diff --git a/src/librustc_mir/interpret/cast.rs b/src/librustc_mir/interpret/cast.rs
index 4bf40091153534fb78505f147dd40e7987518a31..e69e7a522ab73e62bfdc7d5014db72f3cb7392a5 100644
--- a/src/librustc_mir/interpret/cast.rs
+++ b/src/librustc_mir/interpret/cast.rs
@@ -76,8 +76,8 @@ fn cast_from_int(
             // No alignment check needed for raw pointers.  But we have to truncate to target ptr size.
             TyRawPtr(_) => {
                 Ok(Scalar::Bits {
-                    bits: self.memory().truncate_to_ptr(v).0 as u128,
-                    defined: self.memory().pointer_size().bits() as u8,
+                    bits: self.memory.truncate_to_ptr(v).0 as u128,
+                    defined: self.memory.pointer_size().bits() as u8,
                 })
             },
 
@@ -92,7 +92,7 @@ fn cast_from_float(&self, bits: u128, fty: FloatTy, dest_ty: Ty<'tcx>) -> EvalRe
         match dest_ty.sty {
             // float -> uint
             TyUint(t) => {
-                let width = t.bit_width().unwrap_or(self.memory().pointer_size().bits() as usize);
+                let width = t.bit_width().unwrap_or(self.memory.pointer_size().bits() as usize);
                 match fty {
                     FloatTy::F32 => Ok(Scalar::Bits {
                         bits: Single::from_bits(bits).to_u128(width).value,
@@ -106,7 +106,7 @@ fn cast_from_float(&self, bits: u128, fty: FloatTy, dest_ty: Ty<'tcx>) -> EvalRe
             },
             // float -> int
             TyInt(t) => {
-                let width = t.bit_width().unwrap_or(self.memory().pointer_size().bits() as usize);
+                let width = t.bit_width().unwrap_or(self.memory.pointer_size().bits() as usize);
                 match fty {
                     FloatTy::F32 => Ok(Scalar::Bits {
                         bits: Single::from_bits(bits).to_i128(width).value as u128,
diff --git a/src/librustc_mir/interpret/const_eval.rs b/src/librustc_mir/interpret/const_eval.rs
index fe2c46aa48fd86daff59735697f1d7c87c78097f..e84132f27cc62d66090b1f535c63aa6ec8b80f7f 100644
--- a/src/librustc_mir/interpret/const_eval.rs
+++ b/src/librustc_mir/interpret/const_eval.rs
@@ -88,7 +88,7 @@ pub fn value_to_const_value<'tcx>(
             Value::ScalarPair(a, b) => Ok(ConstValue::ScalarPair(a, b)),
             Value::ByRef(ptr, align) => {
                 let ptr = ptr.to_ptr().unwrap();
-                let alloc = ecx.memory().get(ptr.alloc_id)?;
+                let alloc = ecx.memory.get(ptr.alloc_id)?;
                 assert!(alloc.align.abi() >= align.abi());
                 assert!(alloc.bytes.len() as u64 - ptr.offset.bytes() >= layout.size.bytes());
                 let mut alloc = alloc.clone();
@@ -149,7 +149,7 @@ fn eval_body_using_ecx<'a, 'mir, 'tcx>(
     }
     let layout = ecx.layout_of(mir.return_ty().subst(tcx, cid.instance.substs))?;
     assert!(!layout.is_unsized());
-    let ptr = ecx.memory_mut().allocate(
+    let ptr = ecx.memory.allocate(
         layout.size,
         layout.align,
         MemoryKind::Stack,
@@ -185,6 +185,7 @@ fn eval_body_using_ecx<'a, 'mir, 'tcx>(
     Ok((value, ptr, layout.ty))
 }
 
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
 pub struct CompileTimeEvaluator;
 
 impl<'tcx> Into<EvalError<'tcx>> for ConstEvalError {
@@ -486,7 +487,7 @@ pub fn const_variant_index<'a, 'tcx>(
     let (ptr, align) = match value {
         Value::ScalarPair(..) | Value::Scalar(_) => {
             let layout = ecx.layout_of(val.ty)?;
-            let ptr = ecx.memory_mut().allocate(layout.size, layout.align, MemoryKind::Stack)?.into();
+            let ptr = ecx.memory.allocate(layout.size, layout.align, MemoryKind::Stack)?.into();
             ecx.write_value_to_ptr(value, ptr, layout.align, val.ty)?;
             (ptr, layout.align)
         },
@@ -515,9 +516,9 @@ pub fn const_value_to_allocation_provider<'a, 'tcx>(
             ());
         let value = ecx.const_to_value(val.val)?;
         let layout = ecx.layout_of(val.ty)?;
-        let ptr = ecx.memory_mut().allocate(layout.size, layout.align, MemoryKind::Stack)?;
+        let ptr = ecx.memory.allocate(layout.size, layout.align, MemoryKind::Stack)?;
         ecx.write_value_to_ptr(value, ptr.into(), layout.align, val.ty)?;
-        let alloc = ecx.memory().get(ptr.alloc_id)?;
+        let alloc = ecx.memory.get(ptr.alloc_id)?;
         Ok(tcx.intern_const_alloc(alloc.clone()))
     };
     result().expect("unable to convert ConstValue to Allocation")
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index 4699444bd424907d9a4c2575cbee663f2b219ba7..85aeb3c7df51a0bb46f78871ad307b6338242921 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -34,8 +34,11 @@ pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
     /// Bounds in scope for polymorphic evaluations.
     pub param_env: ty::ParamEnv<'tcx>,
 
