Renamed "undef" stuff to "uninit"

1. InvalidUndefBytes -> InvalidUninitBytes
2. ScalarMaybeUndef -> ScalarMaybeUninit
3. UndefMask -> InitMask

Related issue  #71193

20 files changed, 138 insertions, 138 deletions

diff --git a/src/librustc_middle/mir/interpret/allocation.rs b/src/librustc_middle/mir/interpret/allocation.rs
index afc6a958296..2b6cf224e2c 100644
--- a/src/librustc_middle/mir/interpret/allocation.rs
+++ b/src/librustc_middle/mir/interpret/allocation.rs
@@ -10,7 +10,7 @@ use rustc_data_structures::sorted_map::SortedMap;
 use rustc_target::abi::{Align, HasDataLayout, Size};
 
 use super::{
-    read_target_uint, write_target_uint, AllocId, InterpResult, Pointer, Scalar, ScalarMaybeUndef,
+    read_target_uint, write_target_uint, AllocId, InterpResult, Pointer, Scalar, ScalarMaybeUninit,
 };
 
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
@@ -25,7 +25,7 @@ pub struct Allocation<Tag = (), Extra = ()> {
     /// at the given offset.
     relocations: Relocations<Tag>,
     /// Denotes which part of this allocation is initialized.
-    undef_mask: UndefMask,
+    init_mask: InitMask,
     /// The size of the allocation. Currently, must always equal `bytes.len()`.
     pub size: Size,
     /// The alignment of the allocation to detect unaligned reads.
@@ -92,7 +92,7 @@ impl<Tag> Allocation<Tag> {
         Self {
             bytes,
             relocations: Relocations::new(),
-            undef_mask: UndefMask::new(size, true),
+            init_mask: InitMask::new(size, true),
             size,
             align,
             mutability: Mutability::Not,
@@ -108,7 +108,7 @@ impl<Tag> Allocation<Tag> {
         Allocation {
             bytes: vec![0; size.bytes_usize()],
             relocations: Relocations::new(),
-            undef_mask: UndefMask::new(size, false),
+            init_mask: InitMask::new(size, false),
             size,
             align,
             mutability: Mutability::Mut,
@@ -138,7 +138,7 @@ impl Allocation<(), ()> {
                     })
                     .collect(),
             ),
-            undef_mask: self.undef_mask,
+            init_mask: self.init_mask,
             align: self.align,
             mutability: self.mutability,
             extra,
@@ -160,9 +160,9 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         &self.bytes[range]
     }
 
-    /// Returns the undef mask.
-    pub fn undef_mask(&self) -> &UndefMask {
-        &self.undef_mask
+    /// Returns the mask indicating which bytes are initialized.
+    pub fn init_mask(&self) -> &InitMask {
+        &self.init_mask
     }
 
     /// Returns the relocation list.
@@ -358,15 +358,15 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         cx: &impl HasDataLayout,
         ptr: Pointer<Tag>,
         size: Size,
-    ) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
+    ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
         // `get_bytes_unchecked` tests relocation edges.
         let bytes = self.get_bytes_with_undef_and_ptr(cx, ptr, size)?;
-        // Undef check happens *after* we established that the alignment is correct.
+        // Uninit check happens *after* we established that the alignment is correct.
         // We must not return `Ok()` for unaligned pointers!
         if self.is_defined(ptr, size).is_err() {
-            // This inflates undefined bytes to the entire scalar, even if only a few
-            // bytes are undefined.
-            return Ok(ScalarMaybeUndef::Undef);
+            // This inflates uninitialized bytes to the entire scalar, even if only a few
+            // bytes are uninitialized.
+            return Ok(ScalarMaybeUninit::Uninit);
         }
         // Now we do the actual reading.
         let bits = read_target_uint(cx.data_layout().endian, bytes).unwrap();
@@ -377,11 +377,11 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         } else {
             if let Some(&(tag, alloc_id)) = self.relocations.get(&ptr.offset) {
                 let ptr = Pointer::new_with_tag(alloc_id, Size::from_bytes(bits), tag);
-                return Ok(ScalarMaybeUndef::Scalar(ptr.into()));
+                return Ok(ScalarMaybeUninit::Scalar(ptr.into()));
             }
         }
         // We don't. Just return the bits.
-        Ok(ScalarMaybeUndef::Scalar(Scalar::from_uint(bits, size)))
+        Ok(ScalarMaybeUninit::Scalar(Scalar::from_uint(bits, size)))
     }
 
     /// Reads a pointer-sized scalar.
@@ -392,7 +392,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         &self,
         cx: &impl HasDataLayout,
         ptr: Pointer<Tag>,
-    ) -> InterpResult<'tcx, ScalarMaybeUndef<Tag>> {
+    ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
         self.read_scalar(cx, ptr, cx.data_layout().pointer_size)
     }
 
@@ -409,12 +409,12 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         &mut self,
         cx: &impl HasDataLayout,
         ptr: Pointer<Tag>,
-        val: ScalarMaybeUndef<Tag>,
+        val: ScalarMaybeUninit<Tag>,
         type_size: Size,
     ) -> InterpResult<'tcx> {
         let val = match val {
-            ScalarMaybeUndef::Scalar(scalar) => scalar,
-            ScalarMaybeUndef::Undef => {
+            ScalarMaybeUninit::Scalar(scalar) => scalar,
+            ScalarMaybeUninit::Uninit => {
                 self.mark_definedness(ptr, type_size, false);
                 return Ok(());
             }
@@ -445,7 +445,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         &mut self,
         cx: &impl HasDataLayout,
         ptr: Pointer<Tag>,
-        val: ScalarMaybeUndef<Tag>,
+        val: ScalarMaybeUninit<Tag>,
     ) -> InterpResult<'tcx> {
         let ptr_size = cx.data_layout().pointer_size;
         self.write_scalar(cx, ptr, val, ptr_size)
@@ -514,10 +514,10 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
         // Mark parts of the outermost relocations as undefined if they partially fall outside the
         // given range.
         if first < start {
-            self.undef_mask.set_range(first, start, false);
+            self.init_mask.set_range(first, start, false);
         }
         if last > end {
-            self.undef_mask.set_range(end, last, false);
+            self.init_mask.set_range(end, last, false);
         }
 
