jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/jvm/Gen.java@9ca8d8713094 (annotated)

src/share/classes/com/sun/tools/javac/jvm/Gen.java@9ca8d8713094 (annotated)

src/share/classes/com/sun/tools/javac/jvm/Gen.java

Thu, 12 Oct 2017 19:50:01 +0800

author: aoqi
date: Thu, 12 Oct 2017 19:50:01 +0800
changeset 2702: 9ca8d8713094
parent 2657: d42678403377
parent 2525: 2eb010b6cb22
child 2893: ca5783d9a597
permissions: -rw-r--r--

merge

 /*
  * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 package com.sun.tools.javac.jvm;
 import java.util.*;
 import com.sun.tools.javac.util.*;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
 import com.sun.tools.javac.util.List;
 import com.sun.tools.javac.code.*;
 import com.sun.tools.javac.code.Attribute.TypeCompound;
 import com.sun.tools.javac.code.Symbol.VarSymbol;
 import com.sun.tools.javac.comp.*;
 import com.sun.tools.javac.tree.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.jvm.Code.*;
 import com.sun.tools.javac.jvm.Items.*;
 import com.sun.tools.javac.tree.EndPosTable;
 import com.sun.tools.javac.tree.JCTree.*;
 import static com.sun.tools.javac.code.Flags.*;
 import static com.sun.tools.javac.code.Kinds.*;
 import static com.sun.tools.javac.code.TypeTag.*;
 import static com.sun.tools.javac.jvm.ByteCodes.*;
 import static com.sun.tools.javac.jvm.CRTFlags.*;
 import static com.sun.tools.javac.main.Option.*;
 import static com.sun.tools.javac.tree.JCTree.Tag.*;
 /** This pass maps flat Java (i.e. without inner classes) to bytecodes.
  *
  *  <p><b>This is NOT part of any supported API.
  *  If you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public class Gen extends JCTree.Visitor {
     protected static final Context.Key<Gen> genKey =
         new Context.Key<Gen>();
     private final Log log;
     private final Symtab syms;
     private final Check chk;
     private final Resolve rs;
     private final TreeMaker make;
     private final Names names;
     private final Target target;
     private final Type stringBufferType;
     private final Map<Type,Symbol> stringBufferAppend;
     private Name accessDollar;
     private final Types types;
     private final Lower lower;
     private final Flow flow;
     /** Switch: GJ mode?
      */
     private final boolean allowGenerics;
     /** Set when Miranda method stubs are to be generated. */
     private final boolean generateIproxies;
     /** Format of stackmap tables to be generated. */
     private final Code.StackMapFormat stackMap;
     /** A type that serves as the expected type for all method expressions.
      */
     private final Type methodType;
     public static Gen instance(Context context) {
         Gen instance = context.get(genKey);
         if (instance == null)
             instance = new Gen(context);
         return instance;
     }
     /** Constant pool, reset by genClass.
      */
     private Pool pool;
     /** LVTRanges info.
      */
     private LVTRanges lvtRanges;
     private final boolean typeAnnoAsserts;
     protected Gen(Context context) {
         context.put(genKey, this);
         names = Names.instance(context);
         log = Log.instance(context);
         syms = Symtab.instance(context);
         chk = Check.instance(context);
         rs = Resolve.instance(context);
         make = TreeMaker.instance(context);
         target = Target.instance(context);
         types = Types.instance(context);
         methodType = new MethodType(null, null, null, syms.methodClass);
         allowGenerics = Source.instance(context).allowGenerics();
         stringBufferType = target.useStringBuilder()
             ? syms.stringBuilderType
             : syms.stringBufferType;
         stringBufferAppend = new HashMap<Type,Symbol>();
         accessDollar = names.
             fromString("access" + target.syntheticNameChar());
         flow = Flow.instance(context);
         lower = Lower.instance(context);
         Options options = Options.instance(context);
         lineDebugInfo =
             options.isUnset(G_CUSTOM) ||
             options.isSet(G_CUSTOM, "lines");
         varDebugInfo =
             options.isUnset(G_CUSTOM)
             ? options.isSet(G)
             : options.isSet(G_CUSTOM, "vars");
         if (varDebugInfo) {
             lvtRanges = LVTRanges.instance(context);
         }
         genCrt = options.isSet(XJCOV);
         debugCode = options.isSet("debugcode");
         allowInvokedynamic = target.hasInvokedynamic() || options.isSet("invokedynamic");
         pool = new Pool(types);
         typeAnnoAsserts = options.isSet("TypeAnnotationAsserts");
         generateIproxies =
             target.requiresIproxy() ||
             options.isSet("miranda");
         if (target.generateStackMapTable()) {
             // ignore cldc because we cannot have both stackmap formats
             this.stackMap = StackMapFormat.JSR202;
         } else {
             if (target.generateCLDCStackmap()) {
                 this.stackMap = StackMapFormat.CLDC;
             } else {
                 this.stackMap = StackMapFormat.NONE;
             }
         }
         // by default, avoid jsr's for simple finalizers
         int setjsrlimit = 50;
         String jsrlimitString = options.get("jsrlimit");
         if (jsrlimitString != null) {
             try {
                 setjsrlimit = Integer.parseInt(jsrlimitString);
             } catch (NumberFormatException ex) {
                 // ignore ill-formed numbers for jsrlimit
             }
         }
         this.jsrlimit = setjsrlimit;
         this.useJsrLocally = false; // reset in visitTry
     }
     /** Switches
      */
     private final boolean lineDebugInfo;
     private final boolean varDebugInfo;
     private final boolean genCrt;
     private final boolean debugCode;
     private final boolean allowInvokedynamic;
     /** Default limit of (approximate) size of finalizer to inline.
      *  Zero means always use jsr.  100 or greater means never use
      *  jsr.
      */
     private final int jsrlimit;
     /** True if jsr is used.
      */
     private boolean useJsrLocally;
     /** Code buffer, set by genMethod.
      */
     private Code code;
     /** Items structure, set by genMethod.
      */
     private Items items;
     /** Environment for symbol lookup, set by genClass
      */
     private Env<AttrContext> attrEnv;
     /** The top level tree.
      */
     private JCCompilationUnit toplevel;
     /** The number of code-gen errors in this class.
      */
     private int nerrs = 0;
     /** An object containing mappings of syntax trees to their
      *  ending source positions.
      */
     EndPosTable endPosTable;
     /** Generate code to load an integer constant.
      *  @param n     The integer to be loaded.
      */
     void loadIntConst(int n) {
         items.makeImmediateItem(syms.intType, n).load();
     }
     /** The opcode that loads a zero constant of a given type code.
      *  @param tc   The given type code (@see ByteCode).
      */
     public static int zero(int tc) {
         switch(tc) {
         case INTcode: case BYTEcode: case SHORTcode: case CHARcode:
             return iconst_0;
         case LONGcode:
             return lconst_0;
         case FLOATcode:
             return fconst_0;
         case DOUBLEcode:
             return dconst_0;
         default:
             throw new AssertionError("zero");
         }
     }
     /** The opcode that loads a one constant of a given type code.
      *  @param tc   The given type code (@see ByteCode).
      */
     public static int one(int tc) {
         return zero(tc) + 1;
     }
     /** Generate code to load -1 of the given type code (either int or long).
      *  @param tc   The given type code (@see ByteCode).
      */
     void emitMinusOne(int tc) {
         if (tc == LONGcode) {
             items.makeImmediateItem(syms.longType, new Long(-1)).load();
         } else {
             code.emitop0(iconst_m1);
         }
     }
     /** Construct a symbol to reflect the qualifying type that should
      *  appear in the byte code as per JLS 13.1.
      *
      *  For {@literal target >= 1.2}: Clone a method with the qualifier as owner (except
      *  for those cases where we need to work around VM bugs).
      *
      *  For {@literal target <= 1.1}: If qualified variable or method is defined in a
      *  non-accessible class, clone it with the qualifier class as owner.
      *
      *  @param sym    The accessed symbol
      *  @param site   The qualifier's type.
      */
     Symbol binaryQualifier(Symbol sym, Type site) {
         if (site.hasTag(ARRAY)) {
             if (sym == syms.lengthVar ||
                 sym.owner != syms.arrayClass)
                 return sym;
             // array clone can be qualified by the array type in later targets
             Symbol qualifier = target.arrayBinaryCompatibility()
                 ? new ClassSymbol(Flags.PUBLIC, site.tsym.name,
                                   site, syms.noSymbol)
                 : syms.objectType.tsym;
             return sym.clone(qualifier);
         }
         if (sym.owner == site.tsym ||
             (sym.flags() & (STATIC | SYNTHETIC)) == (STATIC | SYNTHETIC)) {
             return sym;
         }
         if (!target.obeyBinaryCompatibility())
             return rs.isAccessible(attrEnv, (TypeSymbol)sym.owner)
                 ? sym
                 : sym.clone(site.tsym);
         if (!target.interfaceFieldsBinaryCompatibility()) {
             if ((sym.owner.flags() & INTERFACE) != 0 && sym.kind == VAR)
                 return sym;
         }
         // leave alone methods inherited from Object
         // JLS 13.1.
         if (sym.owner == syms.objectType.tsym)
             return sym;
         if (!target.interfaceObjectOverridesBinaryCompatibility()) {
             if ((sym.owner.flags() & INTERFACE) != 0 &&
                 syms.objectType.tsym.members().lookup(sym.name).scope != null)
                 return sym;
         }
         return sym.clone(site.tsym);
     }
     /** Insert a reference to given type in the constant pool,
      *  checking for an array with too many dimensions;
      *  return the reference's index.
      *  @param type   The type for which a reference is inserted.
      */
     int makeRef(DiagnosticPosition pos, Type type) {
         checkDimension(pos, type);
         if (type.isAnnotated()) {
             // Treat annotated types separately - we don't want
             // to collapse all of them - at least for annotated
             // exceptions.
             // TODO: review this.
             return pool.put((Object)type);
         } else {
             return pool.put(type.hasTag(CLASS) ? (Object)type.tsym : (Object)type);
         }
     }
     /** Check if the given type is an array with too many dimensions.