-    /// Virtual memory and call stack.
-    pub(crate) state: EvalState<'a, 'mir, 'tcx, M>,
+    /// The virtual memory system.
+    pub memory: Memory<'a, 'mir, 'tcx, M>,
+
+    /// The virtual call stack.
+    pub(crate) stack: Vec<Frame<'mir, 'tcx>>,
 
     /// The maximum number of stack frames allowed
     pub(crate) stack_limit: usize,
@@ -47,50 +50,6 @@ pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
     pub(crate) loop_detector: InfiniteLoopDetector<'a, 'mir, 'tcx, M>,
 }
 
-pub(crate) struct EvalState<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
-    /// The virtual memory system.
-    memory: Memory<'a, 'mir, 'tcx, M>,
-
-    /// The virtual call stack.
-    stack: Vec<Frame<'mir, 'tcx>>,
-}
-
-impl<'a, 'mir, 'tcx, M> Clone for EvalState<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
-          'tcx: 'a + 'mir,
-{
-    fn clone(&self) -> Self {
-        EvalState {
-            memory: self.memory.clone(),
-            stack: self.stack.clone(),
-        }
-    }
-}
-
-impl<'a, 'mir, 'tcx, M> Eq for EvalState<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
-          'tcx: 'a + 'mir,
-{}
-
-impl<'a, 'mir, 'tcx, M> PartialEq for EvalState<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
-          'tcx: 'a + 'mir,
-{
-    fn eq(&self, other: &Self) -> bool {
-        self.memory == other.memory
-            && self.stack == other.stack
-    }
-}
-
-impl<'a, 'mir, 'tcx, M> Hash for EvalState<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
-          'tcx: 'a + 'mir,
-{
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.memory.hash(state);
-        self.stack.hash(state);
-    }
-}
 /// A stack frame.
 #[derive(Clone)]
 pub struct Frame<'mir, 'tcx: 'mir> {
@@ -180,22 +139,26 @@ fn hash<H: Hasher>(&self, state: &mut H) {
     }
 }
 
+/// The virtual machine state during const-evaluation at a given point in time.
+type EvalSnapshot<'a, 'mir, 'tcx, M>
+    = (M, Vec<Frame<'mir, 'tcx>>, Memory<'a, 'mir, 'tcx, M>);
+
 pub(crate) struct InfiniteLoopDetector<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
-    /// The set of all `EvalState` *hashes* observed by this detector.
+    /// The set of all `EvalSnapshot` *hashes* observed by this detector.
     ///
     /// Not a proper bloom filter.
     bloom: FxHashSet<u64>,
 
-    /// The set of all `EvalState`s observed by this detector.
+    /// The set of all `EvalSnapshot`s observed by this detector.
     ///
-    /// An `EvalState` will only be fully cloned once it has caused a collision
+    /// An `EvalSnapshot` will only be fully cloned once it has caused a collision
     /// in `bloom`. As a result, the detector must observe *two* full cycles of
     /// an infinite loop before it triggers.
-    snapshots: FxHashSet<EvalState<'a, 'mir, 'tcx, M>>,
+    snapshots: FxHashSet<EvalSnapshot<'a, 'mir, 'tcx, M>>,
 }
 
 impl<'a, 'mir, 'tcx, M> Default for InfiniteLoopDetector<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
+    where M: Eq + Hash + Machine<'mir, 'tcx>,
           'tcx: 'a + 'mir,
 {
     fn default() -> Self {
@@ -207,10 +170,17 @@ fn default() -> Self {
 }
 
 impl<'a, 'mir, 'tcx, M> InfiniteLoopDetector<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
+    where M: Clone + Eq + Hash + Machine<'mir, 'tcx>,
           'tcx: 'a + 'mir,
 {
-    pub fn observe(&mut self, snapshot: &EvalState<'a, 'mir, 'tcx, M>) -> Result<(), (/*TODO*/)> {
+    pub fn observe(
+        &mut self,
+        machine: &M,
+        stack: &Vec<Frame<'mir, 'tcx>>,
+        memory: &Memory<'a, 'mir, 'tcx, M>,
+    ) -> Result<(), (/*TODO*/)> {
+        let snapshot = (machine, stack, memory);
+
         let mut fx = FxHasher::default();
         snapshot.hash(&mut fx);
         let hash = fx.finish();
@@ -220,7 +190,7 @@ pub fn observe(&mut self, snapshot: &EvalState<'a, 'mir, 'tcx, M>) -> Result<(),
             return Ok(())
         }
 
