naga/common/wgsl/types.rs
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//! 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)
}
}