[core] codegen/types: Implement StructField{,s}

Loosely based on FieldTraversal by lyken.

nac3core/src/codegen/types/mod.rs

@@ -11,6 +11,7 @@ pub use range::*;
 mod list;
 mod ndarray;
 mod range;
+pub mod structure;
 
 /// A LLVM type that is used to represent a corresponding type in NAC3.
 pub trait ProxyType<'ctx>: Into<Self::Base> {

nac3core/src/codegen/types/structure.rs

@@ -0,0 +1,203 @@
+use std::marker::PhantomData;
+
+use inkwell::{
+    context::AsContextRef,
+    types::{BasicTypeEnum, IntType},
+    values::{BasicValue, BasicValueEnum, IntValue, PointerValue, StructValue},
+};
+
+use crate::codegen::CodeGenContext;
+
+/// Trait indicating that the structure is a field-wise representation of an LLVM structure.
+///
+/// # Usage
+///
+/// For example, for a simple C-slice LLVM structure:
+///
+/// ```ignore
+/// struct CSliceFields<'ctx> {
+///     ptr: StructField<'ctx, PointerValue<'ctx>>,
+///     len: StructField<'ctx, IntValue<'ctx>>
+/// }
+/// ```
+pub trait StructFields<'ctx>: Eq + Copy {
+    /// Creates an instance of [`StructFields`] using the given `ctx` and `size_t` types.
+    fn new(ctx: impl AsContextRef<'ctx>, llvm_usize: IntType<'ctx>) -> Self;
+
+    /// Returns a [`Vec`] that contains the fields of the structure in the order as they appear in
+    /// the type definition.
+    #[must_use]
+    fn to_vec(&self) -> Vec<(&'static str, BasicTypeEnum<'ctx>)>;
+
+    /// Returns a [`Iterator`] that contains the fields of the structure in the order as they appear
+    /// in the type definition.
+    #[must_use]
+    fn iter(&self) -> impl Iterator<Item = (&'static str, BasicTypeEnum<'ctx>)> {
+        self.to_vec().into_iter()
+    }
+
+    /// Returns a [`Vec`] that contains the fields of the structure in the order as they appear in
+    /// the type definition.
+    #[must_use]
+    fn into_vec(self) -> Vec<(&'static str, BasicTypeEnum<'ctx>)>
+    where
+        Self: Sized,
+    {
+        self.to_vec()
+    }
+
+    /// Returns a [`Iterator`] that contains the fields of the structure in the order as they appear
+    /// in the type definition.
+    #[must_use]
+    fn into_iter(self) -> impl Iterator<Item = (&'static str, BasicTypeEnum<'ctx>)>
+    where
+        Self: Sized,
+    {
+        self.into_vec().into_iter()
+    }
+}
+
+/// A single field of an LLVM structure.
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub struct StructField<'ctx, Value>
+where
+    Value: BasicValue<'ctx> + TryFrom<BasicValueEnum<'ctx>, Error = ()>,
+{
+    /// The index of this field within the structure.
+    index: u32,
+
+    /// The name of this field.
+    name: &'static str,
+
+    /// The type of this field.
+    ty: BasicTypeEnum<'ctx>,
+
+    /// Instance of [`PhantomData`] containing [`Value`], used to implement automatic downcasts.
+    _value_ty: PhantomData<Value>,
+}
+
+impl<'ctx, Value> StructField<'ctx, Value>
+where
+    Value: BasicValue<'ctx> + TryFrom<BasicValueEnum<'ctx>, Error = ()>,
+{
+    /// Creates an instance of [`StructField`].
+    ///
+    /// * `idx_counter` - The instance of [`FieldIndexCounter`] used to track the current field
+    ///   index.
+    /// * `name` - Name of the field.
+    /// * `ty` - The type of this field.
+    pub fn create(
+        idx_counter: &mut FieldIndexCounter,
+        name: &'static str,
+        ty: impl Into<BasicTypeEnum<'ctx>>,
+    ) -> Self {
+        StructField { index: idx_counter.increment(), name, ty: ty.into(), _value_ty: PhantomData }
+    }
+
+    /// Creates an instance of [`StructField`] with a given index.
+    ///