      */
     private void checkDimension(DiagnosticPosition pos, Type t) {
         switch (t.getTag()) {
         case METHOD:
             checkDimension(pos, t.getReturnType());
             for (List<Type> args = t.getParameterTypes(); args.nonEmpty(); args = args.tail)
                 checkDimension(pos, args.head);
             break;
         case ARRAY:
             if (types.dimensions(t) > ClassFile.MAX_DIMENSIONS) {
                 log.error(pos, "limit.dimensions");
                 nerrs++;
             }
             break;
         default:
             break;
         }
     }
     /** Create a tempory variable.
      *  @param type   The variable's type.
      */
     LocalItem makeTemp(Type type) {
         VarSymbol v = new VarSymbol(Flags.SYNTHETIC,
                                     names.empty,
                                     type,
                                     env.enclMethod.sym);
         code.newLocal(v);
         return items.makeLocalItem(v);
     }
     /** Generate code to call a non-private method or constructor.
      *  @param pos         Position to be used for error reporting.
      *  @param site        The type of which the method is a member.
      *  @param name        The method's name.
      *  @param argtypes    The method's argument types.
      *  @param isStatic    A flag that indicates whether we call a
      *                     static or instance method.
      */
     void callMethod(DiagnosticPosition pos,
                     Type site, Name name, List<Type> argtypes,
                     boolean isStatic) {
         Symbol msym = rs.
             resolveInternalMethod(pos, attrEnv, site, name, argtypes, null);
         if (isStatic) items.makeStaticItem(msym).invoke();
         else items.makeMemberItem(msym, name == names.init).invoke();
     }
     /** Is the given method definition an access method
      *  resulting from a qualified super? This is signified by an odd
      *  access code.
      */
     private boolean isAccessSuper(JCMethodDecl enclMethod) {
         return
             (enclMethod.mods.flags & SYNTHETIC) != 0 &&
             isOddAccessName(enclMethod.name);
     }
     /** Does given name start with "access$" and end in an odd digit?
      */
     private boolean isOddAccessName(Name name) {
         return
             name.startsWith(accessDollar) &&
             (name.getByteAt(name.getByteLength() - 1) & 1) == 1;
     }
 /* ************************************************************************
  * Non-local exits
  *************************************************************************/
     /** Generate code to invoke the finalizer associated with given
      *  environment.
      *  Any calls to finalizers are appended to the environments `cont' chain.
      *  Mark beginning of gap in catch all range for finalizer.
      */
     void genFinalizer(Env<GenContext> env) {
         if (code.isAlive() && env.info.finalize != null)
             env.info.finalize.gen();
     }
     /** Generate code to call all finalizers of structures aborted by
      *  a non-local
      *  exit.  Return target environment of the non-local exit.
      *  @param target      The tree representing the structure that's aborted
      *  @param env         The environment current at the non-local exit.
      */
     Env<GenContext> unwind(JCTree target, Env<GenContext> env) {
         Env<GenContext> env1 = env;
         while (true) {
             genFinalizer(env1);
             if (env1.tree == target) break;
             env1 = env1.next;
         }
         return env1;
     }
     /** Mark end of gap in catch-all range for finalizer.
      *  @param env   the environment which might contain the finalizer
      *               (if it does, env.info.gaps != null).
      */
     void endFinalizerGap(Env<GenContext> env) {
         if (env.info.gaps != null && env.info.gaps.length() % 2 == 1)
             env.info.gaps.append(code.curCP());
     }
     /** Mark end of all gaps in catch-all ranges for finalizers of environments
      *  lying between, and including to two environments.
      *  @param from    the most deeply nested environment to mark
      *  @param to      the least deeply nested environment to mark
      */
     void endFinalizerGaps(Env<GenContext> from, Env<GenContext> to) {
         Env<GenContext> last = null;
         while (last != to) {
             endFinalizerGap(from);
             last = from;
             from = from.next;
         }
     }
     /** Do any of the structures aborted by a non-local exit have
      *  finalizers that require an empty stack?
      *  @param target      The tree representing the structure that's aborted
      *  @param env         The environment current at the non-local exit.
      */
     boolean hasFinally(JCTree target, Env<GenContext> env) {
         while (env.tree != target) {
             if (env.tree.hasTag(TRY) && env.info.finalize.hasFinalizer())
                 return true;
             env = env.next;
         }
         return false;
     }
 /* ************************************************************************
  * Normalizing class-members.
  *************************************************************************/
     /** Distribute member initializer code into constructors and {@code <clinit>}
      *  method.
      *  @param defs         The list of class member declarations.
      *  @param c            The enclosing class.
      */
     List<JCTree> normalizeDefs(List<JCTree> defs, ClassSymbol c) {
         ListBuffer<JCStatement> initCode = new ListBuffer<JCStatement>();
         ListBuffer<Attribute.TypeCompound> initTAs = new ListBuffer<Attribute.TypeCompound>();
         ListBuffer<JCStatement> clinitCode = new ListBuffer<JCStatement>();
         ListBuffer<Attribute.TypeCompound> clinitTAs = new ListBuffer<Attribute.TypeCompound>();
         ListBuffer<JCTree> methodDefs = new ListBuffer<JCTree>();
         // Sort definitions into three listbuffers:
         //  - initCode for instance initializers
         //  - clinitCode for class initializers
         //  - methodDefs for method definitions
         for (List<JCTree> l = defs; l.nonEmpty(); l = l.tail) {
             JCTree def = l.head;
             switch (def.getTag()) {
             case BLOCK:
                 JCBlock block = (JCBlock)def;
                 if ((block.flags & STATIC) != 0)
                     clinitCode.append(block);
                 else
                     initCode.append(block);
                 break;
             case METHODDEF:
                 methodDefs.append(def);
                 break;
             case VARDEF:
                 JCVariableDecl vdef = (JCVariableDecl) def;
                 VarSymbol sym = vdef.sym;
                 checkDimension(vdef.pos(), sym.type);
                 if (vdef.init != null) {
                     if ((sym.flags() & STATIC) == 0) {
                         // Always initialize instance variables.
                         JCStatement init = make.at(vdef.pos()).
                             Assignment(sym, vdef.init);
                         initCode.append(init);
                         endPosTable.replaceTree(vdef, init);
                         initTAs.addAll(getAndRemoveNonFieldTAs(sym));
                     } else if (sym.getConstValue() == null) {
                         // Initialize class (static) variables only if
                         // they are not compile-time constants.
                         JCStatement init = make.at(vdef.pos).
                             Assignment(sym, vdef.init);
                         clinitCode.append(init);
                         endPosTable.replaceTree(vdef, init);
                         clinitTAs.addAll(getAndRemoveNonFieldTAs(sym));
                     } else {
                         checkStringConstant(vdef.init.pos(), sym.getConstValue());
                     }
                 }
                 break;
             default:
                 Assert.error();
             }
         }
         // Insert any instance initializers into all constructors.
         if (initCode.length() != 0) {
             List<JCStatement> inits = initCode.toList();
             initTAs.addAll(c.getInitTypeAttributes());
             List<Attribute.TypeCompound> initTAlist = initTAs.toList();
             for (JCTree t : methodDefs) {
                 normalizeMethod((JCMethodDecl)t, inits, initTAlist);
             }
         }
         // If there are class initializers, create a <clinit> method
         // that contains them as its body.
         if (clinitCode.length() != 0) {
             MethodSymbol clinit = new MethodSymbol(
                 STATIC | (c.flags() & STRICTFP),
                 names.clinit,
                 new MethodType(
                     List.<Type>nil(), syms.voidType,
                     List.<Type>nil(), syms.methodClass),
                 c);
             c.members().enter(clinit);
             List<JCStatement> clinitStats = clinitCode.toList();
             JCBlock block = make.at(clinitStats.head.pos()).Block(0, clinitStats);
             block.endpos = TreeInfo.endPos(clinitStats.last());
             methodDefs.append(make.MethodDef(clinit, block));
             if (!clinitTAs.isEmpty())
                 clinit.appendUniqueTypeAttributes(clinitTAs.toList());
             if (!c.getClassInitTypeAttributes().isEmpty())
                 clinit.appendUniqueTypeAttributes(c.getClassInitTypeAttributes());
         }
         // Return all method definitions.
         return methodDefs.toList();
     }
     private List<Attribute.TypeCompound> getAndRemoveNonFieldTAs(VarSymbol sym) {
         List<TypeCompound> tas = sym.getRawTypeAttributes();
         ListBuffer<Attribute.TypeCompound> fieldTAs = new ListBuffer<Attribute.TypeCompound>();
         ListBuffer<Attribute.TypeCompound> nonfieldTAs = new ListBuffer<Attribute.TypeCompound>();
         for (TypeCompound ta : tas) {
             if (ta.getPosition().type == TargetType.FIELD) {
                 fieldTAs.add(ta);
             } else {
                 if (typeAnnoAsserts) {
                     Assert.error("Type annotation does not have a valid positior");
                 }
                 nonfieldTAs.add(ta);
             }
         }
         sym.setTypeAttributes(fieldTAs.toList());
         return nonfieldTAs.toList();
     }
     /** Check a constant value and report if it is a string that is
      *  too large.
      */
     private void checkStringConstant(DiagnosticPosition pos, Object constValue) {
         if (nerrs != 0 || // only complain about a long string once
             constValue == null ||
             !(constValue instanceof String) ||
             ((String)constValue).length() < Pool.MAX_STRING_LENGTH)
             return;
         log.error(pos, "limit.string");
         nerrs++;
     }
     /** Insert instance initializer code into initial constructor.
      *  @param md        The tree potentially representing a
      *                   constructor's definition.
      *  @param initCode  The list of instance initializer statements.
      *  @param initTAs  Type annotations from the initializer expression.
      */
     void normalizeMethod(JCMethodDecl md, List<JCStatement> initCode, List<TypeCompound> initTAs) {
         if (md.name == names.init && TreeInfo.isInitialConstructor(md)) {
             // We are seeing a constructor that does not call another
             // constructor of the same class.
