } if statements.is_empty() => true,
+                _ => false
+            };
+            if is_resume_block {
+                debug!("simplifying unwind to {:?} from {:?}",
+                       unwind_block, terminator.source_info);
+                *unwind = None;
+            }
+            return is_resume_block;
+        }
+
+        false
+    }
+
     fn strip_nops(&mut self) {
         for blk in self.basic_blocks.iter_mut() {
             blk.statements.retain(|stmt| if let StatementKind::Nop = stmt.kind {
diff --git a/src/librustc_mir/util/elaborate_drops.rs b/src/librustc_mir/util/elaborate_drops.rs
index 07025fcfdb944..9d7c7ec63cfc5 100644
--- a/src/librustc_mir/util/elaborate_drops.rs
+++ b/src/librustc_mir/util/elaborate_drops.rs
@@ -506,8 +506,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
         let ty = self.lvalue_ty(self.lvalue);
         let substs = tcx.mk_substs(iter::once(Kind::from(ty)));
 
-        let re_erased = tcx.mk_region(ty::ReErased);
-        let ref_ty = tcx.mk_ref(re_erased, ty::TypeAndMut {
+        let ref_ty = tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
             ty: ty,
             mutbl: hir::Mutability::MutMutable
         });
@@ -519,7 +518,7 @@ impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D>
                 source_info: self.source_info,
                 kind: StatementKind::Assign(
                     Lvalue::Local(ref_lvalue),
-                    Rvalue::Ref(re_erased, BorrowKind::Mut, self.lvalue.clone())
+                    Rvalue::Ref(tcx.types.re_erased, BorrowKind::Mut, self.lvalue.clone())
                 )
             }],
             terminator: Some(Terminator {
diff --git a/src/librustc_trans/back/symbol_names.rs b/src/librustc_trans/back/symbol_names.rs
index 61b95f098adbd..f21864764ddf1 100644
--- a/src/librustc_trans/back/symbol_names.rs
+++ b/src/librustc_trans/back/symbol_names.rs
@@ -110,7 +110,8 @@ use rustc::hir::map::definitions::DefPathData;
 use rustc::util::common::record_time;
 
 use syntax::attr;
-use syntax::symbol::{Symbol, InternedString};
+
+use std::fmt::Write;
 
 fn get_symbol_hash<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
@@ -252,19 +253,47 @@ pub fn symbol_name<'a, 'tcx>(instance: Instance<'tcx>,
 
     let hash = get_symbol_hash(tcx, Some(def_id), instance_ty, Some(substs));
 
-    let mut buffer = SymbolPathBuffer {
-        names: Vec::new()
-    };
-
+    let mut buffer = SymbolPathBuffer::new();
     item_path::with_forced_absolute_paths(|| {
         tcx.push_item_path(&mut buffer, def_id);
     });
-
-    mangle(buffer.names.into_iter(), &hash)
+    buffer.finish(&hash)
 }
 
+// Follow C++ namespace-mangling style, see
+// http://en.wikipedia.org/wiki/Name_mangling for more info.
+//
+// It turns out that on macOS you can actually have arbitrary symbols in
+// function names (at least when given to LLVM), but this is not possible
+// when using unix's linker. Perhaps one day when we just use a linker from LLVM
+// we won't need to do this name mangling. The problem with name mangling is
+// that it seriously limits the available characters. For example we can't
+// have things like &T in symbol names when one would theoretically
+// want them for things like impls of traits on that type.
+//
+// To be able to work on all platforms and get *some* reasonable output, we
+// use C++ name-mangling.
 struct SymbolPathBuffer {
-    names: Vec<InternedString>,
+    result: String,
+    temp_buf: String
+}
+
+impl SymbolPathBuffer {
+    fn new() -> Self {
+        let mut result = SymbolPathBuffer {
+            result: String::with_capacity(64),
+            temp_buf: String::with_capacity(16)
+        };
+        result.result.push_str("_ZN"); // _Z == Begin name-sequence, N == nested
+        result
+    }
+
+    fn finish(mut self, hash: &str) -> String {
+        // end name-sequence
+        self.push(hash);
+        self.result.push('E');
+        self.result
+    }
 }
 