         // Forget all the relocations.
@@ -548,21 +548,21 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
     /// Returns `Ok(())` if it's defined. Otherwise returns the index of the byte
     /// at which the first undefined access begins.
     fn is_defined(&self, ptr: Pointer<Tag>, size: Size) -> Result<(), Size> {
-        self.undef_mask.is_range_defined(ptr.offset, ptr.offset + size) // `Size` addition
+        self.init_mask.is_range_initialized(ptr.offset, ptr.offset + size) // `Size` addition
     }
 
     /// Checks that a range of bytes is defined. If not, returns the `ReadUndefBytes`
     /// error which will report the first byte which is undefined.
     fn check_defined(&self, ptr: Pointer<Tag>, size: Size) -> InterpResult<'tcx> {
         self.is_defined(ptr, size)
-            .or_else(|idx| throw_ub!(InvalidUndefBytes(Some(Pointer::new(ptr.alloc_id, idx)))))
+            .or_else(|idx| throw_ub!(InvalidUninitBytes(Some(Pointer::new(ptr.alloc_id, idx)))))
     }
 
     pub fn mark_definedness(&mut self, ptr: Pointer<Tag>, size: Size, new_state: bool) {
         if size.bytes() == 0 {
             return;
         }
-        self.undef_mask.set_range(ptr.offset, ptr.offset + size, new_state);
+        self.init_mask.set_range(ptr.offset, ptr.offset + size, new_state);
     }
 }
 
@@ -601,13 +601,13 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         // where each element toggles the state.
 
         let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
-        let initial = self.undef_mask.get(src.offset);
+        let initial = self.init_mask.get(src.offset);
         let mut cur_len = 1;
         let mut cur = initial;
 
         for i in 1..size.bytes() {
             // FIXME: optimize to bitshift the current undef block's bits and read the top bit.
-            if self.undef_mask.get(src.offset + Size::from_bytes(i)) == cur {
+            if self.init_mask.get(src.offset + Size::from_bytes(i)) == cur {
                 cur_len += 1;
             } else {
                 ranges.push(cur_len);
@@ -632,7 +632,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
         // An optimization where we can just overwrite an entire range of definedness bits if
         // they are going to be uniformly `1` or `0`.
         if defined.ranges.len() <= 1 {
-            self.undef_mask.set_range_inbounds(
+            self.init_mask.set_range_inbounds(
                 dest.offset,
                 dest.offset + size * repeat, // `Size` operations
                 defined.initial,
@@ -647,7 +647,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
             for range in &defined.ranges {
                 let old_j = j;
                 j += range;
-                self.undef_mask.set_range_inbounds(
+                self.init_mask.set_range_inbounds(
                     Size::from_bytes(old_j),
                     Size::from_bytes(j),
                     cur,
@@ -739,29 +739,29 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
 type Block = u64;
 
 /// A bitmask where each bit refers to the byte with the same index. If the bit is `true`, the byte
-/// is defined. If it is `false` the byte is undefined.
+/// is initialized. If it is `false` the byte is uninitialized.
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 #[derive(HashStable)]
-pub struct UndefMask {
+pub struct InitMask {
     blocks: Vec<Block>,
     len: Size,
 }
 
-impl UndefMask {
+impl InitMask {
     pub const BLOCK_SIZE: u64 = 64;
 
     pub fn new(size: Size, state: bool) -> Self {
-        let mut m = UndefMask { blocks: vec![], len: Size::ZERO };
+        let mut m = InitMask { blocks: vec![], len: Size::ZERO };
         m.grow(size, state);
         m
     }
 
-    /// Checks whether the range `start..end` (end-exclusive) is entirely defined.
+    /// Checks whether the range `start..end` (end-exclusive) is entirely initialized.
     ///
-    /// Returns `Ok(())` if it's defined. Otherwise returns the index of the byte
-    /// at which the first undefined access begins.
+    /// Returns `Ok(())` if it's initialized. Otherwise returns the index of the byte
+    /// at which the first uninitialized access begins.
     #[inline]
-    pub fn is_range_defined(&self, start: Size, end: Size) -> Result<(), Size> {
+    pub fn is_range_initialized(&self, start: Size, end: Size) -> Result<(), Size> {
         if end > self.len {
             return Err(self.len);
         }
@@ -870,7 +870,7 @@ impl UndefMask {
 #[inline]
 fn bit_index(bits: Size) -> (usize, usize) {
     let bits = bits.bytes();
-    let a = bits / UndefMask::BLOCK_SIZE;
-    let b = bits % UndefMask::BLOCK_SIZE;
+    let a = bits / InitMask::BLOCK_SIZE;
+    let b = bits % InitMask::BLOCK_SIZE;
     (usize::try_from(a).unwrap(), usize::try_from(b).unwrap())
 }
diff --git a/src/librustc_middle/mir/interpret/error.rs b/src/librustc_middle/mir/interpret/error.rs
index ffe71eb3a09..06fe3793b23 100644
--- a/src/librustc_middle/mir/interpret/error.rs
+++ b/src/librustc_middle/mir/interpret/error.rs
@@ -1,4 +1,4 @@
-use super::{AllocId, Pointer, RawConst, ScalarMaybeUndef};
+use super::{AllocId, Pointer, RawConst, ScalarMaybeUninit};
 
