compiler/rustc_middle/src/mir/interpret/value.rs - toolchain/rustc - Git at Google

 use std::convert::{TryFrom, TryInto};
 use std::fmt;

 use rustc_apfloat::{
     ieee::{Double, Single},
     Float,
 };
 use rustc_macros::HashStable;
 use rustc_target::abi::{HasDataLayout, Size};

 use crate::ty::{Lift, ParamEnv, ScalarInt, Ty, TyCtxt};

 use super::{
     AllocId, AllocRange, Allocation, InterpResult, Pointer, PointerArithmetic, Provenance,
 };

 /// Represents the result of const evaluation via the `eval_to_allocation` query.
 #[derive(Copy, Clone, HashStable, TyEncodable, TyDecodable, Debug, Hash, Eq, PartialEq)]
 pub struct ConstAlloc<'tcx> {
     // the value lives here, at offset 0, and that allocation definitely is an `AllocKind::Memory`
     // (so you can use `AllocMap::unwrap_memory`).
     pub alloc_id: AllocId,
     pub ty: Ty<'tcx>,
 }

 /// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for
 /// array length computations, enum discriminants and the pattern matching logic.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Hash)]
 #[derive(HashStable)]
 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 `Uninit`.
     Scalar(Scalar),

     /// Used only for `&[u8]` and `&str`
     Slice { data: &'tcx Allocation, start: usize, end: usize },

     /// A value not represented/representable by `Scalar` or `Slice`
     ByRef {
         /// The backing memory of the value, may contain more memory than needed for just the value
         /// in order to share `Allocation`s between values
         alloc: &'tcx Allocation,
         /// Offset into `alloc`
         offset: Size,
     },
 }

 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(ConstValue<'_>, 32);

 impl<'a, 'tcx> Lift<'tcx> for ConstValue<'a> {
     type Lifted = ConstValue<'tcx>;
     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ConstValue<'tcx>> {
         Some(match self {
             ConstValue::Scalar(s) => ConstValue::Scalar(s),
             ConstValue::Slice { data, start, end } => {
                 ConstValue::Slice { data: tcx.lift(data)?, start, end }
             }
             ConstValue::ByRef { alloc, offset } => {
                 ConstValue::ByRef { alloc: tcx.lift(alloc)?, offset }
             }
         })
     }
 }

 impl<'tcx> ConstValue<'tcx> {
     #[inline]
     pub fn try_to_scalar(&self) -> Option<Scalar<AllocId>> {
         match *self {
             ConstValue::ByRef { .. } | ConstValue::Slice { .. } => None,
             ConstValue::Scalar(val) => Some(val),
         }
     }

     pub fn try_to_scalar_int(&self) -> Option<ScalarInt> {
         Some(self.try_to_scalar()?.assert_int())
     }

     pub fn try_to_bits(&self, size: Size) -> Option<u128> {
         self.try_to_scalar_int()?.to_bits(size).ok()
     }

     pub fn try_to_bool(&self) -> Option<bool> {
         self.try_to_scalar_int()?.try_into().ok()
     }

     pub fn try_to_machine_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
         self.try_to_scalar_int()?.try_to_machine_usize(tcx).ok()
     }

     pub fn try_to_bits_for_ty(
         &self,
         tcx: TyCtxt<'tcx>,
         param_env: ParamEnv<'tcx>,
         ty: Ty<'tcx>,
     ) -> Option<u128> {
         let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
         self.try_to_bits(size)
     }

     pub fn from_bool(b: bool) -> Self {
         ConstValue::Scalar(Scalar::from_bool(b))
     }

     pub fn from_u64(i: u64) -> Self {
         ConstValue::Scalar(Scalar::from_u64(i))
     }

     pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
         ConstValue::Scalar(Scalar::from_machine_usize(i, cx))
     }
 }

 /// A `Scalar` represents an immediate, primitive value existing outside of a
 /// `memory::Allocation`. It is in many ways like a small chunk of an `Allocation`, up to 16 bytes in
 /// size. Like a range of bytes in an `Allocation`, a `Scalar` can either represent the raw bytes
 /// of a simple value or a pointer into another `Allocation`
 ///
 /// These variants would be private if there was a convenient way to achieve that in Rust.
 /// Do *not* match on a `Scalar`! Use the various `to_*` methods instead.
 #[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, TyEncodable, TyDecodable, Hash)]
 #[derive(HashStable)]
 pub enum Scalar<Tag = AllocId> {
     /// The raw bytes of a simple value.
     Int(ScalarInt),

     /// A pointer into an `Allocation`. An `Allocation` in the `memory` module has a list of
     /// relocations, but a `Scalar` is only large enough to contain one, so we just represent the
     /// relocation and its associated offset together as a `Pointer` here.
     ///
     /// We also store the size of the pointer, such that a `Scalar` always knows how big it is.
     /// The size is always the pointer size of the current target, but this is not information
     /// that we always have readily available.
     Ptr(Pointer<Tag>, u8),
 }

 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(Scalar, 24);

