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
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
/*!
Backend for [MSL][msl] (Metal Shading Language).

## Binding model

Metal's bindings are flat per resource. Since there isn't an obvious mapping
from SPIR-V's descriptor sets, we require a separate mapping provided in the options.
This mapping may have one or more resource end points for each descriptor set + index
pair.

## Entry points

Even though MSL and our IR appear to be similar in that the entry points in both can
accept arguments and return values, the restrictions are different.
MSL allows the varyings to be either in separate arguments, or inside a single
`[[stage_in]]` struct. We gather input varyings and form this artificial structure.
We also add all the (non-Private) globals into the arguments.

At the beginning of the entry point, we assign the local constants and re-compose
the arguments as they are declared on IR side, so that the rest of the logic can
pretend that MSL doesn't have all the restrictions it has.

For the result type, if it's a structure, we re-compose it with a temporary value
holding the result.

[msl]: https://developer.apple.com/metal/Metal-Shading-Language-Specification.pdf
*/

use crate::{arena::Handle, proc::index, valid::ModuleInfo};
use std::fmt::{Error as FmtError, Write};

mod keywords;
pub mod sampler;
mod writer;

pub use writer::Writer;

pub type Slot = u8;
pub type InlineSamplerIndex = u8;

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub enum BindSamplerTarget {
    Resource(Slot),
    Inline(InlineSamplerIndex),
}

#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
#[cfg_attr(any(feature = "serialize", feature = "deserialize"), serde(default))]
pub struct BindTarget {
    pub buffer: Option<Slot>,
    pub texture: Option<Slot>,
    pub sampler: Option<BindSamplerTarget>,
    /// If the binding is an unsized binding array, this overrides the size.
    pub binding_array_size: Option<u32>,
    pub mutable: bool,
}

// Using `BTreeMap` instead of `HashMap` so that we can hash itself.
pub type BindingMap = std::collections::BTreeMap<crate::ResourceBinding, BindTarget>;

#[derive(Clone, Debug, Default, Hash, Eq, PartialEq)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
#[cfg_attr(any(feature = "serialize", feature = "deserialize"), serde(default))]
pub struct EntryPointResources {
    pub resources: BindingMap,

    pub push_constant_buffer: Option<Slot>,

    /// The slot of a buffer that contains an array of `u32`,
    /// one for the size of each bound buffer that contains a runtime array,
    /// in order of [`crate::GlobalVariable`] declarations.
    pub sizes_buffer: Option<Slot>,
}

pub type EntryPointResourceMap = std::collections::BTreeMap<String, EntryPointResources>;

enum ResolvedBinding {
    BuiltIn(crate::BuiltIn),
    Attribute(u32),
    Color {
        location: u32,
        second_blend_source: bool,
    },
    User {
        prefix: &'static str,
        index: u32,
        interpolation: Option<ResolvedInterpolation>,
    },
    Resource(BindTarget),
}

#[derive(Copy, Clone)]
enum ResolvedInterpolation {
    CenterPerspective,
    CenterNoPerspective,
    CentroidPerspective,
    CentroidNoPerspective,
    SamplePerspective,
    SampleNoPerspective,
    Flat,
}

// Note: some of these should be removed in favor of proper IR validation.

