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

use crate::arena::{Arena, Handle};
use std::{num::NonZeroU32, ops};

pub type Alignment = NonZeroU32;

/// Alignment information for a type.
#[derive(Clone, Copy, Debug, Hash, PartialEq)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub struct TypeLayout {
    pub size: u32,
    pub alignment: Alignment,
}

/// Helper processor that derives the sizes of all types.
/// It uses the default layout algorithm/table, described in
/// <https://github.com/gpuweb/gpuweb/issues/1393>
#[derive(Debug, Default)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
pub struct Layouter {
    layouts: Vec<TypeLayout>,
}

impl ops::Index<Handle<crate::Type>> for Layouter {
    type Output = TypeLayout;
    fn index(&self, handle: Handle<crate::Type>) -> &TypeLayout {
        &self.layouts[handle.index()]
    }
}

#[derive(Clone, Copy, Debug, PartialEq, thiserror::Error)]
#[error("Base type {0:?} is out of bounds")]
pub struct InvalidBaseType(pub Handle<crate::Type>);

impl Layouter {
    pub fn clear(&mut self) {
        self.layouts.clear();
    }

    pub fn round_up(alignment: Alignment, offset: u32) -> u32 {
        match offset & (alignment.get() - 1) {
            0 => offset,
            other => offset + alignment.get() - other,
        }
    }

    pub fn member_placement(
        &self,
        offset: u32,
        ty: Handle<crate::Type>,
        align: Option<Alignment>,
        size: Option<NonZeroU32>,
    ) -> (ops::Range<u32>, Alignment) {
        let layout = self.layouts[ty.index()];
        let alignment = align.unwrap_or(layout.alignment);
        let start = Self::round_up(alignment, offset);
        let span = match size {
            Some(size) => size.get(),
            None => layout.size,
        };
        (start..start + span, alignment)
    }

    pub fn update(
        &mut self,
        types: &Arena<crate::Type>,
        constants: &Arena<crate::Constant>,
    ) -> Result<(), InvalidBaseType> {
        use crate::TypeInner as Ti;

        for (ty_handle, ty) in types.iter().skip(self.layouts.len()) {
            let size = ty.inner.span(constants);
            let layout = match ty.inner {
                Ti::Scalar { width, .. } | Ti::Atomic { width, .. } => TypeLayout {
                    size,
                    alignment: Alignment::new(width as u32).unwrap(),
                },
                Ti::Vector {
                    size: vec_size,
                    width,
                    ..
                } => TypeLayout {
                    size,
                    alignment: {
                        let count = if vec_size >= crate::VectorSize::Tri {
                            4
                        } else {
                            2
                        };
                        Alignment::new((count * width) as u32).unwrap()
                    },
                },
                Ti::Matrix {
                    columns: _,
                    rows,
                    width,
                } => TypeLayout {
                    size,
                    alignment: {
                        let count = if rows >= crate::VectorSize::Tri { 4 } else { 2 };
                        Alignment::new((count * width) as u32).unwrap()
                    },
                },
                Ti::Pointer { .. } | Ti::ValuePointer { .. } => TypeLayout {
                    size,
                    alignment: Alignment::new(1).unwrap(),
                },
                Ti::Array {
                    base,
                    stride: _,
                    size: _,
                } => TypeLayout {
                    size,
                    alignment: if base < ty_handle {
                        self[base].alignment
                    } else {
                        return Err(InvalidBaseType(base));
                    },
                },
                Ti::Struct {
                    top_level: _,
                    span,
                    ref members,
                } => {
                    let mut alignment = Alignment::new(1).unwrap();
                    for member in members {
                        alignment = if member.ty < ty_handle {
                            alignment.max(self[member.ty].alignment)
                        } else {
                            return Err(InvalidBaseType(member.ty));
                        };
                    }
                    TypeLayout {
                        size: span,
                        alignment,
                    }
                }
                Ti::Image { .. } | Ti::Sampler { .. } => TypeLayout {
                    size,
                    alignment: Alignment::new(1).unwrap(),
                },
            };
            debug_assert!(ty.inner.span(constants) <= layout.size);
            self.layouts.push(layout);
        }

        Ok(())
    }
}