 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
 // all the Miri types.
 impl<Tag: Provenance> fmt::Debug for Scalar<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Scalar::Ptr(ptr, _size) => write!(f, "{:?}", ptr),
             Scalar::Int(int) => write!(f, "{:?}", int),
         }
     }
 }

 impl<Tag: Provenance> fmt::Display for Scalar<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Scalar::Ptr(ptr, _size) => write!(f, "pointer to {:?}", ptr),
             Scalar::Int(int) => write!(f, "{:?}", int),
         }
     }
 }

 impl<Tag> From<Single> for Scalar<Tag> {
     #[inline(always)]
     fn from(f: Single) -> Self {
         Scalar::from_f32(f)
     }
 }

 impl<Tag> From<Double> for Scalar<Tag> {
     #[inline(always)]
     fn from(f: Double) -> Self {
         Scalar::from_f64(f)
     }
 }

 impl<Tag> From<ScalarInt> for Scalar<Tag> {
     #[inline(always)]
     fn from(ptr: ScalarInt) -> Self {
         Scalar::Int(ptr)
     }
 }

 impl<Tag> Scalar<Tag> {
     pub const ZST: Self = Scalar::Int(ScalarInt::ZST);

     #[inline(always)]
     pub fn from_pointer(ptr: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
         Scalar::Ptr(ptr, u8::try_from(cx.pointer_size().bytes()).unwrap())
     }

     /// Create a Scalar from a pointer with an `Option<_>` tag (where `None` represents a plain integer).
     pub fn from_maybe_pointer(ptr: Pointer<Option<Tag>>, cx: &impl HasDataLayout) -> Self {
         match ptr.into_parts() {
             (Some(tag), offset) => Scalar::from_pointer(Pointer::new(tag, offset), cx),
             (None, offset) => {
                 Scalar::Int(ScalarInt::try_from_uint(offset.bytes(), cx.pointer_size()).unwrap())
             }
         }
     }

     #[inline]
     pub fn null_ptr(cx: &impl HasDataLayout) -> Self {
         Scalar::Int(ScalarInt::null(cx.pointer_size()))
     }

     #[inline]
     pub fn from_bool(b: bool) -> Self {
         Scalar::Int(b.into())
     }

     #[inline]
     pub fn from_char(c: char) -> Self {
         Scalar::Int(c.into())
     }

     #[inline]
     pub fn try_from_uint(i: impl Into<u128>, size: Size) -> Option<Self> {
         ScalarInt::try_from_uint(i, size).map(Scalar::Int)
     }

     #[inline]
     pub fn from_uint(i: impl Into<u128>, size: Size) -> Self {
         let i = i.into();
         Self::try_from_uint(i, size)
             .unwrap_or_else(|| bug!("Unsigned value {:#x} does not fit in {} bits", i, size.bits()))
     }

     #[inline]
     pub fn from_u8(i: u8) -> Self {
         Scalar::Int(i.into())
     }

     #[inline]
     pub fn from_u16(i: u16) -> Self {
         Scalar::Int(i.into())
     }

     #[inline]
     pub fn from_u32(i: u32) -> Self {
         Scalar::Int(i.into())
     }

     #[inline]
     pub fn from_u64(i: u64) -> Self {
         Scalar::Int(i.into())
     }

     #[inline]
     pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
         Self::from_uint(i, cx.data_layout().pointer_size)
     }

     #[inline]
     pub fn try_from_int(i: impl Into<i128>, size: Size) -> Option<Self> {
         ScalarInt::try_from_int(i, size).map(Scalar::Int)
     }

     #[inline]
     pub fn from_int(i: impl Into<i128>, size: Size) -> Self {
         let i = i.into();
         Self::try_from_int(i, size)
             .unwrap_or_else(|| bug!("Signed value {:#x} does not fit in {} bits", i, size.bits()))
     }

     #[inline]
     pub fn from_i32(i: i32) -> Self {
         Self::from_int(i, Size::from_bits(32))
     }

     #[inline]
     pub fn from_i64(i: i64) -> Self {
         Self::from_int(i, Size::from_bits(64))
     }

     #[inline]
     pub fn from_machine_isize(i: i64, cx: &impl HasDataLayout) -> Self {
         Self::from_int(i, cx.data_layout().pointer_size)
     }

     #[inline]
     pub fn from_f32(f: Single) -> Self {
         Scalar::Int(f.into())
     }

     #[inline]
     pub fn from_f64(f: Double) -> Self {
         Scalar::Int(f.into())
     }

     /// This is almost certainly not the method you want!  You should dispatch on the type
     /// and use `to_{u8,u16,...}`/`scalar_to_ptr` to perform ptr-to-int / int-to-ptr casts as needed.
     ///
     /// This method only exists for the benefit of low-level operations that truly need to treat the
     /// scalar in whatever form it is.
     #[inline]
     pub fn to_bits_or_ptr_internal(self, target_size: Size) -> Result<u128, Pointer<Tag>> {
         assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
         match self {
             Scalar::Int(int) => Ok(int.assert_bits(target_size)),
             Scalar::Ptr(ptr, sz) => {
                 assert_eq!(target_size.bytes(), u64::from(sz));
                 Err(ptr)
             }
         }
     }
 }

 impl<'tcx, Tag: Provenance> Scalar<Tag> {
     /// Fundamental scalar-to-int (cast) operation. Many convenience wrappers exist below, that you
     /// likely want to use instead.
     ///
     /// Will perform ptr-to-int casts if needed and possible.
     /// If that fails, we know the offset is relative, so we return an "erased" Scalar
     /// (which is useful for error messages but not much else).
     #[inline]
     pub fn try_to_int(self) -> Result<ScalarInt, Scalar<AllocId>> {
         match self {
             Scalar::Int(int) => Ok(int),
             Scalar::Ptr(ptr, sz) => {
                 if Tag::OFFSET_IS_ADDR {
                     Ok(ScalarInt::try_from_uint(ptr.offset.bytes(), Size::from_bytes(sz)).unwrap())
                 } else {
                     // We know `offset` is relative, since `OFFSET_IS_ADDR == false`.
                     let (tag, offset) = ptr.into_parts();
                     Err(Scalar::Ptr(Pointer::new(tag.get_alloc_id(), offset), sz))
                 }
             }
         }
     }

