rustc_abi/layout/
ty.rs

1use std::fmt;
2use std::ops::Deref;
3
4use rustc_data_structures::intern::Interned;
5use rustc_macros::HashStable_Generic;
6
7use crate::{
8    AbiAlign, Align, BackendRepr, FieldsShape, Float, HasDataLayout, LayoutData, Niche,
9    PointeeInfo, Primitive, Size, Variants,
10};
11
12// Explicitly import `Float` to avoid ambiguity with `Primitive::Float`.
13
14rustc_index::newtype_index! {
15    /// The *source-order* index of a field in a variant.
16    ///
17    /// This is how most code after type checking refers to fields, rather than
18    /// using names (as names have hygiene complications and more complex lookup).
19    ///
20    /// Particularly for `repr(Rust)` types, this may not be the same as *layout* order.
21    /// (It is for `repr(C)` `struct`s, however.)
22    ///
23    /// For example, in the following types,
24    /// ```rust
25    /// # enum Never {}
26    /// # #[repr(u16)]
27    /// enum Demo1 {
28    ///    Variant0 { a: Never, b: i32 } = 100,
29    ///    Variant1 { c: u8, d: u64 } = 10,
30    /// }
31    /// struct Demo2 { e: u8, f: u16, g: u8 }
32    /// ```
33    /// `b` is `FieldIdx(1)` in `VariantIdx(0)`,
34    /// `d` is `FieldIdx(1)` in `VariantIdx(1)`, and
35    /// `f` is `FieldIdx(1)` in `VariantIdx(0)`.
36    #[derive(HashStable_Generic)]
37    #[encodable]
38    #[orderable]
39    pub struct FieldIdx {}
40}
41
42impl FieldIdx {
43    /// The second field, at index 1.
44    ///
45    /// For use alongside [`FieldIdx::ZERO`], particularly with scalar pairs.
46    pub const ONE: FieldIdx = FieldIdx::from_u32(1);
47}
48
49rustc_index::newtype_index! {
50    /// The *source-order* index of a variant in a type.
51    ///
52    /// For enums, these are always `0..variant_count`, regardless of any
53    /// custom discriminants that may have been defined, and including any
54    /// variants that may end up uninhabited due to field types.  (Some of the
55    /// variants may not be present in a monomorphized ABI [`Variants`], but
56    /// those skipped variants are always counted when determining the *index*.)
57    ///
58    /// `struct`s, `tuples`, and `unions`s are considered to have a single variant
59    /// with variant index zero, aka [`FIRST_VARIANT`].
60    #[derive(HashStable_Generic)]
61    #[encodable]
62    #[orderable]
63    pub struct VariantIdx {
64        /// Equivalent to `VariantIdx(0)`.
65        const FIRST_VARIANT = 0;
66    }
67}
68#[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable_Generic)]
69#[rustc_pass_by_value]
70pub struct Layout<'a>(pub Interned<'a, LayoutData<FieldIdx, VariantIdx>>);
71
72impl<'a> fmt::Debug for Layout<'a> {
73    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
74        // See comment on `<LayoutData as Debug>::fmt` above.
75        self.0.0.fmt(f)
76    }
77}
78
79impl<'a> Deref for Layout<'a> {
80    type Target = &'a LayoutData<FieldIdx, VariantIdx>;
81    fn deref(&self) -> &&'a LayoutData<FieldIdx, VariantIdx> {
82        &self.0.0
83    }
84}
85
86impl<'a> Layout<'a> {
87    pub fn fields(self) -> &'a FieldsShape<FieldIdx> {
88        &self.0.0.fields
89    }
90
91    pub fn variants(self) -> &'a Variants<FieldIdx, VariantIdx> {
92        &self.0.0.variants
93    }
94
95    pub fn backend_repr(self) -> BackendRepr {
96        self.0.0.backend_repr
97    }
98
99    pub fn largest_niche(self) -> Option<Niche> {
100        self.0.0.largest_niche
101    }
102
103    pub fn align(self) -> AbiAlign {
104        self.0.0.align
105    }
106
107    pub fn size(self) -> Size {
108        self.0.0.size
109    }
110
111    pub fn max_repr_align(self) -> Option<Align> {
112        self.0.0.max_repr_align
113    }
114
115    pub fn unadjusted_abi_align(self) -> Align {
116        self.0.0.unadjusted_abi_align
117    }
118}
119
120/// The layout of a type, alongside the type itself.
