Add instance evaluation and methods to read alloc

The instance evaluation is needed to handle intrinsics such as
`type_id` and `type_name`.

Since we now use Allocation to represent all evaluated constants,
provide a few methods to help process the data inside an allocation.

14 files changed, 295 insertions, 22 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 7f627e2ce6e..e56f05a5b19 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4492,6 +4492,7 @@ dependencies = [
 name = "rustc_smir"
 version = "0.0.0"
 dependencies = [
+ "rustc_abi",
  "rustc_data_structures",
  "rustc_hir",
  "rustc_middle",
diff --git a/compiler/rustc_smir/Cargo.toml b/compiler/rustc_smir/Cargo.toml
index 836ea046ffe..c9e23efcb10 100644
--- a/compiler/rustc_smir/Cargo.toml
+++ b/compiler/rustc_smir/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
+rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_smir/src/rustc_smir/alloc.rs b/compiler/rustc_smir/src/rustc_smir/alloc.rs
index 850a52ce275..48cb164c308 100644
--- a/compiler/rustc_smir/src/rustc_smir/alloc.rs
+++ b/compiler/rustc_smir/src/rustc_smir/alloc.rs
@@ -2,6 +2,7 @@ use rustc_middle::mir::{
     interpret::{alloc_range, AllocRange, Pointer},
     ConstValue,
 };
+use stable_mir::Error;
 
 use crate::rustc_smir::{Stable, Tables};
 use stable_mir::mir::Mutability;
@@ -26,23 +27,35 @@ pub fn new_allocation<'tcx>(
     const_value: ConstValue<'tcx>,
     tables: &mut Tables<'tcx>,
 ) -> Allocation {
-    match const_value {
+    try_new_allocation(ty, const_value, tables).unwrap()
+}
+
+#[allow(rustc::usage_of_qualified_ty)]
+pub fn try_new_allocation<'tcx>(
+    ty: rustc_middle::ty::Ty<'tcx>,
+    const_value: ConstValue<'tcx>,
+    tables: &mut Tables<'tcx>,
+) -> Result<Allocation, Error> {
+    Ok(match const_value {
         ConstValue::Scalar(scalar) => {
             let size = scalar.size();
             let align = tables
                 .tcx
                 .layout_of(rustc_middle::ty::ParamEnv::reveal_all().and(ty))
-                .unwrap()
+                .map_err(|e| e.stable(tables))?
                 .align;
             let mut allocation = rustc_middle::mir::interpret::Allocation::uninit(size, align.abi);
             allocation
                 .write_scalar(&tables.tcx, alloc_range(rustc_target::abi::Size::ZERO, size), scalar)
-                .unwrap();
+                .map_err(|e| e.stable(tables))?;
             allocation.stable(tables)
         }
         ConstValue::ZeroSized => {
-            let align =
-                tables.tcx.layout_of(rustc_middle::ty::ParamEnv::empty().and(ty)).unwrap().align;
+            let align = tables
+                .tcx
+                .layout_of(rustc_middle::ty::ParamEnv::empty().and(ty))
+                .map_err(|e| e.stable(tables))?
+                .align;
             new_empty_allocation(align.abi)
         }
         ConstValue::Slice { data, meta } => {
@@ -51,8 +64,10 @@ pub fn new_allocation<'tcx>(
             let scalar_ptr = rustc_middle::mir::interpret::Scalar::from_pointer(ptr, &tables.tcx);
             let scalar_meta =
                 rustc_middle::mir::interpret::Scalar::from_target_usize(meta, &tables.tcx);
-            let layout =
-                tables.tcx.layout_of(rustc_middle::ty::ParamEnv::reveal_all().and(ty)).unwrap();
+            let layout = tables
+                .tcx
+                .layout_of(rustc_middle::ty::ParamEnv::reveal_all().and(ty))
+                .map_err(|e| e.stable(tables))?;
             let mut allocation =
                 rustc_middle::mir::interpret::Allocation::uninit(layout.size, layout.align.abi);
             allocation
@@ -61,14 +76,14 @@ pub fn new_allocation<'tcx>(
                     alloc_range(rustc_target::abi::Size::ZERO, tables.tcx.data_layout.pointer_size),
                     scalar_ptr,
                 )
-                .unwrap();
+                .map_err(|e| e.stable(tables))?;
             allocation
                 .write_scalar(
                     &tables.tcx,
                     alloc_range(tables.tcx.data_layout.pointer_size, scalar_meta.size()),
                     scalar_meta,
                 )
-                .unwrap();
+                .map_err(|e| e.stable(tables))?;
             allocation.stable(tables)
         }
         ConstValue::Indirect { alloc_id, offset } => {
@@ -76,11 +91,11 @@ pub fn new_allocation<'tcx>(
             let ty_size = tables
                 .tcx
                 .layout_of(rustc_middle::ty::ParamEnv::reveal_all().and(ty))
-                .unwrap()
+                .map_err(|e| e.stable(tables))?
                 .size;
             allocation_filter(&alloc.0, alloc_range(offset, ty_size), tables)
         }
-    }
+    })
 }
 