             List<JCStatement> stats = md.body.stats;
             ListBuffer<JCStatement> newstats = new ListBuffer<JCStatement>();
             if (stats.nonEmpty()) {
                 // Copy initializers of synthetic variables generated in
                 // the translation of inner classes.
                 while (TreeInfo.isSyntheticInit(stats.head)) {
                     newstats.append(stats.head);
                     stats = stats.tail;
                 }
                 // Copy superclass constructor call
                 newstats.append(stats.head);
                 stats = stats.tail;
                 // Copy remaining synthetic initializers.
                 while (stats.nonEmpty() &&
                        TreeInfo.isSyntheticInit(stats.head)) {
                     newstats.append(stats.head);
                     stats = stats.tail;
                 }
                 // Now insert the initializer code.
                 newstats.appendList(initCode);
                 // And copy all remaining statements.
                 while (stats.nonEmpty()) {
                     newstats.append(stats.head);
                     stats = stats.tail;
                 }
             }
             md.body.stats = newstats.toList();
             if (md.body.endpos == Position.NOPOS)
                 md.body.endpos = TreeInfo.endPos(md.body.stats.last());
             md.sym.appendUniqueTypeAttributes(initTAs);
         }
     }
 /* ********************************************************************
  * Adding miranda methods
  *********************************************************************/
     /** Add abstract methods for all methods defined in one of
      *  the interfaces of a given class,
      *  provided they are not already implemented in the class.
      *
      *  @param c      The class whose interfaces are searched for methods
      *                for which Miranda methods should be added.
      */
     void implementInterfaceMethods(ClassSymbol c) {
         implementInterfaceMethods(c, c);
     }
     /** Add abstract methods for all methods defined in one of
      *  the interfaces of a given class,
      *  provided they are not already implemented in the class.
      *
      *  @param c      The class whose interfaces are searched for methods
      *                for which Miranda methods should be added.
      *  @param site   The class in which a definition may be needed.
      */
     void implementInterfaceMethods(ClassSymbol c, ClassSymbol site) {
         for (List<Type> l = types.interfaces(c.type); l.nonEmpty(); l = l.tail) {
             ClassSymbol i = (ClassSymbol)l.head.tsym;
             for (Scope.Entry e = i.members().elems;
                  e != null;
                  e = e.sibling)
             {
                 if (e.sym.kind == MTH && (e.sym.flags() & STATIC) == 0)
                 {
                     MethodSymbol absMeth = (MethodSymbol)e.sym;
                     MethodSymbol implMeth = absMeth.binaryImplementation(site, types);
                     if (implMeth == null)
                         addAbstractMethod(site, absMeth);
                     else if ((implMeth.flags() & IPROXY) != 0)
                         adjustAbstractMethod(site, implMeth, absMeth);
                 }
             }
             implementInterfaceMethods(i, site);
         }
     }
     /** Add an abstract methods to a class
      *  which implicitly implements a method defined in some interface
      *  implemented by the class. These methods are called "Miranda methods".
      *  Enter the newly created method into its enclosing class scope.
      *  Note that it is not entered into the class tree, as the emitter
      *  doesn't need to see it there to emit an abstract method.
      *
      *  @param c      The class to which the Miranda method is added.
      *  @param m      The interface method symbol for which a Miranda method
      *                is added.
      */
     private void addAbstractMethod(ClassSymbol c,
                                    MethodSymbol m) {
         MethodSymbol absMeth = new MethodSymbol(
             m.flags() | IPROXY | SYNTHETIC, m.name,
             m.type, // was c.type.memberType(m), but now only !generics supported
             c);
         c.members().enter(absMeth); // add to symbol table
     }
     private void adjustAbstractMethod(ClassSymbol c,
                                       MethodSymbol pm,
                                       MethodSymbol im) {
         MethodType pmt = (MethodType)pm.type;
         Type imt = types.memberType(c.type, im);
         pmt.thrown = chk.intersect(pmt.getThrownTypes(), imt.getThrownTypes());
     }
 /* ************************************************************************
  * Traversal methods
  *************************************************************************/
     /** Visitor argument: The current environment.
      */
     Env<GenContext> env;
     /** Visitor argument: The expected type (prototype).
      */
     Type pt;
     /** Visitor result: The item representing the computed value.
      */
     Item result;
     /** Visitor method: generate code for a definition, catching and reporting
      *  any completion failures.
      *  @param tree    The definition to be visited.
      *  @param env     The environment current at the definition.
      */
     public void genDef(JCTree tree, Env<GenContext> env) {
         Env<GenContext> prevEnv = this.env;
         try {
             this.env = env;
             tree.accept(this);
         } catch (CompletionFailure ex) {
             chk.completionError(tree.pos(), ex);
         } finally {
             this.env = prevEnv;
         }
     }
     /** Derived visitor method: check whether CharacterRangeTable
      *  should be emitted, if so, put a new entry into CRTable
      *  and call method to generate bytecode.
      *  If not, just call method to generate bytecode.
      *  @see    #genStat(JCTree, Env)
      *
      *  @param  tree     The tree to be visited.
      *  @param  env      The environment to use.
      *  @param  crtFlags The CharacterRangeTable flags
      *                   indicating type of the entry.
      */
     public void genStat(JCTree tree, Env<GenContext> env, int crtFlags) {
         if (!genCrt) {
             genStat(tree, env);
             return;
         }
         int startpc = code.curCP();
         genStat(tree, env);
         if (tree.hasTag(Tag.BLOCK)) crtFlags |= CRT_BLOCK;
         code.crt.put(tree, crtFlags, startpc, code.curCP());
     }
     /** Derived visitor method: generate code for a statement.
      */
     public void genStat(JCTree tree, Env<GenContext> env) {
         if (code.isAlive()) {
             code.statBegin(tree.pos);
             genDef(tree, env);
         } else if (env.info.isSwitch && tree.hasTag(VARDEF)) {
             // variables whose declarations are in a switch
             // can be used even if the decl is unreachable.
             code.newLocal(((JCVariableDecl) tree).sym);
         }
     }
     /** Derived visitor method: check whether CharacterRangeTable
      *  should be emitted, if so, put a new entry into CRTable
      *  and call method to generate bytecode.
      *  If not, just call method to generate bytecode.
      *  @see    #genStats(List, Env)
      *
      *  @param  trees    The list of trees to be visited.
      *  @param  env      The environment to use.
      *  @param  crtFlags The CharacterRangeTable flags
      *                   indicating type of the entry.
      */
     public void genStats(List<JCStatement> trees, Env<GenContext> env, int crtFlags) {
         if (!genCrt) {
             genStats(trees, env);
             return;
         }
         if (trees.length() == 1) {        // mark one statement with the flags
             genStat(trees.head, env, crtFlags | CRT_STATEMENT);
         } else {
             int startpc = code.curCP();
             genStats(trees, env);
             code.crt.put(trees, crtFlags, startpc, code.curCP());
         }
     }
     /** Derived visitor method: generate code for a list of statements.
      */
     public void genStats(List<? extends JCTree> trees, Env<GenContext> env) {
         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
             genStat(l.head, env, CRT_STATEMENT);
     }
     /** Derived visitor method: check whether CharacterRangeTable
      *  should be emitted, if so, put a new entry into CRTable
      *  and call method to generate bytecode.
      *  If not, just call method to generate bytecode.
      *  @see    #genCond(JCTree,boolean)
      *
      *  @param  tree     The tree to be visited.
      *  @param  crtFlags The CharacterRangeTable flags
      *                   indicating type of the entry.
      */
     public CondItem genCond(JCTree tree, int crtFlags) {
         if (!genCrt) return genCond(tree, false);
         int startpc = code.curCP();
         CondItem item = genCond(tree, (crtFlags & CRT_FLOW_CONTROLLER) != 0);
         code.crt.put(tree, crtFlags, startpc, code.curCP());
         return item;
     }
     /** Derived visitor method: generate code for a boolean
      *  expression in a control-flow context.
      *  @param _tree         The expression to be visited.
      *  @param markBranches The flag to indicate that the condition is
      *                      a flow controller so produced conditions
      *                      should contain a proper tree to generate
      *                      CharacterRangeTable branches for them.
      */
     public CondItem genCond(JCTree _tree, boolean markBranches) {
         JCTree inner_tree = TreeInfo.skipParens(_tree);
         if (inner_tree.hasTag(CONDEXPR)) {
             JCConditional tree = (JCConditional)inner_tree;
             CondItem cond = genCond(tree.cond, CRT_FLOW_CONTROLLER);
             if (cond.isTrue()) {
                 code.resolve(cond.trueJumps);
                 CondItem result = genCond(tree.truepart, CRT_FLOW_TARGET);
                 if (markBranches) result.tree = tree.truepart;
                 return result;
             }
             if (cond.isFalse()) {
                 code.resolve(cond.falseJumps);
                 CondItem result = genCond(tree.falsepart, CRT_FLOW_TARGET);
                 if (markBranches) result.tree = tree.falsepart;
                 return result;
             }
             Chain secondJumps = cond.jumpFalse();
             code.resolve(cond.trueJumps);
             CondItem first = genCond(tree.truepart, CRT_FLOW_TARGET);
             if (markBranches) first.tree = tree.truepart;
             Chain falseJumps = first.jumpFalse();
             code.resolve(first.trueJumps);
             Chain trueJumps = code.branch(goto_);
             code.resolve(secondJumps);
             CondItem second = genCond(tree.falsepart, CRT_FLOW_TARGET);
             CondItem result = items.makeCondItem(second.opcode,
                                       Code.mergeChains(trueJumps, second.trueJumps),
                                       Code.mergeChains(falseJumps, second.falseJumps));
             if (markBranches) result.tree = tree.falsepart;
             return result;
         } else {
             CondItem result = genExpr(_tree, syms.booleanType).mkCond();
             if (markBranches) result.tree = _tree;
             return result;
         }
     }
     /** Visitor class for expressions which might be constant expressions.
      *  This class is a subset of TreeScanner. Intended to visit trees pruned by
      *  Lower as long as constant expressions looking for references to any
      *  ClassSymbol. Any such reference will be added to the constant pool so
      *  automated tools can detect class dependencies better.
      */
     class ClassReferenceVisitor extends JCTree.Visitor {
         @Override
         public void visitTree(JCTree tree) {}
         @Override
         public void visitBinary(JCBinary tree) {
             tree.lhs.accept(this);
             tree.rhs.accept(this);
         }
         @Override
         public void visitSelect(JCFieldAccess tree) {
             if (tree.selected.type.hasTag(CLASS)) {
                 makeRef(tree.selected.pos(), tree.selected.type);
             }
         }
         @Override
         public void visitIdent(JCIdent tree) {
             if (tree.sym.owner instanceof ClassSymbol) {
                 pool.put(tree.sym.owner);
             }
         }
         @Override
         public void visitConditional(JCConditional tree) {
             tree.cond.accept(this);
             tree.truepart.accept(this);
             tree.falsepart.accept(this);
         }
         @Override
         public void visitUnary(JCUnary tree) {
             tree.arg.accept(this);
         }
         @Override
         public void visitParens(JCParens tree) {
             tree.expr.accept(this);
         }
         @Override
         public void visitTypeCast(JCTypeCast tree) {
             tree.expr.accept(this);
         }
     }
     private ClassReferenceVisitor classReferenceVisitor = new ClassReferenceVisitor();
     /** Visitor method: generate code for an expression, catching and reporting
      *  any completion failures.