 use crate::mir::interpret::ConstValue;
 use crate::ty::layout::LayoutError;
@@ -378,13 +378,13 @@ pub enum UndefinedBehaviorInfo<'tcx> {
     /// Using a non-character `u32` as character.
     InvalidChar(u32),
     /// An enum discriminant was set to a value which was outside the range of valid values.
-    InvalidDiscriminant(ScalarMaybeUndef),
+    InvalidDiscriminant(ScalarMaybeUninit),
     /// Using a pointer-not-to-a-function as function pointer.
     InvalidFunctionPointer(Pointer),
     /// Using a string that is not valid UTF-8,
     InvalidStr(std::str::Utf8Error),
     /// Using uninitialized data where it is not allowed.
-    InvalidUndefBytes(Option<Pointer>),
+    InvalidUninitBytes(Option<Pointer>),
     /// Working with a local that is not currently live.
     DeadLocal,
     /// Data size is not equal to target size.
@@ -455,12 +455,12 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> {
                 write!(f, "using {} as function pointer but it does not point to a function", p)
             }
             InvalidStr(err) => write!(f, "this string is not valid UTF-8: {}", err),
-            InvalidUndefBytes(Some(p)) => write!(
+            InvalidUninitBytes(Some(p)) => write!(
                 f,
                 "reading uninitialized memory at {}, but this operation requires initialized memory",
                 p
             ),
-            InvalidUndefBytes(None) => write!(
+            InvalidUninitBytes(None) => write!(
                 f,
                 "using uninitialized data, but this operation requires initialized memory"
             ),
diff --git a/src/librustc_middle/mir/interpret/mod.rs b/src/librustc_middle/mir/interpret/mod.rs
index 6b86bbfd197..61d7425de7d 100644
--- a/src/librustc_middle/mir/interpret/mod.rs
+++ b/src/librustc_middle/mir/interpret/mod.rs
@@ -122,9 +122,9 @@ pub use self::error::{
     ResourceExhaustionInfo, UndefinedBehaviorInfo, UnsupportedOpInfo,
 };
 
-pub use self::value::{get_slice_bytes, ConstValue, RawConst, Scalar, ScalarMaybeUndef};
+pub use self::value::{get_slice_bytes, ConstValue, RawConst, Scalar, ScalarMaybeUninit};
 
-pub use self::allocation::{Allocation, AllocationExtra, Relocations, UndefMask};
+pub use self::allocation::{Allocation, AllocationExtra, InitMask, Relocations};
 
 pub use self::pointer::{Pointer, PointerArithmetic};
 
diff --git a/src/librustc_middle/mir/interpret/value.rs b/src/librustc_middle/mir/interpret/value.rs
index ed779d52fb5..0e913ff58bb 100644
--- a/src/librustc_middle/mir/interpret/value.rs
+++ b/src/librustc_middle/mir/interpret/value.rs
@@ -28,7 +28,7 @@ pub struct RawConst<'tcx> {
 pub enum ConstValue<'tcx> {
     /// Used only for types with `layout::abi::Scalar` ABI and ZSTs.
     ///
-    /// Not using the enum `Value` to encode that this must not be `Undef`.
+    /// Not using the enum `Value` to encode that this must not be `Uninit`.
     Scalar(Scalar),
 
     /// Used only for `&[u8]` and `&str`
@@ -542,62 +542,62 @@ impl<Tag> From<Pointer<Tag>> for Scalar<Tag> {
 }
 
 #[derive(Clone, Copy, Eq, PartialEq, RustcEncodable, RustcDecodable, HashStable, Hash)]
-pub enum ScalarMaybeUndef<Tag = ()> {
+pub enum ScalarMaybeUninit<Tag = ()> {
     Scalar(Scalar<Tag>),
-    Undef,
+    Uninit,
 }
 
-impl<Tag> From<Scalar<Tag>> for ScalarMaybeUndef<Tag> {
+impl<Tag> From<Scalar<Tag>> for ScalarMaybeUninit<Tag> {
     #[inline(always)]
     fn from(s: Scalar<Tag>) -> Self {
-        ScalarMaybeUndef::Scalar(s)
+        ScalarMaybeUninit::Scalar(s)
     }
 }
 
-impl<Tag> From<Pointer<Tag>> for ScalarMaybeUndef<Tag> {
+impl<Tag> From<Pointer<Tag>> for ScalarMaybeUninit<Tag> {
     #[inline(always)]
     fn from(s: Pointer<Tag>) -> Self {
-        ScalarMaybeUndef::Scalar(s.into())
+        ScalarMaybeUninit::Scalar(s.into())
     }
 }
 
 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
 // all the Miri types.
-impl<Tag: fmt::Debug> fmt::Debug for ScalarMaybeUndef<Tag> {
+impl<Tag: fmt::Debug> fmt::Debug for ScalarMaybeUninit<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            ScalarMaybeUndef::Undef => write!(f, "<uninitialized>"),
-            ScalarMaybeUndef::Scalar(s) => write!(f, "{:?}", s),
+            ScalarMaybeUninit::Uninit => write!(f, "<uninitialized>"),
+            ScalarMaybeUninit::Scalar(s) => write!(f, "{:?}", s),
         }
     }
 }
 
-impl<Tag: fmt::Debug> fmt::Display for ScalarMaybeUndef<Tag> {
+impl<Tag: fmt::Debug> fmt::Display for ScalarMaybeUninit<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            ScalarMaybeUndef::Undef => write!(f, "uninitialized bytes"),
-            ScalarMaybeUndef::Scalar(s) => write!(f, "{}", s),
+            ScalarMaybeUninit::Uninit => write!(f, "uninitialized bytes"),
+            ScalarMaybeUninit::Scalar(s) => write!(f, "{}", s),
         }
     }
 }
 
-impl<'tcx, Tag> ScalarMaybeUndef<Tag> {
+impl<'tcx, Tag> ScalarMaybeUninit<Tag> {
     /// Erase the tag from the scalar, if any.
     ///
     /// Used by error reporting code to avoid having the error type depend on `Tag`.
     #[inline]
-    pub fn erase_tag(self) -> ScalarMaybeUndef {
+    pub fn erase_tag(self) -> ScalarMaybeUninit {
         match self {
-            ScalarMaybeUndef::Scalar(s) => ScalarMaybeUndef::Scalar(s.erase_tag()),
-            ScalarMaybeUndef::Undef => ScalarMaybeUndef::Undef,
+            ScalarMaybeUninit::Scalar(s) => ScalarMaybeUninit::Scalar(s.erase_tag()),
+            ScalarMaybeUninit::Uninit => ScalarMaybeUninit::Uninit,
         }
     }
 