 /// Creates an `Allocation` only from information within the `AllocRange`.
diff --git a/compiler/rustc_smir/src/rustc_smir/context.rs b/compiler/rustc_smir/src/rustc_smir/context.rs
index b10dfe85914..341c69e9327 100644
--- a/compiler/rustc_smir/src/rustc_smir/context.rs
+++ b/compiler/rustc_smir/src/rustc_smir/context.rs
@@ -11,18 +11,29 @@ use stable_mir::compiler_interface::Context;
 use stable_mir::mir::alloc::GlobalAlloc;
 use stable_mir::mir::mono::{InstanceDef, StaticDef};
 use stable_mir::mir::Body;
+use stable_mir::target::{MachineInfo, MachineSize};
 use stable_mir::ty::{
     AdtDef, AdtKind, Allocation, ClosureDef, ClosureKind, Const, FieldDef, FnDef, GenericArgs,
-    LineInfo, PolyFnSig, RigidTy, Span, TyKind, VariantDef,
+    LineInfo, PolyFnSig, RigidTy, Span, Ty, TyKind, VariantDef,
 };
 use stable_mir::{self, Crate, CrateItem, DefId, Error, Filename, ItemKind, Symbol};
 use std::cell::RefCell;
 
 use crate::rustc_internal::{internal, RustcInternal};
 use crate::rustc_smir::builder::BodyBuilder;
-use crate::rustc_smir::{new_item_kind, smir_crate, Stable, Tables};
+use crate::rustc_smir::{alloc, new_item_kind, smir_crate, Stable, Tables};
 
 impl<'tcx> Context for TablesWrapper<'tcx> {
+    fn target_info(&self) -> MachineInfo {
+        let mut tables = self.0.borrow_mut();
+        MachineInfo {
+            endian: tables.tcx.data_layout.endian.stable(&mut *tables),
+            pointer_width: MachineSize::from_bits(
+                tables.tcx.data_layout.pointer_size.bits().try_into().unwrap(),
+            ),
+        }
+    }
+
     fn entry_fn(&self) -> Option<stable_mir::CrateItem> {
         let mut tables = self.0.borrow_mut();
         let tcx = tables.tcx;
@@ -382,6 +393,21 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         Instance::resolve_closure(tables.tcx, def_id, args_ref, closure_kind).stable(&mut *tables)
     }
 
