Auto merge of #55393 - oli-obk:immediate_immediately, r=RalfJung

Rename `Value` to `Immediate` for miri

r? @RalfJung

14 files changed, 196 insertions, 189 deletions

diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index 38ab21b7c8c..2658d7f59a0 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -32,7 +32,7 @@ use syntax::ast::Mutability;
 use syntax::source_map::{Span, DUMMY_SP};
 
 use interpret::{self,
-    PlaceTy, MemPlace, OpTy, Operand, Value, Scalar, ConstValue, Pointer,
+    PlaceTy, MemPlace, OpTy, Operand, Immediate, Scalar, ConstValue, Pointer,
     EvalResult, EvalError, EvalErrorKind, GlobalId, EvalContext, StackPopCleanup,
     Allocation, AllocId, MemoryKind,
     snapshot, RefTracking,
@@ -115,7 +115,7 @@ pub fn op_to_const<'tcx>(
             _ => false,
         };
     let normalized_op = if normalize {
-        ecx.try_read_value(op)?
+        ecx.try_read_immediate(op)?
     } else {
         match op.op {
             Operand::Indirect(mplace) => Err(mplace),
@@ -137,9 +137,9 @@ pub fn op_to_const<'tcx>(
             let alloc = ecx.tcx.intern_const_alloc(alloc);
             ConstValue::ByRef(ptr.alloc_id, alloc, ptr.offset)
         },
-        Ok(Value::Scalar(x)) =>
+        Ok(Immediate::Scalar(x)) =>
             ConstValue::Scalar(x.not_undef()?),
-        Ok(Value::ScalarPair(a, b)) =>
+        Ok(Immediate::ScalarPair(a, b)) =>
             ConstValue::ScalarPair(a.not_undef()?, b.not_undef()?),
     };
     Ok(ty::Const::from_const_value(ecx.tcx.tcx, val, op.layout.ty))
diff --git a/src/librustc_mir/interpret/cast.rs b/src/librustc_mir/interpret/cast.rs
index b2c8cba4802..01dd995bbee 100644
--- a/src/librustc_mir/interpret/cast.rs
+++ b/src/librustc_mir/interpret/cast.rs
@@ -19,7 +19,7 @@ use rustc::mir::interpret::{
 use rustc::mir::CastKind;
 use rustc_apfloat::Float;
 
-use super::{EvalContext, Machine, PlaceTy, OpTy, Value};
+use super::{EvalContext, Machine, PlaceTy, OpTy, Immediate};
 
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
     fn type_is_fat_ptr(&self, ty: Ty<'tcx>) -> bool {
@@ -45,7 +45,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
             Misc => {
                 let src_layout = src.layout;
-                let src = self.read_value(src)?;
+                let src = self.read_immediate(src)?;
 
                 let src = if M::ENABLE_PTR_TRACKING_HOOKS && src_layout.ty.is_region_ptr() {
                     // The only `Misc` casts on references are those creating raw pointers.
@@ -61,14 +61,14 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 if self.type_is_fat_ptr(src_layout.ty) {
                     match (src, self.type_is_fat_ptr(dest.layout.ty)) {
                         // pointers to extern types
-                        (Value::Scalar(_),_) |
+                        (Immediate::Scalar(_),_) |
                         // slices and trait objects to other slices/trait objects
-                        (Value::ScalarPair(..), true) => {
-                            // No change to value
-                            self.write_value(src, dest)?;
+                        (Immediate::ScalarPair(..), true) => {
+                            // No change to immediate
+                            self.write_immediate(src, dest)?;
                         }
                         // slices and trait objects to thin pointers (dropping the metadata)
-                        (Value::ScalarPair(data, _), false) => {
+                        (Immediate::ScalarPair(data, _), false) => {
                             self.write_scalar(data, dest)?;
                         }
                     }
@@ -118,11 +118,11 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             }
 
             UnsafeFnPointer => {
-                let src = self.read_value(src)?;
+                let src = self.read_immediate(src)?;
                 match dest.layout.ty.sty {
                     ty::FnPtr(_) => {
                         // No change to value
-                        self.write_value(*src, dest)?;
+                        self.write_immediate(*src, dest)?;
                     }
                     ref other => bug!("fn to unsafe fn cast on {:?}", other),
                 }
@@ -144,8 +144,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                             ty::ClosureKind::FnOnce,
                         );
                         let fn_ptr = self.memory.create_fn_alloc(instance).with_default_tag();
-                        let val = Value::Scalar(Scalar::Ptr(fn_ptr.into()).into());
-                        self.write_value(val, dest)?;
+                        let val = Immediate::Scalar(Scalar::Ptr(fn_ptr.into()).into());
+                        self.write_immediate(val, dest)?;
                     }
                     ref other => bug!("closure fn pointer on {:?}", other),
                 }
@@ -326,24 +326,28 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
             (&ty::Array(_, length), &ty::Slice(_)) => {
-                let ptr = self.read_value(src)?.to_scalar_ptr()?;
+                let ptr = self.read_immediate(src)?.to_scalar_ptr()?;
                 // u64 cast is from usize to u64, which is always good
-                let val = Value::new_slice(ptr, length.unwrap_usize(self.tcx.tcx), self.tcx.tcx);
-                self.write_value(val, dest)
+                let val = Immediate::new_slice(
+                    ptr,
+                    length.unwrap_usize(self.tcx.tcx),
+                    self.tcx.tcx,
+                );
+                self.write_immediate(val, dest)
             }
             (&ty::Dynamic(..), &ty::Dynamic(..)) => {
                 // For now, upcasts are limited to changes in marker
                 // traits, and hence never actually require an actual
                 // change to the vtable.
-                let val = self.read_value(src)?;
-                self.write_value(*val, dest)
+                let val = self.read_immediate(src)?;
+                self.write_immediate(*val, dest)
             }
             (_, &ty::Dynamic(ref data, _)) => {
                 // Initial cast from sized to dyn trait
                 let vtable = self.get_vtable(src_pointee_ty, data.principal())?;
-                let ptr = self.read_value(src)?.to_scalar_ptr()?;
-                let val = Value::new_dyn_trait(ptr, vtable);
-                self.write_value(val, dest)
+                let ptr = self.read_immediate(src)?.to_scalar_ptr()?;
+                let val = Immediate::new_dyn_trait(ptr, vtable);
+                self.write_immediate(val, dest)
             }
 