-        if self.snapshots.insert(snapshot.clone()) {
+        if self.snapshots.insert((machine.clone(), stack.clone(), memory.clone())) {
             // Spurious collision or first cycle
             return Ok(())
         }
@@ -322,15 +292,15 @@ pub fn new(
         param_env: ty::ParamEnv<'tcx>,
         machine: M,
         memory_data: M::MemoryData,
-    ) -> Self {
+    ) -> Self
+        where M: Eq + Hash
+    {
         EvalContext {
             machine,
             tcx,
             param_env,
-            state: EvalState {
-                memory: Memory::new(tcx, memory_data),
-                stack: Vec::new(),
-            },
+            memory: Memory::new(tcx, memory_data),
+            stack: Vec::new(),
             stack_limit: tcx.sess.const_eval_stack_frame_limit,
             loop_detector: Default::default(),
             steps_until_detector_enabled: MAX_TERMINATORS,
@@ -338,10 +308,10 @@ pub fn new(
     }
 
     pub(crate) fn with_fresh_body<F: FnOnce(&mut Self) -> R, R>(&mut self, f: F) -> R {
-        let stack = mem::replace(self.stack_mut(), Vec::new());
+        let stack = mem::replace(&mut self.stack, Vec::new());
         let steps = mem::replace(&mut self.steps_until_detector_enabled, MAX_TERMINATORS);
         let r = f(self);
-        *self.stack_mut() = stack;
+        self.stack = stack;
         self.steps_until_detector_enabled = steps;
         r
     }
@@ -350,34 +320,29 @@ pub fn alloc_ptr(&mut self, ty: Ty<'tcx>) -> EvalResult<'tcx, Pointer> {
         let layout = self.layout_of(ty)?;
         assert!(!layout.is_unsized(), "cannot alloc memory for unsized type");
 
-        self.memory_mut().allocate(layout.size, layout.align, MemoryKind::Stack)
+        self.memory.allocate(layout.size, layout.align, MemoryKind::Stack)
     }
 
     pub fn memory(&self) -> &Memory<'a, 'mir, 'tcx, M> {
-        &self.state.memory
+        &self.memory
     }
 
     pub fn memory_mut(&mut self) -> &mut Memory<'a, 'mir, 'tcx, M> {
-        &mut self.state.memory
+        &mut self.memory
     }
 
-    #[inline]
     pub fn stack(&self) -> &[Frame<'mir, 'tcx>] {
-        &self.state.stack
-    }
-
-    pub fn stack_mut(&mut self) -> &mut Vec<Frame<'mir, 'tcx>> {
-        &mut self.state.stack
+        &self.stack
     }
 
     #[inline]
     pub fn cur_frame(&self) -> usize {
-        assert!(self.stack().len() > 0);
-        self.stack().len() - 1
+        assert!(self.stack.len() > 0);
+        self.stack.len() - 1
     }
 
     pub fn str_to_value(&mut self, s: &str) -> EvalResult<'tcx, Value> {
-        let ptr = self.memory_mut().allocate_bytes(s.as_bytes());
+        let ptr = self.memory.allocate_bytes(s.as_bytes());
         Ok(Scalar::Ptr(ptr).to_value_with_len(s.len() as u64, self.tcx.tcx))
     }
 
@@ -395,7 +360,7 @@ pub fn const_to_value(
             }
             ConstValue::ByRef(alloc, offset) => {
                 // FIXME: Allocate new AllocId for all constants inside
-                let id = self.memory_mut().allocate_value(alloc.clone(), MemoryKind::Stack)?;
+                let id = self.memory.allocate_value(alloc.clone(), MemoryKind::Stack)?;
                 Ok(Value::ByRef(Pointer::new(id, offset).into(), alloc.align))
             },
             ConstValue::ScalarPair(a, b) => Ok(Value::ScalarPair(a, b)),
@@ -566,7 +531,7 @@ pub fn push_stack_frame(
             IndexVec::new()
         };
 
-        self.stack_mut().push(Frame {
+        self.stack.push(Frame {
             mir,
             block: mir::START_BLOCK,
             return_to_block,
@@ -577,9 +542,9 @@ pub fn push_stack_frame(
             stmt: 0,
         });
 
-        self.memory_mut().cur_frame = self.cur_frame();
+        self.memory.cur_frame = self.cur_frame();
 
-        if self.stack().len() > self.stack_limit {
+        if self.stack.len() > self.stack_limit {
             err!(StackFrameLimitReached)
         } else {
             Ok(())
@@ -589,18 +554,18 @@ pub fn push_stack_frame(
     pub(super) fn pop_stack_frame(&mut self) -> EvalResult<'tcx> {
         ::log_settings::settings().indentation -= 1;
         M::end_region(self, None)?;
-        let frame = self.stack_mut().pop().expect(
+        let frame = self.stack.pop().expect(
             "tried to pop a stack frame, but there were none",
         );
-        if !self.stack().is_empty() {
+        if !self.stack.is_empty() {
             // TODO: Is this the correct time to start considering these accesses as originating from the returned-to stack frame?
-            self.memory_mut().cur_frame = self.cur_frame();
+            self.memory.cur_frame = self.cur_frame();
         }
         match frame.return_to_block {
             StackPopCleanup::MarkStatic(mutable) => {
                 if let Place::Ptr { ptr, .. } = frame.return_place {
                     // FIXME: to_ptr()? might be too extreme here, static zsts might reach this under certain conditions
-                    self.memory_mut().mark_static_initialized(
+                    self.memory.mark_static_initialized(
                         ptr.to_ptr()?.alloc_id,
                         mutable,
                     )?
@@ -623,8 +588,8 @@ pub fn deallocate_local(&mut self, local: Option<Value>) -> EvalResult<'tcx> {
         if let Some(Value::ByRef(ptr, _align)) = local {
             trace!("deallocating local");
             let ptr = ptr.to_ptr()?;
-            self.memory().dump_alloc(ptr.alloc_id);
-            self.memory_mut().deallocate_local(ptr)?;
+            self.memory.dump_alloc(ptr.alloc_id);
+            self.memory.deallocate_local(ptr)?;
         };
         Ok(())
     }
@@ -637,7 +602,9 @@ pub(super) fn eval_rvalue_into_place(
         &mut self,
         rvalue: &mir::Rvalue<'tcx>,
         place: &mir::Place<'tcx>,
-    ) -> EvalResult<'tcx> {
+    ) -> EvalResult<'tcx>
+        where M: Clone + Eq + Hash,
+    {
         let dest = self.eval_place(place)?;
         let dest_ty = self.place_ty(place);
 