121/// Provides various type traversal APIs (e.g., recursing into fields).
122///
123/// Note that the layout is NOT guaranteed to always be identical
124/// to that obtained from `layout_of(ty)`, as we need to produce
125/// layouts for which Rust types do not exist, such as enum variants
126/// or synthetic fields of enums (i.e., discriminants) and wide pointers.
127#[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable_Generic)]
128pub struct TyAndLayout<'a, Ty> {
129    pub ty: Ty,
130    pub layout: Layout<'a>,
131}
132
133impl<'a, Ty: fmt::Display> fmt::Debug for TyAndLayout<'a, Ty> {
134    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
135        // Print the type in a readable way, not its debug representation.
136        f.debug_struct("TyAndLayout")
137            .field("ty", &format_args!("{}", self.ty))
138            .field("layout", &self.layout)
139            .finish()
140    }
141}
142
143impl<'a, Ty> Deref for TyAndLayout<'a, Ty> {
144    type Target = &'a LayoutData<FieldIdx, VariantIdx>;
145    fn deref(&self) -> &&'a LayoutData<FieldIdx, VariantIdx> {
146        &self.layout.0.0
147    }
148}
149
150impl<'a, Ty> AsRef<LayoutData<FieldIdx, VariantIdx>> for TyAndLayout<'a, Ty> {
151    fn as_ref(&self) -> &LayoutData<FieldIdx, VariantIdx> {
152        &*self.layout.0.0
153    }
154}
155
156/// Trait that needs to be implemented by the higher-level type representation
157/// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality.
158pub trait TyAbiInterface<'a, C>: Sized + std::fmt::Debug + std::fmt::Display {
159    fn ty_and_layout_for_variant(
160        this: TyAndLayout<'a, Self>,
161        cx: &C,
162        variant_index: VariantIdx,
163    ) -> TyAndLayout<'a, Self>;
164    fn ty_and_layout_field(this: TyAndLayout<'a, Self>, cx: &C, i: usize) -> TyAndLayout<'a, Self>;
165    fn ty_and_layout_pointee_info_at(
166        this: TyAndLayout<'a, Self>,
167        cx: &C,
168        offset: Size,
169    ) -> Option<PointeeInfo>;
170    fn is_adt(this: TyAndLayout<'a, Self>) -> bool;
171    fn is_never(this: TyAndLayout<'a, Self>) -> bool;
172    fn is_tuple(this: TyAndLayout<'a, Self>) -> bool;
173    fn is_unit(this: TyAndLayout<'a, Self>) -> bool;
174    fn is_transparent(this: TyAndLayout<'a, Self>) -> bool;
175    fn is_scalable_vector(this: TyAndLayout<'a, Self>) -> bool;
176    /// See [`TyAndLayout::pass_indirectly_in_non_rustic_abis`] for details.