 impl ItemPathBuffer for SymbolPathBuffer {
@@ -274,7 +303,13 @@ impl ItemPathBuffer for SymbolPathBuffer {
     }
 
     fn push(&mut self, text: &str) {
-        self.names.push(Symbol::intern(text).as_str());
+        self.temp_buf.clear();
+        let need_underscore = sanitize(&mut self.temp_buf, text);
+        let _ = write!(self.result, "{}", self.temp_buf.len() + (need_underscore as usize));
+        if need_underscore {
+            self.result.push('_');
+        }
+        self.result.push_str(&self.temp_buf);
     }
 }
 
@@ -283,15 +318,17 @@ pub fn exported_name_from_type_and_prefix<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                     prefix: &str)
                                                     -> String {
     let hash = get_symbol_hash(tcx, None, t, None);
-    let path = [Symbol::intern(prefix).as_str()];
-    mangle(path.iter().cloned(), &hash)
+    let mut buffer = SymbolPathBuffer::new();
+    buffer.push(prefix);
+    buffer.finish(&hash)
 }
 
 // Name sanitation. LLVM will happily accept identifiers with weird names, but
 // gas doesn't!
 // gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $
-pub fn sanitize(s: &str) -> String {
-    let mut result = String::new();
+//
+// returns true if an underscore must be added at the start
+pub fn sanitize(result: &mut String, s: &str) -> bool {
     for c in s.chars() {
         match c {
             // Escape these with $ sequences
@@ -328,44 +365,7 @@ pub fn sanitize(s: &str) -> String {
     }
 
     // Underscore-qualify anything that didn't start as an ident.
-    if !result.is_empty() &&
+    !result.is_empty() &&
         result.as_bytes()[0] != '_' as u8 &&
-        ! (result.as_bytes()[0] as char).is_xid_start() {
-        return format!("_{}", result);
-    }
-
-    return result;
-}
-
-fn mangle<PI: Iterator<Item=InternedString>>(path: PI, hash: &str) -> String {
-    // Follow C++ namespace-mangling style, see
-    // http://en.wikipedia.org/wiki/Name_mangling for more info.
-    //
-    // It turns out that on macOS you can actually have arbitrary symbols in
-    // function names (at least when given to LLVM), but this is not possible
-    // when using unix's linker. Perhaps one day when we just use a linker from LLVM
-    // we won't need to do this name mangling. The problem with name mangling is
-    // that it seriously limits the available characters. For example we can't
-    // have things like &T in symbol names when one would theoretically
-    // want them for things like impls of traits on that type.
-    //
-    // To be able to work on all platforms and get *some* reasonable output, we
-    // use C++ name-mangling.
-
-    let mut n = String::from("_ZN"); // _Z == Begin name-sequence, N == nested
-
-    fn push(n: &mut String, s: &str) {
-        let sani = sanitize(s);
-        n.push_str(&format!("{}{}", sani.len(), sani));
-    }
-
-    // First, connect each component with <len, name> pairs.
-    for data in path {
-        push(&mut n, &data);
-    }
-
-    push(&mut n, hash);
-
-    n.push('E'); // End name-sequence.
-    n
+        ! (result.as_bytes()[0] as char).is_xid_start()
 }
diff --git a/src/librustc_trans/context.rs b/src/librustc_trans/context.rs
index ceb292c13c12a..bef22cf304dcb 100644
--- a/src/librustc_trans/context.rs
+++ b/src/librustc_trans/context.rs
@@ -771,6 +771,10 @@ impl<'a, 'tcx> LayoutTyper<'tcx> for &'a SharedCrateContext<'a, 'tcx> {
     type TyLayout = TyLayout<'tcx>;
 