     #[inline]
     pub fn not_undef(self) -> InterpResult<'static, Scalar<Tag>> {
         match self {
-            ScalarMaybeUndef::Scalar(scalar) => Ok(scalar),
-            ScalarMaybeUndef::Undef => throw_ub!(InvalidUndefBytes(None)),
+            ScalarMaybeUninit::Scalar(scalar) => Ok(scalar),
+            ScalarMaybeUninit::Uninit => throw_ub!(InvalidUninitBytes(None)),
         }
     }
 
diff --git a/src/librustc_mir/const_eval/eval_queries.rs b/src/librustc_mir/const_eval/eval_queries.rs
index d97546e4391..2f635b4a1c1 100644
--- a/src/librustc_mir/const_eval/eval_queries.rs
+++ b/src/librustc_mir/const_eval/eval_queries.rs
@@ -3,7 +3,7 @@ use crate::interpret::eval_nullary_intrinsic;
 use crate::interpret::{
     intern_const_alloc_recursive, Allocation, ConstValue, GlobalId, Immediate, InternKind,
     InterpCx, InterpResult, MPlaceTy, MemoryKind, OpTy, RawConst, RefTracking, Scalar,
-    ScalarMaybeUndef, StackPopCleanup,
+    ScalarMaybeUninit, StackPopCleanup,
 };
 use rustc_hir::def::DefKind;
 use rustc_middle::mir;
@@ -100,9 +100,9 @@ pub(super) fn op_to_const<'tcx>(
 ) -> ConstValue<'tcx> {
     // We do not have value optimizations for everything.
     // Only scalars and slices, since they are very common.
-    // Note that further down we turn scalars of undefined bits back to `ByRef`. These can result
+    // Note that further down we turn scalars of uninitialized bits back to `ByRef`. These can result
     // from scalar unions that are initialized with one of their zero sized variants. We could
-    // instead allow `ConstValue::Scalar` to store `ScalarMaybeUndef`, but that would affect all
+    // instead allow `ConstValue::Scalar` to store `ScalarMaybeUninit`, but that would affect all
     // the usual cases of extracting e.g. a `usize`, without there being a real use case for the
     // `Undef` situation.
     let try_as_immediate = match op.layout.abi {
@@ -149,8 +149,8 @@ pub(super) fn op_to_const<'tcx>(
         // see comment on `let try_as_immediate` above
         Err(imm) => match *imm {
             Immediate::Scalar(x) => match x {
-                ScalarMaybeUndef::Scalar(s) => ConstValue::Scalar(s),
-                ScalarMaybeUndef::Undef => to_const_value(op.assert_mem_place(ecx)),
+                ScalarMaybeUninit::Scalar(s) => ConstValue::Scalar(s),
+                ScalarMaybeUninit::Uninit => to_const_value(op.assert_mem_place(ecx)),
             },
             Immediate::ScalarPair(a, b) => {
                 let (data, start) = match a.not_undef().unwrap() {
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index f668bafe080..9bb7c879505 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -22,7 +22,7 @@ use rustc_target::abi::{Align, HasDataLayout, LayoutOf, Size, TargetDataLayout};
 
 use super::{
     Immediate, MPlaceTy, Machine, MemPlace, MemPlaceMeta, Memory, OpTy, Operand, Place, PlaceTy,
-    ScalarMaybeUndef, StackPopJump,
+    ScalarMaybeUninit, StackPopJump,
 };
 use crate::util::storage::AlwaysLiveLocals;
 
@@ -910,16 +910,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     },
                     LocalValue::Live(Operand::Immediate(Immediate::Scalar(val))) => {
                         write!(msg, " {:?}", val).unwrap();
-                        if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val {
+                        if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val {
                             allocs.push(ptr.alloc_id);
                         }
                     }
                     LocalValue::Live(Operand::Immediate(Immediate::ScalarPair(val1, val2))) => {
                         write!(msg, " ({:?}, {:?})", val1, val2).unwrap();
-                        if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val1 {
+                        if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val1 {
                             allocs.push(ptr.alloc_id);
                         }
-                        if let ScalarMaybeUndef::Scalar(Scalar::Ptr(ptr)) = val2 {
+                        if let ScalarMaybeUninit::Scalar(Scalar::Ptr(ptr)) = val2 {
                             allocs.push(ptr.alloc_id);
                         }
                     }
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index db836d88dd0..81009fd7b98 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -16,7 +16,7 @@ use rustc_target::abi::{VariantIdx, Variants};
 
 use super::{
     from_known_layout, sign_extend, truncate, ConstValue, GlobalId, InterpCx, InterpResult,
-    MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Scalar, ScalarMaybeUndef,
+    MPlaceTy, Machine, MemPlace, Place, PlaceTy, Pointer, Scalar, ScalarMaybeUninit,
 };
 
 /// An `Immediate` represents a single immediate self-contained Rust value.
@@ -28,13 +28,13 @@ use super::{
 /// defined on `Immediate`, and do not have to work with a `Place`.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, Hash)]
 pub enum Immediate<Tag = ()> {
-    Scalar(ScalarMaybeUndef<Tag>),
-    ScalarPair(ScalarMaybeUndef<Tag>, ScalarMaybeUndef<Tag>),
+    Scalar(ScalarMaybeUninit<Tag>),
+    ScalarPair(ScalarMaybeUninit<Tag>, ScalarMaybeUninit<Tag>),
 }
 
-impl<Tag> From<ScalarMaybeUndef<Tag>> for Immediate<Tag> {
+impl<Tag> From<ScalarMaybeUninit<Tag>> for Immediate<Tag> {
     #[inline(always)]
-    fn from(val: ScalarMaybeUndef<Tag>) -> Self {
+    fn from(val: ScalarMaybeUninit<Tag>) -> Self {
         Immediate::Scalar(val)
     }
 }
@@ -63,7 +63,7 @@ impl<'tcx, Tag> Immediate<Tag> {
     }
 