      *  @param tree    The expression to be visited.
      *  @param pt      The expression's expected type (proto-type).
      */
     public Item genExpr(JCTree tree, Type pt) {
         Type prevPt = this.pt;
         try {
             if (tree.type.constValue() != null) {
                 // Short circuit any expressions which are constants
                 tree.accept(classReferenceVisitor);
                 checkStringConstant(tree.pos(), tree.type.constValue());
                 result = items.makeImmediateItem(tree.type, tree.type.constValue());
             } else {
                 this.pt = pt;
                 tree.accept(this);
             }
             return result.coerce(pt);
         } catch (CompletionFailure ex) {
             chk.completionError(tree.pos(), ex);
             code.state.stacksize = 1;
             return items.makeStackItem(pt);
         } finally {
             this.pt = prevPt;
         }
     }
     /** Derived visitor method: generate code for a list of method arguments.
      *  @param trees    The argument expressions to be visited.
      *  @param pts      The expression's expected types (i.e. the formal parameter
      *                  types of the invoked method).
      */
     public void genArgs(List<JCExpression> trees, List<Type> pts) {
         for (List<JCExpression> l = trees; l.nonEmpty(); l = l.tail) {
             genExpr(l.head, pts.head).load();
             pts = pts.tail;
         }
         // require lists be of same length
         Assert.check(pts.isEmpty());
     }
 /* ************************************************************************
  * Visitor methods for statements and definitions
  *************************************************************************/
     /** Thrown when the byte code size exceeds limit.
      */
     public static class CodeSizeOverflow extends RuntimeException {
         private static final long serialVersionUID = 0;
         public CodeSizeOverflow() {}
     }
     public void visitMethodDef(JCMethodDecl tree) {
         // Create a new local environment that points pack at method
         // definition.
         Env<GenContext> localEnv = env.dup(tree);
         localEnv.enclMethod = tree;
         // The expected type of every return statement in this method
         // is the method's return type.
         this.pt = tree.sym.erasure(types).getReturnType();
         checkDimension(tree.pos(), tree.sym.erasure(types));
         genMethod(tree, localEnv, false);
     }
 //where
         /** Generate code for a method.
          *  @param tree     The tree representing the method definition.
          *  @param env      The environment current for the method body.
          *  @param fatcode  A flag that indicates whether all jumps are
          *                  within 32K.  We first invoke this method under
          *                  the assumption that fatcode == false, i.e. all
          *                  jumps are within 32K.  If this fails, fatcode
          *                  is set to true and we try again.
          */
         void genMethod(JCMethodDecl tree, Env<GenContext> env, boolean fatcode) {
             MethodSymbol meth = tree.sym;
             int extras = 0;
             // Count up extra parameters
             if (meth.isConstructor()) {
                 extras++;
                 if (meth.enclClass().isInner() &&
                     !meth.enclClass().isStatic()) {
                     extras++;
                 }
             } else if ((tree.mods.flags & STATIC) == 0) {
                 extras++;
             }
             //      System.err.println("Generating " + meth + " in " + meth.owner); //DEBUG
             if (Code.width(types.erasure(env.enclMethod.sym.type).getParameterTypes()) + extras >
                 ClassFile.MAX_PARAMETERS) {
                 log.error(tree.pos(), "limit.parameters");
                 nerrs++;
             }
             else if (tree.body != null) {
                 // Create a new code structure and initialize it.
                 int startpcCrt = initCode(tree, env, fatcode);
                 try {
                     genStat(tree.body, env);
                 } catch (CodeSizeOverflow e) {
                     // Failed due to code limit, try again with jsr/ret
                     startpcCrt = initCode(tree, env, fatcode);
                     genStat(tree.body, env);
                 }
                 if (code.state.stacksize != 0) {
                     log.error(tree.body.pos(), "stack.sim.error", tree);
                     throw new AssertionError();
                 }
                 // If last statement could complete normally, insert a
                 // return at the end.
                 if (code.isAlive()) {
                     code.statBegin(TreeInfo.endPos(tree.body));
                     if (env.enclMethod == null ||
                         env.enclMethod.sym.type.getReturnType().hasTag(VOID)) {
                         code.emitop0(return_);
                     } else {
                         // sometime dead code seems alive (4415991);
                         // generate a small loop instead
                         int startpc = code.entryPoint();
                         CondItem c = items.makeCondItem(goto_);
                         code.resolve(c.jumpTrue(), startpc);
                     }
                 }
                 if (genCrt)
                     code.crt.put(tree.body,
                                  CRT_BLOCK,
                                  startpcCrt,
                                  code.curCP());
                 code.endScopes(0);
                 // If we exceeded limits, panic
                 if (code.checkLimits(tree.pos(), log)) {
                     nerrs++;
                     return;
                 }
                 // If we generated short code but got a long jump, do it again
                 // with fatCode = true.
                 if (!fatcode && code.fatcode) genMethod(tree, env, true);
                 // Clean up
                 if(stackMap == StackMapFormat.JSR202) {
                     code.lastFrame = null;
                     code.frameBeforeLast = null;
                 }
                 // Compress exception table
                 code.compressCatchTable();
                 // Fill in type annotation positions for exception parameters
                 code.fillExceptionParameterPositions();
             }
         }
         private int initCode(JCMethodDecl tree, Env<GenContext> env, boolean fatcode) {
             MethodSymbol meth = tree.sym;
             // Create a new code structure.
             meth.code = code = new Code(meth,
                                         fatcode,
                                         lineDebugInfo ? toplevel.lineMap : null,
                                         varDebugInfo,
                                         stackMap,
                                         debugCode,
                                         genCrt ? new CRTable(tree, env.toplevel.endPositions)
                                                : null,
                                         syms,
                                         types,
                                         pool,
                                         varDebugInfo ? lvtRanges : null);
             items = new Items(pool, code, syms, types);
             if (code.debugCode) {
                 System.err.println(meth + " for body " + tree);
             }
             // If method is not static, create a new local variable address
             // for `this'.
             if ((tree.mods.flags & STATIC) == 0) {
                 Type selfType = meth.owner.type;
                 if (meth.isConstructor() && selfType != syms.objectType)
                     selfType = UninitializedType.uninitializedThis(selfType);
                 code.setDefined(
                         code.newLocal(
                             new VarSymbol(FINAL, names._this, selfType, meth.owner)));
             }
             // Mark all parameters as defined from the beginning of
             // the method.
             for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
                 checkDimension(l.head.pos(), l.head.sym.type);
                 code.setDefined(code.newLocal(l.head.sym));
             }
             // Get ready to generate code for method body.
             int startpcCrt = genCrt ? code.curCP() : 0;
             code.entryPoint();
             // Suppress initial stackmap
             code.pendingStackMap = false;
             return startpcCrt;
         }
     public void visitVarDef(JCVariableDecl tree) {
         VarSymbol v = tree.sym;
         code.newLocal(v);
         if (tree.init != null) {
             checkStringConstant(tree.init.pos(), v.getConstValue());
             if (v.getConstValue() == null || varDebugInfo) {
                 genExpr(tree.init, v.erasure(types)).load();
                 items.makeLocalItem(v).store();
             }
         }
         checkDimension(tree.pos(), v.type);
     }
     public void visitSkip(JCSkip tree) {
     }
     public void visitBlock(JCBlock tree) {
         int limit = code.nextreg;
         Env<GenContext> localEnv = env.dup(tree, new GenContext());
         genStats(tree.stats, localEnv);
         // End the scope of all block-local variables in variable info.
         if (!env.tree.hasTag(METHODDEF)) {
             code.statBegin(tree.endpos);
             code.endScopes(limit);
             code.pendingStatPos = Position.NOPOS;
         }
     }
     public void visitDoLoop(JCDoWhileLoop tree) {
         genLoop(tree, tree.body, tree.cond, List.<JCExpressionStatement>nil(), false);
     }
     public void visitWhileLoop(JCWhileLoop tree) {
         genLoop(tree, tree.body, tree.cond, List.<JCExpressionStatement>nil(), true);
     }
     public void visitForLoop(JCForLoop tree) {
         int limit = code.nextreg;
         genStats(tree.init, env);
         genLoop(tree, tree.body, tree.cond, tree.step, true);
         code.endScopes(limit);
     }
     //where
         /** Generate code for a loop.
          *  @param loop       The tree representing the loop.
          *  @param body       The loop's body.
          *  @param cond       The loop's controling condition.
          *  @param step       "Step" statements to be inserted at end of
          *                    each iteration.
          *  @param testFirst  True if the loop test belongs before the body.
