naga/front/wgsl/lower/conversion.rs
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//! WGSL's automatic conversions for abstract types.
use crate::{Handle, Span};
impl<'source, 'temp, 'out> super::ExpressionContext<'source, 'temp, 'out> {
/// Try to use WGSL's automatic conversions to convert `expr` to `goal_ty`.
///
/// If no conversions are necessary, return `expr` unchanged.
///
/// If automatic conversions cannot convert `expr` to `goal_ty`, return an
/// [`AutoConversion`] error.
///
/// Although the Load Rule is one of the automatic conversions, this
/// function assumes it has already been applied if appropriate, as
/// indicated by the fact that the Rust type of `expr` is not `Typed<_>`.
///
/// [`AutoConversion`]: super::Error::AutoConversion
pub fn try_automatic_conversions(
&mut self,
expr: Handle<crate::Expression>,
goal_ty: &crate::proc::TypeResolution,
goal_span: Span,
) -> Result<Handle<crate::Expression>, super::Error<'source>> {
let expr_span = self.get_expression_span(expr);
// Keep the TypeResolution so we can get type names for
// structs in error messages.
let expr_resolution = super::resolve!(self, expr);
let types = &self.module.types;
let expr_inner = expr_resolution.inner_with(types);
let goal_inner = goal_ty.inner_with(types);
// If `expr` already has the requested type, we're done.
if expr_inner.equivalent(goal_inner, types) {
return Ok(expr);
}
let (_expr_scalar, goal_scalar) =
match expr_inner.automatically_converts_to(goal_inner, types) {
Some(scalars) => scalars,
None => {
let gctx = &self.module.to_ctx();
let source_type = expr_resolution.to_wgsl(gctx);
let dest_type = goal_ty.to_wgsl(gctx);
return Err(super::Error::AutoConversion {
dest_span: goal_span,
dest_type,
source_span: expr_span,
source_type,
});
}
};
self.convert_leaf_scalar(expr, expr_span, goal_scalar)
}
/// Try to convert `expr`'s leaf scalar to `goal` using automatic conversions.
///
/// If no conversions are necessary, return `expr` unchanged.
///
/// If automatic conversions cannot convert `expr` to `goal_scalar`, return
/// an [`AutoConversionLeafScalar`] error.
///
/// Although the Load Rule is one of the automatic conversions, this
/// function assumes it has already been applied if appropriate, as
/// indicated by the fact that the Rust type of `expr` is not `Typed<_>`.
///
/// [`AutoConversionLeafScalar`]: super::Error::AutoConversionLeafScalar
pub fn try_automatic_conversion_for_leaf_scalar(
&mut self,
expr: Handle<crate::Expression>,
goal_scalar: crate::Scalar,
goal_span: Span,
) -> Result<Handle<crate::Expression>, super::Error<'source>> {
let expr_span = self.get_expression_span(expr);
let expr_resolution = super::resolve!(self, expr);
let types = &self.module.types;
let expr_inner = expr_resolution.inner_with(types);
let make_error = || {
let gctx = &self.module.to_ctx();
let source_type = expr_resolution.to_wgsl(gctx);
super::Error::AutoConversionLeafScalar {
dest_span: goal_span,
dest_scalar: goal_scalar.to_wgsl(),
source_span: expr_span,
source_type,
}
};
let expr_scalar = match expr_inner.scalar() {
Some(scalar) => scalar,
None => return Err(make_error()),
};
if expr_scalar == goal_scalar {
return Ok(expr);
}
if !expr_scalar.automatically_converts_to(goal_scalar) {
return Err(make_error());
}
assert!(expr_scalar.is_abstract());
self.convert_leaf_scalar(expr, expr_span, goal_scalar)
}
fn convert_leaf_scalar(
&mut self,
expr: Handle<crate::Expression>,
expr_span: Span,
goal_scalar: crate::Scalar,
) -> Result<Handle<crate::Expression>, super::Error<'source>> {
let expr_inner = super::resolve_inner!(self, expr);
if let crate::TypeInner::Array { .. } = *expr_inner {
self.as_const_evaluator()
.cast_array(expr, goal_scalar, expr_span)
.map_err(|err| super::Error::ConstantEvaluatorError(err, expr_span))
} else {
let cast = crate::Expression::As {
expr,
kind: goal_scalar.kind,
convert: Some(goal_scalar.width),
};
self.append_expression(cast, expr_span)
}
}
/// Try to convert `exprs` to `goal_ty` using WGSL's automatic conversions.