             _ => bug!("invalid unsizing {:?} -> {:?}", src.layout.ty, dest.layout.ty),
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index bc7ad16dc97..8cb3f9d4d74 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -32,7 +32,7 @@ use rustc::mir::interpret::{
 use rustc_data_structures::fx::FxHashMap;
 
 use super::{
-    Value, Operand, MemPlace, MPlaceTy, Place, PlaceTy, ScalarMaybeUndef,
+    Immediate, Operand, MemPlace, MPlaceTy, Place, PlaceTy, ScalarMaybeUndef,
     Memory, Machine
 };
 
@@ -333,9 +333,9 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tc
         self.layout_of(local_ty)
     }
 
-    pub fn str_to_value(&mut self, s: &str) -> EvalResult<'tcx, Value<M::PointerTag>> {
+    pub fn str_to_immediate(&mut self, s: &str) -> EvalResult<'tcx, Immediate<M::PointerTag>> {
         let ptr = self.memory.allocate_static_bytes(s.as_bytes()).with_default_tag();
-        Ok(Value::new_slice(Scalar::Ptr(ptr), s.len() as u64, self.tcx.tcx))
+        Ok(Immediate::new_slice(Scalar::Ptr(ptr), s.len() as u64, self.tcx.tcx))
     }
 
     /// Return the actual dynamic size and alignment of the place at the given type.
@@ -457,11 +457,11 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tc
 
         // don't allocate at all for trivial constants
         if mir.local_decls.len() > 1 {
-            // We put some marker value into the locals that we later want to initialize.
+            // We put some marker immediate into the locals that we later want to initialize.
             // This can be anything except for LocalValue::Dead -- because *that* is the
             // value we use for things that we know are initially dead.
             let dummy =
-                LocalValue::Live(Operand::Immediate(Value::Scalar(ScalarMaybeUndef::Undef)));
+                LocalValue::Live(Operand::Immediate(Immediate::Scalar(ScalarMaybeUndef::Undef)));
             let mut locals = IndexVec::from_elem(dummy, &mir.local_decls);
             // Return place is handled specially by the `eval_place` functions, and the
             // entry in `locals` should never be used. Make it dead, to be sure.
@@ -652,13 +652,13 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tc
                             ptr => write!(msg, " by integral ref: {:?}", ptr).unwrap(),
                         }
                     }
-                    Ok(Operand::Immediate(Value::Scalar(val))) => {
+                    Ok(Operand::Immediate(Immediate::Scalar(val))) => {
                         write!(msg, " {:?}", val).unwrap();
                         if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val {
                             allocs.push(ptr.alloc_id);
                         }
                     }
-                    Ok(Operand::Immediate(Value::ScalarPair(val1, val2))) => {
+                    Ok(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => {
                         write!(msg, " ({:?}, {:?})", val1, val2).unwrap();
                         if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val1 {
                             allocs.push(ptr.alloc_id);
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 5fa0fef3693..bed938a534f 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -115,8 +115,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             | "add_with_overflow"
             | "sub_with_overflow"
             | "mul_with_overflow" => {
-                let lhs = self.read_value(args[0])?;
-                let rhs = self.read_value(args[1])?;
+                let lhs = self.read_immediate(args[0])?;
+                let rhs = self.read_immediate(args[1])?;
                 let (bin_op, ignore_overflow) = match intrinsic_name {
                     "overflowing_add" => (BinOp::Add, true),
                     "overflowing_sub" => (BinOp::Sub, true),
@@ -133,8 +133,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 }
             }
             "unchecked_shl" | "unchecked_shr" => {
-                let l = self.read_value(args[0])?;
-                let r = self.read_value(args[1])?;
+                let l = self.read_immediate(args[0])?;
+                let r = self.read_immediate(args[1])?;
                 let bin_op = match intrinsic_name {
                     "unchecked_shl" => BinOp::Shl,
                     "unchecked_shr" => BinOp::Shr,
@@ -172,8 +172,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         // Some fn calls are actually BinOp intrinsics
         if let Some((op, oflo)) = self.tcx.is_binop_lang_item(def_id) {
             let dest = dest.expect("128 lowerings can't diverge");
-            let l = self.read_value(args[0])?;
-            let r = self.read_value(args[1])?;
+            let l = self.read_immediate(args[0])?;
+            let r = self.read_immediate(args[1])?;
             if oflo {
                 self.binop_with_overflow(op, l, r, dest)?;
             } else {
@@ -183,7 +183,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         } else if Some(def_id) == self.tcx.lang_items().panic_fn() {
             assert!(args.len() == 1);
             // &(&'static str, &'static str, u32, u32)
-            let ptr = self.read_value(args[0])?;
+            let ptr = self.read_immediate(args[0])?;
             let place = self.ref_to_mplace(ptr)?;
             let (msg, file, line, col) = (
                 self.mplace_field(place, 0)?,
@@ -192,9 +192,9 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 self.mplace_field(place, 3)?,
             );
 
-            let msg_place = self.ref_to_mplace(self.read_value(msg.into())?)?;
+            let msg_place = self.ref_to_mplace(self.read_immediate(msg.into())?)?;
             let msg = Symbol::intern(self.read_str(msg_place)?);
-            let file_place = self.ref_to_mplace(self.read_value(file.into())?)?;
+            let file_place = self.ref_to_mplace(self.read_immediate(file.into())?)?;
             let file = Symbol::intern(self.read_str(file_place)?);
             let line = self.read_scalar(line.into())?.to_u32()?;
             let col = self.read_scalar(col.into())?.to_u32()?;
@@ -203,7 +203,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             assert!(args.len() == 2);
             // &'static str, &(&'static str, u32, u32)
             let msg = args[0];
-            let ptr = self.read_value(args[1])?;
+            let ptr = self.read_immediate(args[1])?;
             let place = self.ref_to_mplace(ptr)?;
             let (file, line, col) = (
                 self.mplace_field(place, 0)?,
@@ -211,9 +211,9 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 self.mplace_field(place, 2)?,
             );
 
-            let msg_place = self.ref_to_mplace(self.read_value(msg.into())?)?;
+            let msg_place = self.ref_to_mplace(self.read_immediate(msg.into())?)?;
             let msg = Symbol::intern(self.read_str(msg_place)?);
-            let file_place = self.ref_to_mplace(self.read_value(file.into())?)?;
+            let file_place = self.ref_to_mplace(self.read_immediate(file.into())?)?;
             let file = Symbol::intern(self.read_str(file_place)?);
             let line = self.read_scalar(line.into())?.to_u32()?;
             let col = self.read_scalar(col.into())?.to_u32()?;
diff --git a/src/librustc_mir/interpret/mod.rs b/src/librustc_mir/interpret/mod.rs
index 5620ea4cee2..6b31c675cc7 100644
--- a/src/librustc_mir/interpret/mod.rs
+++ b/src/librustc_mir/interpret/mod.rs
@@ -36,6 +36,6 @@ pub use self::memory::{Memory, MemoryKind};
 
 pub use self::machine::{Machine, AllocMap, MayLeak};
 