     #[inline(always)]
     pub fn assert_int(self) -> ScalarInt {
         self.try_to_int().unwrap()
     }

     /// This throws UB (instead of ICEing) on a size mismatch since size mismatches can arise in
     /// Miri when someone declares a function that we shim (such as `malloc`) with a wrong type.
     #[inline]
     pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {
         assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
         self.try_to_int().map_err(|_| err_unsup!(ReadPointerAsBytes))?.to_bits(target_size).map_err(
             |size| {
                 err_ub!(ScalarSizeMismatch {
                     target_size: target_size.bytes(),
                     data_size: size.bytes(),
                 })
                 .into()
             },
         )
     }

     #[inline(always)]
     pub fn assert_bits(self, target_size: Size) -> u128 {
         self.to_bits(target_size).unwrap()
     }

     pub fn to_bool(self) -> InterpResult<'tcx, bool> {
         let val = self.to_u8()?;
         match val {
             0 => Ok(false),
             1 => Ok(true),
             _ => throw_ub!(InvalidBool(val)),
         }
     }

     pub fn to_char(self) -> InterpResult<'tcx, char> {
         let val = self.to_u32()?;
         match std::char::from_u32(val) {
             Some(c) => Ok(c),
             None => throw_ub!(InvalidChar(val)),
         }
     }

     #[inline]
     fn to_unsigned_with_bit_width(self, bits: u64) -> InterpResult<'static, u128> {
         let sz = Size::from_bits(bits);
         self.to_bits(sz)
     }

     /// Converts the scalar to produce a `u8`. Fails if the scalar is a pointer.
     pub fn to_u8(self) -> InterpResult<'static, u8> {
         self.to_unsigned_with_bit_width(8).map(|v| u8::try_from(v).unwrap())
     }

     /// Converts the scalar to produce a `u16`. Fails if the scalar is a pointer.
     pub fn to_u16(self) -> InterpResult<'static, u16> {
         self.to_unsigned_with_bit_width(16).map(|v| u16::try_from(v).unwrap())
     }

     /// Converts the scalar to produce a `u32`. Fails if the scalar is a pointer.
     pub fn to_u32(self) -> InterpResult<'static, u32> {
         self.to_unsigned_with_bit_width(32).map(|v| u32::try_from(v).unwrap())
     }

     /// Converts the scalar to produce a `u64`. Fails if the scalar is a pointer.
     pub fn to_u64(self) -> InterpResult<'static, u64> {
         self.to_unsigned_with_bit_width(64).map(|v| u64::try_from(v).unwrap())
     }

     /// Converts the scalar to produce a `u128`. Fails if the scalar is a pointer.
     pub fn to_u128(self) -> InterpResult<'static, u128> {
         self.to_unsigned_with_bit_width(128)
     }

     pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'static, u64> {
         let b = self.to_bits(cx.data_layout().pointer_size)?;
         Ok(u64::try_from(b).unwrap())
     }

     #[inline]
     fn to_signed_with_bit_width(self, bits: u64) -> InterpResult<'static, i128> {
         let sz = Size::from_bits(bits);
         let b = self.to_bits(sz)?;
         Ok(sz.sign_extend(b) as i128)
     }

     /// Converts the scalar to produce an `i8`. Fails if the scalar is a pointer.
     pub fn to_i8(self) -> InterpResult<'static, i8> {
         self.to_signed_with_bit_width(8).map(|v| i8::try_from(v).unwrap())
     }

     /// Converts the scalar to produce an `i16`. Fails if the scalar is a pointer.
     pub fn to_i16(self) -> InterpResult<'static, i16> {
         self.to_signed_with_bit_width(16).map(|v| i16::try_from(v).unwrap())
     }

     /// Converts the scalar to produce an `i32`. Fails if the scalar is a pointer.
     pub fn to_i32(self) -> InterpResult<'static, i32> {
         self.to_signed_with_bit_width(32).map(|v| i32::try_from(v).unwrap())
     }

     /// Converts the scalar to produce an `i64`. Fails if the scalar is a pointer.
     pub fn to_i64(self) -> InterpResult<'static, i64> {
         self.to_signed_with_bit_width(64).map(|v| i64::try_from(v).unwrap())
     }

     /// Converts the scalar to produce an `i128`. Fails if the scalar is a pointer.
     pub fn to_i128(self) -> InterpResult<'static, i128> {
         self.to_signed_with_bit_width(128)
     }

     pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'static, i64> {
         let sz = cx.data_layout().pointer_size;
         let b = self.to_bits(sz)?;
         let b = sz.sign_extend(b) as i128;
         Ok(i64::try_from(b).unwrap())
     }

