spirv-fuzz: Replace OpCopyObject with the pair OpStore and OpLoad instructions

[andreperezmaselco]

If we have %8 = OpCopyObject %type %7, we could create a new variable with type pointer to %type, store %7 to the new variable and load the new variable to %8. The following is an example.

OpStore %fresh_variable_id %7
%8 = OpLoad %type %fresh_variable_id

This transformation protobuf would consist of copy_object_result_id, fresh_variable_id, variable_storage_class, variable_initializer_id.

The transformation is only applicable if the pointer type already exists. The pointer type cannot be a pointer to a pointer.

The fuzzer pass would look for OpCopyObject instructions and create and apply a transformation to add the required pointer type, if needed using FindOrCreatePointerType.

The transformation should add a synonym fact to the fact manager.

This will be similar to TransformationPushIdThroughVariable.

[afd]

@antnkarp can we assign this to you? (We'll help prioritize the order.)

[antonikarp]

Ok, that's great :)

[paulthomson]

A bigger example:

%1 = OpTypeInt 32 0
%2 = OpTypePointer Function %1
%3 = OpConstant %1 42
…
%5 = OpIAdd %1 %3 %3 ; %5 = 42 + 42
%4 = OpCopyObject %1 %5 ; Copy the value 84 into %4.

→
%100 = OpVariable %2 Function ; new variable to store into
...
%5 = OpIAdd %1 %3 %3 ; %5 = 42 + 42
     OpStore %100 %5 ; Store the value 84 into variable %100
%4 = OpLoad %1 %100 ; Load the value 84 from %100.