-pub use self::operand::{ScalarMaybeUndef, Value, ValTy, Operand, OpTy};
+pub use self::operand::{ScalarMaybeUndef, Immediate, ImmTy, Operand, OpTy};
 
 pub use self::validity::RefTracking;
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index d0a32161485..0da03009448 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -144,34 +144,34 @@ impl<'tcx, Tag> ScalarMaybeUndef<Tag> {
 /// primitive values (`ScalarPair`). It allows Miri to avoid making allocations for checked binary
 /// operations and fat pointers. This idea was taken from rustc's codegen.
 /// In particular, thanks to `ScalarPair`, arithmetic operations and casts can be entirely
-/// defined on `Value`, and do not have to work with a `Place`.
+/// defined on `Immediate`, and do not have to work with a `Place`.
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
-pub enum Value<Tag=(), Id=AllocId> {
+pub enum Immediate<Tag=(), Id=AllocId> {
     Scalar(ScalarMaybeUndef<Tag, Id>),
     ScalarPair(ScalarMaybeUndef<Tag, Id>, ScalarMaybeUndef<Tag, Id>),
 }
 
-impl Value {
+impl Immediate {
     #[inline]
-    pub fn with_default_tag<Tag>(self) -> Value<Tag>
+    pub fn with_default_tag<Tag>(self) -> Immediate<Tag>
         where Tag: Default
     {
         match self {
-            Value::Scalar(x) => Value::Scalar(x.with_default_tag()),
-            Value::ScalarPair(x, y) =>
-                Value::ScalarPair(x.with_default_tag(), y.with_default_tag()),
+            Immediate::Scalar(x) => Immediate::Scalar(x.with_default_tag()),
+            Immediate::ScalarPair(x, y) =>
+                Immediate::ScalarPair(x.with_default_tag(), y.with_default_tag()),
         }
     }
 }
 
-impl<'tcx, Tag> Value<Tag> {
+impl<'tcx, Tag> Immediate<Tag> {
     #[inline]
-    pub fn erase_tag(self) -> Value
+    pub fn erase_tag(self) -> Immediate
     {
         match self {
-            Value::Scalar(x) => Value::Scalar(x.erase_tag()),
-            Value::ScalarPair(x, y) =>
-                Value::ScalarPair(x.erase_tag(), y.erase_tag()),
+            Immediate::Scalar(x) => Immediate::Scalar(x.erase_tag()),
+            Immediate::ScalarPair(x, y) =>
+                Immediate::ScalarPair(x.erase_tag(), y.erase_tag()),
         }
     }
 
@@ -180,18 +180,21 @@ impl<'tcx, Tag> Value<Tag> {
         len: u64,
         cx: impl HasDataLayout
     ) -> Self {
-        Value::ScalarPair(val.into(), Scalar::from_uint(len, cx.data_layout().pointer_size).into())
+        Immediate::ScalarPair(
+            val.into(),
+            Scalar::from_uint(len, cx.data_layout().pointer_size).into(),
+        )
     }
 
     pub fn new_dyn_trait(val: Scalar<Tag>, vtable: Pointer<Tag>) -> Self {
-        Value::ScalarPair(val.into(), Scalar::Ptr(vtable).into())
+        Immediate::ScalarPair(val.into(), Scalar::Ptr(vtable).into())
     }
 
     #[inline]
     pub fn to_scalar_or_undef(self) -> ScalarMaybeUndef<Tag> {
         match self {
-            Value::Scalar(val) => val,
-            Value::ScalarPair(..) => bug!("Got a fat pointer where a scalar was expected"),
+            Immediate::Scalar(val) => val,
+            Immediate::ScalarPair(..) => bug!("Got a fat pointer where a scalar was expected"),
         }
     }
 
@@ -203,18 +206,18 @@ impl<'tcx, Tag> Value<Tag> {
     #[inline]
     pub fn to_scalar_pair(self) -> EvalResult<'tcx, (Scalar<Tag>, Scalar<Tag>)> {
         match self {
-            Value::Scalar(..) => bug!("Got a thin pointer where a scalar pair was expected"),
-            Value::ScalarPair(a, b) => Ok((a.not_undef()?, b.not_undef()?))
+            Immediate::Scalar(..) => bug!("Got a thin pointer where a scalar pair was expected"),
+            Immediate::ScalarPair(a, b) => Ok((a.not_undef()?, b.not_undef()?))
         }
     }
 
-    /// Convert the value into a pointer (or a pointer-sized integer).
+    /// Convert the immediate into a pointer (or a pointer-sized integer).
     /// Throws away the second half of a ScalarPair!
     #[inline]
     pub fn to_scalar_ptr(self) -> EvalResult<'tcx, Scalar<Tag>> {
         match self {
-            Value::Scalar(ptr) |
-            Value::ScalarPair(ptr, _) => ptr.not_undef(),
+            Immediate::Scalar(ptr) |
+            Immediate::ScalarPair(ptr, _) => ptr.not_undef(),
         }
     }
 
@@ -223,25 +226,25 @@ impl<'tcx, Tag> Value<Tag> {
     #[inline]
     pub fn to_meta(self) -> EvalResult<'tcx, Option<Scalar<Tag>>> {
         Ok(match self {
-            Value::Scalar(_) => None,
-            Value::ScalarPair(_, meta) => Some(meta.not_undef()?),
+            Immediate::Scalar(_) => None,
+            Immediate::ScalarPair(_, meta) => Some(meta.not_undef()?),
         })
     }
 }
 
-// ScalarPair needs a type to interpret, so we often have a value and a type together
+// ScalarPair needs a type to interpret, so we often have an immediate and a type together
 // as input for binary and cast operations.
 #[derive(Copy, Clone, Debug)]
-pub struct ValTy<'tcx, Tag=()> {
-    value: Value<Tag>,
+pub struct ImmTy<'tcx, Tag=()> {
+    immediate: Immediate<Tag>,
     pub layout: TyLayout<'tcx>,
 }
 
-impl<'tcx, Tag> ::std::ops::Deref for ValTy<'tcx, Tag> {
-    type Target = Value<Tag>;
+impl<'tcx, Tag> ::std::ops::Deref for ImmTy<'tcx, Tag> {
+    type Target = Immediate<Tag>;
     #[inline(always)]
-    fn deref(&self) -> &Value<Tag> {
-        &self.value
+    fn deref(&self) -> &Immediate<Tag> {
+        &self.immediate
     }
 }
 