     #[inline]
     pub fn to_f32(self) -> InterpResult<'static, Single> {
         // Going through `u32` to check size and truncation.
         Ok(Single::from_bits(self.to_u32()?.into()))
     }

     #[inline]
     pub fn to_f64(self) -> InterpResult<'static, Double> {
         // Going through `u64` to check size and truncation.
         Ok(Double::from_bits(self.to_u64()?.into()))
     }
 }

 #[derive(Clone, Copy, Eq, PartialEq, TyEncodable, TyDecodable, HashStable, Hash)]
 pub enum ScalarMaybeUninit<Tag = AllocId> {
     Scalar(Scalar<Tag>),
     Uninit,
 }

 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(ScalarMaybeUninit, 24);

 impl<Tag> From<Scalar<Tag>> for ScalarMaybeUninit<Tag> {
     #[inline(always)]
     fn from(s: Scalar<Tag>) -> Self {
         ScalarMaybeUninit::Scalar(s)
     }
 }

 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
 // all the Miri types.
 impl<Tag: Provenance> fmt::Debug for ScalarMaybeUninit<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             ScalarMaybeUninit::Uninit => write!(f, "<uninitialized>"),
             ScalarMaybeUninit::Scalar(s) => write!(f, "{:?}", s),
         }
     }
 }

 impl<Tag: Provenance> fmt::Display for ScalarMaybeUninit<Tag> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             ScalarMaybeUninit::Uninit => write!(f, "uninitialized bytes"),
             ScalarMaybeUninit::Scalar(s) => write!(f, "{}", s),
         }
     }
 }

 impl<Tag> ScalarMaybeUninit<Tag> {
     #[inline]
     pub fn from_pointer(ptr: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
         ScalarMaybeUninit::Scalar(Scalar::from_pointer(ptr, cx))
     }

     #[inline]
     pub fn from_maybe_pointer(ptr: Pointer<Option<Tag>>, cx: &impl HasDataLayout) -> Self {
         ScalarMaybeUninit::Scalar(Scalar::from_maybe_pointer(ptr, cx))
     }

     #[inline]
     pub fn check_init(self) -> InterpResult<'static, Scalar<Tag>> {
         match self {
             ScalarMaybeUninit::Scalar(scalar) => Ok(scalar),
             ScalarMaybeUninit::Uninit => throw_ub!(InvalidUninitBytes(None)),
         }
     }
 }

 impl<'tcx, Tag: Provenance> ScalarMaybeUninit<Tag> {
     #[inline(always)]
     pub fn to_bool(self) -> InterpResult<'tcx, bool> {
         self.check_init()?.to_bool()
     }

     #[inline(always)]
     pub fn to_char(self) -> InterpResult<'tcx, char> {
         self.check_init()?.to_char()
     }

     #[inline(always)]
     pub fn to_f32(self) -> InterpResult<'tcx, Single> {
         self.check_init()?.to_f32()
     }

     #[inline(always)]
     pub fn to_f64(self) -> InterpResult<'tcx, Double> {
         self.check_init()?.to_f64()
     }

     #[inline(always)]
     pub fn to_u8(self) -> InterpResult<'tcx, u8> {
         self.check_init()?.to_u8()
     }

     #[inline(always)]
     pub fn to_u16(self) -> InterpResult<'tcx, u16> {
         self.check_init()?.to_u16()
     }

     #[inline(always)]
     pub fn to_u32(self) -> InterpResult<'tcx, u32> {
         self.check_init()?.to_u32()
     }

     #[inline(always)]
     pub fn to_u64(self) -> InterpResult<'tcx, u64> {
         self.check_init()?.to_u64()
     }

     #[inline(always)]
     pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
         self.check_init()?.to_machine_usize(cx)
     }

     #[inline(always)]
     pub fn to_i8(self) -> InterpResult<'tcx, i8> {
         self.check_init()?.to_i8()
     }

     #[inline(always)]
     pub fn to_i16(self) -> InterpResult<'tcx, i16> {
         self.check_init()?.to_i16()
     }

     #[inline(always)]
     pub fn to_i32(self) -> InterpResult<'tcx, i32> {
         self.check_init()?.to_i32()
     }

     #[inline(always)]
     pub fn to_i64(self) -> InterpResult<'tcx, i64> {
         self.check_init()?.to_i64()
     }

     #[inline(always)]
     pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, i64> {
         self.check_init()?.to_machine_isize(cx)
     }
 }

 /// Gets the bytes of a constant slice value.
 pub fn get_slice_bytes<'tcx>(cx: &impl HasDataLayout, val: ConstValue<'tcx>) -> &'tcx [u8] {
     if let ConstValue::Slice { data, start, end } = val {
         let len = end - start;
         data.get_bytes(
             cx,
             AllocRange { start: Size::from_bytes(start), size: Size::from_bytes(len) },
         )
         .unwrap_or_else(|err| bug!("const slice is invalid: {:?}", err))
     } else {
         bug!("expected const slice, but found another const value");
     }
 }
	use std::convert::{TryFrom, TryInto};
	use std::fmt;

	use rustc_apfloat::{
	ieee::{Double, Single},
	Float,
	};
	use rustc_macros::HashStable;
	use rustc_target::abi::{HasDataLayout, Size};

	use crate::ty::{Lift, ParamEnv, ScalarInt, Ty, TyCtxt};

	use super::{
	AllocId, AllocRange, Allocation, InterpResult, Pointer, PointerArithmetic, Provenance,
	};

