naga/common/wgsl/
types.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
//! Code for formatting Naga IR types as WGSL source code.

use super::{address_space_str, ToWgsl, TryToWgsl};
use crate::common;
use crate::proc::TypeResolution;
use crate::{Handle, Scalar, TypeInner};

use alloc::string::String;
use core::fmt::Write;

/// A context for printing Naga IR types as WGSL.
///
/// This trait's default methods [`write_type`] and
/// [`write_type_inner`] do the work of formatting types as WGSL.
/// Implementors must provide the remaining methods, to customize
/// behavior for the context at hand.
///
/// For example, the WGSL backend would provide an implementation of
/// [`type_name`] that handles hygienic renaming, whereas the WGSL
/// front end would simply show the name that was given in the source.
///
/// [`write_type`]: TypeContext::write_type
/// [`write_type_inner`]: TypeContext::write_type_inner
/// [`type_name`]: TypeContext::type_name
pub trait TypeContext {
    /// Return the [`Type`] referred to by `handle`.
    ///
    /// [`Type`]: crate::Type
    fn lookup_type(&self, handle: Handle<crate::Type>) -> &crate::Type;

    /// Return the name to be used for the type referred to by
    /// `handle`.
    fn type_name(&self, handle: Handle<crate::Type>) -> &str;

    /// Write the WGSL form of `override` to `out`.
    fn write_override<W: Write>(
        &self,
        r#override: Handle<crate::Override>,
        out: &mut W,
    ) -> core::fmt::Result;

    /// Write a [`TypeInner`] that has no representation as WGSL source,
    /// even including Naga extensions.
    ///
    /// A backend might implement this with a call to the [`unreachable!`]
    /// macro, since backends are allowed to assume that the module has passed
    /// validation.
    ///
    /// The default implementation is appropriate for generating type names to
    /// appear in error messages. It punts to `TypeInner`'s [`core::fmt::Debug`]
    /// implementation, since it's probably best to show the user something they
    /// can act on.
    fn write_non_wgsl_inner<W: Write>(&self, inner: &TypeInner, out: &mut W) -> core::fmt::Result {
        write!(out, "{{non-WGSL Naga type {inner:?}}}")
    }

    /// Write a [`Scalar`] that has no representation as WGSL source,
    /// even including Naga extensions.
    ///
    /// A backend might implement this with a call to the [`unreachable!`]
    /// macro, since backends are allowed to assume that the module has passed
    /// validation.
    ///
    /// The default implementation is appropriate for generating type names to
    /// appear in error messages. It punts to `Scalar`'s [`core::fmt::Debug`]
    /// implementation, since it's probably best to show the user something they
    /// can act on.
    fn write_non_wgsl_scalar<W: Write>(&self, scalar: Scalar, out: &mut W) -> core::fmt::Result {
        match scalar.kind {
            crate::ScalarKind::Sint
            | crate::ScalarKind::Uint
            | crate::ScalarKind::Float
            | crate::ScalarKind::Bool => write!(out, "{{non-WGSL Naga scalar {scalar:?}}}"),

            // The abstract types are kind of an odd quasi-WGSL category:
            // they are definitely part of the spec, but they are not expressible
            // in WGSL itself. So we want to call them out by name in error messages,
            // but the WGSL backend should never generate these.
            crate::ScalarKind::AbstractInt => out.write_str("{AbstractInt}"),
            crate::ScalarKind::AbstractFloat => out.write_str("{AbstractFloat}"),
        }
    }

    /// Write the type `ty` as it would appear in a value's declaration.
    ///
    /// Write the type referred to by `ty` in `module` as it would appear in
    /// a `var`, `let`, etc. declaration, or in a function's argument list.
    fn write_type<W: Write>(&self, handle: Handle<crate::Type>, out: &mut W) -> core::fmt::Result {
        let ty = self.lookup_type(handle);
        match ty.inner {
            TypeInner::Struct { .. } => out.write_str(self.type_name(handle))?,
            ref other => self.write_type_inner(other, out)?,
        }