@@ -250,7 +253,7 @@ impl<'tcx, Tag> ::std::ops::Deref for ValTy<'tcx, Tag> {
 /// memory and to avoid having to store arbitrary-sized data here.
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub enum Operand<Tag=(), Id=AllocId> {
-    Immediate(Value<Tag, Id>),
+    Immediate(Immediate<Tag, Id>),
     Indirect(MemPlace<Tag, Id>),
 }
 
@@ -288,11 +291,11 @@ impl<Tag> Operand<Tag> {
     }
 
     #[inline]
-    pub fn to_immediate(self) -> Value<Tag>
+    pub fn to_immediate(self) -> Immediate<Tag>
         where Tag: ::std::fmt::Debug
     {
         match self {
-            Operand::Immediate(val) => val,
+            Operand::Immediate(imm) => imm,
             _ => bug!("to_immediate: expected Operand::Immediate, got {:?}", self),
 
         }
@@ -323,11 +326,11 @@ impl<'tcx, Tag: Copy> From<MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
     }
 }
 
-impl<'tcx, Tag> From<ValTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
+impl<'tcx, Tag> From<ImmTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
     #[inline(always)]
-    fn from(val: ValTy<'tcx, Tag>) -> Self {
+    fn from(val: ImmTy<'tcx, Tag>) -> Self {
         OpTy {
-            op: Operand::Immediate(val.value),
+            op: Operand::Immediate(val.immediate),
             layout: val.layout
         }
     }
@@ -367,12 +370,12 @@ fn from_known_layout<'tcx>(
 }
 
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
-    /// Try reading a value in memory; this is interesting particularly for ScalarPair.
+    /// Try reading an immediate in memory; this is interesting particularly for ScalarPair.
     /// Return None if the layout does not permit loading this as a value.
-    pub(super) fn try_read_value_from_mplace(
+    pub(super) fn try_read_immediate_from_mplace(
         &self,
         mplace: MPlaceTy<'tcx, M::PointerTag>,
-    ) -> EvalResult<'tcx, Option<Value<M::PointerTag>>> {
+    ) -> EvalResult<'tcx, Option<Immediate<M::PointerTag>>> {
         if mplace.layout.is_unsized() {
             // Don't touch unsized
             return Ok(None);
@@ -383,14 +386,14 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             // Not all ZSTs have a layout we would handle below, so just short-circuit them
             // all here.
             self.memory.check_align(ptr, ptr_align)?;
-            return Ok(Some(Value::Scalar(Scalar::zst().into())));
+            return Ok(Some(Immediate::Scalar(Scalar::zst().into())));
         }
 
         let ptr = ptr.to_ptr()?;
         match mplace.layout.abi {
             layout::Abi::Scalar(..) => {
                 let scalar = self.memory.read_scalar(ptr, ptr_align, mplace.layout.size)?;
-                Ok(Some(Value::Scalar(scalar)))
+                Ok(Some(Immediate::Scalar(scalar)))
             }
             layout::Abi::ScalarPair(ref a, ref b) => {
                 let (a, b) = (&a.value, &b.value);
@@ -401,25 +404,25 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 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)?;
-                Ok(Some(Value::ScalarPair(a_val, b_val)))
+                Ok(Some(Immediate::ScalarPair(a_val, b_val)))
             }
             _ => Ok(None),
         }
     }
 
-    /// Try returning an immediate value for the operand.
-    /// If the layout does not permit loading this as a value, return where in memory
+    /// Try returning an immediate for the operand.
+    /// If the layout does not permit loading this as an immediate, return where in memory
     /// we can find the data.
     /// Note that for a given layout, this operation will either always fail or always
     /// succeed!  Whether it succeeds depends on whether the layout can be represented
-    /// in a `Value`, not on which data is stored there currently.
-    pub(crate) fn try_read_value(
+    /// in a `Immediate`, not on which data is stored there currently.
+    pub(crate) fn try_read_immediate(
         &self,
         src: OpTy<'tcx, M::PointerTag>,
-    ) -> EvalResult<'tcx, Result<Value<M::PointerTag>, MemPlace<M::PointerTag>>> {
+    ) -> EvalResult<'tcx, Result<Immediate<M::PointerTag>, MemPlace<M::PointerTag>>> {
         Ok(match src.try_as_mplace() {
             Ok(mplace) => {
-                if let Some(val) = self.try_read_value_from_mplace(mplace)? {
+                if let Some(val) = self.try_read_immediate_from_mplace(mplace)? {
                     Ok(val)
                 } else {
                     Err(*mplace)
@@ -429,14 +432,14 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         })
     }
 
-    /// Read a value from a place, asserting that that is possible with the given layout.
+    /// Read an immediate from a place, asserting that that is possible with the given layout.
     #[inline(always)]
-    pub fn read_value(
+    pub fn read_immediate(
         &self,
         op: OpTy<'tcx, M::PointerTag>
-    ) -> EvalResult<'tcx, ValTy<'tcx, M::PointerTag>> {
-        if let Ok(value) = self.try_read_value(op)? {
-            Ok(ValTy { value, layout: op.layout })
+    ) -> EvalResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
+        if let Ok(immediate) = self.try_read_immediate(op)? {
+            Ok(ImmTy { immediate, layout: op.layout })
         } else {
             bug!("primitive read failed for type: {:?}", op.layout.ty);
         }
@@ -447,10 +450,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         &self,
         op: OpTy<'tcx, M::PointerTag>
     ) -> EvalResult<'tcx, ScalarMaybeUndef<M::PointerTag>> {
-        match *self.read_value(op)? {
-            Value::ScalarPair(..) => bug!("got ScalarPair for type: {:?}", op.layout.ty),
-            Value::Scalar(val) => Ok(val),
-        }
+        Ok(self.read_immediate(op)?.to_scalar_or_undef())
     }
 
     // Turn the MPlace into a string (must already be dereferenced!)
@@ -470,16 +470,16 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         layout: TyLayout<'tcx>
     ) -> EvalResult<'tcx, Operand<M::PointerTag>> {
         // This decides which types we will use the Immediate optimization for, and hence should
-        // match what `try_read_value` and `eval_place_to_op` support.
+        // match what `try_read_immediate` and `eval_place_to_op` support.
         if layout.is_zst() {
-            return Ok(Operand::Immediate(Value::Scalar(Scalar::zst().into())));
+            return Ok(Operand::Immediate(Immediate::Scalar(Scalar::zst().into())));
         }
 