          */
         private void genLoop(JCStatement loop,
                              JCStatement body,
                              JCExpression cond,
                              List<JCExpressionStatement> step,
                              boolean testFirst) {
             Env<GenContext> loopEnv = env.dup(loop, new GenContext());
             int startpc = code.entryPoint();
             if (testFirst) { //while or for loop
                 CondItem c;
                 if (cond != null) {
                     code.statBegin(cond.pos);
                     c = genCond(TreeInfo.skipParens(cond), CRT_FLOW_CONTROLLER);
                 } else {
                     c = items.makeCondItem(goto_);
                 }
                 Chain loopDone = c.jumpFalse();
                 code.resolve(c.trueJumps);
                 genStat(body, loopEnv, CRT_STATEMENT | CRT_FLOW_TARGET);
                 if (varDebugInfo) {
                     checkLoopLocalVarRangeEnding(loop, body,
                             LoopLocalVarRangeEndingPoint.BEFORE_STEPS);
                 }
                 code.resolve(loopEnv.info.cont);
                 genStats(step, loopEnv);
                 if (varDebugInfo) {
                     checkLoopLocalVarRangeEnding(loop, body,
                             LoopLocalVarRangeEndingPoint.AFTER_STEPS);
                 }
                 code.resolve(code.branch(goto_), startpc);
                 code.resolve(loopDone);
             } else {
                 genStat(body, loopEnv, CRT_STATEMENT | CRT_FLOW_TARGET);
                 if (varDebugInfo) {
                     checkLoopLocalVarRangeEnding(loop, body,
                             LoopLocalVarRangeEndingPoint.BEFORE_STEPS);
                 }
                 code.resolve(loopEnv.info.cont);
                 genStats(step, loopEnv);
                 if (varDebugInfo) {
                     checkLoopLocalVarRangeEnding(loop, body,
                             LoopLocalVarRangeEndingPoint.AFTER_STEPS);
                 }
                 CondItem c;
                 if (cond != null) {
                     code.statBegin(cond.pos);
                     c = genCond(TreeInfo.skipParens(cond), CRT_FLOW_CONTROLLER);
                 } else {
                     c = items.makeCondItem(goto_);
                 }
                 code.resolve(c.jumpTrue(), startpc);
                 code.resolve(c.falseJumps);
             }
             code.resolve(loopEnv.info.exit);
             if (loopEnv.info.exit != null) {
                 loopEnv.info.exit.state.defined.excludeFrom(code.nextreg);
             }
         }
         private enum LoopLocalVarRangeEndingPoint {
             BEFORE_STEPS,
             AFTER_STEPS,
         }
         /**
          *  Checks whether we have reached an alive range ending point for local
          *  variables after a loop.
          *
          *  Local variables alive range ending point for loops varies depending
          *  on the loop type. The range can be closed before or after the code
          *  for the steps sentences has been generated.
          *
          *  - While loops has no steps so in that case the range is closed just
          *  after the body of the loop.
          *
          *  - For-like loops may have steps so as long as the steps sentences
          *  can possibly contain non-synthetic local variables, the alive range
          *  for local variables must be closed after the steps in this case.
         */
         private void checkLoopLocalVarRangeEnding(JCTree loop, JCTree body,
                 LoopLocalVarRangeEndingPoint endingPoint) {
             if (varDebugInfo && lvtRanges.containsKey(code.meth, body)) {
                 switch (endingPoint) {
                     case BEFORE_STEPS:
                         if (!loop.hasTag(FORLOOP)) {
                             code.closeAliveRanges(body);
                         }
                         break;
                     case AFTER_STEPS:
                         if (loop.hasTag(FORLOOP)) {
                             code.closeAliveRanges(body);
                         }
                         break;
                 }
             }
         }
     public void visitForeachLoop(JCEnhancedForLoop tree) {
         throw new AssertionError(); // should have been removed by Lower.
     }
     public void visitLabelled(JCLabeledStatement tree) {
         Env<GenContext> localEnv = env.dup(tree, new GenContext());
         genStat(tree.body, localEnv, CRT_STATEMENT);
         code.resolve(localEnv.info.exit);
     }
     public void visitSwitch(JCSwitch tree) {
         int limit = code.nextreg;
         Assert.check(!tree.selector.type.hasTag(CLASS));
         int startpcCrt = genCrt ? code.curCP() : 0;
         Item sel = genExpr(tree.selector, syms.intType);
         List<JCCase> cases = tree.cases;
         if (cases.isEmpty()) {
             // We are seeing:  switch <sel> {}
             sel.load().drop();
             if (genCrt)
                 code.crt.put(TreeInfo.skipParens(tree.selector),
                              CRT_FLOW_CONTROLLER, startpcCrt, code.curCP());
         } else {
             // We are seeing a nonempty switch.
             sel.load();
             if (genCrt)
                 code.crt.put(TreeInfo.skipParens(tree.selector),
                              CRT_FLOW_CONTROLLER, startpcCrt, code.curCP());
             Env<GenContext> switchEnv = env.dup(tree, new GenContext());
             switchEnv.info.isSwitch = true;
             // Compute number of labels and minimum and maximum label values.
             // For each case, store its label in an array.
             int lo = Integer.MAX_VALUE;  // minimum label.
             int hi = Integer.MIN_VALUE;  // maximum label.
             int nlabels = 0;               // number of labels.
             int[] labels = new int[cases.length()];  // the label array.
             int defaultIndex = -1;     // the index of the default clause.
             List<JCCase> l = cases;
             for (int i = 0; i < labels.length; i++) {
                 if (l.head.pat != null) {
                     int val = ((Number)l.head.pat.type.constValue()).intValue();
                     labels[i] = val;
                     if (val < lo) lo = val;
                     if (hi < val) hi = val;
                     nlabels++;
                 } else {
                     Assert.check(defaultIndex == -1);
                     defaultIndex = i;
                 }
                 l = l.tail;
             }
             // Determine whether to issue a tableswitch or a lookupswitch
             // instruction.
             long table_space_cost = 4 + ((long) hi - lo + 1); // words
             long table_time_cost = 3; // comparisons
             long lookup_space_cost = 3 + 2 * (long) nlabels;
             long lookup_time_cost = nlabels;
             int opcode =
                 nlabels > 0 &&
                 table_space_cost + 3 * table_time_cost <=
                 lookup_space_cost + 3 * lookup_time_cost
                 ?
                 tableswitch : lookupswitch;
             int startpc = code.curCP();    // the position of the selector operation
             code.emitop0(opcode);
             code.align(4);
             int tableBase = code.curCP();  // the start of the jump table
             int[] offsets = null;          // a table of offsets for a lookupswitch
             code.emit4(-1);                // leave space for default offset
             if (opcode == tableswitch) {
                 code.emit4(lo);            // minimum label
                 code.emit4(hi);            // maximum label
                 for (long i = lo; i <= hi; i++) {  // leave space for jump table
                     code.emit4(-1);
                 }
             } else {
                 code.emit4(nlabels);    // number of labels
                 for (int i = 0; i < nlabels; i++) {
                     code.emit4(-1); code.emit4(-1); // leave space for lookup table
                 }
                 offsets = new int[labels.length];
             }
             Code.State stateSwitch = code.state.dup();
             code.markDead();
             // For each case do:
             l = cases;
             for (int i = 0; i < labels.length; i++) {
                 JCCase c = l.head;
                 l = l.tail;
                 int pc = code.entryPoint(stateSwitch);
                 // Insert offset directly into code or else into the
                 // offsets table.
                 if (i != defaultIndex) {
                     if (opcode == tableswitch) {
                         code.put4(
                             tableBase + 4 * (labels[i] - lo + 3),
                             pc - startpc);
                     } else {
                         offsets[i] = pc - startpc;
                     }
                 } else {
                     code.put4(tableBase, pc - startpc);
                 }
                 // Generate code for the statements in this case.
                 genStats(c.stats, switchEnv, CRT_FLOW_TARGET);
                 if (varDebugInfo && lvtRanges.containsKey(code.meth, c.stats.last())) {
                     code.closeAliveRanges(c.stats.last());
                 }
             }
             // Resolve all breaks.
             code.resolve(switchEnv.info.exit);
             // If we have not set the default offset, we do so now.
             if (code.get4(tableBase) == -1) {
                 code.put4(tableBase, code.entryPoint(stateSwitch) - startpc);
             }
             if (opcode == tableswitch) {
                 // Let any unfilled slots point to the default case.
                 int defaultOffset = code.get4(tableBase);
                 for (long i = lo; i <= hi; i++) {
                     int t = (int)(tableBase + 4 * (i - lo + 3));
                     if (code.get4(t) == -1)
                         code.put4(t, defaultOffset);
                 }
             } else {
                 // Sort non-default offsets and copy into lookup table.
                 if (defaultIndex >= 0)
                     for (int i = defaultIndex; i < labels.length - 1; i++) {
                         labels[i] = labels[i+1];
                         offsets[i] = offsets[i+1];
                     }
                 if (nlabels > 0)
                     qsort2(labels, offsets, 0, nlabels - 1);
                 for (int i = 0; i < nlabels; i++) {
                     int caseidx = tableBase + 8 * (i + 1);
                     code.put4(caseidx, labels[i]);
                     code.put4(caseidx + 4, offsets[i]);
                 }
             }
         }
         code.endScopes(limit);
     }
 //where
         /** Sort (int) arrays of keys and values
          */
        static void qsort2(int[] keys, int[] values, int lo, int hi) {
             int i = lo;
             int j = hi;
             int pivot = keys[(i+j)/2];
             do {
                 while (keys[i] < pivot) i++;
                 while (pivot < keys[j]) j--;
                 if (i <= j) {
                     int temp1 = keys[i];
                     keys[i] = keys[j];
                     keys[j] = temp1;
                     int temp2 = values[i];
                     values[i] = values[j];
                     values[j] = temp2;
                     i++;
                     j--;
                 }
             } while (i <= j);
             if (lo < j) qsort2(keys, values, lo, j);
             if (i < hi) qsort2(keys, values, i, hi);
         }
     public void visitSynchronized(JCSynchronized tree) {
         int limit = code.nextreg;
         // Generate code to evaluate lock and save in temporary variable.
         final LocalItem lockVar = makeTemp(syms.objectType);
         genExpr(tree.lock, tree.lock.type).load().duplicate();
         lockVar.store();
         // Generate code to enter monitor.
         code.emitop0(monitorenter);
         code.state.lock(lockVar.reg);
         // Generate code for a try statement with given body, no catch clauses
         // in a new environment with the "exit-monitor" operation as finalizer.
         final Env<GenContext> syncEnv = env.dup(tree, new GenContext());
         syncEnv.info.finalize = new GenFinalizer() {
             void gen() {
                 genLast();
                 Assert.check(syncEnv.info.gaps.length() % 2 == 0);
                 syncEnv.info.gaps.append(code.curCP());
             }
             void genLast() {
                 if (code.isAlive()) {
                     lockVar.load();
                     code.emitop0(monitorexit);
                     code.state.unlock(lockVar.reg);
                 }
             }
         };
         syncEnv.info.gaps = new ListBuffer<Integer>();
         genTry(tree.body, List.<JCCatch>nil(), syncEnv);
         code.endScopes(limit);
     }
     public void visitTry(final JCTry tree) {
         // Generate code for a try statement with given body and catch clauses,
         // in a new environment which calls the finally block if there is one.
         final Env<GenContext> tryEnv = env.dup(tree, new GenContext());
         final Env<GenContext> oldEnv = env;
         if (!useJsrLocally) {
             useJsrLocally =
                 (stackMap == StackMapFormat.NONE) &&
                 (jsrlimit <= 0 ||
                 jsrlimit < 100 &&
                 estimateCodeComplexity(tree.finalizer)>jsrlimit);
         }
         tryEnv.info.finalize = new GenFinalizer() {
             void gen() {
                 if (useJsrLocally) {
                     if (tree.finalizer != null) {
                         Code.State jsrState = code.state.dup();
                         jsrState.push(Code.jsrReturnValue);
                         tryEnv.info.cont =
                             new Chain(code.emitJump(jsr),
                                       tryEnv.info.cont,
                                       jsrState);
                     }
                     Assert.check(tryEnv.info.gaps.length() % 2 == 0);
                     tryEnv.info.gaps.append(code.curCP());
                 } else {
                     Assert.check(tryEnv.info.gaps.length() % 2 == 0);
                     tryEnv.info.gaps.append(code.curCP());
                     genLast();
                 }
             }
             void genLast() {
                 if (tree.finalizer != null)
                     genStat(tree.finalizer, oldEnv, CRT_BLOCK);
             }
             boolean hasFinalizer() {
                 return tree.finalizer != null;
             }
         };
         tryEnv.info.gaps = new ListBuffer<Integer>();
         genTry(tree.body, tree.catchers, tryEnv);
     }
     //where
         /** Generate code for a try or synchronized statement
          *  @param body      The body of the try or synchronized statement.
