Allow inliner policy to decide whether to remove differing targets

Previously, for direct calls, targets that appear to be a different
method from the one specified by the call node's symbol reference would
always be removed.

This behaviour is still the default, but the new query allows downstream
projects to customize the conditions under which those targets are
removed, e.g. by exempting certain methods.

compiler/optimizer/Inliner.cpp

@@ -4061,6 +4061,15 @@ bool OMR_InlinerPolicy::canInlineMethodWhileInstrumenting(TR_ResolvedMethod *met
    return true;
    }
 
+bool OMR_InlinerPolicy::shouldRemoveDifferingTargets(TR::Node *callNode)
+   {
+   //if ilgen and localopts decided that this was a direct call
+   //there isn't much sense to deal with more than one target
+   //either find a matching one
+   //or make any target look like callsite's calleeSymbol
+   return !callNode->getOpCode().isCallIndirect();
+   }
+
 void TR_InlinerBase::applyPolicyToTargets(TR_CallStack *callStack, TR_CallSite *callsite)
    {
    for (int32_t i=0; i<callsite->numTargets(); i++)
@@ -4417,11 +4426,7 @@ TR_CallSite* TR_InlinerBase::findAndUpdateCallSiteInGraph(TR_CallStack *callStac
    if (callNode->getSymbolReference()->getSymbol()->castToMethodSymbol()->isInterface() && callsite->_initialCalleeSymbol)
       debugTrace(tracer(), "findAndUpdateCallSiteInGraph: BAD: Interface call has an initialCalleeSYmbol %p for calNode %p", callsite->_initialCalleeSymbol, callNode);
 
-   //if ilgen and localopts decided that this was a direct call
-   //there isn't much sense to deal with more than one target
-   //either find a matching one
-   //or make any target look like callsite's calleeSymbol
-   if (!callNode->getOpCode().isCallIndirect())
+   if (getPolicy()->shouldRemoveDifferingTargets(callNode))
       {
       //find a matching target if there's any
       for (int32_t i = 0 ; i < callsite->numTargets() ; i++)

compiler/optimizer/Inliner.hpp

@@ -615,6 +615,7 @@ class OMR_InlinerPolicy : public TR::OptimizationPolicy, public OMR_InlinerHelpe
       bool aggressiveSmallAppOpts() { return comp()->getOption(TR_AggressiveOpts); }
       virtual bool willBeInlinedInCodeGen(TR::RecognizedMethod method);
       virtual bool canInlineMethodWhileInstrumenting(TR_ResolvedMethod *method);
+      virtual bool shouldRemoveDifferingTargets(TR::Node *callNode);
 
       /** \brief
        *     Determines whether to skip generation of HCR guards for a particular callee during inlining.