Enum naga::back::spv::block::AccessTypeAdjustment

enum AccessTypeAdjustment {
    None,
    IntroducePointer(StorageClass),
}

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.