Fold VFTLoad from object of known fixed class

When we are loading VFT pointer from an object whose type is known and fixed, we can transform such indirect load to load constant. Signed-off-by: Rahil Shah <rahil@ca.ibm.com>
eclipse · Aug 9, 2021 · 1818cb1 · 1818cb1
1 parent 26b4ee8
commit 1818cb1
Showing 1 changed file with 24 additions and 1 deletion.
diff --git a/compiler/optimizer/VPHandlers.cpp b/compiler/optimizer/VPHandlers.cpp
@@ -339,7 +339,6 @@ static bool tryFoldCompileTimeLoad(
    bool &isGlobal)
    {
    isGlobal = true;
-
    if (!node->getOpCode().isLoad())
       return false;
    else if (node->getOpCode().isLoadReg())
@@ -447,6 +446,30 @@ static bool tryFoldCompileTimeLoad(
                }
             return didSomething;
             }
+         else if (node->getSymbolReference() == vp->comp()->getSymRefTab()->findVftSymbolRef()
+                  && node->getFirstChild() == curNode
+                  && constraint->isNonNullObject()
+                  && constraint->getClassType()
+                  && constraint->getClassType()->asFixedClass()
+                  && constraint->getClass())
+            {
+            TR_OpaqueClassBlock *clazz = constraint->getClass();
+#ifdef J9_PROJECT_SPECIFIC
+            TR_J9VMBase *fej9 = vp->comp()->fej9();
+            // Non SVM AOT can deal with transformed loadaddr of system class only while Symbol Validation Manager can handle any class.
+            // Skip the transformation under non SVM AOT when class is not loaded by bootstrap class loader.
+            if (vp->comp()->compileRelocatableCode() && !vp->comp()->getOption(TR_UseSymbolValidationManager) && fej9->getClassLoader(clazz) != fej9->getSystemClassLoader())
+               return false;
+#endif
+            if (vp->trace())
+               traceMsg(vp->comp(), "VP Transforming VFTLoad to loadaddr: as n%dn is VFT load of known class", node->getGlobalIndex());
+            node->setNumChildren(0);
+            TR::Node::recreateWithSymRef(node, TR::loadaddr, vp->comp()->getSymRefTab()->findOrCreateClassSymbol(vp->comp()->getMethodSymbol(), -1, clazz));
+            node->setFlags(0);
+            vp->removeNode(curNode, true);
+            TR::DebugCounter::incStaticDebugCounter(vp->comp(), TR::DebugCounter::debugCounterName(vp->comp(), "VFTLoadKnownObject/(%s)/%s", vp->comp()->signature(), vp->comp()->getHotnessName(vp->comp()->getMethodHotness())));
+            return true;
+            }
          else if (!curNode->getOpCode().isLoadIndirect())
             {
             if (curNode->getOpCodeValue() == TR::loadaddr