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Fix aggregate and add new abi module
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,194 @@ | ||
| // Copyright Kani Contributors | ||
| // SPDX-License-Identifier: Apache-2.0 OR MIT | ||
| //! This module contains code for handling type abi information. | ||
|
|
||
| use stable_mir::abi::{FieldsShape, LayoutShape}; | ||
| use stable_mir::ty::{RigidTy, Ty, TyKind, UintTy}; | ||
| use tracing::debug; | ||
|
|
||
| /// A struct to encapsulate the layout information for a given type | ||
| #[derive(Clone, Debug, PartialEq, Eq)] | ||
| pub struct LayoutOf { | ||
| ty: Ty, | ||
| layout: LayoutShape, | ||
| } | ||
|
|
||
| #[allow(dead_code)] // TODO: Remove this in https://github.com/model-checking/kani/pull/3687 | ||
| impl LayoutOf { | ||
| /// Create the layout structure for the given type | ||
| pub fn new(ty: Ty) -> LayoutOf { | ||
| LayoutOf { ty, layout: ty.layout().unwrap().shape() } | ||
| } | ||
|
|
||
| /// Return whether the type is sized. | ||
| pub fn is_sized(&self) -> bool { | ||
| self.layout.is_sized() | ||
| } | ||
|
|
||
| /// Return whether the type is unsized and its tail is a foreign item. | ||
| /// | ||
| /// This will also return `true` if the type is foreign. | ||
| pub fn has_foreign_tail(&self) -> bool { | ||
| self.unsized_tail() | ||
| .map_or(false, |t| matches!(t.kind(), TyKind::RigidTy(RigidTy::Foreign(_)))) | ||
| } | ||
|
|
||
| /// Return whether the type is unsized and its tail is a trait object. | ||
| pub fn has_trait_tail(&self) -> bool { | ||
| self.unsized_tail().map_or(false, |t| t.kind().is_trait()) | ||
| } | ||
|
|
||
| /// Return whether the type is unsized and its tail is a slice. | ||
| #[allow(dead_code)] | ||
| pub fn has_slice_tail(&self) -> bool { | ||
| self.unsized_tail().map_or(false, |tail| { | ||
| let kind = tail.kind(); | ||
| kind.is_slice() | kind.is_str() | ||
| }) | ||
| } | ||
|
|
||
| /// Return the unsized tail of the type if this is an unsized type. | ||
| /// | ||
| /// For foreign types, return None. | ||
| /// For unsized types, this should return either a slice, a string slice, a dynamic type. | ||
| /// For other types, this function will return `None`. | ||
| pub fn unsized_tail(&self) -> Option<Ty> { | ||
| if self.layout.is_unsized() { | ||
| match self.ty.kind().rigid().unwrap() { | ||
| RigidTy::Slice(..) | RigidTy::Dynamic(..) | RigidTy::Str => Some(self.ty), | ||
| RigidTy::Adt(..) | RigidTy::Tuple(..) => { | ||
| // Recurse the tail field type until we find the unsized tail. | ||
| self.last_field_layout().unsized_tail() | ||
| } | ||
| RigidTy::Foreign(_) => Some(self.ty), | ||
| _ => unreachable!("Expected unsized type but found `{}`", self.ty), | ||
| } | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| /// Return the type of the elements of the array or slice at the unsized tail of this type. | ||
| /// | ||
| /// For sized types and trait unsized type, this function will return `None`. | ||
| pub fn unsized_tail_elem_ty(&self) -> Option<Ty> { | ||
| self.unsized_tail().and_then(|tail| match tail.kind().rigid().unwrap() { | ||
| RigidTy::Slice(elem_ty) => Some(*elem_ty), | ||
| // String slices have the same layout as slices of u8. | ||
| // https://doc.rust-lang.org/reference/type-layout.html#str-layout | ||
| RigidTy::Str => Some(Ty::unsigned_ty(UintTy::U8)), | ||
| _ => None, | ||
| }) | ||
| } | ||
|
|
||
| /// Return the size of the sized portion of this type. | ||
| /// | ||
| /// For a sized type, this function will return the size of the type. | ||
| /// For an unsized type, this function will return the size of the sized portion including | ||
| /// any padding bytes that lead to the unsized field. | ||
| /// I.e.: the size of the type, excluding the trailing unsized portion. | ||
| /// | ||
| /// For example, this function will return 2 as the sized portion of `*const (u8, [u16])`: | ||
| pub fn size_of_head(&self) -> usize { | ||
| if self.is_sized() { | ||
| self.layout.size.bytes() | ||
| } else { | ||
| match self.ty.kind().rigid().unwrap() { | ||
| RigidTy::Slice(_) | RigidTy::Str | RigidTy::Dynamic(..) | RigidTy::Foreign(..) => 0, | ||
| RigidTy::Adt(..) | RigidTy::Tuple(..) => { | ||