          *  @param catchers  The lis of catch clauses.
          *  @param env       the environment current for the body.
          */
         void genTry(JCTree body, List<JCCatch> catchers, Env<GenContext> env) {
             int limit = code.nextreg;
             int startpc = code.curCP();
             Code.State stateTry = code.state.dup();
             genStat(body, env, CRT_BLOCK);
             int endpc = code.curCP();
             boolean hasFinalizer =
                 env.info.finalize != null &&
                 env.info.finalize.hasFinalizer();
             List<Integer> gaps = env.info.gaps.toList();
             code.statBegin(TreeInfo.endPos(body));
             genFinalizer(env);
             code.statBegin(TreeInfo.endPos(env.tree));
             Chain exitChain = code.branch(goto_);
             if (varDebugInfo && lvtRanges.containsKey(code.meth, body)) {
                 code.closeAliveRanges(body);
             }
             endFinalizerGap(env);
             if (startpc != endpc) for (List<JCCatch> l = catchers; l.nonEmpty(); l = l.tail) {
                 // start off with exception on stack
                 code.entryPoint(stateTry, l.head.param.sym.type);
                 genCatch(l.head, env, startpc, endpc, gaps);
                 genFinalizer(env);
                 if (hasFinalizer || l.tail.nonEmpty()) {
                     code.statBegin(TreeInfo.endPos(env.tree));
                     exitChain = Code.mergeChains(exitChain,
                                                  code.branch(goto_));
                 }
                 endFinalizerGap(env);
             }
             if (hasFinalizer) {
                 // Create a new register segement to avoid allocating
                 // the same variables in finalizers and other statements.
                 code.newRegSegment();
                 // Add a catch-all clause.
                 // start off with exception on stack
                 int catchallpc = code.entryPoint(stateTry, syms.throwableType);
                 // Register all exception ranges for catch all clause.
                 // The range of the catch all clause is from the beginning
                 // of the try or synchronized block until the present
                 // code pointer excluding all gaps in the current
                 // environment's GenContext.
                 int startseg = startpc;
                 while (env.info.gaps.nonEmpty()) {
                     int endseg = env.info.gaps.next().intValue();
                     registerCatch(body.pos(), startseg, endseg,
                                   catchallpc, 0);
                     startseg = env.info.gaps.next().intValue();
                 }
                 code.statBegin(TreeInfo.finalizerPos(env.tree));
                 code.markStatBegin();
                 Item excVar = makeTemp(syms.throwableType);
                 excVar.store();
                 genFinalizer(env);
                 excVar.load();
                 registerCatch(body.pos(), startseg,
                               env.info.gaps.next().intValue(),
                               catchallpc, 0);
                 code.emitop0(athrow);
                 code.markDead();
                 // If there are jsr's to this finalizer, ...
                 if (env.info.cont != null) {
                     // Resolve all jsr's.
                     code.resolve(env.info.cont);
                     // Mark statement line number
                     code.statBegin(TreeInfo.finalizerPos(env.tree));
                     code.markStatBegin();
                     // Save return address.
                     LocalItem retVar = makeTemp(syms.throwableType);
                     retVar.store();
                     // Generate finalizer code.
                     env.info.finalize.genLast();
                     // Return.
                     code.emitop1w(ret, retVar.reg);
                     code.markDead();
                 }
             }
             // Resolve all breaks.
             code.resolve(exitChain);
             code.endScopes(limit);
         }
         /** Generate code for a catch clause.
          *  @param tree     The catch clause.
          *  @param env      The environment current in the enclosing try.
          *  @param startpc  Start pc of try-block.
          *  @param endpc    End pc of try-block.
          */
         void genCatch(JCCatch tree,
                       Env<GenContext> env,
                       int startpc, int endpc,
                       List<Integer> gaps) {
             if (startpc != endpc) {
                 List<JCExpression> subClauses = TreeInfo.isMultiCatch(tree) ?
                         ((JCTypeUnion)tree.param.vartype).alternatives :
                         List.of(tree.param.vartype);
                 while (gaps.nonEmpty()) {
                     for (JCExpression subCatch : subClauses) {
                         int catchType = makeRef(tree.pos(), subCatch.type);
                         int end = gaps.head.intValue();
                         registerCatch(tree.pos(),
                                       startpc,  end, code.curCP(),
                                       catchType);
                         if (subCatch.type.isAnnotated()) {
                             for (Attribute.TypeCompound tc :
                                      subCatch.type.getAnnotationMirrors()) {
                                 tc.position.type_index = catchType;
                             }
                         }
                     }
                     gaps = gaps.tail;
                     startpc = gaps.head.intValue();
                     gaps = gaps.tail;
                 }
                 if (startpc < endpc) {
                     for (JCExpression subCatch : subClauses) {
                         int catchType = makeRef(tree.pos(), subCatch.type);
                         registerCatch(tree.pos(),
                                       startpc, endpc, code.curCP(),
                                       catchType);
                         if (subCatch.type.isAnnotated()) {
                             for (Attribute.TypeCompound tc :
                                      subCatch.type.getAnnotationMirrors()) {
                                 tc.position.type_index = catchType;
                             }
                         }
                     }
                 }
                 VarSymbol exparam = tree.param.sym;
                 code.statBegin(tree.pos);
                 code.markStatBegin();
                 int limit = code.nextreg;
                 int exlocal = code.newLocal(exparam);
                 items.makeLocalItem(exparam).store();
                 code.statBegin(TreeInfo.firstStatPos(tree.body));
                 genStat(tree.body, env, CRT_BLOCK);
                 code.endScopes(limit);
                 code.statBegin(TreeInfo.endPos(tree.body));
             }
         }
         /** Register a catch clause in the "Exceptions" code-attribute.
          */
         void registerCatch(DiagnosticPosition pos,
                            int startpc, int endpc,
                            int handler_pc, int catch_type) {
             char startpc1 = (char)startpc;
             char endpc1 = (char)endpc;
             char handler_pc1 = (char)handler_pc;
             if (startpc1 == startpc &&
                 endpc1 == endpc &&
                 handler_pc1 == handler_pc) {
                 code.addCatch(startpc1, endpc1, handler_pc1,
                               (char)catch_type);
             } else {
                 if (!useJsrLocally && !target.generateStackMapTable()) {
                     useJsrLocally = true;
                     throw new CodeSizeOverflow();
                 } else {
                     log.error(pos, "limit.code.too.large.for.try.stmt");
                     nerrs++;
                 }
             }
         }
     /** Very roughly estimate the number of instructions needed for
      *  the given tree.
      */
     int estimateCodeComplexity(JCTree tree) {
         if (tree == null) return 0;
         class ComplexityScanner extends TreeScanner {
             int complexity = 0;
             public void scan(JCTree tree) {
                 if (complexity > jsrlimit) return;
                 super.scan(tree);
             }
             public void visitClassDef(JCClassDecl tree) {}
             public void visitDoLoop(JCDoWhileLoop tree)
                 { super.visitDoLoop(tree); complexity++; }
             public void visitWhileLoop(JCWhileLoop tree)
                 { super.visitWhileLoop(tree); complexity++; }
             public void visitForLoop(JCForLoop tree)
                 { super.visitForLoop(tree); complexity++; }
             public void visitSwitch(JCSwitch tree)
                 { super.visitSwitch(tree); complexity+=5; }
             public void visitCase(JCCase tree)
                 { super.visitCase(tree); complexity++; }
             public void visitSynchronized(JCSynchronized tree)
                 { super.visitSynchronized(tree); complexity+=6; }
             public void visitTry(JCTry tree)
                 { super.visitTry(tree);
                   if (tree.finalizer != null) complexity+=6; }
             public void visitCatch(JCCatch tree)
                 { super.visitCatch(tree); complexity+=2; }
             public void visitConditional(JCConditional tree)
                 { super.visitConditional(tree); complexity+=2; }
             public void visitIf(JCIf tree)
                 { super.visitIf(tree); complexity+=2; }
             // note: for break, continue, and return we don't take unwind() into account.