     #[inline]
-    pub fn to_scalar_or_undef(self) -> ScalarMaybeUndef<Tag> {
+    pub fn to_scalar_or_undef(self) -> ScalarMaybeUninit<Tag> {
         match self {
             Immediate::Scalar(val) => val,
             Immediate::ScalarPair(..) => bug!("Got a wide pointer where a scalar was expected"),
@@ -97,14 +97,14 @@ impl<Tag: Copy> std::fmt::Display for ImmTy<'tcx, Tag> {
         /// Helper function for printing a scalar to a FmtPrinter
         fn p<'a, 'tcx, F: std::fmt::Write, Tag>(
             cx: FmtPrinter<'a, 'tcx, F>,
-            s: ScalarMaybeUndef<Tag>,
+            s: ScalarMaybeUninit<Tag>,
             ty: Ty<'tcx>,
         ) -> Result<FmtPrinter<'a, 'tcx, F>, std::fmt::Error> {
             match s {
-                ScalarMaybeUndef::Scalar(s) => {
+                ScalarMaybeUninit::Scalar(s) => {
                     cx.pretty_print_const_scalar(s.erase_tag(), ty, true)
                 }
-                ScalarMaybeUndef::Undef => cx.typed_value(
+                ScalarMaybeUninit::Uninit => cx.typed_value(
                     |mut this| {
                         this.write_str("{undef ")?;
                         Ok(this)
@@ -319,7 +319,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     pub fn read_scalar(
         &self,
         op: OpTy<'tcx, M::PointerTag>,
-    ) -> InterpResult<'tcx, ScalarMaybeUndef<M::PointerTag>> {
+    ) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>> {
         Ok(self.read_immediate(op)?.to_scalar_or_undef())
     }
 
@@ -644,7 +644,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let variants_end = niche_variants.end().as_u32();
                 let raw_discr = raw_discr
                     .not_undef()
-                    .map_err(|_| err_ub!(InvalidDiscriminant(ScalarMaybeUndef::Undef)))?;
+                    .map_err(|_| err_ub!(InvalidDiscriminant(ScalarMaybeUninit::Uninit)))?;
                 match raw_discr.to_bits_or_ptr(discr_val.layout.size, self) {
                     Err(ptr) => {
                         // The niche must be just 0 (which an inbounds pointer value never is)
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index fee9ca0c02e..2e8b1e64aed 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -15,7 +15,7 @@ use rustc_target::abi::{HasDataLayout, LayoutOf, Size, VariantIdx, Variants};
 use super::{
     mir_assign_valid_types, truncate, AllocId, AllocMap, Allocation, AllocationExtra, ImmTy,
     Immediate, InterpCx, InterpResult, LocalValue, Machine, MemoryKind, OpTy, Operand, Pointer,
-    PointerArithmetic, RawConst, Scalar, ScalarMaybeUndef,
+    PointerArithmetic, RawConst, Scalar, ScalarMaybeUninit,
 };
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable)]
@@ -645,7 +645,7 @@ where
     #[inline(always)]
     pub fn write_scalar(
         &mut self,
-        val: impl Into<ScalarMaybeUndef<M::PointerTag>>,
+        val: impl Into<ScalarMaybeUninit<M::PointerTag>>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
         self.write_immediate(Immediate::Scalar(val.into()), dest)
@@ -697,19 +697,19 @@ where
             // This is a very common path, avoid some checks in release mode
             assert!(!dest.layout.is_unsized(), "Cannot write unsized data");
             match src {
-                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Ptr(_))) => assert_eq!(
+                Immediate::Scalar(ScalarMaybeUninit::Scalar(Scalar::Ptr(_))) => assert_eq!(
                     self.pointer_size(),
                     dest.layout.size,
                     "Size mismatch when writing pointer"
                 ),
-                Immediate::Scalar(ScalarMaybeUndef::Scalar(Scalar::Raw { size, .. })) => {
+                Immediate::Scalar(ScalarMaybeUninit::Scalar(Scalar::Raw { size, .. })) => {
                     assert_eq!(
                         Size::from_bytes(size),
                         dest.layout.size,
                         "Size mismatch when writing bits"
                     )
                 }
-                Immediate::Scalar(ScalarMaybeUndef::Undef) => {} // undef can have any size
+                Immediate::Scalar(ScalarMaybeUninit::Uninit) => {} // undef can have any size
                 Immediate::ScalarPair(_, _) => {
                     // FIXME: Can we check anything here?
                 }
diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 9f2e79bbee3..92575855ad6 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -365,7 +365,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
         let place = try_validation!(
             self.ecx.ref_to_mplace(value),
             self.path,
-            err_ub!(InvalidUndefBytes(..)) => { "uninitialized {}", kind },
+            err_ub!(InvalidUninitBytes(..)) => { "uninitialized {}", kind },
         );
         if place.layout.is_unsized() {
             self.check_wide_ptr_meta(place.meta, place.layout)?;
@@ -513,7 +513,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 let place = try_validation!(
                     self.ecx.ref_to_mplace(self.ecx.read_immediate(value)?),
                     self.path,
-                    err_ub!(InvalidUndefBytes(..)) => { "uninitialized raw pointer" },
+                    err_ub!(InvalidUninitBytes(..)) => { "uninitialized raw pointer" },
                 );
                 if place.layout.is_unsized() {
                     self.check_wide_ptr_meta(place.meta, place.layout)?;
@@ -592,7 +592,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
         let value = try_validation!(
             value.not_undef(),
             self.path,
-            err_ub!(InvalidUndefBytes(..)) => { "{}", value }
+            err_ub!(InvalidUninitBytes(..)) => { "{}", value }
                 expected { "something {}", wrapping_range_format(valid_range, max_hi) },
         );
         let bits = match value.to_bits_or_ptr(op.layout.size, self.ecx) {
@@ -802,7 +802,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
                         // For some errors we might be able to provide extra information.
                         // (This custom logic does not fit the `try_validation!` macro.)
                         match err.kind {
-                            err_ub!(InvalidUndefBytes(Some(ptr))) => {
+                            err_ub!(InvalidUninitBytes(Some(ptr))) => {
                                 // Some byte was uninitialized, determine which
                                 // element that byte belongs to so we can
                                 // provide an index.
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 7926bf535b3..4be95b69850 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -29,7 +29,7 @@ use crate::const_eval::error_to_const_error;
 use crate::interpret::{
     self, compile_time_machine, intern_const_alloc_recursive, AllocId, Allocation, Frame, ImmTy,
     Immediate, InternKind, InterpCx, LocalState, LocalValue, Memory, MemoryKind, OpTy,
-    Operand as InterpOperand, PlaceTy, Pointer, ScalarMaybeUndef, StackPopCleanup,
+    Operand as InterpOperand, PlaceTy, Pointer, ScalarMaybeUninit, StackPopCleanup,
 };
 use crate::transform::{MirPass, MirSource};
 
