Be more confident about single interface implementer profiled guards

These guards used to be nop guards. They no longer are, but only because
certain kinds of bytecode are technically allowed to be loaded. Bytecode
that is problematic in this way should be exceedingly rare though, so
treat these guards more like the nop guards we used to have by marking
the taken side cold and by making sure to allow privatized argument
rematerialization.

runtime/compiler/optimizer/InlinerTempForJ9.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2021 IBM Corp. and others
+ * Copyright (c) 2000, 2022 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -2847,7 +2847,7 @@ TR_MultipleCallTargetInliner::eliminateTailRecursion(
       backEdge = TR::CFGEdge::createEdge(gotoBlock,  branchDestination, trMemory());
       callerCFG->addEdge(backEdge);
       callerCFG->removeEdge(origEdge);
-      if (guard->_kind == TR_ProfiledGuard)
+      if (guard->_kind == TR_ProfiledGuard && !guard->_forceTakenSideCold)
          {
          if (block->getFrequency() < 0)
             block2->setFrequency(block->getFrequency());
@@ -6784,7 +6784,11 @@ TR_J9InlinerPolicy::suitableForRemat(TR::Compilation *comp, TR::Node *callNode,
 
    bool suitableForRemat = true;
    TR_AddressInfo *valueInfo = static_cast<TR_AddressInfo*>(TR_ValueProfileInfoManager::getProfiledValueInfo(callNode, comp, AddressInfo));
-   if (guard->isHighProbablityProfiledGuard())
+   if (guard->_forceTakenSideCold)
+      {
+      // remat ok
+      }
+   else if (guard->isHighProbablityProfiledGuard())
       {
       if (comp->getMethodHotness() <= warm && comp->getPersistentInfo()->getJitState() == STARTUP_STATE)
          {

runtime/compiler/optimizer/J9Inliner.cpp

@@ -944,6 +944,20 @@ bool TR_J9InterfaceCallSite::findCallSiteTargetImpl(TR_CallStack *callStack, TR_
             new (comp()->trHeapMemory()) TR_VirtualGuardSelection(
                kind, testType, thisClass);
 
+         if (kind == TR_ProfiledGuard)
+            {
+            // Almost all bytecode would pass type checking even including
+            // interface types. So even though this can't be a nop guard
+            // (because verification doesn't check interface types), treat it
+            // as much like a nop guard as possible. In particular, this will
+            // ensure that the block containing the cold call is actually
+            // marked cold, and ensure that priv. arg remat is allowed.
+            guard->_forceTakenSideCold = true;
+
+            // It is still a high-probability profiled guard...
+            guard->setIsHighProbablityProfiledGuard();
+            }
+
          addTarget(
             comp()->trMemory(),
             inliner,