             public void visitBreak(JCBreak tree)
                 { super.visitBreak(tree); complexity+=1; }
             public void visitContinue(JCContinue tree)
                 { super.visitContinue(tree); complexity+=1; }
             public void visitReturn(JCReturn tree)
                 { super.visitReturn(tree); complexity+=1; }
             public void visitThrow(JCThrow tree)
                 { super.visitThrow(tree); complexity+=1; }
             public void visitAssert(JCAssert tree)
                 { super.visitAssert(tree); complexity+=5; }
             public void visitApply(JCMethodInvocation tree)
                 { super.visitApply(tree); complexity+=2; }
             public void visitNewClass(JCNewClass tree)
                 { scan(tree.encl); scan(tree.args); complexity+=2; }
             public void visitNewArray(JCNewArray tree)
                 { super.visitNewArray(tree); complexity+=5; }
             public void visitAssign(JCAssign tree)
                 { super.visitAssign(tree); complexity+=1; }
             public void visitAssignop(JCAssignOp tree)
                 { super.visitAssignop(tree); complexity+=2; }
             public void visitUnary(JCUnary tree)
                 { complexity+=1;
                   if (tree.type.constValue() == null) super.visitUnary(tree); }
             public void visitBinary(JCBinary tree)
                 { complexity+=1;
                   if (tree.type.constValue() == null) super.visitBinary(tree); }
             public void visitTypeTest(JCInstanceOf tree)
                 { super.visitTypeTest(tree); complexity+=1; }
             public void visitIndexed(JCArrayAccess tree)
                 { super.visitIndexed(tree); complexity+=1; }
             public void visitSelect(JCFieldAccess tree)
                 { super.visitSelect(tree);
                   if (tree.sym.kind == VAR) complexity+=1; }
             public void visitIdent(JCIdent tree) {
                 if (tree.sym.kind == VAR) {
                     complexity+=1;
                     if (tree.type.constValue() == null &&
                         tree.sym.owner.kind == TYP)
                         complexity+=1;
                 }
             }
             public void visitLiteral(JCLiteral tree)
                 { complexity+=1; }
             public void visitTree(JCTree tree) {}
             public void visitWildcard(JCWildcard tree) {
                 throw new AssertionError(this.getClass().getName());
             }
         }
         ComplexityScanner scanner = new ComplexityScanner();
         tree.accept(scanner);
         return scanner.complexity;
     }
     public void visitIf(JCIf tree) {
         int limit = code.nextreg;
         Chain thenExit = null;
         CondItem c = genCond(TreeInfo.skipParens(tree.cond),
                              CRT_FLOW_CONTROLLER);
         Chain elseChain = c.jumpFalse();
         if (!c.isFalse()) {
             code.resolve(c.trueJumps);
             genStat(tree.thenpart, env, CRT_STATEMENT | CRT_FLOW_TARGET);
             thenExit = code.branch(goto_);
             if (varDebugInfo && lvtRanges.containsKey(code.meth, tree.thenpart)) {
                 code.closeAliveRanges(tree.thenpart, code.cp);
             }
         }
         if (elseChain != null) {
             code.resolve(elseChain);
             if (tree.elsepart != null) {
                 genStat(tree.elsepart, env,CRT_STATEMENT | CRT_FLOW_TARGET);
                 if (varDebugInfo && lvtRanges.containsKey(code.meth, tree.elsepart)) {
                     code.closeAliveRanges(tree.elsepart);
                 }
             }
         }
         code.resolve(thenExit);
         code.endScopes(limit);
     }
     public void visitExec(JCExpressionStatement tree) {
         // Optimize x++ to ++x and x-- to --x.
         JCExpression e = tree.expr;
         switch (e.getTag()) {
             case POSTINC:
                 ((JCUnary) e).setTag(PREINC);
                 break;
             case POSTDEC:
                 ((JCUnary) e).setTag(PREDEC);
                 break;
         }
         genExpr(tree.expr, tree.expr.type).drop();
     }
     public void visitBreak(JCBreak tree) {
         Env<GenContext> targetEnv = unwind(tree.target, env);
         Assert.check(code.state.stacksize == 0);
         targetEnv.info.addExit(code.branch(goto_));
         endFinalizerGaps(env, targetEnv);
     }
     public void visitContinue(JCContinue tree) {
         Env<GenContext> targetEnv = unwind(tree.target, env);
         Assert.check(code.state.stacksize == 0);
         targetEnv.info.addCont(code.branch(goto_));
         endFinalizerGaps(env, targetEnv);
     }
     public void visitReturn(JCReturn tree) {
         int limit = code.nextreg;
         final Env<GenContext> targetEnv;
         if (tree.expr != null) {
             Item r = genExpr(tree.expr, pt).load();
             if (hasFinally(env.enclMethod, env)) {
                 r = makeTemp(pt);
                 r.store();
             }
             targetEnv = unwind(env.enclMethod, env);
             r.load();
             code.emitop0(ireturn + Code.truncate(Code.typecode(pt)));
         } else {
             /*  If we have a statement like:
              *
              *  return;
              *
              *  we need to store the code.pendingStatPos value before generating
              *  the finalizer.
              */
             int tmpPos = code.pendingStatPos;
             targetEnv = unwind(env.enclMethod, env);
             code.pendingStatPos = tmpPos;
             code.emitop0(return_);
         }
         endFinalizerGaps(env, targetEnv);
         code.endScopes(limit);
     }
     public void visitThrow(JCThrow tree) {
         genExpr(tree.expr, tree.expr.type).load();
         code.emitop0(athrow);
     }
 /* ************************************************************************
  * Visitor methods for expressions
  *************************************************************************/
     public void visitApply(JCMethodInvocation tree) {
         setTypeAnnotationPositions(tree.pos);
         // Generate code for method.
         Item m = genExpr(tree.meth, methodType);
         // Generate code for all arguments, where the expected types are
         // the parameters of the method's external type (that is, any implicit
         // outer instance of a super(...) call appears as first parameter).
         MethodSymbol msym = (MethodSymbol)TreeInfo.symbol(tree.meth);
         genArgs(tree.args,
                 msym.externalType(types).getParameterTypes());
         if (!msym.isDynamic()) {
             code.statBegin(tree.pos);
         }
         result = m.invoke();
     }
     public void visitConditional(JCConditional tree) {
         Chain thenExit = null;
         CondItem c = genCond(tree.cond, CRT_FLOW_CONTROLLER);
         Chain elseChain = c.jumpFalse();
         if (!c.isFalse()) {
             code.resolve(c.trueJumps);
             int startpc = genCrt ? code.curCP() : 0;
             genExpr(tree.truepart, pt).load();
             code.state.forceStackTop(tree.type);
             if (genCrt) code.crt.put(tree.truepart, CRT_FLOW_TARGET,
                                      startpc, code.curCP());
             thenExit = code.branch(goto_);
         }
         if (elseChain != null) {
             code.resolve(elseChain);
             int startpc = genCrt ? code.curCP() : 0;
             genExpr(tree.falsepart, pt).load();
             code.state.forceStackTop(tree.type);
             if (genCrt) code.crt.put(tree.falsepart, CRT_FLOW_TARGET,
                                      startpc, code.curCP());
         }
         code.resolve(thenExit);
         result = items.makeStackItem(pt);
     }
     private void setTypeAnnotationPositions(int treePos) {
         MethodSymbol meth = code.meth;
         boolean initOrClinit = code.meth.getKind() == javax.lang.model.element.ElementKind.CONSTRUCTOR
                 || code.meth.getKind() == javax.lang.model.element.ElementKind.STATIC_INIT;
         for (Attribute.TypeCompound ta : meth.getRawTypeAttributes()) {
             if (ta.hasUnknownPosition())
                 ta.tryFixPosition();
             if (ta.position.matchesPos(treePos))
                 ta.position.updatePosOffset(code.cp);
         }
         if (!initOrClinit)
             return;
         for (Attribute.TypeCompound ta : meth.owner.getRawTypeAttributes()) {
             if (ta.hasUnknownPosition())
                 ta.tryFixPosition();
             if (ta.position.matchesPos(treePos))
                 ta.position.updatePosOffset(code.cp);
         }
         ClassSymbol clazz = meth.enclClass();
         for (Symbol s : new com.sun.tools.javac.model.FilteredMemberList(clazz.members())) {
             if (!s.getKind().isField())
                 continue;
             for (Attribute.TypeCompound ta : s.getRawTypeAttributes()) {
                 if (ta.hasUnknownPosition())
                     ta.tryFixPosition();
                 if (ta.position.matchesPos(treePos))
                     ta.position.updatePosOffset(code.cp);
             }
         }
     }
     public void visitNewClass(JCNewClass tree) {
         // Enclosing instances or anonymous classes should have been eliminated
         // by now.
         Assert.check(tree.encl == null && tree.def == null);
         setTypeAnnotationPositions(tree.pos);
         code.emitop2(new_, makeRef(tree.pos(), tree.type));
         code.emitop0(dup);
         // Generate code for all arguments, where the expected types are
         // the parameters of the constructor's external type (that is,
         // any implicit outer instance appears as first parameter).
         genArgs(tree.args, tree.constructor.externalType(types).getParameterTypes());
         items.makeMemberItem(tree.constructor, true).invoke();
         result = items.makeStackItem(tree.type);
     }
     public void visitNewArray(JCNewArray tree) {
         setTypeAnnotationPositions(tree.pos);
         if (tree.elems != null) {
             Type elemtype = types.elemtype(tree.type);
             loadIntConst(tree.elems.length());
             Item arr = makeNewArray(tree.pos(), tree.type, 1);
             int i = 0;
             for (List<JCExpression> l = tree.elems; l.nonEmpty(); l = l.tail) {
                 arr.duplicate();
                 loadIntConst(i);
                 i++;
                 genExpr(l.head, elemtype).load();
                 items.makeIndexedItem(elemtype).store();
             }
             result = arr;
         } else {
             for (List<JCExpression> l = tree.dims; l.nonEmpty(); l = l.tail) {
                 genExpr(l.head, syms.intType).load();
             }
             result = makeNewArray(tree.pos(), tree.type, tree.dims.length());
         }
     }
 //where
         /** Generate code to create an array with given element type and number
          *  of dimensions.