     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
+        if let Some(&layout) = self.tcx().layout_cache.borrow().get(&ty) {
+            return TyLayout { ty: ty, layout: layout, variant_index: None };
+        }
+
         self.tcx().infer_ctxt((), traits::Reveal::All).enter(|infcx| {
             infcx.layout_of(ty).unwrap_or_else(|e| {
                 match e {
@@ -781,6 +785,10 @@ impl<'a, 'tcx> LayoutTyper<'tcx> for &'a SharedCrateContext<'a, 'tcx> {
             })
         })
     }
+
+    fn normalize_projections(self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        self.tcx().normalize_associated_type(&ty)
+    }
 }
 
 impl<'a, 'tcx> LayoutTyper<'tcx> for &'a CrateContext<'a, 'tcx> {
@@ -789,6 +797,10 @@ impl<'a, 'tcx> LayoutTyper<'tcx> for &'a CrateContext<'a, 'tcx> {
     fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
         self.shared.layout_of(ty)
     }
+
+    fn normalize_projections(self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        self.shared.normalize_projections(ty)
+    }
 }
 
 pub struct TypeOfDepthLock<'a, 'tcx: 'a>(&'a LocalCrateContext<'a, 'tcx>);
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs
index dbae79e034daa..e938913a3f117 100644
--- a/src/librustc_trans/mir/constant.rs
+++ b/src/librustc_trans/mir/constant.rs
@@ -708,7 +708,7 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                 let tr_lvalue = self.const_lvalue(lvalue, span)?;
 
                 let ty = tr_lvalue.ty;
-                let ref_ty = tcx.mk_ref(tcx.mk_region(ty::ReErased),
+                let ref_ty = tcx.mk_ref(tcx.types.re_erased,
                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() });
 
                 let base = match tr_lvalue.base {
diff --git a/src/librustc_trans/mir/rvalue.rs b/src/librustc_trans/mir/rvalue.rs
index de1c1e492f39b..b8e9a490b0e7c 100644
--- a/src/librustc_trans/mir/rvalue.rs
+++ b/src/librustc_trans/mir/rvalue.rs
@@ -329,7 +329,7 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
                 let ty = tr_lvalue.ty.to_ty(bcx.tcx());
                 let ref_ty = bcx.tcx().mk_ref(
-                    bcx.tcx().mk_region(ty::ReErased),
+                    bcx.tcx().types.re_erased,
                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() }
                 );
 
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 9426d601dfcce..5137ae6ff4222 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -109,7 +109,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         let tcx = self.tcx();
         let r = match tcx.named_region_map.defs.get(&lifetime.id) {
             Some(&rl::Region::Static) => {
-                tcx.mk_region(ty::ReStatic)
+                tcx.types.re_static
             }
 
             Some(&rl::Region::LateBound(debruijn, id)) => {
@@ -171,7 +171,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                     .emit();
 
                 return Substs::for_item(tcx, def_id, |_, _| {
-                    tcx.mk_region(ty::ReStatic)
+                    tcx.types.re_static
                 }, |_, _| {
                     tcx.types.err
                 });
@@ -254,7 +254,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
             if let Some(lifetime) = lifetimes.get(i) {
                 self.ast_region_to_region(lifetime, Some(def))
             } else {
-                tcx.mk_region(ty::ReStatic)
+                tcx.types.re_static
             }
         }, |def, substs| {
             let i = def.index as usize;
@@ -715,7 +715,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                         span_err!(tcx.sess, span, E0228,
                                   "the lifetime bound for this object type cannot be deduced \
                                    from context; please supply an explicit bound");
-                        tcx.mk_region(ty::ReStatic)
+                        tcx.types.re_static
                     })
                 }
             })
@@ -1357,7 +1357,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         // If any of the derived region bounds are 'static, that is always
         // the best choice.
         if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
-            return Some(tcx.mk_region(ty::ReStatic));
+            return Some(tcx.types.re_static);
         }
 
