MethodHandleTransformer.hpp

/*******************************************************************************
 * Copyright IBM Corp. and others 2021
 *
 * This program and the accompanying materials are made available under
 * the terms of the Eclipse Public License 2.0 which accompanies this
 * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
 * or the Apache License, Version 2.0 which accompanies this distribution and
 * is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * This Source Code may also be made available under the following
 * Secondary Licenses when the conditions for such availability set
 * forth in the Eclipse Public License, v. 2.0 are satisfied: GNU
 * General Public License, version 2 with the GNU Classpath
 * Exception [1] and GNU General Public License, version 2 with the
 * OpenJDK Assembly Exception [2].
 *
 * [1] https://www.gnu.org/software/classpath/license.html
 * [2] https://openjdk.org/legal/assembly-exception.html
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
 *******************************************************************************/

#ifndef METHODHANDLETRANSFORMER_INCL
#define METHODHANDLETRANSFORMER_INCL

#include <set>
#include <vector>
#include "il/ParameterSymbol.hpp"
#include "compile/Compilation.hpp"
#include "infra/List.hpp"
#include "optimizer/Optimization.hpp"
#include "optimizer/OptimizationManager.hpp"
#include "env/KnownObjectTable.hpp"

/*
 * This transformer is used to transform OpenJDK MethodHandle related methods,
 * to make sure those methods are optimized for performance.
 *
 * Most of the transformation require knowledge of object-type node. Sources of
 * object info include the following:
 *  1. Prex arg info if under inlining
 *  2. Nodes with known object index
 *  3. Nodes whose value can be compile-time inferred and is a known object
 *
 * We'd like the object info be avaliable at places where we want to do transformation,
 * however, the objects will be stored into autos and autos will be used instead of
 * nodes with known object index. Thus we need to track the object info while walking
 * the trees.
 *
 * Data flow analysis is expensive and we can't afford it especially in ilgen. Most of
 * the methods we want to optimize should have only one store to an auto, i.e. most of
 * the autos are not shared. So we can track the object info in autos with a reverse
 * post-order traversal of CFG. Update object info while walking trees of a block, and
 * propagate it to the block's successor. When visiting a block, if there exist a
 * predecessor unvisited, simply clear the object info inherited from the successors.
 *
 * This opt will also try to discover as many known objects as possible.
 */

class TR_MethodHandleTransformer : public TR::Optimization
   {
   public:
   TR_MethodHandleTransformer(TR::OptimizationManager *manager)
      : TR::Optimization(manager),
      _numLocals(0),
      _currentObjectInfo(NULL),
      _blockEndObjectInfos(NULL)
      {}

   static TR::Optimization *create(TR::OptimizationManager *manager)
      {
      return new (manager->allocator()) TR_MethodHandleTransformer(manager);
      }

   virtual int32_t perform();
   virtual const char * optDetailString() const throw();

   typedef TR::typed_allocator<TR::KnownObjectTable::Index, TR::Region &> ObjectInfoAllocator;
   typedef std::vector<TR::KnownObjectTable::Index, ObjectInfoAllocator> ObjectInfo;

   // Walk through trees and nodes in block, update local object info
   // Also discover new known objects through field folding
   //
   void processBlockAndUpdateObjectInfo(TR::Block *block, ObjectInfo *objectInfo);

   // Merge ObjectInfo from second into first
   //
   void mergeObjectInfo(ObjectInfo *first, ObjectInfo *second);

   // Obect info at method entry or first block of the method
   // The object info comes from prex arg info
   //
   ObjectInfo* getMethodEntryObjectInfo();

   // Object info of a block can be derived from its predecessors
   //
   ObjectInfo* blockStartObjectInfoFromPredecessors(TR::Block* block);

   // Assign local index to autos
   //
   void assignLocalIndices();
   // Walk trees and collect autos into a list
   //
   void collectAutosFromTrees(List<TR::SymbolReference> &autosList);

   // Given an address-typed node, try to figure out it's object info
   //
   TR::KnownObjectTable::Index getObjectInfoOfNode(TR::Node* node);

   // The folowing visit functions will visit different types of node, update object info,
   // and/or do transformations
   //
   void visitIndirectLoad(TR::TreeTop* tt, TR::Node* node);
   void visitStoreToLocalVariable(TR::TreeTop* tt, TR::Node* node);
   void visitCall(TR::TreeTop* tt, TR::Node* node);
   void visitNode(TR::TreeTop* tt, TR::Node* node, TR::NodeChecklist &visitedNodes);

   // Refine MethodHandle.invokeBasic with known object info
   //
   void process_java_lang_invoke_MethodHandle_invokeBasic(TR::TreeTop* tt, TR::Node* node);

   // Refine MethodHandle.linkTo* with known object info
   //
   void process_java_lang_invoke_MethodHandle_linkTo(TR::TreeTop* tt, TR::Node* node);

   /** \brief
    *    Transforms calls to java/lang/invoke/Invokers.checkExactType to ZEROCHK, or eliminated
    *    entirely if the check can be performed at compile time
    *
    *  \param tt
    *    The treetop of the call node
    *
    *  \param node
    *    The call node representing the call to java/lang/invoke/Invokers.checkExactType
    */
   void process_java_lang_invoke_Invokers_checkExactType(TR::TreeTop* tt, TR::Node* node);

   /** \brief
    *    Eliminates calls to java/lang/invoke/Invokers.checkCustomized when its argument
    *    is a known object
    *
    *  \param tt
    *    The treetop of the call node
    *
    *  \param node
    *    The call node representing the call to java/lang/invoke/Invokers.checkCustomized
    */
   void process_java_lang_invoke_Invokers_checkCustomized(TR::TreeTop* tt, TR::Node* node);

   private:
   int32_t _numLocals; // Number of parms, autos and temps
   ObjectInfo * _currentObjectInfo;  // Object info for current block being processed

   typedef TR::typed_allocator<std::pair<const int32_t, ObjectInfo *>, TR::Region &> ResultAllocator;
   typedef std::map<int32_t, ObjectInfo *, std::less<int32_t>, ResultAllocator> BlockResultMap;

   BlockResultMap* _blockEndObjectInfos; // A map of object info at the end of blocks
   };

#endif