Guarantee functional correctness of rdbar/wrtbar

This change guarantee the correctness of rdbar/wrtbar from the following
aspects:
1. Consider rdbar/wrtbar as GC points
2. Make optimizations consider shape of rdbar/wrtbar when doing
transformations
3. Disable opts not supporting newly added rdbar/wrtbar when seeing
the opcodes

Signed-off-by: Yi Zhang <yizhang@ca.ibm.com>

runtime/compiler/codegen/J9CodeGenerator.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corp. and others
+ * Copyright (c) 2000, 2019 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
@@ -351,7 +351,7 @@ J9::CodeGenerator::lowerCompressedRefs(
 
       // base object
       address = loadOrStoreNode->getFirstChild();
-      loadOrStoreOp = TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads() ? self()->comp()->il.opCodeForIndirectReadBarrier(TR::Int32) :
+      loadOrStoreOp = TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads() || loadOrStoreNode->getOpCode().isReadBar() ? self()->comp()->il.opCodeForIndirectReadBarrier(TR::Int32) :
                                                                                    self()->comp()->il.opCodeForIndirectLoad(TR::Int32);
       }
    else if ((loadOrStoreNode->getOpCode().isStoreIndirect() ||
@@ -2926,13 +2926,19 @@ J9::CodeGenerator::compressedReferenceRematerialization()
 
    static bool disableRematforCP = feGetEnv("TR_DisableWrtBarOpt") != NULL;
 
-   if (TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads())
+   // The compressedrefs remat opt removes decompression/compression sequences from
+   // loads/stores where there doesn't exist a gc point between the load and the store,
+   // and the load doesn't need to be dereferenced.
+   // The opt needs to be disabled for the following cases:
+   // 1. In Guarded Storage, we can't not do a guarded load because the object that is loaded may
+   // not be in the root set, and as a consequence, may get moved.
+   // 2. For read barriers in field watch, the vmhelpers are GC points and therefore the object might be moved
+   if (TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads() || self()->comp()->getOption(TR_EnableFieldWatch))
       {
-      // We need this restriction because the compressedrefs remat opt
-      // removes decompression/compression sequences from loads/stores where there doesn't exist
-      // a gc point between the load and the store, and the load doesn't need to be dereferenced.
-      // In Guarded Storage, we can't not do a guarded load because the object that is loaded may
-      // not be in the root set, and as a consequence, may get moved.
+      if (TR::Compiler->om.shouldGenerateReadBarriersForFieldLoads())
+         traceMsg(self()->comp(), "The compressedrefs remat opt is disabled because Concurrent Scavenger is enabled\n");
+      if (self()->comp()->getOption(TR_EnableFieldWatch))
+         traceMsg(self()->comp(), "The compressedrefs remat opt is disabled because field watch is enabled\n");
       disableRematforCP = true;
       }
 

runtime/compiler/compile/J9Compilation.cpp

@@ -1398,3 +1398,9 @@ J9::Compilation::notYetRunMeansCold()
       return true;
    }
 
+bool
+J9::Compilation::incompleteOptimizerSupportForReadWriteBarriers()
+   {
+   return self()->getOption(TR_EnableFieldWatch);
+   }
+

runtime/compiler/compile/J9Compilation.hpp

@@ -311,6 +311,8 @@ class OMR_EXTENSIBLE Compilation : public OMR::CompilationConnector
 
    TR_RelocationRuntime *reloRuntime() { return _reloRuntime; }
 
+   bool incompleteOptimizerSupportForReadWriteBarriers();
+
    TR::SymbolValidationManager *getSymbolValidationManager() { return _symbolValidationManager; }
 
 private:

runtime/compiler/optimizer/EscapeAnalysis.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corp. and others
+ * Copyright (c) 2000, 2019 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
@@ -179,6 +179,12 @@ int32_t TR_EscapeAnalysis::perform()
    if (comp()->isOptServer() && (comp()->getMethodHotness() <= warm))
       return 0;
 
+   // EA generates direct stores/loads to instance field which is different
+   // from a normal instance field read/write. Field watch would need special handling
+   // for stores/loads genearted by EA.
+   if (comp()->incompleteOptimizerSupportForReadWriteBarriers())
+      return 0;
+
    static char *doESCNonQuiet = feGetEnv("TR_ESCAPENONQUIET");
    if (doESCNonQuiet && comp()->getOutFile() == NULL)
       return 0;

runtime/compiler/optimizer/IdiomRecognition.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corp. and others
+ * Copyright (c) 2000, 2019 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
@@ -2302,6 +2302,10 @@ TR_CISCNode *
 TR_CISCTransformer::addAllSubNodes(TR_CISCGraph *const graph, TR::Block *const block, TR::TreeTop *const top,
                                    TR::Node *const parent, TR::Node *const node, const int32_t dagId)
    {
+   //IdiomRecognition doesn't know how to handle rdbar/wrtbar for now
+   if (comp()->incompleteOptimizerSupportForReadWriteBarriers() &&
+       (node->getOpCode().isReadBar() || node->getOpCode().isWrtBar()))
+      return 0;
    int32_t i;
    int32_t numChildren = node->getNumChildren();
    TR_ScratchList<TR_CISCNode> childList(trMemory());

runtime/compiler/optimizer/J9TransformUtil.cpp

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2018 IBM Corp. and others
+ * Copyright (c) 2000, 2019 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
@@ -1077,6 +1077,16 @@ J9::TransformUtil::canFoldStaticFinalField(TR::Compilation *comp, TR::Node* node
    return TR_maybe;
    }
 
+/*
+ * Load const node should have zero children
+ */
+static void prepareNodeToBeLoadConst(TR::Node *node)
+   {
+   for (int i=0; i < node->getNumChildren(); i++)
+      node->getAndDecChild(i);
+   node->setNumChildren(0);
+   }
+
 bool
 J9::TransformUtil::foldStaticFinalFieldImpl(TR::Compilation *comp, TR::Node *node)
    {
@@ -1143,6 +1153,7 @@ J9::TransformUtil::foldStaticFinalFieldImpl(TR::Compilation *comp, TR::Node *nod
       if (performTransformation(comp, "O^O foldStaticFinalField: turn [%p] %s %s into load const\n", node, node->getOpCode().getName(), symRef->getName(comp->getDebug())))
          {
          TR::VMAccessCriticalSection isConsitble(comp->fej9());
+         prepareNodeToBeLoadConst(node);
          switch (loadType)
             {
             case TR::Int8:
@@ -1191,6 +1202,7 @@ J9::TransformUtil::foldStaticFinalFieldImpl(TR::Compilation *comp, TR::Node *nod
          default:
             if (performTransformation(comp, "O^O transformDirectLoad: [%p] field is null - change to aconst NULL\n", node))
                {
+               prepareNodeToBeLoadConst(node);
                TR::Node::recreate(node, TR::aconst);
                node->setAddress(0);
                node->setIsNull(true);