	/// Represents the result of const evaluation via the `eval_to_allocation` query.
	#[derive(Copy, Clone, HashStable, TyEncodable, TyDecodable, Debug, Hash, Eq, PartialEq)]
	pub struct ConstAlloc<'tcx> {
	// the value lives here, at offset 0, and that allocation definitely is an `AllocKind::Memory`
	// (so you can use `AllocMap::unwrap_memory`).
	pub alloc_id: AllocId,
	pub ty: Ty<'tcx>,
	}

	/// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for
	/// array length computations, enum discriminants and the pattern matching logic.
	#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Hash)]
	#[derive(HashStable)]
	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 `Uninit`.
	Scalar(Scalar),

	/// Used only for `&[u8]` and `&str`
	Slice { data: &'tcx Allocation, start: usize, end: usize },

	/// A value not represented/representable by `Scalar` or `Slice`
	ByRef {
	/// The backing memory of the value, may contain more memory than needed for just the value
	/// in order to share `Allocation`s between values
	alloc: &'tcx Allocation,
	/// Offset into `alloc`
	offset: Size,
	},
	}

	#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
	static_assert_size!(ConstValue<'_>, 32);

	impl<'a, 'tcx> Lift<'tcx> for ConstValue<'a> {
	type Lifted = ConstValue<'tcx>;
	fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ConstValue<'tcx>> {
	Some(match self {
	ConstValue::Scalar(s) => ConstValue::Scalar(s),
	ConstValue::Slice { data, start, end } => {
	ConstValue::Slice { data: tcx.lift(data)?, start, end }
	}
	ConstValue::ByRef { alloc, offset } => {
	ConstValue::ByRef { alloc: tcx.lift(alloc)?, offset }
	}
	})
	}
	}

	impl<'tcx> ConstValue<'tcx> {
	#[inline]
	pub fn try_to_scalar(&self) -> Option<Scalar<AllocId>> {
	match *self {
	ConstValue::ByRef { .. } \| ConstValue::Slice { .. } => None,
	ConstValue::Scalar(val) => Some(val),
	}
	}

	pub fn try_to_scalar_int(&self) -> Option<ScalarInt> {
	Some(self.try_to_scalar()?.assert_int())
	}

	pub fn try_to_bits(&self, size: Size) -> Option<u128> {
	self.try_to_scalar_int()?.to_bits(size).ok()
	}

	pub fn try_to_bool(&self) -> Option<bool> {
	self.try_to_scalar_int()?.try_into().ok()
	}

	pub fn try_to_machine_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
	self.try_to_scalar_int()?.try_to_machine_usize(tcx).ok()
	}

	pub fn try_to_bits_for_ty(
	&self,
	tcx: TyCtxt<'tcx>,
	param_env: ParamEnv<'tcx>,
	ty: Ty<'tcx>,
	) -> Option<u128> {
	let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
	self.try_to_bits(size)
	}

	pub fn from_bool(b: bool) -> Self {
	ConstValue::Scalar(Scalar::from_bool(b))
	}

	pub fn from_u64(i: u64) -> Self {
	ConstValue::Scalar(Scalar::from_u64(i))
	}

	pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
	ConstValue::Scalar(Scalar::from_machine_usize(i, cx))
	}
	}

	/// A `Scalar` represents an immediate, primitive value existing outside of a
	/// `memory::Allocation`. It is in many ways like a small chunk of an `Allocation`, up to 16 bytes in
	/// size. Like a range of bytes in an `Allocation`, a `Scalar` can either represent the raw bytes
	/// of a simple value or a pointer into another `Allocation`
	///
	/// These variants would be private if there was a convenient way to achieve that in Rust.
	/// Do not match on a `Scalar`! Use the various `to_*` methods instead.
	#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd, TyEncodable, TyDecodable, Hash)]
	#[derive(HashStable)]
	pub enum Scalar<Tag = AllocId> {
	/// The raw bytes of a simple value.
	Int(ScalarInt),

	/// A pointer into an `Allocation`. An `Allocation` in the `memory` module has a list of
	/// relocations, but a `Scalar` is only large enough to contain one, so we just represent the
	/// relocation and its associated offset together as a `Pointer` here.
	///
	/// We also store the size of the pointer, such that a `Scalar` always knows how big it is.
	/// The size is always the pointer size of the current target, but this is not information
	/// that we always have readily available.
	Ptr(Pointer<Tag>, u8),
	}

	#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
	static_assert_size!(Scalar, 24);

	// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
	// all the Miri types.
	impl<Tag: Provenance> fmt::Debug for Scalar<Tag> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match self {
	Scalar::Ptr(ptr, _size) => write!(f, "{:?}", ptr),
	Scalar::Int(int) => write!(f, "{:?}", int),
	}
	}
	}

	impl<Tag: Provenance> fmt::Display for Scalar<Tag> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match self {
	Scalar::Ptr(ptr, _size) => write!(f, "pointer to {:?}", ptr),
	Scalar::Int(int) => write!(f, "{:?}", int),
	}
	}
	}

	impl<Tag> From<Single> for Scalar<Tag> {
	#[inline(always)]
	fn from(f: Single) -> Self {
	Scalar::from_f32(f)
	}
	}

	impl<Tag> From<Double> for Scalar<Tag> {
	#[inline(always)]
	fn from(f: Double) -> Self {
	Scalar::from_f64(f)
	}
	}

	impl<Tag> From<ScalarInt> for Scalar<Tag> {
	#[inline(always)]
	fn from(ptr: ScalarInt) -> Self {
	Scalar::Int(ptr)
	}
	}

	impl<Tag> Scalar<Tag> {
	pub const ZST: Self = Scalar::Int(ScalarInt::ZST);

	#[inline(always)]
	pub fn from_pointer(ptr: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
	Scalar::Ptr(ptr, u8::try_from(cx.pointer_size().bytes()).unwrap())
	}

	/// Create a Scalar from a pointer with an `Option<_>` tag (where `None` represents a plain integer).
	pub fn from_maybe_pointer(ptr: Pointer<Option<Tag>>, cx: &impl HasDataLayout) -> Self {
	match ptr.into_parts() {
	(Some(tag), offset) => Scalar::from_pointer(Pointer::new(tag, offset), cx),
	(None, offset) => {
	Scalar::Int(ScalarInt::try_from_uint(offset.bytes(), cx.pointer_size()).unwrap())
	}
	}
	}

	#[inline]
	pub fn null_ptr(cx: &impl HasDataLayout) -> Self {
	Scalar::Int(ScalarInt::null(cx.pointer_size()))
	}

	#[inline]
	pub fn from_bool(b: bool) -> Self {
	Scalar::Int(b.into())
	}

	#[inline]
	pub fn from_char(c: char) -> Self {
	Scalar::Int(c.into())
	}

	#[inline]
	pub fn try_from_uint(i: impl Into<u128>, size: Size) -> Option<Self> {
	ScalarInt::try_from_uint(i, size).map(Scalar::Int)
	}

	#[inline]
	pub fn from_uint(i: impl Into<u128>, size: Size) -> Self {
	let i = i.into();
	Self::try_from_uint(i, size)
	.unwrap_or_else(\|\| bug!("Unsigned value {:#x} does not fit in {} bits", i, size.bits()))
	}

	#[inline]
	pub fn from_u8(i: u8) -> Self {
	Scalar::Int(i.into())
	}

	#[inline]
	pub fn from_u16(i: u16) -> Self {
	Scalar::Int(i.into())
	}

	#[inline]
	pub fn from_u32(i: u32) -> Self {
	Scalar::Int(i.into())
	}

	#[inline]
	pub fn from_u64(i: u64) -> Self {
	Scalar::Int(i.into())
	}

	#[inline]
	pub fn from_machine_usize(i: u64, cx: &impl HasDataLayout) -> Self {
	Self::from_uint(i, cx.data_layout().pointer_size)
	}

	#[inline]
	pub fn try_from_int(i: impl Into<i128>, size: Size) -> Option<Self> {
	ScalarInt::try_from_int(i, size).map(Scalar::Int)
	}

	#[inline]
	pub fn from_int(i: impl Into<i128>, size: Size) -> Self {
	let i = i.into();
	Self::try_from_int(i, size)
	.unwrap_or_else(\|\| bug!("Signed value {:#x} does not fit in {} bits", i, size.bits()))
	}

	#[inline]
	pub fn from_i32(i: i32) -> Self {
	Self::from_int(i, Size::from_bits(32))
	}

	#[inline]
	pub fn from_i64(i: i64) -> Self {
	Self::from_int(i, Size::from_bits(64))
	}

	#[inline]
	pub fn from_machine_isize(i: i64, cx: &impl HasDataLayout) -> Self {
	Self::from_int(i, cx.data_layout().pointer_size)
	}

	#[inline]
	pub fn from_f32(f: Single) -> Self {
	Scalar::Int(f.into())
	}

	#[inline]
	pub fn from_f64(f: Double) -> Self {
	Scalar::Int(f.into())
	}

	/// This is almost certainly not the method you want! You should dispatch on the type
	/// and use `to_{u8,u16,...}`/`scalar_to_ptr` to perform ptr-to-int / int-to-ptr casts as needed.
	///
	/// This method only exists for the benefit of low-level operations that truly need to treat the
	/// scalar in whatever form it is.
	#[inline]
	pub fn to_bits_or_ptr_internal(self, target_size: Size) -> Result<u128, Pointer<Tag>> {
	assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
	match self {
	Scalar::Int(int) => Ok(int.assert_bits(target_size)),
	Scalar::Ptr(ptr, sz) => {
	assert_eq!(target_size.bytes(), u64::from(sz));
	Err(ptr)
	}
	}
	}
	}

	impl<'tcx, Tag: Provenance> Scalar<Tag> {
	/// Fundamental scalar-to-int (cast) operation. Many convenience wrappers exist below, that you
	/// likely want to use instead.
	///
	/// Will perform ptr-to-int casts if needed and possible.
	/// If that fails, we know the offset is relative, so we return an "erased" Scalar
	/// (which is useful for error messages but not much else).
	#[inline]
	pub fn try_to_int(self) -> Result<ScalarInt, Scalar<AllocId>> {
	match self {
	Scalar::Int(int) => Ok(int),
	Scalar::Ptr(ptr, sz) => {
	if Tag::OFFSET_IS_ADDR {
	Ok(ScalarInt::try_from_uint(ptr.offset.bytes(), Size::from_bytes(sz)).unwrap())
	} else {
	// We know `offset` is relative, since `OFFSET_IS_ADDR == false`.
	let (tag, offset) = ptr.into_parts();
	Err(Scalar::Ptr(Pointer::new(tag.get_alloc_id(), offset), sz))
	}
	}
	}
	}