@@ -744,7 +711,7 @@ pub(super) fn eval_rvalue_into_place(
                 let src = self.eval_place(place)?;
                 let ty = self.place_ty(place);
                 let (_, len) = src.elem_ty_and_len(ty, self.tcx.tcx);
-                let defined = self.memory().pointer_size().bits() as u8;
+                let defined = self.memory.pointer_size().bits() as u8;
                 self.write_scalar(
                     dest,
                     Scalar::Bits {
@@ -786,7 +753,7 @@ pub(super) fn eval_rvalue_into_place(
                 let layout = self.layout_of(ty)?;
                 assert!(!layout.is_unsized(),
                         "SizeOf nullary MIR operator called for unsized type");
-                let defined = self.memory().pointer_size().bits() as u8;
+                let defined = self.memory.pointer_size().bits() as u8;
                 self.write_scalar(
                     dest,
                     Scalar::Bits {
@@ -881,7 +848,7 @@ pub(super) fn eval_rvalue_into_place(
                                     def_id,
                                     substs,
                                 ).ok_or_else(|| EvalErrorKind::TooGeneric.into());
-                                let fn_ptr = self.memory_mut().create_fn_alloc(instance?);
+                                let fn_ptr = self.memory.create_fn_alloc(instance?);
                                 let valty = ValTy {
                                     value: Value::Scalar(fn_ptr.into()),
                                     ty: dest_ty,
@@ -917,7 +884,7 @@ pub(super) fn eval_rvalue_into_place(
                                     substs,
                                     ty::ClosureKind::FnOnce,
                                 );
-                                let fn_ptr = self.memory_mut().create_fn_alloc(instance);
+                                let fn_ptr = self.memory.create_fn_alloc(instance);
                                 let valty = ValTy {
                                     value: Value::Scalar(fn_ptr.into()),
                                     ty: dest_ty,
@@ -1194,7 +1161,7 @@ pub fn const_eval(&self, gid: GlobalId<'tcx>) -> EvalResult<'tcx, &'tcx ty::Cons
     pub fn force_allocation(&mut self, place: Place) -> EvalResult<'tcx, Place> {
         let new_place = match place {
             Place::Local { frame, local } => {
-                match self.stack()[frame].locals[local] {
+                match self.stack[frame].locals[local] {
                     None => return err!(DeadLocal),
                     Some(Value::ByRef(ptr, align)) => {
                         Place::Ptr {
@@ -1204,11 +1171,11 @@ pub fn force_allocation(&mut self, place: Place) -> EvalResult<'tcx, Place> {
                         }
                     }
                     Some(val) => {
-                        let ty = self.stack()[frame].mir.local_decls[local].ty;
-                        let ty = self.monomorphize(ty, self.stack()[frame].instance.substs);
+                        let ty = self.stack[frame].mir.local_decls[local].ty;
+                        let ty = self.monomorphize(ty, self.stack[frame].instance.substs);
                         let layout = self.layout_of(ty)?;
                         let ptr = self.alloc_ptr(ty)?;
-                        self.stack_mut()[frame].locals[local] =
+                        self.stack[frame].locals[local] =
                             Some(Value::ByRef(ptr.into(), layout.align)); // it stays live
                         let place = Place::from_ptr(ptr, layout.align);
                         self.write_value(ValTy { value: val, ty }, place)?;
@@ -1290,10 +1257,10 @@ pub fn write_value(
             }
 