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error(transparent)]
    Format(#[from] FmtError),
    #[error("bind target {0:?} is empty")]
    UnimplementedBindTarget(BindTarget),
    #[error("composing of {0:?} is not implemented yet")]
    UnsupportedCompose(Handle<crate::Type>),
    #[error("operation {0:?} is not implemented yet")]
    UnsupportedBinaryOp(crate::BinaryOperator),
    #[error("standard function '{0}' is not implemented yet")]
    UnsupportedCall(String),
    #[error("feature '{0}' is not implemented yet")]
    FeatureNotImplemented(String),
    #[error("internal naga error: module should not have validated: {0}")]
    GenericValidation(String),
    #[error("BuiltIn {0:?} is not supported")]
    UnsupportedBuiltIn(crate::BuiltIn),
    #[error("capability {0:?} is not supported")]
    CapabilityNotSupported(crate::valid::Capabilities),
    #[error("attribute '{0}' is not supported for target MSL version")]
    UnsupportedAttribute(String),
    #[error("function '{0}' is not supported for target MSL version")]
    UnsupportedFunction(String),
    #[error("can not use writeable storage buffers in fragment stage prior to MSL 1.2")]
    UnsupportedWriteableStorageBuffer,
    #[error("can not use writeable storage textures in {0:?} stage prior to MSL 1.2")]
    UnsupportedWriteableStorageTexture(crate::ShaderStage),
    #[error("can not use read-write storage textures prior to MSL 1.2")]
    UnsupportedRWStorageTexture,
    #[error("array of '{0}' is not supported for target MSL version")]
    UnsupportedArrayOf(String),
    #[error("array of type '{0:?}' is not supported")]
    UnsupportedArrayOfType(Handle<crate::Type>),
    #[error("ray tracing is not supported prior to MSL 2.3")]
    UnsupportedRayTracing,
    #[error("overrides should not be present at this stage")]
    Override,
}

#[derive(Clone, Debug, PartialEq, thiserror::Error)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub enum EntryPointError {
    #[error("global '{0}' doesn't have a binding")]
    MissingBinding(String),
    #[error("mapping of {0:?} is missing")]
    MissingBindTarget(crate::ResourceBinding),
    #[error("mapping for push constants is missing")]
    MissingPushConstants,
    #[error("mapping for sizes buffer is missing")]
    MissingSizesBuffer,
}

/// Points in the MSL code where we might emit a pipeline input or output.
///
/// Note that, even though vertex shaders' outputs are always fragment
/// shaders' inputs, we still need to distinguish `VertexOutput` and
/// `FragmentInput`, since there are certain differences in the way
/// [`ResolvedBinding`s] are represented on either side.
///
/// [`ResolvedBinding`s]: ResolvedBinding
#[derive(Clone, Copy, Debug)]
enum LocationMode {
    /// Input to the vertex shader.
    VertexInput,

    /// Output from the vertex shader.
    VertexOutput,

    /// Input to the fragment shader.
    FragmentInput,

    /// Output from the fragment shader.
    FragmentOutput,

    /// Compute shader input or output.
    Uniform,
}

#[derive(Clone, Debug, Hash, PartialEq, Eq)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub struct Options {
    /// (Major, Minor) target version of the Metal Shading Language.
    pub lang_version: (u8, u8),
    /// Map of entry-point resources, indexed by entry point function name, to slots.
    pub per_entry_point_map: EntryPointResourceMap,
    /// Samplers to be inlined into the code.
    pub inline_samplers: Vec<sampler::InlineSampler>,
    /// Make it possible to link different stages via SPIRV-Cross.
    pub spirv_cross_compatibility: bool,
    /// Don't panic on missing bindings, instead generate invalid MSL.
    pub fake_missing_bindings: bool,
    /// Bounds checking policies.
    #[cfg_attr(feature = "deserialize", serde(default))]
    pub bounds_check_policies: index::BoundsCheckPolicies,
    /// Should workgroup variables be zero initialized (by polyfilling)?
    pub zero_initialize_workgroup_memory: bool,
}

impl Default for Options {
    fn default() -> Self {
        Options {
            lang_version: (1, 0),
            per_entry_point_map: EntryPointResourceMap::default(),
            inline_samplers: Vec::new(),
            spirv_cross_compatibility: false,
            fake_missing_bindings: true,
            bounds_check_policies: index::BoundsCheckPolicies::default(),
            zero_initialize_workgroup_memory: true,
        }
    }
}

