naga/back/spv/
helpers.rs

1use alloc::{vec, vec::Vec};
2
3use spirv::Word;
4
5use crate::{Handle, UniqueArena};
6
7pub(super) fn bytes_to_words(bytes: &[u8]) -> Vec<Word> {
8    bytes
9        .chunks(4)
10        .map(|chars| chars.iter().rev().fold(0u32, |u, c| (u << 8) | *c as u32))
11        .collect()
12}
13
14pub(super) fn string_to_words(input: &str) -> Vec<Word> {
15    let bytes = input.as_bytes();
16
17    str_bytes_to_words(bytes)
18}
19
20pub(super) fn str_bytes_to_words(bytes: &[u8]) -> Vec<Word> {
21    let mut words = bytes_to_words(bytes);
22    if bytes.len() % 4 == 0 {
23        // nul-termination
24        words.push(0x0u32);
25    }
26
27    words
28}
29
30/// split a string into chunks and keep utf8 valid
31#[allow(unstable_name_collisions)]
32pub(super) fn string_to_byte_chunks(input: &str, limit: usize) -> Vec<&[u8]> {
33    let mut offset: usize = 0;
34    let mut start: usize = 0;
35    let mut words = vec![];
36    while offset < input.len() {
37        offset = input.floor_char_boundary(offset + limit);
38        words.push(input[start..offset].as_bytes());
39        start = offset;
40    }
41
42    words
43}
44
45pub(super) const fn map_storage_class(space: crate::AddressSpace) -> spirv::StorageClass {
46    match space {
47        crate::AddressSpace::Handle => spirv::StorageClass::UniformConstant,
48        crate::AddressSpace::Function => spirv::StorageClass::Function,
49        crate::AddressSpace::Private => spirv::StorageClass::Private,
50        crate::AddressSpace::Storage { .. } => spirv::StorageClass::StorageBuffer,
51        crate::AddressSpace::Uniform => spirv::StorageClass::Uniform,
52        crate::AddressSpace::WorkGroup => spirv::StorageClass::Workgroup,
53        crate::AddressSpace::PushConstant => spirv::StorageClass::PushConstant,
54    }
55}
56
57pub(super) fn contains_builtin(
58    binding: Option<&crate::Binding>,
59    ty: Handle<crate::Type>,
60    arena: &UniqueArena<crate::Type>,
61    built_in: crate::BuiltIn,
62) -> bool {
63    if let Some(&crate::Binding::BuiltIn(bi)) = binding {
64        bi == built_in
65    } else if let crate::TypeInner::Struct { ref members, .. } = arena[ty].inner {
66        members
67            .iter()
68            .any(|member| contains_builtin(member.binding.as_ref(), member.ty, arena, built_in))
69    } else {
70        false // unreachable
71    }
72}
73
74impl crate::AddressSpace {
75    pub(super) const fn to_spirv_semantics_and_scope(
76        self,
77    ) -> (spirv::MemorySemantics, spirv::Scope) {
78        match self {
79            Self::Storage { .. } => (spirv::MemorySemantics::UNIFORM_MEMORY, spirv::Scope::Device),
80            Self::WorkGroup => (
81                spirv::MemorySemantics::WORKGROUP_MEMORY,
82                spirv::Scope::Workgroup,
83            ),
84            _ => (spirv::MemorySemantics::empty(), spirv::Scope::Invocation),
85        }
86    }
87}
88
89/// Return true if the global requires a type decorated with `Block`.
90///
91/// See [`back::spv::GlobalVariable`] for details.
92///
93/// [`back::spv::GlobalVariable`]: super::GlobalVariable
94pub fn global_needs_wrapper(ir_module: &crate::Module, var: &crate::GlobalVariable) -> bool {
95    match var.space {
96        crate::AddressSpace::Uniform
97        | crate::AddressSpace::Storage { .. }
98        | crate::AddressSpace::PushConstant => {}
99        _ => return false,
100    };
101    match ir_module.types[var.ty].inner {
102        crate::TypeInner::Struct {
103            ref members,
104            span: _,
105        } => match members.last() {
106            Some(member) => match ir_module.types[member.ty].inner {
107                // Structs with dynamically sized arrays can't be copied and can't be wrapped.
108                crate::TypeInner::Array {
109                    size: crate::ArraySize::Dynamic,
110                    ..
111                } => false,
112                _ => true,
113            },
114            None => false,
115        },
116        crate::TypeInner::BindingArray { .. } => false,
117        // if it's not a structure or a binding array, let's wrap it to be able to put "Block"
118        _ => true,
119    }
120}
121
122///HACK: this is taken from std unstable, remove it when std's floor_char_boundary is stable
123trait U8Internal {
124    fn is_utf8_char_boundary(&self) -> bool;
125}
126
127impl U8Internal for u8 {
128    fn is_utf8_char_boundary(&self) -> bool {
129        // This is bit magic equivalent to: b < 128 || b >= 192
130        (*self as i8) >= -0x40
131    }
132}
133
134trait StrUnstable {
135    fn floor_char_boundary(&self, index: usize) -> usize;
136}
137
138impl StrUnstable for str {
139    fn floor_char_boundary(&self, index: usize) -> usize {
140        if index >= self.len() {
141            self.len()
142        } else {
143            let lower_bound = index.saturating_sub(3);
144            let new_index = self.as_bytes()[lower_bound..=index]
145                .iter()
146                .rposition(|b| b.is_utf8_char_boundary());
147
148            // SAFETY: we know that the character boundary will be within four bytes
149            unsafe { lower_bound + new_index.unwrap_unchecked() }
150        }
151    }
152}
naga/back/spv/helpers.rs

naga/back/spv/
helpers.rs
