Vendor things

third-party/vendor/naga/src/proc/layouter.rs

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+use crate::arena::Handle;
+use std::{fmt::Display, num::NonZeroU32, ops};
+
+/// A newtype struct where its only valid values are powers of 2
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
+#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
+pub struct Alignment(NonZeroU32);
+
+impl Alignment {
+    pub const ONE: Self = Self(unsafe { NonZeroU32::new_unchecked(1) });
+    pub const TWO: Self = Self(unsafe { NonZeroU32::new_unchecked(2) });
+    pub const FOUR: Self = Self(unsafe { NonZeroU32::new_unchecked(4) });
+    pub const EIGHT: Self = Self(unsafe { NonZeroU32::new_unchecked(8) });
+    pub const SIXTEEN: Self = Self(unsafe { NonZeroU32::new_unchecked(16) });
+
+    pub const MIN_UNIFORM: Self = Self::SIXTEEN;
+
+    pub const fn new(n: u32) -> Option<Self> {
+        if n.is_power_of_two() {
+            // SAFETY: value can't be 0 since we just checked if it's a power of 2
+            Some(Self(unsafe { NonZeroU32::new_unchecked(n) }))
+        } else {
+            None
+        }
+    }
+
+    /// # Panics
+    /// If `width` is not a power of 2
+    pub fn from_width(width: u8) -> Self {
+        Self::new(width as u32).unwrap()
+    }
+
+    /// Returns whether or not `n` is a multiple of this alignment.
+    pub const fn is_aligned(&self, n: u32) -> bool {
+        // equivalent to: `n % self.0.get() == 0` but much faster
+        n & (self.0.get() - 1) == 0
+    }
+
+    /// Round `n` up to the nearest alignment boundary.
+    pub const fn round_up(&self, n: u32) -> u32 {
+        // equivalent to:
+        // match n % self.0.get() {
+        //     0 => n,
+        //     rem => n + (self.0.get() - rem),
+        // }
+        let mask = self.0.get() - 1;
+        (n + mask) & !mask
+    }
+}
+
+impl Display for Alignment {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.get().fmt(f)
+    }
+}
+
+impl ops::Mul<u32> for Alignment {
+    type Output = u32;
+
+    fn mul(self, rhs: u32) -> Self::Output {
+        self.0.get() * rhs
+    }
+}
+
+impl ops::Mul for Alignment {
+    type Output = Alignment;
+
+    fn mul(self, rhs: Alignment) -> Self::Output {
+        // SAFETY: both lhs and rhs are powers of 2, the result will be a power of 2
+        Self(unsafe { NonZeroU32::new_unchecked(self.0.get() * rhs.0.get()) })
+    }
+}
+
+impl From<crate::VectorSize> for Alignment {
+    fn from(size: crate::VectorSize) -> Self {
+        match size {
+            crate::VectorSize::Bi => Alignment::TWO,
+            crate::VectorSize::Tri => Alignment::FOUR,
+            crate::VectorSize::Quad => Alignment::FOUR,
+        }
+    }
+}
+
+/// Size and 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,
+}
+
+impl TypeLayout {
+    /// Produce the stride as if this type is a base of an array.
+    pub const fn to_stride(&self) -> u32 {
+        self.alignment.round_up(self.size)
+    }
+}
+
+/// Helper processor that derives the sizes of all types.
+///
+/// `Layouter` uses the default layout algorithm/table, described in
+/// [WGSL §4.3.7, "Memory Layout"]
+///
+/// A `Layouter` may be indexed by `Handle<Type>` values: `layouter[handle]` is the
+/// layout of the type whose handle is `handle`.
+///
+/// [WGSL §4.3.7, "Memory Layout"](https://gpuweb.github.io/gpuweb/wgsl/#memory-layouts)
+#[derive(Debug, Default)]
+#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
+#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
+pub struct Layouter {
+    /// Layouts for types in an arena, indexed by `Handle` index.
