Re-evaluate JITServer known object table bypassed operations at the server

[a7ehuo]

A few KOT related optimizations/operations will be bypassed at the server [1][2] due to various reasons. They would require an re-evaluation in the near future in case if there is any potential performance impact.

1. Currently there is no implementation/infrastructure in OMR code to send messages from the server to the client when VM access is required.

   • int32_t TR_InvariantArgumentPreexistence::perform()
   • https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L6844-L6851
   • https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L6987-L7000
   • void TR_InvariantArgumentPreexistence::processIndirectCall()
   • https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L7290-L7306
   • static bool addKnownObjectConstraints(OMR::ValuePropagation *vp, TR::Node *node)
   • https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/VPHandlers.cpp#L1530-L1535

2. Not directly related to KOT but the following VM access could be called at the server.

   • TR::Node * J9::TransformUtil::transformIndirectLoad(TR::Compilation *comp, TR::Node *node)
   • https://github.com/eclipse/openj9/blob/ebec356635a35ff2acbd4e3958752c309b9bcdc4/runtime/compiler/optimizer/J9TransformUtil.cpp#L741
   • bool J9::TransformUtil::transformIndirectLoadChain()
   • https://github.com/eclipse/openj9/blob/ebec356635a35ff2acbd4e3958752c309b9bcdc4/runtime/compiler/optimizer/J9TransformUtil.cpp#L1477

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[1] eclipse/omr#4829 [2] eclipse/openj9#8527

[dmitry-ten]

Some of the bypassed operations can be re-enabled without too many additional changes.

• https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L6844-L6851
• https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L6987-L7000
• https://github.com/eclipse/omr/blob/892a0fef24c7bc781cda8aab530b4cd18cea6814/compiler/optimizer/LocalOpts.cpp#L7290-L7306

All of these can be rewritten to use a recently added front-end query TR_J9VM::getObjectClassFromKnownObjectIndex. However, since these are defined in OpenJ9 only, we'd need to add a new OMR::ClassEnv query objectClassFromKnownObjectIndex that would be overridden in OpenJ9 and call the corresponding front-end query.