@@ -633,7 +633,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
         if let Some(Ok(imm)) = imm {
             match *imm {
-                interpret::Immediate::Scalar(ScalarMaybeUndef::Scalar(scalar)) => {
+                interpret::Immediate::Scalar(ScalarMaybeUninit::Scalar(scalar)) => {
                     *rval = Rvalue::Use(self.operand_from_scalar(
                         scalar,
                         value.layout.ty,
@@ -641,8 +641,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     ));
                 }
                 Immediate::ScalarPair(
-                    ScalarMaybeUndef::Scalar(one),
-                    ScalarMaybeUndef::Scalar(two),
+                    ScalarMaybeUninit::Scalar(one),
+                    ScalarMaybeUninit::Scalar(two),
                 ) => {
                     // Found a value represented as a pair. For now only do cont-prop if type of
                     // Rvalue is also a pair with two scalars. The more general case is more
@@ -693,12 +693,12 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         }
 
         match *op {
-            interpret::Operand::Immediate(Immediate::Scalar(ScalarMaybeUndef::Scalar(s))) => {
+            interpret::Operand::Immediate(Immediate::Scalar(ScalarMaybeUninit::Scalar(s))) => {
                 s.is_bits()
             }
             interpret::Operand::Immediate(Immediate::ScalarPair(
-                ScalarMaybeUndef::Scalar(l),
-                ScalarMaybeUndef::Scalar(r),
+                ScalarMaybeUninit::Scalar(l),
+                ScalarMaybeUninit::Scalar(r),
             )) => l.is_bits() && r.is_bits(),
             interpret::Operand::Indirect(_) if mir_opt_level >= 2 => {
                 let mplace = op.assert_mem_place(&self.ecx);
@@ -889,7 +889,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
             TerminatorKind::Assert { expected, ref msg, ref mut cond, .. } => {
                 if let Some(value) = self.eval_operand(&cond, source_info) {
                     trace!("assertion on {:?} should be {:?}", value, expected);
-                    let expected = ScalarMaybeUndef::from(Scalar::from_bool(*expected));
+                    let expected = ScalarMaybeUninit::from(Scalar::from_bool(*expected));
                     let value_const = self.ecx.read_scalar(value).unwrap();
                     if expected != value_const {
                         // Poison all places this operand references so that further code
@@ -936,7 +936,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                         );
                     } else {
                         if self.should_const_prop(value) {
-                            if let ScalarMaybeUndef::Scalar(scalar) = value_const {
+                            if let ScalarMaybeUninit::Scalar(scalar) = value_const {
                                 *cond = self.operand_from_scalar(
                                     scalar,
                                     self.tcx.types.bool,
@@ -950,7 +950,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
             TerminatorKind::SwitchInt { ref mut discr, switch_ty, .. } => {
                 if let Some(value) = self.eval_operand(&discr, source_info) {
                     if self.should_const_prop(value) {
-                        if let ScalarMaybeUndef::Scalar(scalar) =
+                        if let ScalarMaybeUninit::Scalar(scalar) =
                             self.ecx.read_scalar(value).unwrap()
                         {
                             *discr = self.operand_from_scalar(scalar, switch_ty, source_info.span);
@@ -1003,9 +1003,9 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                                     // and use it to do const-prop here and everywhere else
                                     // where it makes sense.
                                     if let interpret::Operand::Immediate(
-                                        interpret::Immediate::Scalar(
-                                            interpret::ScalarMaybeUndef::Scalar(scalar),
-                                        ),
+                                        interpret::Immediate::Scalar(ScalarMaybeUninit::Scalar(
+                                            scalar,
+                                        )),
                                     ) = *value
                                     {
                                         *opr = self.operand_from_scalar(
diff --git a/src/librustc_mir/util/pretty.rs b/src/librustc_mir/util/pretty.rs
index 098601626db..5e8515ccdde 100644
--- a/src/librustc_mir/util/pretty.rs
+++ b/src/librustc_mir/util/pretty.rs
@@ -774,7 +774,7 @@ fn write_allocation_bytes<Tag: Copy + Debug, Extra>(
                 ascii.push('╼');
                 i += ptr_size;
             }
-        } else if alloc.undef_mask().is_range_defined(i, i + Size::from_bytes(1)).is_ok() {
+        } else if alloc.init_mask().is_range_initialized(i, i + Size::from_bytes(1)).is_ok() {
             let j = i.bytes_usize();
 
             // Checked definedness (and thus range) and relocations. This access also doesn't
diff --git a/src/test/mir-opt/const_prop/control-flow-simplification/rustc.hello.ConstProp.diff b/src/test/mir-opt/const_prop/control-flow-simplification/rustc.hello.ConstProp.diff
index 07a144942ca..b4d1f087391 100644
--- a/src/test/mir-opt/const_prop/control-flow-simplification/rustc.hello.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/control-flow-simplification/rustc.hello.ConstProp.diff
@@ -51,10 +51,10 @@
                                            // + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
                                            // mir::Constant
                                            // + span: $SRC_DIR/libstd/macros.rs:LL:COL
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
       }
   }
   