         Ok(match layout.abi {
             layout::Abi::Scalar(..) =>
-                Operand::Immediate(Value::Scalar(ScalarMaybeUndef::Undef)),
+                Operand::Immediate(Immediate::Scalar(ScalarMaybeUndef::Undef)),
             layout::Abi::ScalarPair(..) =>
-                Operand::Immediate(Value::ScalarPair(
+                Operand::Immediate(Immediate::ScalarPair(
                     ScalarMaybeUndef::Undef,
                     ScalarMaybeUndef::Undef,
                 )),
@@ -510,22 +510,22 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         let field = field.try_into().unwrap();
         let field_layout = op.layout.field(self, field)?;
         if field_layout.is_zst() {
-            let val = Value::Scalar(Scalar::zst().into());
-            return Ok(OpTy { op: Operand::Immediate(val), layout: field_layout });
+            let immediate = Immediate::Scalar(Scalar::zst().into());
+            return Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout });
         }
         let offset = op.layout.fields.offset(field);
-        let value = match base {
+        let immediate = match base {
             // the field covers the entire type
             _ if offset.bytes() == 0 && field_layout.size == op.layout.size => base,
             // extract fields from types with `ScalarPair` ABI
-            Value::ScalarPair(a, b) => {
+            Immediate::ScalarPair(a, b) => {
                 let val = if offset.bytes() == 0 { a } else { b };
-                Value::Scalar(val)
+                Immediate::Scalar(val)
             },
-            Value::Scalar(val) =>
+            Immediate::Scalar(val) =>
                 bug!("field access on non aggregate {:#?}, {:#?}", val, op.layout),
         };
-        Ok(OpTy { op: Operand::Immediate(value), layout: field_layout })
+        Ok(OpTy { op: Operand::Immediate(immediate), layout: field_layout })
     }
 
     pub fn operand_downcast(
@@ -551,7 +551,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         &self,
         src: OpTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
-        let val = self.read_value(src)?;
+        let val = self.read_immediate(src)?;
         trace!("deref to {} on {:?}", val.layout.ty, *val);
         Ok(self.ref_to_mplace(val)?)
     }
@@ -568,7 +568,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             Deref => self.deref_operand(base)?.into(),
             Subslice { .. } | ConstantIndex { .. } | Index(_) => if base.layout.is_zst() {
                 OpTy {
-                    op: Operand::Immediate(Value::Scalar(Scalar::zst().into())),
+                    op: Operand::Immediate(Immediate::Scalar(Scalar::zst().into())),
                     // the actual index doesn't matter, so we just pick a convenient one like 0
                     layout: base.layout.field(self, 0)?,
                 }
@@ -682,9 +682,12 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 ).with_default_tag())
             },
             ConstValue::ScalarPair(a, b) =>
-                Ok(Operand::Immediate(Value::ScalarPair(a.into(), b.into())).with_default_tag()),
+                Ok(Operand::Immediate(Immediate::ScalarPair(
+                    a.into(),
+                    b.into(),
+                )).with_default_tag()),
             ConstValue::Scalar(x) =>
-                Ok(Operand::Immediate(Value::Scalar(x.into())).with_default_tag()),
+                Ok(Operand::Immediate(Immediate::Scalar(x.into())).with_default_tag()),
         }
     }
     pub fn const_to_op(
@@ -722,7 +725,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
         }
         // read raw discriminant value
         let discr_op = self.operand_field(rval, 0)?;
-        let discr_val = self.read_value(discr_op)?;
+        let discr_val = self.read_immediate(discr_op)?;
         let raw_discr = discr_val.to_scalar()?;
         trace!("discr value: {:?}", raw_discr);
         // post-process
diff --git a/src/librustc_mir/interpret/operator.rs b/src/librustc_mir/interpret/operator.rs
index 5f4bafc39f3..2c6b8732fdb 100644
--- a/src/librustc_mir/interpret/operator.rs
+++ b/src/librustc_mir/interpret/operator.rs
@@ -15,7 +15,7 @@ use rustc_apfloat::ieee::{Double, Single};
 use rustc_apfloat::Float;
 use rustc::mir::interpret::{EvalResult, Scalar};
 
-use super::{EvalContext, PlaceTy, Value, Machine, ValTy};
+use super::{EvalContext, PlaceTy, Immediate, Machine, ImmTy};
 
 
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
@@ -24,13 +24,13 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
     pub fn binop_with_overflow(
         &mut self,
         op: mir::BinOp,
-        left: ValTy<'tcx, M::PointerTag>,
-        right: ValTy<'tcx, M::PointerTag>,
+        left: ImmTy<'tcx, M::PointerTag>,
+        right: ImmTy<'tcx, M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
         let (val, overflowed) = self.binary_op_val(op, left, right)?;
-        let val = Value::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
-        self.write_value(val, dest)
+        let val = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
+        self.write_immediate(val, dest)
     }
 
     /// Applies the binary operation `op` to the arguments and writes the result to the
@@ -38,8 +38,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
     pub fn binop_ignore_overflow(
         &mut self,
         op: mir::BinOp,
-        left: ValTy<'tcx, M::PointerTag>,
-        right: ValTy<'tcx, M::PointerTag>,
+        left: ImmTy<'tcx, M::PointerTag>,
+        right: ImmTy<'tcx, M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
         let (val, _overflowed) = self.binary_op_val(op, left, right)?;
@@ -288,8 +288,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
     pub fn binary_op_val(
         &self,
         bin_op: mir::BinOp,
-        left: ValTy<'tcx, M::PointerTag>,
-        right: ValTy<'tcx, M::PointerTag>,
+        left: ImmTy<'tcx, M::PointerTag>,
+        right: ImmTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, (Scalar<M::PointerTag>, bool)> {
         self.binary_op(
             bin_op,
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 3b104e2284f..58e4e3ce96b 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -25,7 +25,7 @@ use rustc::mir::interpret::{
 };
 use super::{
     EvalContext, Machine, AllocMap,
-    Value, ValTy, ScalarMaybeUndef, Operand, OpTy, MemoryKind
+    Immediate, ImmTy, ScalarMaybeUndef, Operand, OpTy, MemoryKind
 };
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
@@ -201,10 +201,10 @@ impl<'tcx, Tag> MPlaceTy<'tcx, Tag> {
 
 impl<'tcx, Tag: ::std::fmt::Debug> OpTy<'tcx, Tag> {
     #[inline(always)]
-    pub fn try_as_mplace(self) -> Result<MPlaceTy<'tcx, Tag>, Value<Tag>> {
+    pub fn try_as_mplace(self) -> Result<MPlaceTy<'tcx, Tag>, Immediate<Tag>> {
         match self.op {
             Operand::Indirect(mplace) => Ok(MPlaceTy { mplace, layout: self.layout }),
-            Operand::Immediate(value) => Err(value),
+            Operand::Immediate(imm) => Err(imm),
         }
     }
 
