Autogen customisation and value

[Skepfyr]

Currently, lots of bits of rspirv are generated from the JSON grammar, this is to allow fast and correct updating and bulk feature addition. However, as rspirv grows more and more of this will need to be customised, some of these may be able to be upstreamed into the grammar file, some will not. The goal of this issue is to make sure that the cost of these customisations doesn't exceed the value of the autogen. If that does happen then the auto-generated code will be inlined and all updates will need to be provided manually.

Below is a list of all of the current customisations to auto-generated code, feel free to edit the list if you spot, or add, some more.

• spirv.core.grammar.json: Branch instructions have their class renamed from Terminator to Branch (should be upstreamed)
• spirv.core.grammar.json: OpPhi's third operand renamed from 'Variable, Parent, ...' to 'ValueLabelPairs' (could be upstreamed?)
• OpPhi in general is treated uniquely
• autogen/binary: LiteralInteger has special method name handling
• autogen/binary: All possible pair kinds are hardcoded
• autogen/binary: "IdResultType", "IdResult", "LiteralContextDependentNumber", "LiteralSpecConstantOpInteger" are all handled manually
• autogen/binary: NaN has dodgy snake_casing rules
• autogen/dr: IdResult treated separately
• autogen/dr: OpReturn and OpReturnValue have special function names (as return is a keyword)
• autogen/dr: LiteralString has different get_init_list handling
• autogen/dr: Pair types treated separately again, in get_push_extras
• autogen/dr: All number kinds hardcoded
• autogen/dr: Pointer types filtered out in gen_dr_builder_types
• autogen/header: NaN has special snake casing rules
• autogen/header: Dim types have Dim prepended as types can't start with numbers
• autogen/sr: Lots of operand types have special name and typing rules
• autogen/sr: Decoration ops treated completely separately
• autogen/sr: gen_sr_code_from_instruction_grammar skips constants
• autogen/sr: gen_sr_code_from_instruction_grammar has special casing for types, function ops, branches, terminators and phi instructions
• autogen/util: Literal numbers get unique operand kind
• autogen/util: underlying type for pairs, literals and ids are all special
• autogen/util: Parameter name for IdResultType hardcoded

[antiagainst]

+100. Nice list! I love this. :)

I think it would be nice to avoid having an in-tree spirv.core.grammar.json as a first step. The modifications in the in-tree spirv.core.grammar.json mainly fall into two categories: assign categories to instructions so we can handle similar instructions in a batch using their category. I think this part is upstreamable. The other changes are mainly for adjusting the name so we can generate better parameter names in APIs. I don't think this part is upstreamable given that the names in the orignial JSON file are used to generate the spec. We can maintain a Rust list somewhere so we have a centralized place for the adjustment when generating names for instruction operands.