Check array-shadow symbol and DataType for refineArrayAliasing

[rmnattas]

This is to check that the array access is an array-shadow symbol and that the symbol DataType matches the node DataType before performing TR_LoopUnroller::refineArrayAliasing on that list of accesses.

This prevents array-accesses that are not array-shadow (e.g. <unsafe shadow sym>) or cases where the symbol DataType and the node DataType don't match (e.g. loading from Byte[] String.value using a short-load node) from being refined, and incorrectly changed to an array-shadow or to the wrong DataType, that might cause a crash during compilation.

DLT stderr _ZN3OMR20SymbolReferenceTable33createRefinedArrayShadowSymbolRefEN2TR8DataTypeE+0x2c (0x000077BF124D5C3C [libj9jit29.so+0x6b5c3c])
DLT stderr _ZN15TR_LoopUnroller19refineArrayAliasingEv+0x144 (0x000077BF125DACD4 [libj9jit29.so+0x7bacd4])
DLT stderr _ZN15TR_LoopUnroller6unrollEP18TR_RegionStructureP24TR_StructureSubGraphNode+0x17c (0x000077BF125E668C [libj9jit29.so+0x7c668c])
DLT stderr _ZN15TR_LoopUnroller6unrollEPN2TR11CompilationEP18TR_RegionStructureP27TR_PrimaryInductionVariableNS_10UnrollKindEiiPNS0_9OptimizerE.part.265+0x814 (0x000077BF125E70B4 [libj9jit29.so+0x7c70b4])
DLT stderr _ZN22TR_GeneralLoopUnroller7performEv+0x54c (0x000077BF125E801C [libj9jit29.so+0x7c801c])
DLT stderr _ZN3OMR9Optimizer19performOptimizationEPK20OptimizationStrategyiii+0x1814 (0x000077BF1276E6F4 [libj9jit29.so+0x94e6f4])
DLT stderr _ZN3OMR9Optimizer8optimizeEv+0x204 (0x000077BF1276F3F4 [libj9jit29.so+0x94f3f4])
DLT stderr _ZN3OMR11Compilation20performOptimizationsEv+0x3c (0x000077BF124DDD9C [libj9jit29.so+0x6bdd9c])

[rmnattas]

fyi: @vijaysun-omr @jdmpapin

[jdmpapin]

I've been quite involved in this fix, so it would be best for someone else to review

[vijaysun-omr]

I will review this and shepherd to merging. Thanks

[vijaysun-omr]

jenkins build all

[vijaysun-omr]

While the change itself looks safe/conservative, I think it would be good if the PR mentioned briefly (in a sentence or two) what could go wrong if this change was not done. i.e. what happens if the sym ref is not an array shadow sym ref of a consistent type ?

[rmnattas]

Updated PR 👍

[vijaysun-omr]

jenkins build win

[vijaysun-omr]

Thanks, checks have passed. Merging.