             Place::Local { frame, local } => {
-                let dest = self.stack()[frame].get_local(local)?;
+                let dest = self.stack[frame].get_local(local)?;
                 self.write_value_possibly_by_val(
                     src_val,
-                    |this, val| this.stack_mut()[frame].set_local(local, val),
+                    |this, val| this.stack[frame].set_local(local, val),
                     dest,
                     dest_ty,
                 )
@@ -1335,7 +1302,7 @@ fn write_value_possibly_by_val<F: FnOnce(&mut Self, Value) -> EvalResult<'tcx>>(
             } else {
                 let dest_ptr = self.alloc_ptr(dest_ty)?.into();
                 let layout = self.layout_of(dest_ty)?;
-                self.memory_mut().copy(src_ptr, align.min(layout.align), dest_ptr, layout.align, layout.size, false)?;
+                self.memory.copy(src_ptr, align.min(layout.align), dest_ptr, layout.align, layout.size, false)?;
                 write_dest(self, Value::ByRef(dest_ptr, layout.align))?;
             }
         } else {
@@ -1357,7 +1324,7 @@ pub fn write_value_to_ptr(
         trace!("write_value_to_ptr: {:#?}, {}, {:#?}", value, dest_ty, layout);
         match value {
             Value::ByRef(ptr, align) => {
-                self.memory_mut().copy(ptr, align.min(layout.align), dest, dest_align.min(layout.align), layout.size, false)
+                self.memory.copy(ptr, align.min(layout.align), dest, dest_align.min(layout.align), layout.size, false)
             }
             Value::Scalar(scalar) => {
                 let signed = match layout.abi {
@@ -1370,7 +1337,7 @@ pub fn write_value_to_ptr(
                         _ => bug!("write_value_to_ptr: invalid ByVal layout: {:#?}", layout),
                     }
                 };
-                self.memory_mut().write_scalar(dest, dest_align, scalar, layout.size, signed)
+                self.memory.write_scalar(dest, dest_align, scalar, layout.size, signed)
             }
             Value::ScalarPair(a_val, b_val) => {
                 trace!("write_value_to_ptr valpair: {:#?}", layout);
@@ -1383,8 +1350,8 @@ pub fn write_value_to_ptr(
                 let b_offset = a_size.abi_align(b.align(&self));
                 let b_ptr = dest.ptr_offset(b_offset, &self)?.into();
                 // TODO: What about signedess?
-                self.memory_mut().write_scalar(a_ptr, dest_align, a_val, a_size, false)?;
-                self.memory_mut().write_scalar(b_ptr, dest_align, b_val, b_size, false)
+                self.memory.write_scalar(a_ptr, dest_align, a_val, a_size, false)?;
+                self.memory.write_scalar(b_ptr, dest_align, b_val, b_size, false)
             }
         }
     }
@@ -1415,8 +1382,8 @@ pub(crate) fn read_ptr(
         ptr_align: Align,
         pointee_ty: Ty<'tcx>,
     ) -> EvalResult<'tcx, Value> {
-        let ptr_size = self.memory().pointer_size();
-        let p: Scalar = self.memory().read_ptr_sized(ptr, ptr_align)?.into();
+        let ptr_size = self.memory.pointer_size();
+        let p: Scalar = self.memory.read_ptr_sized(ptr, ptr_align)?.into();
         if self.type_is_sized(pointee_ty) {
             Ok(p.to_value())
         } else {
@@ -1424,11 +1391,11 @@ pub(crate) fn read_ptr(
             let extra = ptr.offset(ptr_size, self)?;
             match self.tcx.struct_tail(pointee_ty).sty {
                 ty::TyDynamic(..) => Ok(p.to_value_with_vtable(
-                    self.memory().read_ptr_sized(extra, ptr_align)?.to_ptr()?,
+                    self.memory.read_ptr_sized(extra, ptr_align)?.to_ptr()?,
                 )),
                 ty::TySlice(..) | ty::TyStr => {
                     let len = self
-                        .memory()
+                        .memory
                         .read_ptr_sized(extra, ptr_align)?
                         .to_bits(ptr_size)?;
                     Ok(p.to_value_with_len(len as u64, self.tcx.tcx))
@@ -1446,10 +1413,10 @@ pub fn validate_ptr_target(
     ) -> EvalResult<'tcx> {
         match ty.sty {
             ty::TyBool => {
-                self.memory().read_scalar(ptr, ptr_align, Size::from_bytes(1))?.to_bool()?;
+                self.memory.read_scalar(ptr, ptr_align, Size::from_bytes(1))?.to_bool()?;
             }
             ty::TyChar => {
-                let c = self.memory().read_scalar(ptr, ptr_align, Size::from_bytes(4))?.to_bits(Size::from_bytes(4))? as u32;
+                let c = self.memory.read_scalar(ptr, ptr_align, Size::from_bytes(4))?.to_bits(Size::from_bytes(4))? as u32;
                 match ::std::char::from_u32(c) {
                     Some(..) => (),
                     None => return err!(InvalidChar(c as u128)),
@@ -1457,7 +1424,7 @@ pub fn validate_ptr_target(
             }
 
             ty::TyFnPtr(_) => {
-                self.memory().read_ptr_sized(ptr, ptr_align)?;
+                self.memory.read_ptr_sized(ptr, ptr_align)?;
             },
             ty::TyRef(_, rty, _) |
             ty::TyRawPtr(ty::TypeAndMut { ty: rty, .. }) => {
@@ -1472,7 +1439,7 @@ pub fn validate_ptr_target(
 
                 if let layout::Abi::Scalar(ref scalar) = self.layout_of(ty)?.abi {
                     let size = scalar.value.size(self);
-                    self.memory().read_scalar(ptr, ptr_align, size)?;
+                    self.memory.read_scalar(ptr, ptr_align, size)?;
                 }
             }
 
@@ -1493,7 +1460,7 @@ pub fn try_read_by_ref(&self, mut val: Value, ty: Ty<'tcx>) -> EvalResult<'tcx,
 
     pub fn try_read_value(&self, ptr: Scalar, ptr_align: Align, ty: Ty<'tcx>) -> EvalResult<'tcx, Option<Value>> {
         let layout = self.layout_of(ty)?;
-        self.memory().check_align(ptr, ptr_align)?;
+        self.memory.check_align(ptr, ptr_align)?;
 
         if layout.size.bytes() == 0 {
             return Ok(Some(Value::Scalar(Scalar::undef())));
@@ -1506,7 +1473,7 @@ pub fn try_read_value(&self, ptr: Scalar, ptr_align: Align, ty: Ty<'tcx>) -> Eva
 