/// A subset of options that are meant to be changed per pipeline.
#[derive(Debug, Default, Clone)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub struct PipelineOptions {
    /// Allow `BuiltIn::PointSize` and inject it if doesn't exist.
    ///
    /// Metal doesn't like this for non-point primitive topologies and requires it for
    /// point primitive topologies.
    ///
    /// Enable this for vertex shaders with point primitive topologies.
    pub allow_and_force_point_size: bool,
}

impl Options {
    fn resolve_local_binding(
        &self,
        binding: &crate::Binding,
        mode: LocationMode,
    ) -> Result<ResolvedBinding, Error> {
        match *binding {
            crate::Binding::BuiltIn(mut built_in) => {
                match built_in {
                    crate::BuiltIn::Position { ref mut invariant } => {
                        if *invariant && self.lang_version < (2, 1) {
                            return Err(Error::UnsupportedAttribute("invariant".to_string()));
                        }

                        // The 'invariant' attribute may only appear on vertex
                        // shader outputs, not fragment shader inputs.
                        if !matches!(mode, LocationMode::VertexOutput) {
                            *invariant = false;
                        }
                    }
                    crate::BuiltIn::BaseInstance if self.lang_version < (1, 2) => {
                        return Err(Error::UnsupportedAttribute("base_instance".to_string()));
                    }
                    crate::BuiltIn::InstanceIndex if self.lang_version < (1, 2) => {
                        return Err(Error::UnsupportedAttribute("instance_id".to_string()));
                    }
                    // macOS: Since Metal 2.2
                    // iOS: Since Metal 2.3 (check depends on https://github.com/gfx-rs/naga/issues/2164)
                    crate::BuiltIn::PrimitiveIndex if self.lang_version < (2, 2) => {
                        return Err(Error::UnsupportedAttribute("primitive_id".to_string()));
                    }
                    _ => {}
                }

                Ok(ResolvedBinding::BuiltIn(built_in))
            }
            crate::Binding::Location {
                location,
                interpolation,
                sampling,
                second_blend_source,
            } => match mode {
                LocationMode::VertexInput => Ok(ResolvedBinding::Attribute(location)),
                LocationMode::FragmentOutput => {
                    if second_blend_source && self.lang_version < (1, 2) {
                        return Err(Error::UnsupportedAttribute(
                            "second_blend_source".to_string(),
                        ));
                    }
                    Ok(ResolvedBinding::Color {
                        location,
                        second_blend_source,
                    })
                }
                LocationMode::VertexOutput | LocationMode::FragmentInput => {
                    Ok(ResolvedBinding::User {
                        prefix: if self.spirv_cross_compatibility {
                            "locn"
                        } else {
                            "loc"
                        },
                        index: location,
                        interpolation: {
                            // unwrap: The verifier ensures that vertex shader outputs and fragment
                            // shader inputs always have fully specified interpolation, and that
                            // sampling is `None` only for Flat interpolation.
                            let interpolation = interpolation.unwrap();
                            let sampling = sampling.unwrap_or(crate::Sampling::Center);
                            Some(ResolvedInterpolation::from_binding(interpolation, sampling))
                        },
                    })
                }
                LocationMode::Uniform => Err(Error::GenericValidation(format!(
                    "Unexpected Binding::Location({}) for the Uniform mode",
                    location
                ))),
            },
        }
    }

    fn get_entry_point_resources(&self, ep: &crate::EntryPoint) -> Option<&EntryPointResources> {
        self.per_entry_point_map.get(&ep.name)
    }

    fn get_resource_binding_target(
        &self,
        ep: &crate::EntryPoint,
        res_binding: &crate::ResourceBinding,
    ) -> Option<&BindTarget> {
        self.get_entry_point_resources(ep)
            .and_then(|res| res.resources.get(res_binding))
    }

    fn resolve_resource_binding(
        &self,
        ep: &crate::EntryPoint,
        res_binding: &crate::ResourceBinding,
    ) -> Result<ResolvedBinding, EntryPointError> {
        let target = self.get_resource_binding_target(ep, res_binding);
        match target {
            Some(target) => Ok(ResolvedBinding::Resource(target.clone())),
            None if self.fake_missing_bindings => Ok(ResolvedBinding::User {
                prefix: "fake",
                index: 0,
                interpolation: None,
            }),
            None => Err(EntryPointError::MissingBindTarget(res_binding.clone())),
        }
    }