+    fn eval_instance(&self, def: InstanceDef, const_ty: Ty) -> Result<Allocation, Error> {
+        let mut tables = self.0.borrow_mut();
+        let instance = tables.instances[def];
+        let result = tables.tcx.const_eval_instance(
+            ParamEnv::reveal_all(),
+            instance,
+            Some(tables.tcx.def_span(instance.def_id())),
+        );
+        result
+            .map(|const_val| {
+                alloc::try_new_allocation(const_ty.internal(&mut *tables), const_val, &mut *tables)
+            })
+            .map_err(|e| e.stable(&mut *tables))?
+    }
+
     fn eval_static_initializer(&self, def: StaticDef) -> Result<Allocation, Error> {
         let mut tables = self.0.borrow_mut();
         let def_id = def.0.internal(&mut *tables);
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/error.rs b/compiler/rustc_smir/src/rustc_smir/convert/error.rs
new file mode 100644
index 00000000000..6c582b799f8
--- /dev/null
+++ b/compiler/rustc_smir/src/rustc_smir/convert/error.rs
@@ -0,0 +1,22 @@
+//! Handle the conversion of different internal errors into a stable version.
+//!
+//! Currently we encode everything as [stable_mir::Error], which is represented as a string.
+use crate::rustc_smir::{Stable, Tables};
+use rustc_middle::mir::interpret::AllocError;
+use rustc_middle::ty::layout::LayoutError;
+
+impl<'tcx> Stable<'tcx> for LayoutError<'tcx> {
+    type T = stable_mir::Error;
+
+    fn stable(&self, _tables: &mut Tables<'tcx>) -> Self::T {
+        stable_mir::Error::new(format!("{self:?}"))
+    }
+}
+
+impl<'tcx> Stable<'tcx> for AllocError {
+    type T = stable_mir::Error;
+
+    fn stable(&self, _tables: &mut Tables<'tcx>) -> Self::T {
+        stable_mir::Error::new(format!("{self:?}"))
+    }
+}
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/mod.rs b/compiler/rustc_smir/src/rustc_smir/convert/mod.rs
index 9c0b2b29bca..a83ff0663b9 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/mod.rs
@@ -5,6 +5,7 @@ use stable_mir::ty::{IndexedVal, VariantIdx};
 
 use crate::rustc_smir::{Stable, Tables};
 
+mod error;
 mod mir;
 mod ty;
 
@@ -75,3 +76,14 @@ impl<'tcx> Stable<'tcx> for rustc_span::Span {
         tables.create_span(*self)
     }
 }
+
+impl<'tcx> Stable<'tcx> for rustc_abi::Endian {
+    type T = stable_mir::target::Endian;
+
+    fn stable(&self, _tables: &mut Tables<'tcx>) -> Self::T {
+        match self {
+            rustc_abi::Endian::Little => stable_mir::target::Endian::Little,
+            rustc_abi::Endian::Big => stable_mir::target::Endian::Big,
+        }
+    }
+}
diff --git a/compiler/stable_mir/src/compiler_interface.rs b/compiler/stable_mir/src/compiler_interface.rs
index 7916d04250d..928f320c2fa 100644
--- a/compiler/stable_mir/src/compiler_interface.rs
+++ b/compiler/stable_mir/src/compiler_interface.rs
@@ -8,6 +8,7 @@ use std::cell::Cell;
 use crate::mir::alloc::{AllocId, GlobalAlloc};
 use crate::mir::mono::{Instance, InstanceDef, StaticDef};
 use crate::mir::Body;
+use crate::target::MachineInfo;
 use crate::ty::{
     AdtDef, AdtKind, Allocation, ClosureDef, ClosureKind, Const, FieldDef, FnDef, GenericArgs,
     GenericPredicates, Generics, ImplDef, ImplTrait, LineInfo, PolyFnSig, RigidTy, Span, TraitDecl,
@@ -150,6 +151,9 @@ pub trait Context {
     /// Evaluate a static's initializer.
     fn eval_static_initializer(&self, def: StaticDef) -> Result<Allocation, Error>;
 
+    /// Try to evaluate an instance into a constant.
+    fn eval_instance(&self, def: InstanceDef, const_ty: Ty) -> Result<Allocation, Error>;
+
     /// Retrieve global allocation for the given allocation ID.
     fn global_alloc(&self, id: AllocId) -> GlobalAlloc;
 
@@ -157,6 +161,9 @@ pub trait Context {
     fn vtable_allocation(&self, global_alloc: &GlobalAlloc) -> Option<AllocId>;
     fn krate(&self, def_id: DefId) -> Crate;
     fn instance_name(&self, def: InstanceDef, trimmed: bool) -> Symbol;
+
+    /// Return the number of bytes for a pointer size.
+    fn target_info(&self) -> MachineInfo;
 }
 