         // Determine whether there is exactly one unique region in the set
diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index 4a04464244442..1086773041c93 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -55,7 +55,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         let expected_ty = self.structurally_resolved_type(pat.span, expected);
                         if let ty::TyRef(_, mt) = expected_ty.sty {
                             if let ty::TySlice(_) = mt.ty.sty {
-                                pat_ty = tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
+                                pat_ty = tcx.mk_imm_ref(tcx.types.re_static,
                                                          tcx.mk_slice(tcx.types.u8))
                             }
                         }
diff --git a/src/librustc_typeck/check/dropck.rs b/src/librustc_typeck/check/dropck.rs
index b71ff58ccec33..09bfe45f5404b 100644
--- a/src/librustc_typeck/check/dropck.rs
+++ b/src/librustc_typeck/check/dropck.rs
@@ -626,7 +626,7 @@ fn revise_self_ty<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
             let impl_self_orig = self_substs.region_for_def(def);
             let r = if let ty::Region::ReEarlyBound(ref ebr) = *impl_self_orig {
                 if impl_bindings.region_param(ebr).pure_wrt_drop {
-                    tcx.mk_region(ty::ReStatic)
+                    tcx.types.re_static
                 } else {
                     r_orig
                 }
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index cd58fcd4806da..bf7649242fa71 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -36,7 +36,7 @@ fn equate_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let def_id = tcx.hir.local_def_id(it.id);
 
     let substs = Substs::for_item(tcx, def_id,
-                                  |_, _| tcx.mk_region(ty::ReErased),
+                                  |_, _| tcx.types.re_erased,
                                   |def, _| tcx.mk_param_from_def(def));
 
     let fty = tcx.mk_fn_def(def_id, substs, ty::Binder(tcx.mk_fn_sig(
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 59dbbfe49f0a9..80f9372eb54c4 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -1063,7 +1063,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
         // In general, during probing we erase regions. See
         // `impl_self_ty()` for an explanation.
-        let region = tcx.mk_region(ty::ReErased);
+        let region = tcx.types.re_erased;
 
         // Search through mutabilities in order to find one where pick works:
         [hir::MutImmutable, hir::MutMutable]
@@ -1325,7 +1325,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                 } else {
                     // In general, during probe we erase regions. See
                     // `impl_self_ty()` for an explanation.
-                    self.tcx.mk_region(ty::ReErased)
+                    self.tcx.types.re_erased
                 }
             }, |def, cur_substs| {
                 let i = def.index as usize;
@@ -1345,7 +1345,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
 
         let substs = Substs::for_item(self.tcx,
                                       impl_def_id,
-                                      |_, _| self.tcx.mk_region(ty::ReErased),
+                                      |_, _| self.tcx.types.re_erased,
                                       |_, _| self.next_ty_var(
                                         TypeVariableOrigin::SubstitutionPlaceholder(
                                             self.tcx.def_span(impl_def_id))));
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 839af0fa6706c..098e8c53a52c1 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1954,7 +1954,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         //
         // FIXME(#27579) all uses of this should be migrated to register_wf_obligation eventually
         let cause = traits::ObligationCause::new(span, self.body_id, code);
-        self.register_region_obligation(ty, self.tcx.mk_region(ty::ReEmpty), cause);
+        self.register_region_obligation(ty, self.tcx.types.re_empty, cause);
     }
 
