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[naga spv-out] Abstract out OpAccessChain index production.

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Abstract the code from `write_expression_pointer` to handle one
indexing operation out into its own function,
`BlockContext::write_access_chain_index`.
This commit is contained in:
Jim Blandy 2024-10-01 10:39:37 -07:00
parent 3d85781f05
commit 69ab63ca34
1 changed files with 36 additions and 19 deletions
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55
naga/src/back/spv/block.rs
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@ -1828,26 +1828,10 @@ impl<'w> BlockContext<'w> {
is_non_uniform_binding_array |=
self.is_nonuniform_binding_array_access(base, index);
let index_id = match self.write_bounds_check(base, index, block)? {
BoundsCheckResult::KnownInBounds(known_index) => {
// Even if the index is known, `OpAccessChain`
// requires expression operands, not literals.
let scalar = crate::Literal::U32(known_index);
self.writer.get_constant_scalar(scalar)
}
BoundsCheckResult::Computed(computed_index_id) => computed_index_id,
BoundsCheckResult::Conditional(comparison_id) => {
self.extend_bounds_check_condition_chain(
&mut accumulated_checks,
comparison_id,
block,
);
// Use the index from the `Access` expression unchanged.
self.cached[index]
}
};
let index_id =
self.write_access_chain_index(base, index, &mut accumulated_checks, block)?;
self.temp_list.push(index_id);
base
}
crate::Expression::AccessIndex { base, index } => {
@ -1927,6 +1911,39 @@ impl<'w> BlockContext<'w> {
self.fun_info[index].uniformity.non_uniform_result.is_some()
}
/// Compute a single index operand to an `OpAccessChain` instruction.
///
/// Given that we are indexing `base` with `index`, apply the appropriate
/// bounds check policies, emitting code to `block` to clamp `index` or
/// determine whether it's in bounds. Return the SPIR-V instruction id of
/// the index value we should actually use.
///
/// Extend `accumulated_checks` to include the results of any needed bounds
/// checks. See [`BlockContext::extend_bounds_check_condition_chain`].
fn write_access_chain_index(
&mut self,
base: Handle<crate::Expression>,
index: Handle<crate::Expression>,
accumulated_checks: &mut Option<Word>,
block: &mut Block,
) -> Result<Word, Error> {
match self.write_bounds_check(base, index, block)? {
BoundsCheckResult::KnownInBounds(known_index) => {
// Even if the index is known, `OpAccessChain`
// requires expression operands, not literals.
let scalar = crate::Literal::U32(known_index);
Ok(self.writer.get_constant_scalar(scalar))
}
BoundsCheckResult::Computed(computed_index_id) => Ok(computed_index_id),
BoundsCheckResult::Conditional(comparison_id) => {
self.extend_bounds_check_condition_chain(accumulated_checks, comparison_id, block);
// Use the index from the `Access` expression unchanged.
Ok(self.cached[index])
}
}
}
/// Add a condition to a chain of bounds checks.
///
/// As we build an `OpAccessChain` instruction govered by