177    fn is_pass_indirectly_in_non_rustic_abis_flag_set(this: TyAndLayout<'a, Self>) -> bool;
178}
179
180impl<'a, Ty> TyAndLayout<'a, Ty> {
181    pub fn for_variant<C>(self, cx: &C, variant_index: VariantIdx) -> Self
182    where
183        Ty: TyAbiInterface<'a, C>,
184    {
185        Ty::ty_and_layout_for_variant(self, cx, variant_index)
186    }
187
188    pub fn field<C>(self, cx: &C, i: usize) -> Self
189    where
190        Ty: TyAbiInterface<'a, C>,
191    {
192        Ty::ty_and_layout_field(self, cx, i)
193    }
194
195    pub fn pointee_info_at<C>(self, cx: &C, offset: Size) -> Option<PointeeInfo>
196    where
197        Ty: TyAbiInterface<'a, C>,
198    {
199        Ty::ty_and_layout_pointee_info_at(self, cx, offset)
200    }
201
202    pub fn is_single_fp_element<C>(self, cx: &C) -> bool
203    where
204        Ty: TyAbiInterface<'a, C>,
205        C: HasDataLayout,
206    {
207        match self.backend_repr {
208            BackendRepr::Scalar(scalar) => {
209                matches!(scalar.primitive(), Primitive::Float(Float::F32 | Float::F64))
210            }
211            BackendRepr::Memory { .. } => {
212                if self.fields.count() == 1 && self.fields.offset(0).bytes() == 0 {
213                    self.field(cx, 0).is_single_fp_element(cx)
214                } else {
215                    false
216                }
217            }
218            _ => false,
219        }
220    }
221
222    pub fn is_single_vector_element<C>(self, cx: &C, expected_size: Size) -> bool
223    where
224        Ty: TyAbiInterface<'a, C>,
225        C: HasDataLayout,
226    {
227        match self.backend_repr {
228            BackendRepr::SimdVector { .. } => self.size == expected_size,
229            BackendRepr::Memory { .. } => {
230                if self.fields.count() == 1 && self.fields.offset(0).bytes() == 0 {
231                    self.field(cx, 0).is_single_vector_element(cx, expected_size)
232                } else {
233                    false
234                }
235            }
236            _ => false,
237        }
238    }
239
240    pub fn is_adt<C>(self) -> bool
241    where
242        Ty: TyAbiInterface<'a, C>,
243    {
244        Ty::is_adt(self)
245    }
246
247    pub fn is_never<C>(self) -> bool
248    where
249        Ty: TyAbiInterface<'a, C>,
250    {
251        Ty::is_never(self)
252    }
253
254    pub fn is_tuple<C>(self) -> bool
255    where
256        Ty: TyAbiInterface<'a, C>,
257    {
258        Ty::is_tuple(self)
259    }
260
261    pub fn is_unit<C>(self) -> bool
262    where
263        Ty: TyAbiInterface<'a, C>,
264    {
265        Ty::is_unit(self)
266    }
267
268    pub fn is_transparent<C>(self) -> bool
269    where
270        Ty: TyAbiInterface<'a, C>,
271    {
272        Ty::is_transparent(self)
273    }
274
275    pub fn is_scalable_vector<C>(self) -> bool
276    where
277        Ty: TyAbiInterface<'a, C>,
278    {
279        Ty::is_scalable_vector(self)
280    }
281
282    /// If this method returns `true`, then this type should always have a `PassMode` of
283    /// `Indirect { on_stack: false, .. }` when being used as the argument type of a function with a
284    /// non-Rustic ABI (this is true for structs annotated with the
285    /// `#[rustc_pass_indirectly_in_non_rustic_abis]` attribute).
286    ///
287    /// This is used to replicate some of the behaviour of C array-to-pointer decay; however unlike
288    /// C any changes the caller makes to the passed value will not be reflected in the callee, so
289    /// the attribute is only useful for types where observing the value in the caller after the
290    /// function call isn't allowed (a.k.a. `va_list`).
291    ///
292    /// This function handles transparent types automatically.
293    pub fn pass_indirectly_in_non_rustic_abis<C>(mut self, cx: &C) -> bool
294    where
295        Ty: TyAbiInterface<'a, C> + Copy,
296    {
297        while self.is_transparent()
298            && let Some((_, field)) = self.non_1zst_field(cx)
299        {
300            self = field;
301        }
302
303        Ty::is_pass_indirectly_in_non_rustic_abis_flag_set(self)
304    }
305
306    /// Finds the one field that is not a 1-ZST.
307    /// Returns `None` if there are multiple non-1-ZST fields or only 1-ZST-fields.
308    pub fn non_1zst_field<C>(&self, cx: &C) -> Option<(FieldIdx, Self)>
309    where
310        Ty: TyAbiInterface<'a, C> + Copy,
311    {
312        let mut found = None;
313        for field_idx in 0..self.fields.count() {
314            let field = self.field(cx, field_idx);
315            if field.is_1zst() {
316                continue;
317            }
318            if found.is_some() {
319                // More than one non-1-ZST field.
320                return None;
321            }
322            found = Some((FieldIdx::from_usize(field_idx), field));
323        }
324        found
325    }
326}
rustc_abi/layout/ty.rs

rustc_abi/layout/
ty.rs
