For Unsafe.get()/put(), reorder blocks to optimize fallthrough path

There are three possible cases regarding the type of the object being operated on for Unsafe.get()/put(): 1.) array object 2.) java/lang/Class object 3.) none of the above Since case (3) is the most likely, we want the block corresponding to this case (directAccessBlock) to be on the fallthrough path. Signed-off-by: midronij <[email protected]>
eclipse-openj9 · Nov 21, 2023 · a2c8471 · a2c8471
1 parent 0aabde1
commit a2c8471
Showing 1 changed file with 38 additions and 1 deletion.
diff --git a/runtime/compiler/optimizer/InlinerTempForJ9.cpp b/runtime/compiler/optimizer/InlinerTempForJ9.cpp
@@ -999,9 +999,46 @@ TR_J9InlinerPolicy::genCodeForUnsafeGetPut(TR::Node* unsafeAddress,
          traceMsg(comp(),"\t\t Generating an isArray test as j9class of java/lang/Class is NULL");
          directAccessBlock->getEntry()->insertTreeTopsBeforeMe(lowTagCmpBlock->getEntry(), lowTagCmpBlock->getExit());
          lowTagCmpTree->getNode()->setBranchDestination(indirectAccessBlock->getEntry());
-         }
+         }     
+
       lowTagCmpBlock->getEntry()->insertTreeTopsBeforeMe(isArrayBlock->getEntry(),
                                                          isArrayBlock->getExit());
+
+      //reorder directAccess, arrayDirectAccess, and indirectAccess blocks to optimize fallthrough paths
+      // (want directAccess (i.e.: non array and non class object) case on fallthrough path)
+      if (arrayBlockNeeded)
+      {
+         //switch indirectAccessBlock and directAccessBlock
+         TR::Block *indirectPrevBlock = indirectAccessBlock->getEntry()->getPrevTreeTop()->getEnclosingBlock();
+         TR::Block *indirectNextBlock = indirectAccessBlock->getExit()->getNextTreeTop()->getEnclosingBlock();
+         TR::Block *directPrevBlock = directAccessBlock->getEntry()->getPrevTreeTop()->getEnclosingBlock();
+         TR::Block *directNextBlock = directAccessBlock->getExit()->getNextTreeTop()->getEnclosingBlock();
+
+         indirectAccessBlock->getEntry()->setPrevTreeTop(directPrevBlock->getExit());
+         directPrevBlock->getExit()->setNextTreeTop(indirectAccessBlock->getEntry());
+         indirectAccessBlock->getExit()->setNextTreeTop(directNextBlock->getEntry());
+         directNextBlock->getEntry()->setPrevTreeTop(indirectAccessBlock->getExit());
+
+         directAccessBlock->getEntry()->setPrevTreeTop(indirectPrevBlock->getExit());
+         indirectPrevBlock->getExit()->setNextTreeTop(directAccessBlock->getEntry());
+         directAccessBlock->getExit()->setNextTreeTop(indirectNextBlock->getEntry());
+         indirectNextBlock->getEntry()->setPrevTreeTop(directAccessBlock->getExit());
+
+         if (indirectPrevBlock == lowTagCmpTree->getEnclosingBlock())
+         {
+            //add goto to the end of indirectAccessBlock, since it's no longer on the fallthrough path
+            indirectAccessBlock->append(TR::TreeTop::create(comp(), TR::Node::create(indirectAccessBlock->getEntry()->getNode(), TR::Goto, 0, directAccessBlock->getExit()->getNextTreeTop())));
+
+            //since the directAccessBlock is now accessible via fallthrough, we need change the condition/destination
+            //of the conditional branch in the lowTagCmp block so that it can reach the indirectAccessBlock
+            TR::ILOpCodes lowTagCmpOpCode = lowTagCmpTree->getNode()->getOpCodeValue();
+            TR::ILOpCodes newOpCode = lowTagCmpOpCode == TR::ificmpne ? TR::ificmpeq : TR::iflcmpeq;
+
+            lowTagCmpTree->getNode()->getOpCode().setOpCodeValue(newOpCode);
+            lowTagCmpTree->getNode()->setBranchDestination(indirectAccessBlock->getEntry());
+         }
+      }
+
       cfg->addEdge(TR::CFGEdge::createEdge(isArrayBlock,  lowTagCmpBlock, trMemory()));
       cfg->addEdge(TR::CFGEdge::createEdge(lowTagCmpBlock, indirectAccessBlock, trMemory()));
       cfg->addEdge(TR::CFGEdge::createEdge(isArrayBlock, arrayBlockNeeded ? arrayDirectAccessBlock : directAccessBlock, trMemory()));