    fn resolve_push_constants(
        &self,
        ep: &crate::EntryPoint,
    ) -> Result<ResolvedBinding, EntryPointError> {
        let slot = self
            .get_entry_point_resources(ep)
            .and_then(|res| res.push_constant_buffer);
        match slot {
            Some(slot) => Ok(ResolvedBinding::Resource(BindTarget {
                buffer: Some(slot),
                ..Default::default()
            })),
            None if self.fake_missing_bindings => Ok(ResolvedBinding::User {
                prefix: "fake",
                index: 0,
                interpolation: None,
            }),
            None => Err(EntryPointError::MissingPushConstants),
        }
    }

    fn resolve_sizes_buffer(
        &self,
        ep: &crate::EntryPoint,
    ) -> Result<ResolvedBinding, EntryPointError> {
        let slot = self
            .get_entry_point_resources(ep)
            .and_then(|res| res.sizes_buffer);
        match slot {
            Some(slot) => Ok(ResolvedBinding::Resource(BindTarget {
                buffer: Some(slot),
                ..Default::default()
            })),
            None if self.fake_missing_bindings => Ok(ResolvedBinding::User {
                prefix: "fake",
                index: 0,
                interpolation: None,
            }),
            None => Err(EntryPointError::MissingSizesBuffer),
        }
    }
}

impl ResolvedBinding {
    fn as_inline_sampler<'a>(&self, options: &'a Options) -> Option<&'a sampler::InlineSampler> {
        match *self {
            Self::Resource(BindTarget {
                sampler: Some(BindSamplerTarget::Inline(index)),
                ..
            }) => Some(&options.inline_samplers[index as usize]),
            _ => None,
        }
    }

    const fn as_bind_target(&self) -> Option<&BindTarget> {
        match *self {
            Self::Resource(ref target) => Some(target),
            _ => None,
        }
    }

    fn try_fmt<W: Write>(&self, out: &mut W) -> Result<(), Error> {
        write!(out, " [[")?;
        match *self {
            Self::BuiltIn(built_in) => {
                use crate::BuiltIn as Bi;
                let name = match built_in {
                    Bi::Position { invariant: false } => "position",
                    Bi::Position { invariant: true } => "position, invariant",
                    // vertex
                    Bi::BaseInstance => "base_instance",
                    Bi::BaseVertex => "base_vertex",
                    Bi::ClipDistance => "clip_distance",
                    Bi::InstanceIndex => "instance_id",
                    Bi::PointSize => "point_size",
                    Bi::VertexIndex => "vertex_id",
                    // fragment
                    Bi::FragDepth => "depth(any)",
                    Bi::PointCoord => "point_coord",
                    Bi::FrontFacing => "front_facing",
                    Bi::PrimitiveIndex => "primitive_id",
                    Bi::SampleIndex => "sample_id",
                    Bi::SampleMask => "sample_mask",
                    // compute
                    Bi::GlobalInvocationId => "thread_position_in_grid",
                    Bi::LocalInvocationId => "thread_position_in_threadgroup",
                    Bi::LocalInvocationIndex => "thread_index_in_threadgroup",
                    Bi::WorkGroupId => "threadgroup_position_in_grid",
                    Bi::WorkGroupSize => "dispatch_threads_per_threadgroup",
                    Bi::NumWorkGroups => "threadgroups_per_grid",
                    // subgroup
                    Bi::NumSubgroups => "simdgroups_per_threadgroup",
                    Bi::SubgroupId => "simdgroup_index_in_threadgroup",
                    Bi::SubgroupSize => "threads_per_simdgroup",
                    Bi::SubgroupInvocationId => "thread_index_in_simdgroup",
                    Bi::CullDistance | Bi::ViewIndex => {
                        return Err(Error::UnsupportedBuiltIn(built_in))
                    }
                };
                write!(out, "{name}")?;
            }
            Self::Attribute(index) => write!(out, "attribute({index})")?,
            Self::Color {
                location,
                second_blend_source,
            } => {
                if second_blend_source {
                    write!(out, "color({location}) index(1)")?
                } else {
                    write!(out, "color({location})")?
                }
            }
            Self::User {
                prefix,
                index,
                interpolation,
            } => {
                write!(out, "user({prefix}{index})")?;
                if let Some(interpolation) = interpolation {
                    write!(out, ", ")?;
                    interpolation.try_fmt(out)?;
                }
            }
            Self::Resource(ref target) => {
                if let Some(id) = target.buffer {
                    write!(out, "buffer({id})")?;
                } else if let Some(id) = target.texture {
                    write!(out, "texture({id})")?;
                } else if let Some(BindSamplerTarget::Resource(id)) = target.sampler {
                    write!(out, "sampler({id})")?;
                } else {
                    return Err(Error::UnimplementedBindTarget(target.clone()));
                }
            }
        }
        write!(out, "]]")?;
        Ok(())
    }
}

