Missing SPIR-V 1.4 features/changes

[MrSidims]

Following my AR from OpenCL Tooling TSG. The translator claims SPIR-V 1.4 support, yet there are few features missing

• OpCopyLogical instruction
• OpPtrEqual and OpPtrNotEqual instructions
• OpPtrDiff instruction
• OpCopyMemory and OpCopyMemorySized instructions since 1.4 have optional Memory Operands
• DecorateString and OpMemberDecorateString instructions
• CounterBuffer decoration

[MrSidims]

Comments:

1. At this point of time I don't see an LLVM counterpart, so guess it's implementable only via SPIR-V friendly translation;

2 and 3. We can consider translating ptrtoint + cmp / sub to these instructions during forward translation, but probably we should instead just recognize SPIR-V friendly input and then during reverse translation generate ptrtoint + cmp / sub (either way with Builder::CreatePtrDiff)

4. Pretty much straightforward;

5. these decoration instructions are odd. I only see a single use-case for UserSemantic decorations for them, meanwhile the translator uses OpDecorate and OpMemberDecorate to store UserSemantic. And the translator is right in doing so as the spec puts no restrictions of what kind of literals to used for these 2 instructions;

6. unlikely to represent right now, but probably should recognize it and skip.

[vmaksimo]

The only thing left is to clarify the possible cases where we actually need to use DecorateString and MemberDecorateString instructions.
@MrSidims please link registry issue here once it's created. Thanks!