         match layout.abi {
             layout::Abi::Scalar(..) => {
-                let scalar = self.memory().read_scalar(ptr, ptr_align, layout.size)?;
+                let scalar = self.memory.read_scalar(ptr, ptr_align, layout.size)?;
                 Ok(Some(Value::Scalar(scalar)))
             }
             layout::Abi::ScalarPair(ref a, ref b) => {
@@ -1515,8 +1482,8 @@ pub fn try_read_value(&self, ptr: Scalar, ptr_align: Align, ty: Ty<'tcx>) -> Eva
                 let a_ptr = ptr;
                 let b_offset = a_size.abi_align(b.align(self));
                 let b_ptr = ptr.offset(b_offset, self)?.into();
-                let a_val = self.memory().read_scalar(a_ptr, ptr_align, a_size)?;
-                let b_val = self.memory().read_scalar(b_ptr, ptr_align, b_size)?;
+                let a_val = self.memory.read_scalar(a_ptr, ptr_align, a_size)?;
+                let b_val = self.memory.read_scalar(b_ptr, ptr_align, b_size)?;
                 Ok(Some(Value::ScalarPair(a_val, b_val)))
             }
             _ => Ok(None),
@@ -1524,11 +1491,11 @@ pub fn try_read_value(&self, ptr: Scalar, ptr_align: Align, ty: Ty<'tcx>) -> Eva
     }
 
     pub fn frame(&self) -> &Frame<'mir, 'tcx> {
-        self.stack().last().expect("no call frames exist")
+        self.stack.last().expect("no call frames exist")
     }
 
     pub fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
-        self.stack_mut().last_mut().expect("no call frames exist")
+        self.stack.last_mut().expect("no call frames exist")
     }
 
     pub(super) fn mir(&self) -> &'mir mir::Mir<'tcx> {
@@ -1536,7 +1503,7 @@ pub(super) fn mir(&self) -> &'mir mir::Mir<'tcx> {
     }
 
     pub fn substs(&self) -> &'tcx Substs<'tcx> {
-        if let Some(frame) = self.stack().last() {
+        if let Some(frame) = self.stack.last() {
             frame.instance.substs
         } else {
             Substs::empty()
@@ -1682,7 +1649,7 @@ pub fn dump_local(&self, place: Place) {
                 }
                 write!(msg, ":").unwrap();
 
-                match self.stack()[frame].get_local(local) {
+                match self.stack[frame].get_local(local) {
                     Err(err) => {
                         if let EvalErrorKind::DeadLocal = err.kind {
                             write!(msg, " is dead").unwrap();
@@ -1717,13 +1684,13 @@ pub fn dump_local(&self, place: Place) {
                 }
 
                 trace!("{}", msg);
-                self.memory().dump_allocs(allocs);
+                self.memory.dump_allocs(allocs);
             }
             Place::Ptr { ptr, align, .. } => {
                 match ptr {
                     Scalar::Ptr(ptr) => {
                         trace!("by align({}) ref:", align.abi());
-                        self.memory().dump_alloc(ptr.alloc_id);
+                        self.memory.dump_alloc(ptr.alloc_id);
                     }
                     ptr => trace!(" integral by ref: {:?}", ptr),
                 }
@@ -1736,12 +1703,12 @@ pub fn modify_local<F>(&mut self, frame: usize, local: mir::Local, f: F) -> Eval
     where
         F: FnOnce(&mut Self, Value) -> EvalResult<'tcx, Value>,
     {
-        let val = self.stack()[frame].get_local(local)?;
+        let val = self.stack[frame].get_local(local)?;
         let new_val = f(self, val)?;
-        self.stack_mut()[frame].set_local(local, new_val)?;
+        self.stack[frame].set_local(local, new_val)?;
         // FIXME(solson): Run this when setting to Undef? (See previous version of this code.)
-        // if let Value::ByRef(ptr) = self.stack()[frame].get_local(local) {
-        //     self.memory().deallocate(ptr)?;
+        // if let Value::ByRef(ptr) = self.stack[frame].get_local(local) {
+        //     self.memory.deallocate(ptr)?;
         // }
         Ok(())
     }
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index 98ab361c239ee7b5d9273b86fbac6feb8c9b5019..e8994cdac4c2eabf6cdb536d4d45874f7eef1921 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -32,6 +32,7 @@ pub enum MemoryKind<T> {
 // Top-level interpreter memory
 ////////////////////////////////////////////////////////////////////////////////
 
+#[derive(Clone)]
 pub struct Memory<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
     /// Additional data required by the Machine
     pub data: M::MemoryData,
@@ -48,21 +49,6 @@ pub struct Memory<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
     pub tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
 }
 
-impl<'a, 'mir, 'tcx, M> Clone for Memory<'a, 'mir, 'tcx, M>
-    where M: Machine<'mir, 'tcx>,
-          'tcx: 'a + 'mir,
-{
-    fn clone(&self) -> Self {
-        Memory {
-            data: self.data.clone(),
-            alloc_kind: self.alloc_kind.clone(),
-            alloc_map: self.alloc_map.clone(),
-            cur_frame: self.cur_frame.clone(),
-            tcx: self.tcx.clone(),
-        }
-    }
-}
-
 impl<'a, 'mir, 'tcx, M> Eq for Memory<'a, 'mir, 'tcx, M>
     where M: Machine<'mir, 'tcx>,
           'tcx: 'a + 'mir,
@@ -1067,12 +1053,12 @@ fn memory(&self) -> &Memory<'a, 'mir, 'tcx, M> {
 impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> HasMemory<'a, 'mir, 'tcx, M> for EvalContext<'a, 'mir, 'tcx, M> {
     #[inline]
     fn memory_mut(&mut self) -> &mut Memory<'a, 'mir, 'tcx, M> {
-        self.memory_mut()
+        &mut self.memory
     }
 