diff --git a/src/test/mir-opt/inline/inline-into-box-place/32bit/rustc.main.Inline.diff b/src/test/mir-opt/inline/inline-into-box-place/32bit/rustc.main.Inline.diff
index eca7ae0f549..40d56c22413 100644
--- a/src/test/mir-opt/inline/inline-into-box-place/32bit/rustc.main.Inline.diff
+++ b/src/test/mir-opt/inline/inline-into-box-place/32bit/rustc.main.Inline.diff
@@ -24,7 +24,7 @@
 -                                          // + ty: fn() -> std::vec::Vec<u32> {std::vec::Vec::<u32>::new}
 -                                          // + val: Value(Scalar(<ZST>))
 +                                          // + ty: alloc::raw_vec::RawVec<u32>
-+                                          // + val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 2 }, mutability: Not, extra: () }, offset: Size { raw: 0 } })
++                                          // + val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 2 }, mutability: Not, extra: () }, offset: Size { raw: 0 } })
                                            // mir::Constant
 -                                          // + span: $DIR/inline-into-box-place.rs:8:33: 8:41
 -                                          // + user_ty: UserType(1)
@@ -38,7 +38,7 @@
 -     bb2: {
 +                                          // + span: $SRC_DIR/liballoc/vec.rs:LL:COL
 +                                          // + user_ty: UserType(0)
-+                                          // + literal: Const { ty: alloc::raw_vec::RawVec<u32>, val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 2 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) }
++                                          // + literal: Const { ty: alloc::raw_vec::RawVec<u32>, val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 2 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) }
 +         ((*_4).1: usize) = const 0usize; // scope 2 at $SRC_DIR/liballoc/vec.rs:LL:COL
 +                                          // ty::Const
 +                                          // + ty: usize
diff --git a/src/test/mir-opt/inline/inline-into-box-place/64bit/rustc.main.Inline.diff b/src/test/mir-opt/inline/inline-into-box-place/64bit/rustc.main.Inline.diff
index a371fa214f2..0b1b3d96cbf 100644
--- a/src/test/mir-opt/inline/inline-into-box-place/64bit/rustc.main.Inline.diff
+++ b/src/test/mir-opt/inline/inline-into-box-place/64bit/rustc.main.Inline.diff
@@ -24,7 +24,7 @@
 -                                          // + ty: fn() -> std::vec::Vec<u32> {std::vec::Vec::<u32>::new}
 -                                          // + val: Value(Scalar(<ZST>))
 +                                          // + ty: alloc::raw_vec::RawVec<u32>
-+                                          // + val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [65535], len: Size { raw: 16 } }, size: Size { raw: 16 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } })
++                                          // + val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [65535], len: Size { raw: 16 } }, size: Size { raw: 16 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } })
                                            // mir::Constant
 -                                          // + span: $DIR/inline-into-box-place.rs:8:33: 8:41
 -                                          // + user_ty: UserType(1)
@@ -38,7 +38,7 @@
 -     bb2: {
 +                                          // + span: $SRC_DIR/liballoc/vec.rs:LL:COL
 +                                          // + user_ty: UserType(0)
-+                                          // + literal: Const { ty: alloc::raw_vec::RawVec<u32>, val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [65535], len: Size { raw: 16 } }, size: Size { raw: 16 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) }
++                                          // + literal: Const { ty: alloc::raw_vec::RawVec<u32>, val: Value(ByRef { alloc: Allocation { bytes: [4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [65535], len: Size { raw: 16 } }, size: Size { raw: 16 }, align: Align { pow2: 3 }, mutability: Not, extra: () }, offset: Size { raw: 0 } }) }
 +         ((*_4).1: usize) = const 0usize; // scope 2 at $SRC_DIR/liballoc/vec.rs:LL:COL
 +                                          // ty::Const
 +                                          // + ty: usize
diff --git a/src/test/mir-opt/no-drop-for-inactive-variant/rustc.unwrap.SimplifyCfg-elaborate-drops.after.mir b/src/test/mir-opt/no-drop-for-inactive-variant/rustc.unwrap.SimplifyCfg-elaborate-drops.after.mir
index a20a3c0e603..eb6911735a5 100644
--- a/src/test/mir-opt/no-drop-for-inactive-variant/rustc.unwrap.SimplifyCfg-elaborate-drops.after.mir
+++ b/src/test/mir-opt/no-drop-for-inactive-variant/rustc.unwrap.SimplifyCfg-elaborate-drops.after.mir
@@ -32,10 +32,10 @@ fn unwrap(_1: std::option::Option<T>) -> T {
                                          // + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
                                          // mir::Constant
                                          // + span: $SRC_DIR/libstd/macros.rs:LL:COL
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
     }
 
     bb3: {
diff --git a/src/test/mir-opt/no-spurious-drop-after-call/rustc.main.ElaborateDrops.before.mir b/src/test/mir-opt/no-spurious-drop-after-call/rustc.main.ElaborateDrops.before.mir
index e1ab6cc0b94..0af213e425f 100644
--- a/src/test/mir-opt/no-spurious-drop-after-call/rustc.main.ElaborateDrops.before.mir
+++ b/src/test/mir-opt/no-spurious-drop-after-call/rustc.main.ElaborateDrops.before.mir
@@ -15,10 +15,10 @@ fn main() -> () {
         _4 = const "";                   // scope 0 at $DIR/no-spurious-drop-after-call.rs:9:20: 9:22
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [], len: Size { raw: 0 } }, size: Size { raw: 0 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 0 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [], len: Size { raw: 0 } }, size: Size { raw: 0 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 0 })
                                          // mir::Constant
                                          // + span: $DIR/no-spurious-drop-after-call.rs:9:20: 9:22
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [], len: Size { raw: 0 } }, size: Size { raw: 0 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 0 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [], len: Size { raw: 0 } }, size: Size { raw: 0 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 0 }) }
         _3 = &(*_4);                     // scope 0 at $DIR/no-spurious-drop-after-call.rs:9:20: 9:22
         _2 = const <str as std::string::ToString>::to_string(move _3) -> bb2; // scope 0 at $DIR/no-spurious-drop-after-call.rs:9:20: 9:34
                                          // ty::Const
diff --git a/src/test/mir-opt/storage_live_dead_in_statics/rustc.XXX.mir_map.0.mir b/src/test/mir-opt/storage_live_dead_in_statics/rustc.XXX.mir_map.0.mir
index e7815da73aa..62b7535f2b5 100644
--- a/src/test/mir-opt/storage_live_dead_in_statics/rustc.XXX.mir_map.0.mir
+++ b/src/test/mir-opt/storage_live_dead_in_statics/rustc.XXX.mir_map.0.mir
@@ -653,10 +653,10 @@ static XXX: &Foo = {
         _2 = Foo { tup: const "hi", data: move _3 }; // scope 0 at $DIR/storage_live_dead_in_statics.rs:5:29: 23:2
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [104, 105], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [3], len: Size { raw: 2 } }, size: Size { raw: 2 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 2 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [104, 105], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [3], len: Size { raw: 2 } }, size: Size { raw: 2 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 2 })
                                          // mir::Constant
                                          // + span: $DIR/storage_live_dead_in_statics.rs:6:10: 6:14
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [104, 105], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [3], len: Size { raw: 2 } }, size: Size { raw: 2 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 2 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [104, 105], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [3], len: Size { raw: 2 } }, size: Size { raw: 2 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 2 }) }
         _1 = &_2;                        // scope 0 at $DIR/storage_live_dead_in_statics.rs:5:28: 23:2
         _0 = &(*_1);                     // scope 0 at $DIR/storage_live_dead_in_statics.rs:5:28: 23:2
         StorageDead(_5);                 // scope 0 at $DIR/storage_live_dead_in_statics.rs:23:1: 23:2
diff --git a/src/test/mir-opt/uninhabited_enum_branching/rustc.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir b/src/test/mir-opt/uninhabited_enum_branching/rustc.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir
index 4d65f8d1047..df6c90fc7fb 100644
--- a/src/test/mir-opt/uninhabited_enum_branching/rustc.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir
+++ b/src/test/mir-opt/uninhabited_enum_branching/rustc.main.SimplifyCfg-after-uninhabited-enum-branching.after.mir
@@ -21,10 +21,10 @@ fn main() -> () {
         _5 = const "C";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:23:21: 23:24
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                          // mir::Constant
                                          // + span: $DIR/uninhabited_enum_branching.rs:23:21: 23:24
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
         _1 = &(*_5);                     // scope 0 at $DIR/uninhabited_enum_branching.rs:23:21: 23:24
         StorageDead(_5);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:23:23: 23:24
         StorageDead(_2);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:24:6: 24:7
@@ -41,10 +41,10 @@ fn main() -> () {
         _9 = const "E";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:28:21: 28:24
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                          // mir::Constant
                                          // + span: $DIR/uninhabited_enum_branching.rs:28:21: 28:24
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
         _6 = &(*_9);                     // scope 0 at $DIR/uninhabited_enum_branching.rs:28:21: 28:24
         StorageDead(_9);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:28:23: 28:24
         goto -> bb3;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:26:5: 29:6
@@ -54,10 +54,10 @@ fn main() -> () {
         _6 = const "D";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:27:21: 27:24
                                          // ty::Const
                                          // + ty: &str
-                                         // + val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                         // + val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                          // mir::Constant
                                          // + span: $DIR/uninhabited_enum_branching.rs:27:21: 27:24
-                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                         // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
         goto -> bb3;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:26:5: 29:6
     }
 