+    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)]
+pub enum LayoutErrorInner {
+    #[error("Array element type {0:?} doesn't exist")]
+    InvalidArrayElementType(Handle<crate::Type>),
+    #[error("Struct member[{0}] type {1:?} doesn't exist")]
+    InvalidStructMemberType(u32, Handle<crate::Type>),
+    #[error("Type width must be a power of two")]
+    NonPowerOfTwoWidth,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, thiserror::Error)]
+#[error("Error laying out type {ty:?}: {inner}")]
+pub struct LayoutError {
+    pub ty: Handle<crate::Type>,
+    pub inner: LayoutErrorInner,
+}
+
+impl LayoutErrorInner {
+    const fn with(self, ty: Handle<crate::Type>) -> LayoutError {
+        LayoutError { ty, inner: self }
+    }
+}
+
+impl Layouter {
+    /// Remove all entries from this `Layouter`, retaining storage.
+    pub fn clear(&mut self) {
+        self.layouts.clear();
+    }
+
+    /// Extend this `Layouter` with layouts for any new entries in `types`.
+    ///
+    /// Ensure that every type in `types` has a corresponding [TypeLayout] in
+    /// [`self.layouts`].
+    ///
+    /// Some front ends need to be able to compute layouts for existing types
+    /// while module construction is still in progress and new types are still
+    /// being added. This function assumes that the `TypeLayout` values already
+    /// present in `self.layouts` cover their corresponding entries in `types`,
+    /// and extends `self.layouts` as needed to cover the rest. Thus, a front
+    /// end can call this function at any time, passing its current type and
+    /// constant arenas, and then assume that layouts are available for all
+    /// types.
+    #[allow(clippy::or_fun_call)]
+    pub fn update(&mut self, gctx: super::GlobalCtx) -> Result<(), LayoutError> {
+        use crate::TypeInner as Ti;
+
+        for (ty_handle, ty) in gctx.types.iter().skip(self.layouts.len()) {
+            let size = ty.inner.size(gctx);
+            let layout = match ty.inner {
+                Ti::Scalar { width, .. } | Ti::Atomic { width, .. } => {
+                    let alignment = Alignment::new(width as u32)
+                        .ok_or(LayoutErrorInner::NonPowerOfTwoWidth.with(ty_handle))?;
+                    TypeLayout { size, alignment }
+                }
+                Ti::Vector {
+                    size: vec_size,
+                    width,
+                    ..
+                } => {
+                    let alignment = Alignment::new(width as u32)
+                        .ok_or(LayoutErrorInner::NonPowerOfTwoWidth.with(ty_handle))?;
+                    TypeLayout {
+                        size,
+                        alignment: Alignment::from(vec_size) * alignment,
+                    }
+                }
+                Ti::Matrix {
+                    columns: _,
+                    rows,
+                    width,
+                } => {
+                    let alignment = Alignment::new(width as u32)
+                        .ok_or(LayoutErrorInner::NonPowerOfTwoWidth.with(ty_handle))?;
+                    TypeLayout {
+                        size,
+                        alignment: Alignment::from(rows) * alignment,
+                    }
+                }
+                Ti::Pointer { .. } | Ti::ValuePointer { .. } => TypeLayout {
+                    size,
+                    alignment: Alignment::ONE,
+                },
+                Ti::Array {
+                    base,
+                    stride: _,
+                    size: _,
+                } => TypeLayout {
+                    size,
+                    alignment: if base < ty_handle {
+                        self[base].alignment
+                    } else {
+                        return Err(LayoutErrorInner::InvalidArrayElementType(base).with(ty_handle));
+                    },
+                },
+                Ti::Struct { span, ref members } => {
+                    let mut alignment = Alignment::ONE;
+                    for (index, member) in members.iter().enumerate() {
+                        alignment = if member.ty < ty_handle {
+                            alignment.max(self[member.ty].alignment)
+                        } else {
+                            return Err(LayoutErrorInner::InvalidStructMemberType(
+                                index as u32,
+                                member.ty,
+                            )
+                            .with(ty_handle));
+                        };
+                    }
+                    TypeLayout {
+                        size: span,
+                        alignment,
+                    }
+                }
+                Ti::Image { .. }
+                | Ti::Sampler { .. }
+                | Ti::AccelerationStructure
+                | Ti::RayQuery
+                | Ti::BindingArray { .. } => TypeLayout {
+                    size,
+                    alignment: Alignment::ONE,
+                },
+            };
+            debug_assert!(size <= layout.size);
+            self.layouts.push(layout);
+        }
+
+        Ok(())
+    }
+}