 // A thread local variable that stores a pointer to the tables mapping between TyCtxt
diff --git a/compiler/stable_mir/src/error.rs b/compiler/stable_mir/src/error.rs
index bb5e1a34180..c6da3ae41d3 100644
--- a/compiler/stable_mir/src/error.rs
+++ b/compiler/stable_mir/src/error.rs
@@ -6,11 +6,11 @@
 
 use std::convert::From;
 use std::fmt::{Debug, Display, Formatter};
-use std::{error, fmt};
+use std::{error, fmt, io};
 
 macro_rules! error {
      ($fmt: literal $(,)?) => { Error(format!($fmt)) };
-     ($fmt: literal, $($arg:tt)*) => { Error(format!($fmt, $($arg:tt)*)) };
+     ($fmt: literal, $($arg:tt)*) => { Error(format!($fmt, $($arg)*)) };
  }
 
 /// An error type used to represent an error that has already been reported by the compiler.
@@ -79,3 +79,9 @@ where
 
 impl error::Error for Error {}
 impl<T> error::Error for CompilerError<T> where T: Display + Debug {}
+
+impl From<io::Error> for Error {
+    fn from(value: io::Error) -> Self {
+        Error(value.to_string())
+    }
+}
diff --git a/compiler/stable_mir/src/lib.rs b/compiler/stable_mir/src/lib.rs
index 1e7495009d8..8c66bfb2e98 100644
--- a/compiler/stable_mir/src/lib.rs
+++ b/compiler/stable_mir/src/lib.rs
@@ -39,6 +39,7 @@ pub mod compiler_interface;
 #[macro_use]
 pub mod error;
 pub mod mir;
+pub mod target;
 pub mod ty;
 pub mod visitor;
 
diff --git a/compiler/stable_mir/src/mir/alloc.rs b/compiler/stable_mir/src/mir/alloc.rs
index af951bcef8c..c780042ff26 100644
--- a/compiler/stable_mir/src/mir/alloc.rs
+++ b/compiler/stable_mir/src/mir/alloc.rs
@@ -1,7 +1,9 @@
 //! This module provides methods to retrieve allocation information, such as static variables.
 use crate::mir::mono::{Instance, StaticDef};
+use crate::target::{Endian, MachineInfo};
 use crate::ty::{Allocation, Binder, ExistentialTraitRef, IndexedVal, Ty};
-use crate::with;
+use crate::{with, Error};
+use std::io::Read;
 
 /// An allocation in the SMIR global memory can be either a function pointer,
 /// a static, or a "real" allocation with some data in it.
@@ -38,7 +40,7 @@ impl GlobalAlloc {
 }
 
 /// A unique identification number for each provenance
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub struct AllocId(usize);
 