diff --git a/src/test/mir-opt/uninhabited_enum_branching/rustc.main.UninhabitedEnumBranching.diff b/src/test/mir-opt/uninhabited_enum_branching/rustc.main.UninhabitedEnumBranching.diff
index da9dd8b0963..fa1474aa049 100644
--- a/src/test/mir-opt/uninhabited_enum_branching/rustc.main.UninhabitedEnumBranching.diff
+++ b/src/test/mir-opt/uninhabited_enum_branching/rustc.main.UninhabitedEnumBranching.diff
@@ -27,10 +27,10 @@
           _5 = const "C";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:23:21: 23:24
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                            // mir::Constant
                                            // + span: $DIR/uninhabited_enum_branching.rs:23:21: 23:24
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [67], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
           _1 = &(*_5);                     // scope 0 at $DIR/uninhabited_enum_branching.rs:23:21: 23:24
           StorageDead(_5);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:23:23: 23:24
           goto -> bb4;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:20:5: 24:6
@@ -40,10 +40,10 @@
           _1 = const "A(Empty)";           // scope 0 at $DIR/uninhabited_enum_branching.rs:21:24: 21:34
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [65, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [65, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 })
                                            // mir::Constant
                                            // + span: $DIR/uninhabited_enum_branching.rs:21:24: 21:34
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [65, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [65, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 }) }
           goto -> bb4;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:20:5: 24:6
       }
   
@@ -52,10 +52,10 @@
           _4 = const "B(Empty)";           // scope 0 at $DIR/uninhabited_enum_branching.rs:22:24: 22:34
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [66, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [66, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 })
                                            // mir::Constant
                                            // + span: $DIR/uninhabited_enum_branching.rs:22:24: 22:34
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [66, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [66, 40, 69, 109, 112, 116, 121, 41], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [255], len: Size { raw: 8 } }, size: Size { raw: 8 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 8 }) }
           _1 = &(*_4);                     // scope 0 at $DIR/uninhabited_enum_branching.rs:22:24: 22:34
           StorageDead(_4);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:22:33: 22:34
           goto -> bb4;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:20:5: 24:6
@@ -76,10 +76,10 @@
           _9 = const "E";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:28:21: 28:24
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                            // mir::Constant
                                            // + span: $DIR/uninhabited_enum_branching.rs:28:21: 28:24
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [69], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
           _6 = &(*_9);                     // scope 0 at $DIR/uninhabited_enum_branching.rs:28:21: 28:24
           StorageDead(_9);                 // scope 0 at $DIR/uninhabited_enum_branching.rs:28:23: 28:24
           goto -> bb7;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:26:5: 29:6
@@ -89,10 +89,10 @@
           _6 = const "D";                  // scope 0 at $DIR/uninhabited_enum_branching.rs:27:21: 27:24
                                            // ty::Const
                                            // + ty: &str
-                                           // + val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
+                                           // + val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 })
                                            // mir::Constant
                                            // + span: $DIR/uninhabited_enum_branching.rs:27:21: 27:24
-                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), undef_mask: UndefMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [68], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [1], len: Size { raw: 1 } }, size: Size { raw: 1 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 1 }) }
           goto -> bb7;                     // scope 0 at $DIR/uninhabited_enum_branching.rs:26:5: 29:6
       }
   
diff --git a/src/test/ui-fulldeps/undef_mask.rs b/src/test/ui-fulldeps/uninit_mask.rs
index 656d0b451bc..84ce291016a 100644
--- a/src/test/ui-fulldeps/undef_mask.rs
+++ b/src/test/ui-fulldeps/uninit_mask.rs
@@ -7,11 +7,11 @@
 extern crate rustc_middle;
 extern crate rustc_target;
 
-use rustc_middle::mir::interpret::UndefMask;
+use rustc_middle::mir::interpret::InitMask;
 use rustc_target::abi::Size;
 
 fn main() {
-    let mut mask = UndefMask::new(Size::from_bytes(500), false);
+    let mut mask = InitMask::new(Size::from_bytes(500), false);
     assert!(!mask.get(Size::from_bytes(499)));
     mask.set(Size::from_bytes(499), true);
     assert!(mask.get(Size::from_bytes(499)));