Create an IL Validation Rule for checking Binary OpCode child layout

[rbanerjee]

As @vijaysun-omr pointed out here, one of the implicit expectations that our IL currently makes is:

For binary commutative operations, constants (if present) can only appear in the rightmost child.

With the ILValidator now in place (via https://github.com/eclipse/omr/pull/1826), this implicit expectation should be made into an IL Validation rule.

The process would involve implementing the steps outlined below:

• [ ] Create a TR::NodeValidation Rule that checks the child layout for Binary OpCodes against the said expectation

• [ ] Make this ILValidationRule a part the "appropriate" ILValidationStrategy array. [This would require investigating where exactly in the Compilation phase does this Rule get satisfied, I.e, right after ILGen, immediately before going into codegen etc.]

• [ ] Add the associated Tril ILValidatorTests

[fjeremic]

Does this assume that simplifier will be a mandatory optimization pass on all optimization levels? IIRC simplifier is the pass which canonicalizes such IL, among other things.

[Leonardo2718]

@fjeremic For the time being that's correct. Simplifier is already implicitly mandatory because existing evaluators will misbehave when given "un-canonicalized" IL (and I'm quite sure the different code generators are not consistent about this either).

Ideally, we should have a better definition of "canonicalized" IL, other than just "whatever the output of simplifier is". These new validation rules will hopefully help us get there. 🙂

[rbanerjee]

Does this assume that simplifier will be a mandatory optimization pass on all optimization levels?

@fjeremic Sorry it took me so long to circle back to this. @Leonardo2718 is correct. There's also this Issue #2161, which is partly related to identifying which Optimizations should even be part of the "mandatory optimization pass".