 impl IndexedVal for AllocId {
@@ -49,3 +51,33 @@ impl IndexedVal for AllocId {
         self.0
     }
 }
+
+/// Utility function used to read an allocation data into a unassigned integer.
+pub(crate) fn read_target_uint(mut bytes: &[u8]) -> Result<u128, Error> {
+    let mut buf = [0u8; std::mem::size_of::<u128>()];
+    match MachineInfo::target_endianess() {
+        Endian::Little => {
+            bytes.read(&mut buf)?;
+            Ok(u128::from_le_bytes(buf))
+        }
+        Endian::Big => {
+            bytes.read(&mut buf[16 - bytes.len()..])?;
+            Ok(u128::from_be_bytes(buf))
+        }
+    }
+}
+
+/// Utility function used to read an allocation data into an assigned integer.
+pub(crate) fn read_target_int(mut bytes: &[u8]) -> Result<i128, Error> {
+    let mut buf = [0u8; std::mem::size_of::<i128>()];
+    match MachineInfo::target_endianess() {
+        Endian::Little => {
+            bytes.read(&mut buf)?;
+            Ok(i128::from_le_bytes(buf))
+        }
+        Endian::Big => {
+            bytes.read(&mut buf[16 - bytes.len()..])?;
+            Ok(i128::from_be_bytes(buf))
+        }
+    }
+}
diff --git a/compiler/stable_mir/src/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
index 90bd7aa7d18..d03ded20e9b 100644
--- a/compiler/stable_mir/src/mir/body.rs
+++ b/compiler/stable_mir/src/mir/body.rs
@@ -832,7 +832,7 @@ pub enum MutBorrowKind {
     ClosureCapture,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum Mutability {
     Not,
     Mut,
diff --git a/compiler/stable_mir/src/mir/mono.rs b/compiler/stable_mir/src/mir/mono.rs
index 5c27f9281de..acf268e56b3 100644
--- a/compiler/stable_mir/src/mir/mono.rs
+++ b/compiler/stable_mir/src/mir/mono.rs
@@ -132,6 +132,14 @@ impl Instance {
     pub fn is_empty_shim(&self) -> bool {
         self.kind == InstanceKind::Shim && with(|cx| cx.is_empty_drop_shim(self.def))
     }
+
+    /// Try to constant evaluate the instance into a constant with the given type.
+    ///
+    /// This can be used to retrieve a constant that represents an intrinsic return such as
+    /// `type_id`.
+    pub fn try_const_eval(&self, const_ty: Ty) -> Result<Allocation, Error> {
+        with(|cx| cx.eval_instance(self.def, const_ty))
+    }
 }
 
 impl Debug for Instance {
diff --git a/compiler/stable_mir/src/target.rs b/compiler/stable_mir/src/target.rs
new file mode 100644
index 00000000000..bed1dbc4c00
--- /dev/null
+++ b/compiler/stable_mir/src/target.rs
@@ -0,0 +1,50 @@
+//! Provide information about the machine that this is being compiled into.
+
+use crate::compiler_interface::with;
+
+/// The properties of the target machine being compiled into.
+#[derive(Clone, PartialEq, Eq)]
+pub struct MachineInfo {
+    pub endian: Endian,
+    pub pointer_width: MachineSize,
+}
+
+impl MachineInfo {
+    pub fn target() -> MachineInfo {
+        with(|cx| cx.target_info().clone())
+    }
+
+    pub fn target_endianess() -> Endian {
+        with(|cx| cx.target_info().endian)
+    }
+
+    pub fn target_pointer_width() -> MachineSize {
+        with(|cx| cx.target_info().pointer_width)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Endian {
+    Little,
+    Big,
+}
+
+/// Represent the size of a component.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct MachineSize {
+    num_bits: usize,
+}
+
+impl MachineSize {
+    pub fn bytes(self) -> usize {
+        self.num_bits / 8
+    }
+
+    pub fn bits(self) -> usize {
+        self.num_bits
+    }
+
+    pub fn from_bits(num_bits: usize) -> MachineSize {
+        MachineSize { num_bits }
+    }
+}
diff --git a/compiler/stable_mir/src/ty.rs b/compiler/stable_mir/src/ty.rs
index c922264f8a3..4caac575c1e 100644
--- a/compiler/stable_mir/src/ty.rs
+++ b/compiler/stable_mir/src/ty.rs
@@ -4,9 +4,11 @@ use super::{
     with, DefId, Error, Symbol,
 };
 use crate::crate_def::CrateDef;
-use crate::mir::alloc::AllocId;
+use crate::mir::alloc::{read_target_int, read_target_uint, AllocId};
+use crate::target::MachineInfo;
 use crate::{Filename, Opaque};
 use std::fmt::{self, Debug, Display, Formatter};
+use std::ops::Range;
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct Ty(pub usize);
@@ -366,6 +368,19 @@ pub enum IntTy {
     I128,
 }
 