     #[inline]
     fn memory(&self) -> &Memory<'a, 'mir, 'tcx, M> {
-        self.memory()
+        &self.memory
     }
 }
 
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index bde2e5945f5d47c0ba1fccee74d63b7bc62bd6f4..bb8e5c99d499be8fc3e64017db1fff181a851d1a 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -201,7 +201,7 @@ pub fn read_place(&self, place: Place) -> EvalResult<'tcx, Value> {
                 assert_eq!(extra, PlaceExtra::None);
                 Ok(Value::ByRef(ptr, align))
             }
-            Place::Local { frame, local } => self.stack()[frame].get_local(local),
+            Place::Local { frame, local } => self.stack[frame].get_local(local),
         }
     }
 
@@ -261,7 +261,7 @@ pub fn place_field(
         let (base_ptr, base_align, base_extra) = match base {
             Place::Ptr { ptr, align, extra } => (ptr, align, extra),
             Place::Local { frame, local } => {
-                match (&self.stack()[frame].get_local(local)?, &base_layout.abi) {
+                match (&self.stack[frame].get_local(local)?, &base_layout.abi) {
                     // in case the field covers the entire type, just return the value
                     (&Value::Scalar(_), &layout::Abi::Scalar(_)) |
                     (&Value::ScalarPair(..), &layout::Abi::ScalarPair(..))
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index e8eabe2b1bf6ff36990ee13ad7f0830a4a271592..dac7c0610c0ef2e503064086706f2b23f43bd030 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -2,18 +2,22 @@
 //!
 //! The main entry point is the `step` method.
 
+use std::hash::Hash;
+
 use rustc::mir;
 
 use rustc::mir::interpret::EvalResult;
 use super::{EvalContext, Machine};
 
-impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
+impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
+    where M: Clone + Eq + Hash,
+{
     pub fn inc_step_counter_and_detect_loops(&mut self, n: usize) {
         self.steps_until_detector_enabled
             = self.steps_until_detector_enabled.saturating_sub(n);
 
         if self.steps_until_detector_enabled == 0 {
-            let _ = self.loop_detector.observe(&self.state); // TODO: Handle error
+            let _ = self.loop_detector.observe(&self.machine, &self.stack, &self.memory); // TODO: Handle error
 
             // FIXME(#49980): make this warning a lint
             self.tcx.sess.span_warn(self.frame().span, "Constant evaluating a complex constant, this might take some time");
@@ -23,7 +27,7 @@ pub fn inc_step_counter_and_detect_loops(&mut self, n: usize) {
 
     /// Returns true as long as there are more things to do.
     pub fn step(&mut self) -> EvalResult<'tcx, bool> {
-        if self.stack().is_empty() {
+        if self.stack.is_empty() {
             return Ok(false);
         }
 
@@ -57,7 +61,7 @@ fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> EvalResult<'tcx> {
         // *before* executing the statement.
         let frame_idx = self.cur_frame();
         self.tcx.span = stmt.source_info.span;
-        self.memory_mut().tcx.span = stmt.source_info.span;
+        self.memory.tcx.span = stmt.source_info.span;
 
         match stmt.kind {
             Assign(ref place, ref rvalue) => self.eval_rvalue_into_place(rvalue, place)?,
@@ -106,16 +110,16 @@ fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> EvalResult<'tcx> {
             InlineAsm { .. } => return err!(InlineAsm),
         }
 
-        self.stack_mut()[frame_idx].stmt += 1;
+        self.stack[frame_idx].stmt += 1;
         Ok(())
     }
 
     fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> EvalResult<'tcx> {
         trace!("{:?}", terminator.kind);
         self.tcx.span = terminator.source_info.span;
-        self.memory_mut().tcx.span = terminator.source_info.span;
+        self.memory.tcx.span = terminator.source_info.span;
         self.eval_terminator(terminator)?;
-        if !self.stack().is_empty() {
+        if !self.stack.is_empty() {
             trace!("// {:?}", self.frame().block);
         }
         Ok(())
diff --git a/src/librustc_mir/interpret/terminator/mod.rs b/src/librustc_mir/interpret/terminator/mod.rs
index 61670769d01ad40562a548e4ce078fe548079d62..2994b1b387f3fa37c2e47a3621246da76bfbaef9 100644
--- a/src/librustc_mir/interpret/terminator/mod.rs
+++ b/src/librustc_mir/interpret/terminator/mod.rs
@@ -71,7 +71,7 @@ pub(super) fn eval_terminator(
                 let (fn_def, sig) = match func.ty.sty {
                     ty::TyFnPtr(sig) => {
                         let fn_ptr = self.value_to_scalar(func)?.to_ptr()?;
-                        let instance = self.memory().get_fn(fn_ptr)?;
+                        let instance = self.memory.get_fn(fn_ptr)?;
                         let instance_ty = instance.ty(*self.tcx);
                         match instance_ty.sty {
                             ty::TyFnDef(..) => {
@@ -377,14 +377,14 @@ fn eval_fn_call(
             }
             // cannot use the shim here, because that will only result in infinite recursion
             ty::InstanceDef::Virtual(_, idx) => {
-                let ptr_size = self.memory().pointer_size();
+                let ptr_size = self.memory.pointer_size();
                 let ptr_align = self.tcx.data_layout.pointer_align;
                 let (ptr, vtable) = self.into_ptr_vtable_pair(args[0].value)?;
-                let fn_ptr = self.memory().read_ptr_sized(
+                let fn_ptr = self.memory.read_ptr_sized(
                     vtable.offset(ptr_size * (idx as u64 + 3), &self)?,
                     ptr_align
                 )?.to_ptr()?;
-                let instance = self.memory().get_fn(fn_ptr)?;
+                let instance = self.memory.get_fn(fn_ptr)?;
                 let mut args = args.to_vec();
                 let ty = self.layout_of(args[0].ty)?.field(&self, 0)?.ty;
                 args[0].ty = ty;
diff --git a/src/librustc_mir/interpret/traits.rs b/src/librustc_mir/interpret/traits.rs
index 2a9129498ad52caa6b23338614bcb6eb2abc92c7..b6c7feda19fa813377fff50213a3b046deb3b96c 100644
--- a/src/librustc_mir/interpret/traits.rs
+++ b/src/librustc_mir/interpret/traits.rs
@@ -25,26 +25,26 @@ pub fn get_vtable(
         let size = layout.size.bytes();
         let align = layout.align.abi();
 