impl ResolvedInterpolation {
    const fn from_binding(interpolation: crate::Interpolation, sampling: crate::Sampling) -> Self {
        use crate::Interpolation as I;
        use crate::Sampling as S;

        match (interpolation, sampling) {
            (I::Perspective, S::Center) => Self::CenterPerspective,
            (I::Perspective, S::Centroid) => Self::CentroidPerspective,
            (I::Perspective, S::Sample) => Self::SamplePerspective,
            (I::Linear, S::Center) => Self::CenterNoPerspective,
            (I::Linear, S::Centroid) => Self::CentroidNoPerspective,
            (I::Linear, S::Sample) => Self::SampleNoPerspective,
            (I::Flat, _) => Self::Flat,
        }
    }

    fn try_fmt<W: Write>(self, out: &mut W) -> Result<(), Error> {
        let identifier = match self {
            Self::CenterPerspective => "center_perspective",
            Self::CenterNoPerspective => "center_no_perspective",
            Self::CentroidPerspective => "centroid_perspective",
            Self::CentroidNoPerspective => "centroid_no_perspective",
            Self::SamplePerspective => "sample_perspective",
            Self::SampleNoPerspective => "sample_no_perspective",
            Self::Flat => "flat",
        };
        out.write_str(identifier)?;
        Ok(())
    }
}

/// Information about a translated module that is required
/// for the use of the result.
pub struct TranslationInfo {
    /// Mapping of the entry point names. Each item in the array
    /// corresponds to an entry point index.
    ///
    ///Note: Some entry points may fail translation because of missing bindings.
    pub entry_point_names: Vec<Result<String, EntryPointError>>,
}

pub fn write_string(
    module: &crate::Module,
    info: &ModuleInfo,
    options: &Options,
    pipeline_options: &PipelineOptions,
) -> Result<(String, TranslationInfo), Error> {
    let mut w = writer::Writer::new(String::new());
    let info = w.write(module, info, options, pipeline_options)?;
    Ok((w.finish(), info))
}

#[test]
fn test_error_size() {
    use std::mem::size_of;
    assert_eq!(size_of::<Error>(), 32);
}

impl crate::AtomicFunction {
    fn to_msl(self) -> Result<&'static str, Error> {
        Ok(match self {
            Self::Add => "fetch_add",
            Self::Subtract => "fetch_sub",
            Self::And => "fetch_and",
            Self::InclusiveOr => "fetch_or",
            Self::ExclusiveOr => "fetch_xor",
            Self::Min => "fetch_min",
            Self::Max => "fetch_max",
            Self::Exchange { compare: None } => "exchange",
            Self::Exchange { compare: Some(_) } => Err(Error::FeatureNotImplemented(
                "atomic CompareExchange".to_string(),
            ))?,
        })
    }
}