@@ -269,7 +269,7 @@ where
     /// Alignment is just based on the type.  This is the inverse of `create_ref`.
     pub fn ref_to_mplace(
         &self,
-        val: ValTy<'tcx, M::PointerTag>,
+        val: ImmTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
         let pointee_type = val.layout.ty.builtin_deref(true).unwrap().ty;
         let layout = self.layout_of(pointee_type)?;
@@ -304,7 +304,7 @@ where
         &mut self,
         place: MPlaceTy<'tcx, M::PointerTag>,
         mutbl: Option<hir::Mutability>,
-    ) -> EvalResult<'tcx, Value<M::PointerTag>> {
+    ) -> EvalResult<'tcx, Immediate<M::PointerTag>> {
         // Pointer tag tracking might want to adjust the tag
         let place = if M::ENABLE_PTR_TRACKING_HOOKS {
             let (size, _) = self.size_and_align_of_mplace(place)?
@@ -315,8 +315,8 @@ where
             *place
         };
         Ok(match place.meta {
-            None => Value::Scalar(place.ptr.into()),
-            Some(meta) => Value::ScalarPair(place.ptr.into(), meta.into()),
+            None => Immediate::Scalar(place.ptr.into()),
+            Some(meta) => Immediate::ScalarPair(place.ptr.into(), meta.into()),
         })
     }
 
@@ -629,17 +629,17 @@ where
         val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
-        self.write_value(Value::Scalar(val.into()), dest)
+        self.write_immediate(Immediate::Scalar(val.into()), dest)
     }
 
-    /// Write a value to a place
+    /// Write an immediate to a place
     #[inline(always)]
-    pub fn write_value(
+    pub fn write_immediate(
         &mut self,
-        src_val: Value<M::PointerTag>,
+        src: Immediate<M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
-        self.write_value_no_validate(src_val, dest)?;
+        self.write_immediate_no_validate(src, dest)?;
 
         if M::enforce_validity(self) {
             // Data got changed, better make sure it matches the type!
@@ -649,40 +649,40 @@ where
         Ok(())
     }
 
-    /// Write a value to a place.
+    /// Write an immediate to a place.
     /// If you use this you are responsible for validating that things got copied at the
     /// right type.
-    fn write_value_no_validate(
+    fn write_immediate_no_validate(
         &mut self,
-        src_val: Value<M::PointerTag>,
+        src: Immediate<M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
         if cfg!(debug_assertions) {
             // This is a very common path, avoid some checks in release mode
             assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
-            match src_val {
-                Value::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) =>
+            match src {
+                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) =>
                     assert_eq!(self.pointer_size(), dest.layout.size,
                         "Size mismatch when writing pointer"),
-                Value::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { size, .. })) =>
+                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits { size, .. })) =>
                     assert_eq!(Size::from_bytes(size.into()), dest.layout.size,
                         "Size mismatch when writing bits"),
-                Value::Scalar(ScalarMaybeUndef::Undef) => {}, // undef can have any size
-                Value::ScalarPair(_, _) => {
+                Immediate::Scalar(ScalarMaybeUndef::Undef) => {}, // undef can have any size
+                Immediate::ScalarPair(_, _) => {
                     // FIXME: Can we check anything here?
                 }
             }
         }
-        trace!("write_value: {:?} <- {:?}: {}", *dest, src_val, dest.layout.ty);
+        trace!("write_immediate: {:?} <- {:?}: {}", *dest, src, dest.layout.ty);
 
-        // See if we can avoid an allocation. This is the counterpart to `try_read_value`,
+        // See if we can avoid an allocation. This is the counterpart to `try_read_immediate`,
         // but not factored as a separate function.
         let mplace = match dest.place {
             Place::Local { frame, local } => {
                 match *self.stack[frame].locals[local].access_mut()? {
                     Operand::Immediate(ref mut dest_val) => {
                         // Yay, we can just change the local directly.
-                        *dest_val = src_val;
+                        *dest_val = src;
                         return Ok(());
                     },
                     Operand::Indirect(mplace) => mplace, // already in memory
@@ -693,15 +693,15 @@ where
         let dest = MPlaceTy { mplace, layout: dest.layout };
 
         // This is already in memory, write there.
-        self.write_value_to_mplace_no_validate(src_val, dest)
+        self.write_immediate_to_mplace_no_validate(src, dest)
     }
 
-    /// Write a value to memory.
+    /// Write an immediate to memory.
     /// If you use this you are responsible for validating that things git copied at the
     /// right type.
-    fn write_value_to_mplace_no_validate(
+    fn write_immediate_to_mplace_no_validate(
         &mut self,
-        value: Value<M::PointerTag>,
+        value: Immediate<M::PointerTag>,
         dest: MPlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx> {
         let (ptr, ptr_align) = dest.to_scalar_ptr_align();
@@ -721,10 +721,10 @@ where
         // memory.  The code below is not sufficient, with enough padding it might not
         // cover all the bytes!
         match value {
-            Value::Scalar(scalar) => {
+            Immediate::Scalar(scalar) => {
                 match dest.layout.abi {
                     layout::Abi::Scalar(_) => {}, // fine
-                    _ => bug!("write_value_to_mplace: invalid Scalar layout: {:#?}",
+                    _ => bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}",
                             dest.layout)
                 }
 
@@ -732,10 +732,10 @@ where
                     ptr, ptr_align.min(dest.layout.align), scalar, dest.layout.size
                 )
             }
-            Value::ScalarPair(a_val, b_val) => {
+            Immediate::ScalarPair(a_val, b_val) => {
                 let (a, b) = match dest.layout.abi {
                     layout::Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
-                    _ => bug!("write_value_to_mplace: invalid ScalarPair layout: {:#?}",
+                    _ => bug!("write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
                               dest.layout)
                 };
                 let (a_size, b_size) = (a.size(&self), b.size(&self));
@@ -788,10 +788,10 @@ where
             "Layout mismatch when copying!\nsrc: {:#?}\ndest: {:#?}", src, dest);
 