	#[inline(always)]
	pub fn assert_int(self) -> ScalarInt {
	self.try_to_int().unwrap()
	}

	/// This throws UB (instead of ICEing) on a size mismatch since size mismatches can arise in
	/// Miri when someone declares a function that we shim (such as `malloc`) with a wrong type.
	#[inline]
	pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {
	assert_ne!(target_size.bytes(), 0, "you should never look at the bits of a ZST");
	self.try_to_int().map_err(\|_\| err_unsup!(ReadPointerAsBytes))?.to_bits(target_size).map_err(
	\|size\| {
	err_ub!(ScalarSizeMismatch {
	target_size: target_size.bytes(),
	data_size: size.bytes(),
	})
	.into()
	},
	)
	}

	#[inline(always)]
	pub fn assert_bits(self, target_size: Size) -> u128 {
	self.to_bits(target_size).unwrap()
	}

	pub fn to_bool(self) -> InterpResult<'tcx, bool> {
	let val = self.to_u8()?;
	match val {
	0 => Ok(false),
	1 => Ok(true),
	_ => throw_ub!(InvalidBool(val)),
	}
	}

	pub fn to_char(self) -> InterpResult<'tcx, char> {
	let val = self.to_u32()?;
	match std::char::from_u32(val) {
	Some(c) => Ok(c),
	None => throw_ub!(InvalidChar(val)),
	}
	}

	#[inline]
	fn to_unsigned_with_bit_width(self, bits: u64) -> InterpResult<'static, u128> {
	let sz = Size::from_bits(bits);
	self.to_bits(sz)
	}

	/// Converts the scalar to produce a `u8`. Fails if the scalar is a pointer.
	pub fn to_u8(self) -> InterpResult<'static, u8> {
	self.to_unsigned_with_bit_width(8).map(\|v\| u8::try_from(v).unwrap())
	}

	/// Converts the scalar to produce a `u16`. Fails if the scalar is a pointer.
	pub fn to_u16(self) -> InterpResult<'static, u16> {
	self.to_unsigned_with_bit_width(16).map(\|v\| u16::try_from(v).unwrap())
	}

	/// Converts the scalar to produce a `u32`. Fails if the scalar is a pointer.
	pub fn to_u32(self) -> InterpResult<'static, u32> {
	self.to_unsigned_with_bit_width(32).map(\|v\| u32::try_from(v).unwrap())
	}

	/// Converts the scalar to produce a `u64`. Fails if the scalar is a pointer.
	pub fn to_u64(self) -> InterpResult<'static, u64> {
	self.to_unsigned_with_bit_width(64).map(\|v\| u64::try_from(v).unwrap())
	}

	/// Converts the scalar to produce a `u128`. Fails if the scalar is a pointer.
	pub fn to_u128(self) -> InterpResult<'static, u128> {
	self.to_unsigned_with_bit_width(128)
	}

	pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'static, u64> {
	let b = self.to_bits(cx.data_layout().pointer_size)?;
	Ok(u64::try_from(b).unwrap())
	}

	#[inline]
	fn to_signed_with_bit_width(self, bits: u64) -> InterpResult<'static, i128> {
	let sz = Size::from_bits(bits);
	let b = self.to_bits(sz)?;
	Ok(sz.sign_extend(b) as i128)
	}

	/// Converts the scalar to produce an `i8`. Fails if the scalar is a pointer.
	pub fn to_i8(self) -> InterpResult<'static, i8> {
	self.to_signed_with_bit_width(8).map(\|v\| i8::try_from(v).unwrap())
	}

	/// Converts the scalar to produce an `i16`. Fails if the scalar is a pointer.
	pub fn to_i16(self) -> InterpResult<'static, i16> {
	self.to_signed_with_bit_width(16).map(\|v\| i16::try_from(v).unwrap())
	}

	/// Converts the scalar to produce an `i32`. Fails if the scalar is a pointer.
	pub fn to_i32(self) -> InterpResult<'static, i32> {
	self.to_signed_with_bit_width(32).map(\|v\| i32::try_from(v).unwrap())
	}

	/// Converts the scalar to produce an `i64`. Fails if the scalar is a pointer.
	pub fn to_i64(self) -> InterpResult<'static, i64> {
	self.to_signed_with_bit_width(64).map(\|v\| i64::try_from(v).unwrap())
	}

	/// Converts the scalar to produce an `i128`. Fails if the scalar is a pointer.
	pub fn to_i128(self) -> InterpResult<'static, i128> {
	self.to_signed_with_bit_width(128)
	}

	pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'static, i64> {
	let sz = cx.data_layout().pointer_size;
	let b = self.to_bits(sz)?;
	let b = sz.sign_extend(b) as i128;
	Ok(i64::try_from(b).unwrap())
	}