     /// Registers obligations that all types appearing in `substs` are well-formed.
@@ -2513,7 +2513,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         match lit.node {
             ast::LitKind::Str(..) => tcx.mk_static_str(),
             ast::LitKind::ByteStr(ref v) => {
-                tcx.mk_imm_ref(tcx.mk_region(ty::ReStatic),
+                tcx.mk_imm_ref(tcx.types.re_static,
                                 tcx.mk_array(tcx.types.u8, v.len()))
             }
             ast::LitKind::Byte(_) => tcx.types.u8,
diff --git a/src/librustc_typeck/check/writeback.rs b/src/librustc_typeck/check/writeback.rs
index f196aa82b1ef3..35b2e8f8afcb8 100644
--- a/src/librustc_typeck/check/writeback.rs
+++ b/src/librustc_typeck/check/writeback.rs
@@ -288,8 +288,8 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
             let outside_ty = gcx.fold_regions(&inside_ty, &mut false, |r, _| {
                 match *r {
                     // 'static is valid everywhere.
-                    ty::ReStatic |
-                    ty::ReEmpty => gcx.mk_region(*r),
+                    ty::ReStatic => gcx.types.re_static,
+                    ty::ReEmpty => gcx.types.re_empty,
 
                     // Free regions that come from early-bound regions are valid.
                     ty::ReFree(ty::FreeRegion {
@@ -307,7 +307,7 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
                         span_err!(self.tcx().sess, span, E0564,
                                   "only named lifetimes are allowed in `impl Trait`, \
                                    but `{}` was found in the type `{}`", r, inside_ty);
-                        gcx.mk_region(ty::ReStatic)
+                        gcx.types.re_static
                     }
 
                     ty::ReVar(_) |
@@ -526,7 +526,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
         match self.infcx.fully_resolve(&r) {
             Ok(r) => r,
             Err(_) => {
-                self.tcx.mk_region(ty::ReStatic)
+                self.tcx.types.re_static
             }
         }
     }
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 855d156f6f26a..1f2310c49e3a0 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -99,6 +99,7 @@ pub fn provide(providers: &mut Providers) {
         trait_def,
         adt_def,
         impl_trait_ref,
+        impl_polarity,
         is_foreign_item,
         ..*providers
     };
@@ -1133,6 +1134,16 @@ fn impl_trait_ref<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }
 }
 
+fn impl_polarity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                           def_id: DefId)
+                           -> hir::ImplPolarity {
+    let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
+    match tcx.hir.expect_item(node_id).node {
+        hir::ItemImpl(_, polarity, ..) => polarity,
+        ref item => bug!("trait_impl_polarity: {:?} not an impl", item)
+    }
+}
+
 // Is it marked with ?Sized
 fn is_unsized<'gcx: 'tcx, 'tcx>(astconv: &AstConv<'gcx, 'tcx>,
                                 ast_bounds: &[hir::TyParamBound],
diff --git a/src/test/codegen/drop.rs b/src/test/codegen/drop.rs
index a4bd5cf2c158e..d7e2cb6d9a50b 100644
--- a/src/test/codegen/drop.rs
+++ b/src/test/codegen/drop.rs
@@ -36,7 +36,7 @@ pub fn droppy() {
 // CHECK-NOT: call{{.*}}drop{{.*}}SomeUniqueName
 // CHECK: invoke{{.*}}drop{{.*}}SomeUniqueName
 // CHECK: invoke{{.*}}drop{{.*}}SomeUniqueName
-// CHECK: invoke{{.*}}drop{{.*}}SomeUniqueName
+// CHECK: call{{.*}}drop{{.*}}SomeUniqueName
 // CHECK-NOT: {{(call|invoke).*}}drop{{.*}}SomeUniqueName
 // The next line checks for the } that ends the function definition
 // CHECK-LABEL: {{^[}]}}
diff --git a/src/test/codegen/personality_lifetimes.rs b/src/test/codegen/personality_lifetimes.rs
index e0de64b26df47..9fd600b32e6c7 100644
--- a/src/test/codegen/personality_lifetimes.rs
+++ b/src/test/codegen/personality_lifetimes.rs
@@ -37,5 +37,6 @@ pub fn test() {
     // CHECK: bitcast{{.*}}personalityslot
     // CHECK-NEXT: call void @llvm.lifetime.start
     might_unwind();
+    let _t = S;
     might_unwind();
 }