| let fields_sorted = self.layout.fields.fields_by_offset_order(); | ||
| let last = *fields_sorted.last().unwrap(); | ||
| let FieldsShape::Arbitrary { ref offsets } = self.layout.fields else { | ||
| unreachable!() | ||
| }; | ||
|
|
||
| // We compute the size of the sized portion by taking the position of the | ||
| // last element + the sized portion of that element. | ||
| let unsized_offset_unadjusted = offsets[last].bytes(); | ||
| debug!(ty=?self.ty, ?unsized_offset_unadjusted, "size_of_sized_portion"); | ||
| unsized_offset_unadjusted + self.last_field_layout().size_of_head() | ||
| } | ||
| _ => { | ||
| unreachable!("Expected sized type, but found: `{}`", self.ty) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Return the alignment of the fields that are sized from the head of the object. | ||
| /// | ||
| /// For a sized type, this function will return the alignment of the type. | ||
| /// | ||
| /// For an unsized type, this function will return the alignment of the sized portion. | ||
| /// The alignment of the type will be the maximum of the alignment of the sized portion | ||
| /// and the alignment of the unsized portion. | ||
| /// | ||
| /// If there's no sized portion, this function will return the minimum alignment (i.e.: 1). | ||
| pub fn align_of_head(&self) -> usize { | ||
| if self.is_sized() { | ||
| self.layout.abi_align.try_into().unwrap() | ||
| } else { | ||
| match self.ty.kind().rigid().unwrap() { | ||
| RigidTy::Slice(_) | RigidTy::Str | RigidTy::Dynamic(..) | RigidTy::Foreign(..) => 1, | ||
| RigidTy::Adt(..) | RigidTy::Tuple(..) => { | ||
| // We have to recurse and get the maximum alignment of all sized portions. | ||
| let field_layout = self.last_field_layout(); | ||
| field_layout.align_of_head().max(self.layout.abi_align.try_into().unwrap()) | ||
| } | ||
| _ => { | ||
| unreachable!("Expected sized type, but found: `{}`", self.ty); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Return the size of the type if it's known at compilation type. | ||
| pub fn size_of(&self) -> Option<usize> { | ||
| if self.is_sized() { Some(self.layout.size.bytes()) } else { None } | ||
| } | ||
|
|
||
| /// Return the alignment of the type if it's know at compilation time. | ||
| /// | ||
| /// The alignment is known at compilation type for sized types and types with slice tail. | ||
| /// | ||
| /// Note: We assume u64 and usize are the same since Kani is only supported in 64bits machines. | ||
| /// Add a configuration in case we ever decide to port this to a 32-bits machine. | ||
| #[cfg(target_pointer_width = "64")] | ||
| pub fn align_of(&self) -> Option<usize> { | ||
| if self.is_sized() || self.has_slice_tail() { | ||
| self.layout.abi_align.try_into().ok() | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| /// Return the layout of the last field of the type. | ||
| /// | ||
| /// This function is used to get the layout of the last field of an unsized type. | ||
| /// For example, if we have `*const (u8, [u16])`, the last field is `[u16]`. | ||
| /// This function will return the layout of `[u16]`. | ||
| /// | ||
| /// If the type is not a struct, an enum, or a tuple, with at least one field, this function | ||
| /// will panic. | ||
| fn last_field_layout(&self) -> LayoutOf { | ||
| match self.ty.kind().rigid().unwrap() { | ||
| RigidTy::Adt(adt_def, adt_args) => { | ||
| let fields = adt_def.variants_iter().next().unwrap().fields(); | ||
| let fields_sorted = self.layout.fields.fields_by_offset_order(); | ||
| let last_field_idx = *fields_sorted.last().unwrap(); | ||
| LayoutOf::new(fields[last_field_idx].ty_with_args(adt_args)) | ||
| } | ||
| RigidTy::Tuple(tys) => { | ||
| // For tuples, the unsized field is currently the last declared. | ||
| // To be on the safe side, we still get the sorted list by offset order. | ||
| let fields_sorted = self.layout.fields.fields_by_offset_order(); | ||
| let last_field_idx = *fields_sorted.last().unwrap(); | ||
| let last_ty = tys[last_field_idx]; | ||
| LayoutOf::new(last_ty) | ||
| } | ||
| _ => { | ||
| unreachable!("Expected struct, enum or tuple. Found: `{}`", self.ty); | ||
| } | ||
| } | ||
| } | ||
| } |
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