pub fn try_automatic_conversions_slice(
&mut self,
exprs: &mut [Handle<crate::Expression>],
goal_ty: &crate::proc::TypeResolution,
goal_span: Span,
) -> Result<(), super::Error<'source>> {
for expr in exprs.iter_mut() {
*expr = self.try_automatic_conversions(*expr, goal_ty, goal_span)?;
}
Ok(())
}
/// Apply WGSL's automatic conversions to a vector constructor's arguments.
///
/// When calling a vector constructor like `vec3<f32>(...)`, the parameters
/// can be a mix of scalars and vectors, with the latter being spread out to
/// contribute each of their components as a component of the new value.
/// When the element type is explicit, as with `<f32>` in the example above,
/// WGSL's automatic conversions should convert abstract scalar and vector
/// parameters to the constructor's required scalar type.
pub fn try_automatic_conversions_for_vector(
&mut self,
exprs: &mut [Handle<crate::Expression>],
goal_scalar: crate::Scalar,
goal_span: Span,
) -> Result<(), super::Error<'source>> {
use crate::proc::TypeResolution as Tr;
use crate::TypeInner as Ti;
let goal_scalar_res = Tr::Value(Ti::Scalar(goal_scalar));
for (i, expr) in exprs.iter_mut().enumerate() {
// Keep the TypeResolution so we can get full type names
// in error messages.
let expr_resolution = super::resolve!(self, *expr);
let types = &self.module.types;
let expr_inner = expr_resolution.inner_with(types);
match *expr_inner {
Ti::Scalar(_) => {
*expr = self.try_automatic_conversions(*expr, &goal_scalar_res, goal_span)?;
}
Ti::Vector { size, scalar: _ } => {
let goal_vector_res = Tr::Value(Ti::Vector {
size,
scalar: goal_scalar,
});
*expr = self.try_automatic_conversions(*expr, &goal_vector_res, goal_span)?;
}
_ => {
let span = self.get_expression_span(*expr);
return Err(super::Error::InvalidConstructorComponentType(
span, i as i32,
));
}
}
}
Ok(())
}
/// Convert `expr` to the leaf scalar type `scalar`.
pub fn convert_to_leaf_scalar(
&mut self,
expr: &mut Handle<crate::Expression>,
goal: crate::Scalar,
) -> Result<(), super::Error<'source>> {
let inner = super::resolve_inner!(self, *expr);
// Do nothing if `inner` doesn't even have leaf scalars;
// it's a type error that validation will catch.
if inner.scalar() != Some(goal) {
let cast = crate::Expression::As {
expr: *expr,
kind: goal.kind,
convert: Some(goal.width),
};
let expr_span = self.get_expression_span(*expr);
*expr = self.append_expression(cast, expr_span)?;
}
Ok(())
}
/// Convert all expressions in `exprs` to a common scalar type.
///
/// Note that the caller is responsible for making sure these
/// conversions are actually justified. This function simply
/// generates `As` expressions, regardless of whether they are
/// permitted WGSL automatic conversions. Callers intending to
/// implement automatic conversions need to determine for
/// themselves whether the casts we we generate are justified,
/// perhaps by calling `TypeInner::automatically_converts_to` or
/// `Scalar::automatic_conversion_combine`.
pub fn convert_slice_to_common_leaf_scalar(
&mut self,
exprs: &mut [Handle<crate::Expression>],
goal: crate::Scalar,
) -> Result<(), super::Error<'source>> {
for expr in exprs.iter_mut() {
self.convert_to_leaf_scalar(expr, goal)?;
}
Ok(())
}
/// Return an expression for the concretized value of `expr`.