         // Let us see if the layout is simple so we take a shortcut, avoid force_allocation.
-        let src = match self.try_read_value(src)? {
+        let src = match self.try_read_immediate(src)? {
             Ok(src_val) => {
                 // Yay, we got a value that we can write directly.
-                return self.write_value_no_validate(src_val, dest);
+                return self.write_immediate_no_validate(src_val, dest);
             }
             Err(mplace) => mplace,
         };
@@ -873,7 +873,7 @@ where
                         let ptr = self.allocate(local_layout, MemoryKind::Stack)?;
                         // We don't have to validate as we can assume the local
                         // was already valid for its type.
-                        self.write_value_to_mplace_no_validate(value, ptr)?;
+                        self.write_immediate_to_mplace_no_validate(value, ptr)?;
                         let mplace = ptr.mplace;
                         // Update the local
                         *self.stack[frame].locals[local].access_mut()? =
diff --git a/src/librustc_mir/interpret/snapshot.rs b/src/librustc_mir/interpret/snapshot.rs
index cff2288fd87..0926ddb5966 100644
--- a/src/librustc_mir/interpret/snapshot.rs
+++ b/src/librustc_mir/interpret/snapshot.rs
@@ -24,7 +24,7 @@ use syntax::ast::Mutability;
 use syntax::source_map::Span;
 
 use super::eval_context::{LocalValue, StackPopCleanup};
-use super::{Frame, Memory, Operand, MemPlace, Place, Value, ScalarMaybeUndef};
+use super::{Frame, Memory, Operand, MemPlace, Place, Immediate, ScalarMaybeUndef};
 use const_eval::CompileTimeInterpreter;
 
 #[derive(Default)]
@@ -237,11 +237,11 @@ impl<'a, Ctx> Snapshot<'a, Ctx> for Place
     }
 }
 
-impl_stable_hash_for!(enum ::interpret::Value {
+impl_stable_hash_for!(enum ::interpret::Immediate {
     Scalar(x),
     ScalarPair(x, y),
 });
-impl_snapshot_for!(enum Value {
+impl_snapshot_for!(enum Immediate {
     Scalar(s),
     ScalarPair(s, t),
 });
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index 97431cfe680..ea8fcfe260b 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -159,9 +159,9 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
             BinaryOp(bin_op, ref left, ref right) => {
                 let layout = if binop_left_homogeneous(bin_op) { Some(dest.layout) } else { None };
-                let left = self.read_value(self.eval_operand(left, layout)?)?;
+                let left = self.read_immediate(self.eval_operand(left, layout)?)?;
                 let layout = if binop_right_homogeneous(bin_op) { Some(left.layout) } else { None };
-                let right = self.read_value(self.eval_operand(right, layout)?)?;
+                let right = self.read_immediate(self.eval_operand(right, layout)?)?;
                 self.binop_ignore_overflow(
                     bin_op,
                     left,
@@ -172,9 +172,9 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
             CheckedBinaryOp(bin_op, ref left, ref right) => {
                 // Due to the extra boolean in the result, we can never reuse the `dest.layout`.
-                let left = self.read_value(self.eval_operand(left, None)?)?;
+                let left = self.read_immediate(self.eval_operand(left, None)?)?;
                 let layout = if binop_right_homogeneous(bin_op) { Some(left.layout) } else { None };
-                let right = self.read_value(self.eval_operand(right, layout)?)?;
+                let right = self.read_immediate(self.eval_operand(right, layout)?)?;
                 self.binop_with_overflow(
                     bin_op,
                     left,
@@ -185,7 +185,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
             UnaryOp(un_op, ref operand) => {
                 // The operand always has the same type as the result.
-                let val = self.read_value(self.eval_operand(operand, Some(dest.layout))?)?;
+                let val = self.read_immediate(self.eval_operand(operand, Some(dest.layout))?)?;
                 let val = self.unary_op(un_op, val.to_scalar()?, dest.layout)?;
                 self.write_scalar(val, dest)?;
             }
@@ -259,7 +259,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                         hir::MutImmutable,
                 };
                 let val = self.create_ref(val, Some(mutbl))?;
-                self.write_value(val, dest)?;
+                self.write_immediate(val, dest)?;
             }
 
             NullaryOp(mir::NullOp::Box, _) => {
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index ee84e49022f..44262aeae02 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -17,7 +17,7 @@ use rustc_target::spec::abi::Abi;
 
 use rustc::mir::interpret::{EvalResult, PointerArithmetic, EvalErrorKind, Scalar};
 use super::{
-    EvalContext, Machine, Value, OpTy, PlaceTy, MPlaceTy, Operand, StackPopCleanup
+    EvalContext, Machine, Immediate, OpTy, PlaceTy, MPlaceTy, Operand, StackPopCleanup
 };
 
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
@@ -51,7 +51,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 ref targets,
                 ..
             } => {
-                let discr = self.read_value(self.eval_operand(discr, None)?)?;
+                let discr = self.read_immediate(self.eval_operand(discr, None)?)?;
                 trace!("SwitchInt({:?})", *discr);
 
                 // Branch to the `otherwise` case by default, if no match is found.
@@ -138,7 +138,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 target,
                 ..
             } => {
-                let cond_val = self.read_value(self.eval_operand(cond, None)?)?
+                let cond_val = self.read_immediate(self.eval_operand(cond, None)?)?
                     .to_scalar()?.to_bool()?;
                 if expected == cond_val {
                     self.goto_block(Some(target))?;
@@ -147,10 +147,10 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                     use rustc::mir::interpret::EvalErrorKind::*;
                     return match *msg {
                         BoundsCheck { ref len, ref index } => {
-                            let len = self.read_value(self.eval_operand(len, None)?)
+                            let len = self.read_immediate(self.eval_operand(len, None)?)
                                 .expect("can't eval len").to_scalar()?
                                 .to_bits(self.memory().pointer_size())? as u64;
-                            let index = self.read_value(self.eval_operand(index, None)?)
+                            let index = self.read_immediate(self.eval_operand(index, None)?)
                                 .expect("can't eval index").to_scalar()?
                                 .to_bits(self.memory().pointer_size())? as u64;
                             err!(BoundsCheck { len, index })
@@ -402,7 +402,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             ty::InstanceDef::Virtual(_, idx) => {
                 let ptr_size = self.pointer_size();
                 let ptr_align = self.tcx.data_layout.pointer_align;
-                let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
+                let ptr = self.ref_to_mplace(self.read_immediate(args[0])?)?;
                 let vtable = ptr.vtable()?;
                 let fn_ptr = self.memory.read_ptr_sized(
                     vtable.offset(ptr_size * (idx as u64 + 3), &self)?,
@@ -417,7 +417,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
                 let pointee = args[0].layout.ty.builtin_deref(true).unwrap().ty;
                 let fake_fat_ptr_ty = self.tcx.mk_mut_ptr(pointee);
                 args[0].layout = self.layout_of(fake_fat_ptr_ty)?.field(&self, 0)?;
-                args[0].op = Operand::Immediate(Value::Scalar(ptr.ptr.into())); // strip vtable
+                args[0].op = Operand::Immediate(Immediate::Scalar(ptr.ptr.into())); // strip vtable
                 trace!("Patched self operand to {:#?}", args[0]);
                 // recurse with concrete function
                 self.eval_fn_call(instance, span, caller_abi, &args, dest, ret)
diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 15d0a9166a6..4dbae3c8c3d 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -20,7 +20,7 @@ use rustc::mir::interpret::{
 };
 