	#[inline]
	pub fn to_f32(self) -> InterpResult<'static, Single> {
	// Going through `u32` to check size and truncation.
	Ok(Single::from_bits(self.to_u32()?.into()))
	}

	#[inline]
	pub fn to_f64(self) -> InterpResult<'static, Double> {
	// Going through `u64` to check size and truncation.
	Ok(Double::from_bits(self.to_u64()?.into()))
	}
	}

	#[derive(Clone, Copy, Eq, PartialEq, TyEncodable, TyDecodable, HashStable, Hash)]
	pub enum ScalarMaybeUninit<Tag = AllocId> {
	Scalar(Scalar<Tag>),
	Uninit,
	}

	#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
	static_assert_size!(ScalarMaybeUninit, 24);

	impl<Tag> From<Scalar<Tag>> for ScalarMaybeUninit<Tag> {
	#[inline(always)]
	fn from(s: Scalar<Tag>) -> Self {
	ScalarMaybeUninit::Scalar(s)
	}
	}

	// We want the `Debug` output to be readable as it is used by `derive(Debug)` for
	// all the Miri types.
	impl<Tag: Provenance> fmt::Debug for ScalarMaybeUninit<Tag> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match self {
	ScalarMaybeUninit::Uninit => write!(f, "<uninitialized>"),
	ScalarMaybeUninit::Scalar(s) => write!(f, "{:?}", s),
	}
	}
	}

	impl<Tag: Provenance> fmt::Display for ScalarMaybeUninit<Tag> {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	match self {
	ScalarMaybeUninit::Uninit => write!(f, "uninitialized bytes"),
	ScalarMaybeUninit::Scalar(s) => write!(f, "{}", s),
	}
	}
	}

	impl<Tag> ScalarMaybeUninit<Tag> {
	#[inline]
	pub fn from_pointer(ptr: Pointer<Tag>, cx: &impl HasDataLayout) -> Self {
	ScalarMaybeUninit::Scalar(Scalar::from_pointer(ptr, cx))
	}

	#[inline]
	pub fn from_maybe_pointer(ptr: Pointer<Option<Tag>>, cx: &impl HasDataLayout) -> Self {
	ScalarMaybeUninit::Scalar(Scalar::from_maybe_pointer(ptr, cx))
	}

	#[inline]
	pub fn check_init(self) -> InterpResult<'static, Scalar<Tag>> {
	match self {
	ScalarMaybeUninit::Scalar(scalar) => Ok(scalar),
	ScalarMaybeUninit::Uninit => throw_ub!(InvalidUninitBytes(None)),
	}
	}
	}

	impl<'tcx, Tag: Provenance> ScalarMaybeUninit<Tag> {
	#[inline(always)]
	pub fn to_bool(self) -> InterpResult<'tcx, bool> {
	self.check_init()?.to_bool()
	}

	#[inline(always)]
	pub fn to_char(self) -> InterpResult<'tcx, char> {
	self.check_init()?.to_char()
	}

	#[inline(always)]
	pub fn to_f32(self) -> InterpResult<'tcx, Single> {
	self.check_init()?.to_f32()
	}

	#[inline(always)]
	pub fn to_f64(self) -> InterpResult<'tcx, Double> {
	self.check_init()?.to_f64()
	}

	#[inline(always)]
	pub fn to_u8(self) -> InterpResult<'tcx, u8> {
	self.check_init()?.to_u8()
	}

	#[inline(always)]
	pub fn to_u16(self) -> InterpResult<'tcx, u16> {
	self.check_init()?.to_u16()
	}

	#[inline(always)]
	pub fn to_u32(self) -> InterpResult<'tcx, u32> {
	self.check_init()?.to_u32()
	}

	#[inline(always)]
	pub fn to_u64(self) -> InterpResult<'tcx, u64> {
	self.check_init()?.to_u64()
	}

	#[inline(always)]
	pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, u64> {
	self.check_init()?.to_machine_usize(cx)
	}

	#[inline(always)]
	pub fn to_i8(self) -> InterpResult<'tcx, i8> {
	self.check_init()?.to_i8()
	}

	#[inline(always)]
	pub fn to_i16(self) -> InterpResult<'tcx, i16> {
	self.check_init()?.to_i16()
	}

	#[inline(always)]
	pub fn to_i32(self) -> InterpResult<'tcx, i32> {
	self.check_init()?.to_i32()
	}

	#[inline(always)]
	pub fn to_i64(self) -> InterpResult<'tcx, i64> {
	self.check_init()?.to_i64()
	}

	#[inline(always)]
	pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'tcx, i64> {
	self.check_init()?.to_machine_isize(cx)
	}
	}

	/// Gets the bytes of a constant slice value.
	pub fn get_slice_bytes<'tcx>(cx: &impl HasDataLayout, val: ConstValue<'tcx>) -> &'tcx [u8] {
	if let ConstValue::Slice { data, start, end } = val {
	let len = end - start;
	data.get_bytes(
	cx,
	AllocRange { start: Size::from_bytes(start), size: Size::from_bytes(len) },
	)
	.unwrap_or_else(\|err\| bug!("const slice is invalid: {:?}", err))
	} else {
	bug!("expected const slice, but found another const value");
	}
	}