///
/// If `expr` is already concrete, return it unchanged.
pub fn concretize(
&mut self,
mut expr: Handle<crate::Expression>,
) -> Result<Handle<crate::Expression>, super::Error<'source>> {
let inner = super::resolve_inner!(self, expr);
if let Some(scalar) = inner.automatically_convertible_scalar(&self.module.types) {
let concretized = scalar.concretize();
if concretized != scalar {
assert!(scalar.is_abstract());
let expr_span = self.get_expression_span(expr);
expr = self
.as_const_evaluator()
.cast_array(expr, concretized, expr_span)
.map_err(|err| {
// A `TypeResolution` includes the type's full name, if
// it has one. Also, avoid holding the borrow of `inner`
// across the call to `cast_array`.
let expr_type = &self.typifier()[expr];
super::Error::ConcretizationFailed {
expr_span,
expr_type: expr_type.to_wgsl(&self.module.to_ctx()),
scalar: concretized.to_wgsl(),
inner: err,
}
})?;
}
}
Ok(expr)
}
/// Find the consensus scalar of `components` under WGSL's automatic
/// conversions.
///
/// If `components` can all be converted to any common scalar via
/// WGSL's automatic conversions, return the best such scalar.
///
/// The `components` slice must not be empty. All elements' types must
/// have been resolved.
///
/// If `components` are definitely not acceptable as arguments to such
/// constructors, return `Err(i)`, where `i` is the index in
/// `components` of some problematic argument.
///
/// This function doesn't fully type-check the arguments - it only
/// considers their leaf scalar types. This means it may return `Ok`
/// even when the Naga validator will reject the resulting
/// construction expression later.
pub fn automatic_conversion_consensus<'handle, I>(
&self,
components: I,
) -> Result<crate::Scalar, usize>
where
I: IntoIterator<Item = &'handle Handle<crate::Expression>>,
I::IntoIter: Clone, // for debugging
{
let types = &self.module.types;
let mut inners = components
.into_iter()
.map(|&c| self.typifier()[c].inner_with(types));
log::debug!(
"wgsl automatic_conversion_consensus: {:?}",
inners
.clone()
.map(|inner| inner.to_wgsl(&self.module.to_ctx()))
.collect::<Vec<String>>()
);
let mut best = inners.next().unwrap().scalar().ok_or(0_usize)?;
for (inner, i) in inners.zip(1..) {
let scalar = inner.scalar().ok_or(i)?;
match best.automatic_conversion_combine(scalar) {
Some(new_best) => {
best = new_best;
}
None => return Err(i),
}
}
log::debug!(" consensus: {:?}", best.to_wgsl());
Ok(best)
}
}
impl crate::TypeInner {
/// Determine whether `self` automatically converts to `goal`.
///
/// If WGSL's automatic conversions (excluding the Load Rule) will
/// convert `self` to `goal`, then return a pair `(from, to)`,
/// where `from` and `to` are the scalar types of the leaf values
/// of `self` and `goal`.
///
/// This function assumes that `self` and `goal` are different
/// types. Callers should first check whether any conversion is
/// needed at all.
///
/// If the automatic conversions cannot convert `self` to `goal`,
/// return `None`.
fn automatically_converts_to(
&self,
goal: &Self,
types: &crate::UniqueArena<crate::Type>,
) -> Option<(crate::Scalar, crate::Scalar)> {
use crate::ScalarKind as Sk;
use crate::TypeInner as Ti;
// Automatic conversions only change the scalar type of a value's leaves
// (e.g., `vec4<AbstractFloat>` to `vec4<f32>`), never the type
// constructors applied to those scalar types (e.g., never scalar to
// `vec4`, or `vec2` to `vec3`). So first we check that the type
// constructors match, extracting the leaf scalar types in the process.