 use super::{
-    ValTy, OpTy, MPlaceTy, Machine, EvalContext, ScalarMaybeUndef
+    ImmTy, OpTy, MPlaceTy, Machine, EvalContext, ScalarMaybeUndef
 };
 
 macro_rules! validation_failure {
@@ -144,7 +144,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
     /// Make sure that `value` is valid for `ty`, *assuming* `ty` is a primitive type.
     fn validate_primitive_type(
         &self,
-        value: ValTy<'tcx, M::PointerTag>,
+        value: ImmTy<'tcx, M::PointerTag>,
         path: &Vec<PathElem>,
         ref_tracking: Option<&mut RefTracking<'tcx, M::PointerTag>>,
         const_mode: bool,
@@ -465,7 +465,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             _ => dest.layout.ty.builtin_deref(true).is_some(),
         };
         if primitive {
-            let value = try_validation!(self.read_value(dest),
+            let value = try_validation!(self.read_immediate(dest),
                 "uninitialized or unrepresentable data", path);
             return self.validate_primitive_type(
                 value,
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 8ee009db023..24d9e761d97 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -28,7 +28,7 @@ use rustc::ty::layout::{
     HasTyCtxt, TargetDataLayout, HasDataLayout,
 };
 
-use interpret::{self, EvalContext, ScalarMaybeUndef, Value, OpTy, MemoryKind};
+use interpret::{self, EvalContext, ScalarMaybeUndef, Immediate, OpTy, MemoryKind};
 use const_eval::{CompileTimeInterpreter, error_to_const_error, eval_promoted, mk_borrowck_eval_cx};
 use transform::{MirPass, MirSource};
 
@@ -354,7 +354,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
             Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
                 type_size_of(self.tcx, self.param_env, ty).and_then(|n| Some((
                     OpTy {
-                        op: interpret::Operand::Immediate(Value::Scalar(
+                        op: interpret::Operand::Immediate(Immediate::Scalar(
                             Scalar::Bits {
                                 bits: n as u128,
                                 size: self.tcx.data_layout.pointer_size.bytes() as u8,
@@ -397,7 +397,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
                     this.ecx.unary_op(op, prim, arg.layout)
                 })?;
                 let res = OpTy {
-                    op: interpret::Operand::Immediate(Value::Scalar(val.into())),
+                    op: interpret::Operand::Immediate(Immediate::Scalar(val.into())),
                     layout: place_layout,
                 };
                 Some((res, span))
@@ -418,7 +418,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
                 }
 
                 let r = self.use_ecx(source_info, |this| {
-                    this.ecx.read_value(right.0)
+                    this.ecx.read_immediate(right.0)
                 })?;
                 if op == BinOp::Shr || op == BinOp::Shl {
                     let left_ty = left.ty(self.mir, self.tcx);
@@ -451,14 +451,14 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
                 }
                 let left = self.eval_operand(left, source_info)?;
                 let l = self.use_ecx(source_info, |this| {
-                    this.ecx.read_value(left.0)
+                    this.ecx.read_immediate(left.0)
                 })?;
                 trace!("const evaluating {:?} for {:?} and {:?}", op, left, right);
                 let (val, overflow) = self.use_ecx(source_info, |this| {
                     this.ecx.binary_op_val(op, l, r)
                 })?;
                 let val = if let Rvalue::CheckedBinaryOp(..) = *rvalue {
-                    Value::ScalarPair(
+                    Immediate::ScalarPair(
                         val.into(),
                         Scalar::from_bool(overflow).into(),
                     )
@@ -468,7 +468,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;
                     }
-                    Value::Scalar(val.into())
+                    Immediate::Scalar(val.into())
                 };
                 let res = OpTy {
                     op: interpret::Operand::Immediate(val),
@@ -591,7 +591,7 @@ impl<'b, 'a, 'tcx> Visitor<'tcx> for ConstPropagator<'b, 'a, 'tcx> {
         if let TerminatorKind::Assert { expected, msg, cond, .. } = kind {
             if let Some(value) = self.eval_operand(cond, source_info) {
                 trace!("assertion on {:?} should be {:?}", value, expected);
-                let expected = Value::Scalar(Scalar::from_bool(*expected).into());
+                let expected = Immediate::Scalar(Scalar::from_bool(*expected).into());
                 if expected != value.0.to_immediate() {
                     // poison all places this operand references so that further code
                     // doesn't use the invalid value
@@ -629,7 +629,7 @@ impl<'b, 'a, 'tcx> Visitor<'tcx> for ConstPropagator<'b, 'a, 'tcx> {
                                 .eval_operand(len, source_info)
                                 .expect("len must be const");
                             let len = match len.0.to_immediate() {
-                                Value::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits {
+                                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits {
                                     bits, ..
                                 })) => bits,
                                 _ => bug!("const len not primitive: {:?}", len),
@@ -638,7 +638,7 @@ impl<'b, 'a, 'tcx> Visitor<'tcx> for ConstPropagator<'b, 'a, 'tcx> {
                                 .eval_operand(index, source_info)
                                 .expect("index must be const");
                             let index = match index.0.to_immediate() {
-                                Value::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits {
+                                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Bits {
                                     bits, ..
                                 })) => bits,
                                 _ => bug!("const index not primitive: {:?}", index),
diff --git a/src/tools/linkchecker/main.rs b/src/tools/linkchecker/main.rs
index 41ad4e7180e..ca7e0224dc3 100644
--- a/src/tools/linkchecker/main.rs
+++ b/src/tools/linkchecker/main.rs
@@ -133,7 +133,7 @@ fn check(cache: &mut Cache,
     // whitelists to get this past `make check` today.
     // FIXME(#32129)
     if file.ends_with("std/string/struct.String.html") ||
-       file.ends_with("interpret/struct.ValTy.html") ||
+       file.ends_with("interpret/struct.ImmTy.html") ||
        file.ends_with("symbol/struct.InternedString.html") ||
        file.ends_with("ast/struct.ThinVec.html") ||
        file.ends_with("util/struct.ThinVec.html") ||