Should the builder cache types?

[MaikKlein]

For example:

    let void = b.type_void();
    let void1 = b.type_void();

results in

%2 = OpTypeVoid
%3 = OpTypeVoid

I expected just:

%2 = OpTypeVoid

Should the builder cache types? Or should duplicate instructions be removed in a later stage?

[antiagainst]

The SPIR-V spec requires that "Non-structure types (scalars, vectors, arrays, etc.) with the same operand parameterization cannot be type aliases." So it is actually invalid to have two <result-id>s for the void type.

However, it is arguable whether this kind of "semantic" validation checks should happen in mr::Builder. mr::Builder is designed to be low-level with little sanity check. It is intended to be used by some higher level builder actually. (Sorry about this maybe unnecessary layers and abstractions.) Besides, SPIR-V spec 2.16 contains a bunch of validation rules. If we enable this one, what about the others?

I am planning a higher level builder (#5) and started writing code for it, but cannot find time for it right now. We'll definitely need a type cache there. ;-P

[MaikKlein]

Okay sorry I haven't completely read the spec yet, I should probably do that now.