let expr_scalar;
let goal_scalar;
match (self, goal) {
(&Ti::Scalar(expr), &Ti::Scalar(goal)) => {
expr_scalar = expr;
goal_scalar = goal;
}
(
&Ti::Vector {
size: expr_size,
scalar: expr,
},
&Ti::Vector {
size: goal_size,
scalar: goal,
},
) if expr_size == goal_size => {
expr_scalar = expr;
goal_scalar = goal;
}
(
&Ti::Matrix {
rows: expr_rows,
columns: expr_columns,
scalar: expr,
},
&Ti::Matrix {
rows: goal_rows,
columns: goal_columns,
scalar: goal,
},
) if expr_rows == goal_rows && expr_columns == goal_columns => {
expr_scalar = expr;
goal_scalar = goal;
}
(
&Ti::Array {
base: expr_base,
size: expr_size,
stride: _,
},
&Ti::Array {
base: goal_base,
size: goal_size,
stride: _,
},
) if expr_size == goal_size => {
return types[expr_base]
.inner
.automatically_converts_to(&types[goal_base].inner, types);
}
_ => return None,
}
match (expr_scalar.kind, goal_scalar.kind) {
(Sk::AbstractFloat, Sk::Float) => {}
(Sk::AbstractInt, Sk::Sint | Sk::Uint | Sk::AbstractFloat | Sk::Float) => {}
_ => return None,
}
log::trace!(" okay: expr {expr_scalar:?}, goal {goal_scalar:?}");
Some((expr_scalar, goal_scalar))
}
fn automatically_convertible_scalar(
&self,
types: &crate::UniqueArena<crate::Type>,
) -> Option<crate::Scalar> {
use crate::TypeInner as Ti;
match *self {
Ti::Scalar(scalar) | Ti::Vector { scalar, .. } | Ti::Matrix { scalar, .. } => {
Some(scalar)
}
Ti::Array { base, .. } => types[base].inner.automatically_convertible_scalar(types),
Ti::Atomic(_)
| Ti::Pointer { .. }
| Ti::ValuePointer { .. }
| Ti::Struct { .. }
| Ti::Image { .. }
| Ti::Sampler { .. }
| Ti::AccelerationStructure
| Ti::RayQuery
| Ti::BindingArray { .. } => None,
}
}
}
impl crate::Scalar {
/// Find the common type of `self` and `other` under WGSL's
/// automatic conversions.
///
/// If there are any scalars to which WGSL's automatic conversions
/// will convert both `self` and `other`, return the best such
/// scalar. Otherwise, return `None`.
pub const fn automatic_conversion_combine(self, other: Self) -> Option<crate::Scalar> {
use crate::ScalarKind as Sk;
match (self.kind, other.kind) {
// When the kinds match...
(Sk::AbstractFloat, Sk::AbstractFloat)
| (Sk::AbstractInt, Sk::AbstractInt)
| (Sk::Sint, Sk::Sint)
| (Sk::Uint, Sk::Uint)
| (Sk::Float, Sk::Float)
| (Sk::Bool, Sk::Bool) => {
if self.width == other.width {
// ... either no conversion is necessary ...
Some(self)
} else {
// ... or no conversion is possible.
// We never convert concrete to concrete, and
// abstract types should have only one size.
None
}
}
// AbstractInt converts to AbstractFloat.
(Sk::AbstractFloat, Sk::AbstractInt) => Some(self),
(Sk::AbstractInt, Sk::AbstractFloat) => Some(other),
// AbstractFloat converts to Float.
(Sk::AbstractFloat, Sk::Float) => Some(other),
(Sk::Float, Sk::AbstractFloat) => Some(self),
// AbstractInt converts to concrete integer or float.
(Sk::AbstractInt, Sk::Uint | Sk::Sint | Sk::Float) => Some(other),
(Sk::Uint | Sk::Sint | Sk::Float, Sk::AbstractInt) => Some(self),
// AbstractFloat can't be reconciled with concrete integer types.
(Sk::AbstractFloat, Sk::Uint | Sk::Sint) | (Sk::Uint | Sk::Sint, Sk::AbstractFloat) => {
None
}
// Nothing can be reconciled with `bool`.
(Sk::Bool, _) | (_, Sk::Bool) => None,
// Different concrete types cannot be reconciled.
(Sk::Sint | Sk::Uint | Sk::Float, Sk::Sint | Sk::Uint | Sk::Float) => None,
}
}
/// Return `true` if automatic conversions will covert `self` to `goal`.
pub fn automatically_converts_to(self, goal: Self) -> bool {
self.automatic_conversion_combine(goal) == Some(goal)
}
const fn concretize(self) -> Self {
use crate::ScalarKind as Sk;
match self.kind {
Sk::Sint | Sk::Uint | Sk::Float | Sk::Bool => self,
Sk::AbstractInt => Self::I32,
Sk::AbstractFloat => Self::F32,
}
}
}