        Ok(())
    }

    /// Write the [`TypeInner`] `inner` as it would appear in a value's declaration.
    ///
    /// Write `inner` as it would appear in a `var`, `let`, etc.
    /// declaration, or in a function's argument list.
    ///
    /// Note that this cannot handle writing [`Struct`] types: those
    /// must be referred to by name, but the name isn't available in
    /// [`TypeInner`].
    ///
    /// [`Struct`]: TypeInner::Struct
    fn write_type_inner<W: Write>(&self, inner: &TypeInner, out: &mut W) -> core::fmt::Result {
        match try_write_type_inner(self, inner, out) {
            Ok(()) => Ok(()),
            Err(WriteTypeError::Format(err)) => Err(err),
            Err(WriteTypeError::NonWgsl) => self.write_non_wgsl_inner(inner, out),
        }
    }

    /// Write the [`Scalar`] `scalar` as a WGSL type.
    fn write_scalar<W: Write>(&self, scalar: Scalar, out: &mut W) -> core::fmt::Result {
        match scalar.try_to_wgsl() {
            Some(string) => out.write_str(string),
            None => self.write_non_wgsl_scalar(scalar, out),
        }
    }

    /// Write the [`TypeResolution`] `resolution` as a WGSL type.
    fn write_type_resolution<W: Write>(
        &self,
        resolution: &TypeResolution,
        out: &mut W,
    ) -> core::fmt::Result {
        match *resolution {
            TypeResolution::Handle(handle) => self.write_type(handle, out),
            TypeResolution::Value(ref inner) => self.write_type_inner(inner, out),
        }
    }

    fn type_to_string(&self, handle: Handle<crate::Type>) -> String {
        let mut buf = String::new();
        self.write_type(handle, &mut buf).unwrap();
        buf
    }

    fn type_inner_to_string(&self, inner: &TypeInner) -> String {
        let mut buf = String::new();
        self.write_type_inner(inner, &mut buf).unwrap();
        buf
    }

    fn type_resolution_to_string(&self, resolution: &TypeResolution) -> String {
        let mut buf = String::new();
        self.write_type_resolution(resolution, &mut buf).unwrap();
        buf
    }
}

fn try_write_type_inner<C, W>(ctx: &C, inner: &TypeInner, out: &mut W) -> Result<(), WriteTypeError>
where
    C: TypeContext + ?Sized,
    W: Write,
{
    match *inner {
        TypeInner::Vector { size, scalar } => {
            write!(out, "vec{}<", common::vector_size_str(size))?;
            ctx.write_scalar(scalar, out)?;
            out.write_str(">")?;
        }
        TypeInner::Sampler { comparison: false } => {
            write!(out, "sampler")?;
        }
        TypeInner::Sampler { comparison: true } => {
            write!(out, "sampler_comparison")?;
        }
        TypeInner::Image {
            dim,
            arrayed,
            class,
        } => {
            // More about texture types: https://gpuweb.github.io/gpuweb/wgsl/#sampled-texture-type
            use crate::ImageClass as Ic;