+    /// * `index` - The index of this field within its enclosing structure.
+    /// * `name` - Name of the field.
+    /// * `ty` - The type of this field.
+    pub fn create_at(index: u32, name: &'static str, ty: impl Into<BasicTypeEnum<'ctx>>) -> Self {
+        StructField { index, name, ty: ty.into(), _value_ty: PhantomData }
+    }
+
+    /// Creates a pointer to this field in an arbitrary structure by performing a `getelementptr i32
+    /// {idx...}, i32 {self.index}`.
+    pub fn ptr_by_array_gep(
+        &self,
+        ctx: &CodeGenContext<'ctx, '_>,
+        pobj: PointerValue<'ctx>,
+        idx: &[IntValue<'ctx>],
+    ) -> PointerValue<'ctx> {
+        unsafe {
+            ctx.builder.build_in_bounds_gep(
+                pobj,
+                &[idx, &[ctx.ctx.i32_type().const_int(u64::from(self.index), false)]].concat(),
+                "",
+            )
+        }
+        .unwrap()
+    }
+
+    /// Creates a pointer to this field in an arbitrary structure by performing the equivalent of
+    /// `getelementptr i32 0, i32 {self.index}`.
+    pub fn ptr_by_gep(
+        &self,
+        ctx: &CodeGenContext<'ctx, '_>,
+        pobj: PointerValue<'ctx>,
+        obj_name: Option<&'ctx str>,
+    ) -> PointerValue<'ctx> {
+        ctx.builder
+            .build_struct_gep(
+                pobj,
+                self.index,
+                &obj_name.map(|name| format!("{name}.{}.addr", self.name)).unwrap_or_default(),
+            )
+            .unwrap()
+    }
+
+    /// Gets the value of this field for a given `obj`.
+    #[must_use]
+    pub fn get_from_value(&self, obj: StructValue<'ctx>) -> Value {
+        obj.get_field_at_index(self.index).and_then(|value| Value::try_from(value).ok()).unwrap()
+    }
+
+    /// Sets the value of this field for a given `obj`.
+    pub fn set_from_value(&self, obj: StructValue<'ctx>, value: Value) {
+        obj.set_field_at_index(self.index, value);
+    }
+
+    /// Gets the value of this field for a pointer-to-structure.
+    pub fn get(
+        &self,
+        ctx: &CodeGenContext<'ctx, '_>,
+        pobj: PointerValue<'ctx>,
+        obj_name: Option<&'ctx str>,
+    ) -> Value {
+        ctx.builder
+            .build_load(
+                self.ptr_by_gep(ctx, pobj, obj_name),
+                &obj_name.map(|name| format!("{name}.{}", self.name)).unwrap_or_default(),
+            )
+            .map_err(|_| ())
+            .and_then(|value| Value::try_from(value))
+            .unwrap()
+    }
+
+    /// Sets the value of this field for a pointer-to-structure.
+    pub fn set(
+        &self,
+        ctx: &CodeGenContext<'ctx, '_>,
+        pobj: PointerValue<'ctx>,
+        value: Value,
+        obj_name: Option<&'ctx str>,
+    ) {
+        ctx.builder.build_store(self.ptr_by_gep(ctx, pobj, obj_name), value).unwrap();
+    }
+}
+
+impl<'ctx, Value> From<StructField<'ctx, Value>> for (&'static str, BasicTypeEnum<'ctx>)
+where
+    Value: BasicValue<'ctx> + TryFrom<BasicValueEnum<'ctx>, Error = ()>,
+{
+    fn from(value: StructField<'ctx, Value>) -> Self {
+        (value.name, value.ty)
+    }
+}
+
+/// A counter that tracks the next index of a field using a monotonically increasing counter.
+#[derive(Default, Debug, PartialEq, Eq, Clone, Copy)]
+pub struct FieldIndexCounter(u32);
+
+impl FieldIndexCounter {
+    /// Increments the number stored by this counter, returning the previous value.
+    ///
+    /// Functionally equivalent to `i++` in C-based languages.
+    pub fn increment(&mut self) -> u32 {
+        let v = self.0;
+        self.0 += 1;
+        v
+    }
+}