Use baseObj for Unsafe.CAS CardMarking for OffHeap on Z

When evaluating Unsafe.CAS while running with Balanced GC and OffHeap enabled, if the object child is the dataAddrPointer load, pass the baseObj to VMCardCheckEvaluator for correct card marking. Using the VMCardCheckEvaluator ability to clobberDstReg, we use baseObjReg instead of the temp epReg. Signed-off-by: Abdulrahman Alattas <[email protected]>
eclipse-openj9 · Sep 30, 2024 · 19953fd · 19953fd
1 parent 15acde9
commit 19953fd
Showing 1 changed file with 23 additions and 3 deletions.
diff --git a/runtime/compiler/z/codegen/J9TreeEvaluator.cpp b/runtime/compiler/z/codegen/J9TreeEvaluator.cpp
@@ -12013,6 +12013,12 @@ J9::Z::TreeEvaluator::VMinlineCompareAndSwap(TR::Node *node, TR::CodeGenerator *
 
    // Eval old and new vals
    //
+#if defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION)
+   bool isObjOffHeapDataAddr = (TR::Compiler->om.writeBarrierType() == gc_modron_wrtbar_cardmark_incremental && TR::Compiler->om.isOffHeapAllocationEnabled() && objNode->isDataAddrPointer());
+   TR::Register *baseObjReg = NULL;
+   if (isObjOffHeapDataAddr)
+      baseObjReg = cg->gprClobberEvaluate(objNode->getFirstChild());
+#endif /* defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION) */
    objReg  = cg->evaluate(objNode);
    oldVReg = cg->gprClobberEvaluate(oldVNode);  //  CS oldReg, newReg, OFF(objReg)
    newVReg = cg->evaluate(newVNode);                    //    oldReg is clobbered
@@ -12110,15 +12116,24 @@ J9::Z::TreeEvaluator::VMinlineCompareAndSwap(TR::Node *node, TR::CodeGenerator *
    if (isObj && (doWrtBar || doCrdMrk))
       {
       TR::LabelSymbol *doneLabelWrtBar = generateLabelSymbol(cg);
-      TR::Register *epReg = cg->allocateRegister();
+      TR::Register *epReg;
+#if defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION)
+      if (!isObjOffHeapDataAddr)
+#endif /* defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION) */
+         epReg = cg->allocateRegister();
       TR::Register *raReg = cg->allocateRegister();
       TR::RegisterDependencyConditions* condWrtBar = new (cg->trHeapMemory()) TR::RegisterDependencyConditions(0, 5, cg);
       condWrtBar->addPostCondition(objReg, TR::RealRegister::GPR1);
       if (compressedValueRegister != newVReg)
          condWrtBar->addPostCondition(newVReg, TR::RealRegister::AssignAny); //defect 92001
       if (compressedValueRegister != objReg)  // add this because I got conflicting dependencies on GPR1 and GPR2!
          condWrtBar->addPostCondition(compressedValueRegister, TR::RealRegister::GPR2); //defect 92001
-      condWrtBar->addPostCondition(epReg, cg->getEntryPointRegister());
+#if defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION)
+      if (isObjOffHeapDataAddr)
+         condWrtBar->addPostCondition(baseObjReg, cg->getEntryPointRegister());
+      else
+#endif /* defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION) */
+         condWrtBar->addPostCondition(epReg, cg->getEntryPointRegister());
       condWrtBar->addPostCondition(raReg, cg->getReturnAddressRegister());
       // Cardmarking is not inlined for gencon. Consider doing so when perf issue arises.
       if (doWrtBar)
@@ -12135,7 +12150,12 @@ J9::Z::TreeEvaluator::VMinlineCompareAndSwap(TR::Node *node, TR::CodeGenerator *
 
       else if (doCrdMrk)
          {
-         VMCardCheckEvaluator(node, objReg, epReg, condWrtBar, cg, false, doneLabelWrtBar, false);
+#if defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION)
+         if (isObjOffHeapDataAddr)
+            VMCardCheckEvaluator(node, baseObjReg, NULL, condWrtBar, cg, true, doneLabelWrtBar, false);
+         else
+#endif /* defined(J9VM_GC_ENABLE_SPARSE_HEAP_ALLOCATION) */
+            VMCardCheckEvaluator(node, objReg, epReg, condWrtBar, cg, false, doneLabelWrtBar, false);
                                                                            // true #1 -> copy of objReg just happened, it's safe to clobber tempReg
                                                                            // false #2 -> Don't do compile time check for heap obj
          }