            let dim_str = dim.to_wgsl();
            let arrayed_str = if arrayed { "_array" } else { "" };
            match class {
                Ic::Sampled { kind, multi } => {
                    let multisampled_str = if multi { "multisampled_" } else { "" };
                    write!(out, "texture_{multisampled_str}{dim_str}{arrayed_str}<")?;
                    ctx.write_scalar(Scalar { kind, width: 4 }, out)?;
                    out.write_str(">")?;
                }
                Ic::Depth { multi } => {
                    let multisampled_str = if multi { "multisampled_" } else { "" };
                    write!(
                        out,
                        "texture_depth_{multisampled_str}{dim_str}{arrayed_str}"
                    )?;
                }
                Ic::Storage { format, access } => {
                    let format_str = format.to_wgsl();
                    let access_str = if access.contains(crate::StorageAccess::ATOMIC) {
                        ",atomic"
                    } else if access
                        .contains(crate::StorageAccess::LOAD | crate::StorageAccess::STORE)
                    {
                        ",read_write"
                    } else if access.contains(crate::StorageAccess::LOAD) {
                        ",read"
                    } else {
                        ",write"
                    };
                    write!(
                        out,
                        "texture_storage_{dim_str}{arrayed_str}<{format_str}{access_str}>"
                    )?;
                }
            }
        }
        TypeInner::Scalar(scalar) => {
            ctx.write_scalar(scalar, out)?;
        }
        TypeInner::Atomic(scalar) => {
            out.write_str("atomic<")?;
            ctx.write_scalar(scalar, out)?;
            out.write_str(">")?;
        }
        TypeInner::Array {
            base,
            size,
            stride: _,
        } => {
            // More info https://gpuweb.github.io/gpuweb/wgsl/#array-types
            // array<A, 3> -- Constant array
            // array<A> -- Dynamic array
            write!(out, "array<")?;
            match size {
                crate::ArraySize::Constant(len) => {
                    ctx.write_type(base, out)?;
                    write!(out, ", {len}")?;
                }
                crate::ArraySize::Pending(r#override) => {
                    ctx.write_override(r#override, out)?;
                }
                crate::ArraySize::Dynamic => {
                    ctx.write_type(base, out)?;
                }
            }
            write!(out, ">")?;
        }
        TypeInner::BindingArray { base, size } => {
            // More info https://github.com/gpuweb/gpuweb/issues/2105
            write!(out, "binding_array<")?;
            match size {
                crate::ArraySize::Constant(len) => {
                    ctx.write_type(base, out)?;
                    write!(out, ", {len}")?;
                }
                crate::ArraySize::Pending(r#override) => {
                    ctx.write_override(r#override, out)?;
                }
                crate::ArraySize::Dynamic => {
                    ctx.write_type(base, out)?;
                }
            }
            write!(out, ">")?;
        }
        TypeInner::Matrix {
            columns,
            rows,
            scalar,
        } => {
            write!(
                out,
                "mat{}x{}<",
                common::vector_size_str(columns),
                common::vector_size_str(rows),
            )?;
            ctx.write_scalar(scalar, out)?;
            out.write_str(">")?;
        }
        TypeInner::Pointer { base, space } => {
            let (address, maybe_access) = address_space_str(space);
            // Everything but `AddressSpace::Handle` gives us a `address` name, but
            // Naga IR never produces pointers to handles, so it doesn't matter much
            // how we write such a type. Just write it as the base type alone.
            if let Some(space) = address {
                write!(out, "ptr<{space}, ")?;
            }
            ctx.write_type(base, out)?;
            if address.is_some() {
                if let Some(access) = maybe_access {
                    write!(out, ", {access}")?;
                }
                write!(out, ">")?;
            }
        }
        TypeInner::ValuePointer {
            size: None,
            scalar,
            space,
        } => {
            let (address, maybe_access) = address_space_str(space);
            if let Some(space) = address {
                write!(out, "ptr<{}, ", space)?;
                ctx.write_scalar(scalar, out)?;
                if let Some(access) = maybe_access {
                    write!(out, ", {access}")?;
                }
                write!(out, ">")?;
            } else {
                return Err(WriteTypeError::NonWgsl);
            }
        }
        TypeInner::ValuePointer {
            size: Some(size),
            scalar,
            space,
        } => {
            let (address, maybe_access) = address_space_str(space);
            if let Some(space) = address {
                write!(out, "ptr<{}, vec{}<", space, common::vector_size_str(size),)?;
                ctx.write_scalar(scalar, out)?;
                out.write_str(">")?;
                if let Some(access) = maybe_access {
                    write!(out, ", {access}")?;
                }
                write!(out, ">")?;
            } else {
                return Err(WriteTypeError::NonWgsl);
            }
            write!(out, ">")?;
        }
        TypeInner::AccelerationStructure { vertex_return } => {
            let caps = if vertex_return { "<vertex_return>" } else { "" };
            write!(out, "acceleration_structure{}", caps)?
        }
        TypeInner::Struct { .. } => {
            unreachable!("structs can only be referenced by name in WGSL");
        }
        TypeInner::RayQuery { vertex_return } => {
            let caps = if vertex_return { "<vertex_return>" } else { "" };
            write!(out, "ray_query{}", caps)?
        }
    }

    Ok(())
}

/// Error type returned by `try_write_type_inner`.
///
/// This type is private to the module.
enum WriteTypeError {
    Format(core::fmt::Error),
    NonWgsl,
}

impl From<core::fmt::Error> for WriteTypeError {
    fn from(err: core::fmt::Error) -> Self {
        Self::Format(err)
    }
}