Enum AccessTypeAdjustment 

enum AccessTypeAdjustment {
    None,
    IntroducePointer(StorageClass),
    UseStd140CompatType,
}

How to derive the type of OpAccessChain instructions from Naga IR.

Most of the time, we compile Naga IR to SPIR-V instructions whose result types are simply the direct SPIR-V analog of the Naga IR’s. But in some cases, the Naga IR and SPIR-V types need to diverge.

This enum specifies how BlockContext::write_access_chain should choose a SPIR-V result type for the OpAccessChain it generates, based on the type of the given Naga IR Expression it’s generating code for.

Variants

None

No adjustment needed: the SPIR-V type should be the direct analog of the Naga IR expression type.

For most access chains, this is the right thing: the Naga IR access expression produces a Pointer to the element / component, and the SPIR-V OpAccessChain instruction does the same.

IntroducePointer(StorageClass)

The SPIR-V type should be an OpPointer to the direct analog of the Naga IR expression’s type.

This is necessary for indexing binding arrays in the Handle address space:

• In Naga IR, referencing a binding array GlobalVariable in the Handle address space produces a value of type BindingArray, not a pointer to such. And Access and AccessIndex expressions operate on handle binding arrays by value, and produce handle values, not pointers.

• In SPIR-V, a binding array OpVariable produces a pointer to an array, and OpAccessChain instructions operate on pointers, regardless of whether the elements are opaque types or not.

See also the documentation for BindingArray.

UseStd140CompatType

The SPIR-V type should be an OpPointer to the std140 layout compatible variant of the Naga IR expression’s base type.

This is used when accessing a type through an AddressSpace::Uniform pointer in cases where the original type is incompatible with std140 layout requirements and we have therefore declared the uniform to be of an alternative std140 compliant type.

Trait Implementations

impl Clone for AccessTypeAdjustment

fn clone(&self) -> AccessTypeAdjustment

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for AccessTypeAdjustment