-        let ptr_size = self.memory().pointer_size();
+        let ptr_size = self.memory.pointer_size();
         let ptr_align = self.tcx.data_layout.pointer_align;
         let methods = self.tcx.vtable_methods(trait_ref);
-        let vtable = self.memory_mut().allocate(
+        let vtable = self.memory.allocate(
             ptr_size * (3 + methods.len() as u64),
             ptr_align,
             MemoryKind::Stack,
         )?;
 
         let drop = ::monomorphize::resolve_drop_in_place(*self.tcx, ty);
-        let drop = self.memory_mut().create_fn_alloc(drop);
-        self.memory_mut().write_ptr_sized_unsigned(vtable, ptr_align, drop.into())?;
+        let drop = self.memory.create_fn_alloc(drop);
+        self.memory.write_ptr_sized_unsigned(vtable, ptr_align, drop.into())?;
 
         let size_ptr = vtable.offset(ptr_size, &self)?;
-        self.memory_mut().write_ptr_sized_unsigned(size_ptr, ptr_align, Scalar::Bits {
+        self.memory.write_ptr_sized_unsigned(size_ptr, ptr_align, Scalar::Bits {
             bits: size as u128,
             defined: ptr_size.bits() as u8,
         })?;
         let align_ptr = vtable.offset(ptr_size * 2, &self)?;
-        self.memory_mut().write_ptr_sized_unsigned(align_ptr, ptr_align, Scalar::Bits {
+        self.memory.write_ptr_sized_unsigned(align_ptr, ptr_align, Scalar::Bits {
             bits: align as u128,
             defined: ptr_size.bits() as u8,
         })?;
@@ -52,13 +52,13 @@ pub fn get_vtable(
         for (i, method) in methods.iter().enumerate() {
             if let Some((def_id, substs)) = *method {
                 let instance = self.resolve(def_id, substs)?;
-                let fn_ptr = self.memory_mut().create_fn_alloc(instance);
+                let fn_ptr = self.memory.create_fn_alloc(instance);
                 let method_ptr = vtable.offset(ptr_size * (3 + i as u64), &self)?;
-                self.memory_mut().write_ptr_sized_unsigned(method_ptr, ptr_align, fn_ptr.into())?;
+                self.memory.write_ptr_sized_unsigned(method_ptr, ptr_align, fn_ptr.into())?;
             }
         }
 
-        self.memory_mut().mark_static_initialized(
+        self.memory.mark_static_initialized(
             vtable.alloc_id,
             Mutability::Immutable,
         )?;
@@ -76,7 +76,7 @@ pub fn read_drop_type_from_vtable(
         match self.read_ptr(vtable, pointer_align, self.tcx.mk_nil_ptr())? {
             // some values don't need to call a drop impl, so the value is null
             Value::Scalar(Scalar::Bits { bits: 0, defined} ) if defined == pointer_size => Ok(None),
-            Value::Scalar(Scalar::Ptr(drop_fn)) => self.memory().get_fn(drop_fn).map(Some),
+            Value::Scalar(Scalar::Ptr(drop_fn)) => self.memory.get_fn(drop_fn).map(Some),
             _ => err!(ReadBytesAsPointer),
         }
     }
@@ -85,10 +85,10 @@ pub fn read_size_and_align_from_vtable(
         &self,
         vtable: Pointer,
     ) -> EvalResult<'tcx, (Size, Align)> {
-        let pointer_size = self.memory().pointer_size();
+        let pointer_size = self.memory.pointer_size();
         let pointer_align = self.tcx.data_layout.pointer_align;
-        let size = self.memory().read_ptr_sized(vtable.offset(pointer_size, self)?, pointer_align)?.to_bits(pointer_size)? as u64;
-        let align = self.memory().read_ptr_sized(
+        let size = self.memory.read_ptr_sized(vtable.offset(pointer_size, self)?, pointer_align)?.to_bits(pointer_size)? as u64;
+        let align = self.memory.read_ptr_sized(
             vtable.offset(pointer_size * 2, self)?,
             pointer_align
         )?.to_bits(pointer_size)? as u64;