+impl IntTy {
+    pub fn num_bytes(self) -> usize {
+        match self {
+            IntTy::Isize => crate::target::MachineInfo::target_pointer_width().bytes().into(),
+            IntTy::I8 => 1,
+            IntTy::I16 => 2,
+            IntTy::I32 => 4,
+            IntTy::I64 => 8,
+            IntTy::I128 => 16,
+        }
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum UintTy {
     Usize,
@@ -376,6 +391,19 @@ pub enum UintTy {
     U128,
 }
 
+impl UintTy {
+    pub fn num_bytes(self) -> usize {
+        match self {
+            UintTy::Usize => crate::target::MachineInfo::target_pointer_width().bytes().into(),
+            UintTy::U8 => 1,
+            UintTy::U16 => 2,
+            UintTy::U32 => 4,
+            UintTy::U64 => 8,
+            UintTy::U128 => 16,
+        }
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum FloatTy {
     F32,
@@ -821,21 +849,21 @@ pub struct BoundTy {
 pub type Bytes = Vec<Option<u8>>;
 pub type Size = usize;
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub struct Prov(pub AllocId);
 pub type Align = u64;
 pub type Promoted = u32;
 pub type InitMaskMaterialized = Vec<u64>;
 
 /// Stores the provenance information of pointers stored in memory.
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub struct ProvenanceMap {
     /// Provenance in this map applies from the given offset for an entire pointer-size worth of
     /// bytes. Two entries in this map are always at least a pointer size apart.
     pub ptrs: Vec<(Size, Prov)>,
 }
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub struct Allocation {
     pub bytes: Bytes,
     pub provenance: ProvenanceMap,
@@ -843,6 +871,70 @@ pub struct Allocation {
     pub mutability: Mutability,
 }
 
+impl Allocation {
+    /// Get a vector of bytes for an Allocation that has been fully initialized
+    pub fn raw_bytes(&self) -> Result<Vec<u8>, Error> {
+        self.bytes
+            .iter()
+            .copied()
+            .collect::<Option<Vec<_>>>()
+            .ok_or_else(|| error!("Found uninitialized bytes: `{:?}`", self.bytes))
+    }
+
+    /// Read a uint value from the specified range.
+    pub fn read_partial_uint(&self, range: Range<usize>) -> Result<u128, Error> {
+        if range.end - range.start > 16 {
+            return Err(error!("Allocation is bigger than largest integer"));
+        }
+        if range.end > self.bytes.len() {
+            return Err(error!(
+                "Range is out of bounds. Allocation length is `{}`, but requested range `{:?}`",
+                self.bytes.len(),
+                range
+            ));
+        }
+        let raw = self.bytes[range]
+            .iter()
+            .copied()
+            .collect::<Option<Vec<_>>>()
+            .ok_or_else(|| error!("Found uninitialized bytes: `{:?}`", self.bytes))?;
+        read_target_uint(&raw)
+    }
+
+    pub fn read_uint(&self) -> Result<u128, Error> {
+        if self.bytes.len() > 16 {
+            return Err(error!("Allocation is bigger than largest integer"));
+        }
+        let raw = self.raw_bytes()?;
+        read_target_uint(&raw)
+    }
+
+    pub fn read_int(&self) -> Result<i128, Error> {
+        if self.bytes.len() > 16 {
+            return Err(error!("Allocation is bigger than largest integer"));
+        }
+        let raw = self.raw_bytes()?;
+        read_target_int(&raw)
+    }
+
+    pub fn read_bool(&self) -> Result<bool, Error> {
+        match self.read_int()? {
+            0 => Ok(false),
+            1 => Ok(true),
+            val @ _ => Err(error!("Unexpected value for bool: `{val}`")),
+        }
+    }
+
+    pub fn is_null(&self) -> Result<bool, Error> {
+        let len = self.bytes.len();
+        let ptr_len = MachineInfo::target_pointer_width().bytes();
+        if len != ptr_len {
+            return Err(error!("Expected width of pointer (`{ptr_len}`), but found: `{len}`"));
+        }
+        Ok(self.read_uint()? == 0)
+    }
+}
+
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum ConstantKind {
     Allocated(Allocation),