          */
         Item makeNewArray(DiagnosticPosition pos, Type type, int ndims) {
             Type elemtype = types.elemtype(type);
             if (types.dimensions(type) > ClassFile.MAX_DIMENSIONS) {
                 log.error(pos, "limit.dimensions");
                 nerrs++;
             }
             int elemcode = Code.arraycode(elemtype);
             if (elemcode == 0 || (elemcode == 1 && ndims == 1)) {
                 code.emitAnewarray(makeRef(pos, elemtype), type);
             } else if (elemcode == 1) {
                 code.emitMultianewarray(ndims, makeRef(pos, type), type);
             } else {
                 code.emitNewarray(elemcode, type);
             }
             return items.makeStackItem(type);
         }
     public void visitParens(JCParens tree) {
         result = genExpr(tree.expr, tree.expr.type);
     }
     public void visitAssign(JCAssign tree) {
         Item l = genExpr(tree.lhs, tree.lhs.type);
         genExpr(tree.rhs, tree.lhs.type).load();
         result = items.makeAssignItem(l);
     }
     public void visitAssignop(JCAssignOp tree) {
         OperatorSymbol operator = (OperatorSymbol) tree.operator;
         Item l;
         if (operator.opcode == string_add) {
             // Generate code to make a string buffer
             makeStringBuffer(tree.pos());
             // Generate code for first string, possibly save one
             // copy under buffer
             l = genExpr(tree.lhs, tree.lhs.type);
             if (l.width() > 0) {
                 code.emitop0(dup_x1 + 3 * (l.width() - 1));
             }
             // Load first string and append to buffer.
             l.load();
             appendString(tree.lhs);
             // Append all other strings to buffer.
             appendStrings(tree.rhs);
             // Convert buffer to string.
             bufferToString(tree.pos());
         } else {
             // Generate code for first expression
             l = genExpr(tree.lhs, tree.lhs.type);
             // If we have an increment of -32768 to +32767 of a local
             // int variable we can use an incr instruction instead of
             // proceeding further.
             if ((tree.hasTag(PLUS_ASG) || tree.hasTag(MINUS_ASG)) &&
                 l instanceof LocalItem &&
                 tree.lhs.type.getTag().isSubRangeOf(INT) &&
                 tree.rhs.type.getTag().isSubRangeOf(INT) &&
                 tree.rhs.type.constValue() != null) {
                 int ival = ((Number) tree.rhs.type.constValue()).intValue();
                 if (tree.hasTag(MINUS_ASG)) ival = -ival;
                 ((LocalItem)l).incr(ival);
                 result = l;
                 return;
             }
             // Otherwise, duplicate expression, load one copy
             // and complete binary operation.
             l.duplicate();
             l.coerce(operator.type.getParameterTypes().head).load();
             completeBinop(tree.lhs, tree.rhs, operator).coerce(tree.lhs.type);
         }
         result = items.makeAssignItem(l);
     }
     public void visitUnary(JCUnary tree) {
         OperatorSymbol operator = (OperatorSymbol)tree.operator;
         if (tree.hasTag(NOT)) {
             CondItem od = genCond(tree.arg, false);
             result = od.negate();
         } else {
             Item od = genExpr(tree.arg, operator.type.getParameterTypes().head);
             switch (tree.getTag()) {
             case POS:
                 result = od.load();
                 break;
             case NEG:
                 result = od.load();
                 code.emitop0(operator.opcode);
                 break;
             case COMPL:
                 result = od.load();
                 emitMinusOne(od.typecode);
                 code.emitop0(operator.opcode);
                 break;
             case PREINC: case PREDEC:
                 od.duplicate();
                 if (od instanceof LocalItem &&
                     (operator.opcode == iadd || operator.opcode == isub)) {
                     ((LocalItem)od).incr(tree.hasTag(PREINC) ? 1 : -1);
                     result = od;
                 } else {
                     od.load();
                     code.emitop0(one(od.typecode));
                     code.emitop0(operator.opcode);
                     // Perform narrowing primitive conversion if byte,
                     // char, or short.  Fix for 4304655.
                     if (od.typecode != INTcode &&
                         Code.truncate(od.typecode) == INTcode)
                       code.emitop0(int2byte + od.typecode - BYTEcode);
                     result = items.makeAssignItem(od);
                 }
                 break;
             case POSTINC: case POSTDEC:
                 od.duplicate();
                 if (od instanceof LocalItem &&
                     (operator.opcode == iadd || operator.opcode == isub)) {
                     Item res = od.load();
                     ((LocalItem)od).incr(tree.hasTag(POSTINC) ? 1 : -1);
                     result = res;
                 } else {
                     Item res = od.load();
                     od.stash(od.typecode);
                     code.emitop0(one(od.typecode));
                     code.emitop0(operator.opcode);
                     // Perform narrowing primitive conversion if byte,
                     // char, or short.  Fix for 4304655.
                     if (od.typecode != INTcode &&
                         Code.truncate(od.typecode) == INTcode)
                       code.emitop0(int2byte + od.typecode - BYTEcode);
                     od.store();
                     result = res;
                 }
                 break;
             case NULLCHK:
                 result = od.load();
                 code.emitop0(dup);
                 genNullCheck(tree.pos());
                 break;
             default:
                 Assert.error();
             }
         }
     }
     /** Generate a null check from the object value at stack top. */
     private void genNullCheck(DiagnosticPosition pos) {
         callMethod(pos, syms.objectType, names.getClass,
                    List.<Type>nil(), false);
         code.emitop0(pop);
     }
     public void visitBinary(JCBinary tree) {
         OperatorSymbol operator = (OperatorSymbol)tree.operator;
         if (operator.opcode == string_add) {
             // Create a string buffer.
             makeStringBuffer(tree.pos());
             // Append all strings to buffer.
             appendStrings(tree);
             // Convert buffer to string.
             bufferToString(tree.pos());
             result = items.makeStackItem(syms.stringType);
         } else if (tree.hasTag(AND)) {
             CondItem lcond = genCond(tree.lhs, CRT_FLOW_CONTROLLER);
             if (!lcond.isFalse()) {
                 Chain falseJumps = lcond.jumpFalse();
                 code.resolve(lcond.trueJumps);
                 CondItem rcond = genCond(tree.rhs, CRT_FLOW_TARGET);
                 result = items.
                     makeCondItem(rcond.opcode,
                                  rcond.trueJumps,
                                  Code.mergeChains(falseJumps,
                                                   rcond.falseJumps));
             } else {
                 result = lcond;
             }
         } else if (tree.hasTag(OR)) {
             CondItem lcond = genCond(tree.lhs, CRT_FLOW_CONTROLLER);
             if (!lcond.isTrue()) {
                 Chain trueJumps = lcond.jumpTrue();
                 code.resolve(lcond.falseJumps);
                 CondItem rcond = genCond(tree.rhs, CRT_FLOW_TARGET);
                 result = items.
                     makeCondItem(rcond.opcode,
                                  Code.mergeChains(trueJumps, rcond.trueJumps),
                                  rcond.falseJumps);
             } else {
                 result = lcond;
             }
         } else {
             Item od = genExpr(tree.lhs, operator.type.getParameterTypes().head);
             od.load();
             result = completeBinop(tree.lhs, tree.rhs, operator);
         }
     }
 //where
         /** Make a new string buffer.
          */
         void makeStringBuffer(DiagnosticPosition pos) {
             code.emitop2(new_, makeRef(pos, stringBufferType));
             code.emitop0(dup);
             callMethod(
                 pos, stringBufferType, names.init, List.<Type>nil(), false);
         }
         /** Append value (on tos) to string buffer (on tos - 1).
          */
         void appendString(JCTree tree) {
             Type t = tree.type.baseType();
             if (!t.isPrimitive() && t.tsym != syms.stringType.tsym) {
                 t = syms.objectType;
             }
             items.makeMemberItem(getStringBufferAppend(tree, t), false).invoke();
         }
         Symbol getStringBufferAppend(JCTree tree, Type t) {
             Assert.checkNull(t.constValue());
             Symbol method = stringBufferAppend.get(t);
             if (method == null) {
                 method = rs.resolveInternalMethod(tree.pos(),
                                                   attrEnv,
                                                   stringBufferType,
                                                   names.append,
                                                   List.of(t),
                                                   null);
                 stringBufferAppend.put(t, method);
             }
             return method;
         }
         /** Add all strings in tree to string buffer.
          */
         void appendStrings(JCTree tree) {
             tree = TreeInfo.skipParens(tree);
             if (tree.hasTag(PLUS) && tree.type.constValue() == null) {
                 JCBinary op = (JCBinary) tree;
                 if (op.operator.kind == MTH &&
                     ((OperatorSymbol) op.operator).opcode == string_add) {
                     appendStrings(op.lhs);
                     appendStrings(op.rhs);
                     return;
                 }
             }
             genExpr(tree, tree.type).load();
             appendString(tree);
         }
         /** Convert string buffer on tos to string.
          */
         void bufferToString(DiagnosticPosition pos) {
             callMethod(
                 pos,
                 stringBufferType,
                 names.toString,
                 List.<Type>nil(),
                 false);
         }
         /** Complete generating code for operation, with left operand
          *  already on stack.
          *  @param lhs       The tree representing the left operand.
          *  @param rhs       The tree representing the right operand.
          *  @param operator  The operator symbol.
          */
         Item completeBinop(JCTree lhs, JCTree rhs, OperatorSymbol operator) {
             MethodType optype = (MethodType)operator.type;
             int opcode = operator.opcode;
             if (opcode >= if_icmpeq && opcode <= if_icmple &&
                 rhs.type.constValue() instanceof Number &&
                 ((Number) rhs.type.constValue()).intValue() == 0) {
                 opcode = opcode + (ifeq - if_icmpeq);
             } else if (opcode >= if_acmpeq && opcode <= if_acmpne &&
                        TreeInfo.isNull(rhs)) {
                 opcode = opcode + (if_acmp_null - if_acmpeq);
             } else {
                 // The expected type of the right operand is
                 // the second parameter type of the operator, except for
                 // shifts with long shiftcount, where we convert the opcode
                 // to a short shift and the expected type to int.
                 Type rtype = operator.erasure(types).getParameterTypes().tail.head;
                 if (opcode >= ishll && opcode <= lushrl) {
                     opcode = opcode + (ishl - ishll);
                     rtype = syms.intType;
                 }
                 // Generate code for right operand and load.
                 genExpr(rhs, rtype).load();
                 // If there are two consecutive opcode instructions,
                 // emit the first now.
                 if (opcode >= (1 << preShift)) {
                     code.emitop0(opcode >> preShift);
                     opcode = opcode & 0xFF;
                 }
             }
             if (opcode >= ifeq && opcode <= if_acmpne ||
                 opcode == if_acmp_null || opcode == if_acmp_nonnull) {
                 return items.makeCondItem(opcode);
             } else {
                 code.emitop0(opcode);
                 return items.makeStackItem(optype.restype);
             }
         }
     public void visitTypeCast(JCTypeCast tree) {
         setTypeAnnotationPositions(tree.pos);
         result = genExpr(tree.expr, tree.clazz.type).load();
         // Additional code is only needed if we cast to a reference type
         // which is not statically a supertype of the expression's type.
         // For basic types, the coerce(...) in genExpr(...) will do
         // the conversion.
         if (!tree.clazz.type.isPrimitive() &&
             types.asSuper(tree.expr.type, tree.clazz.type.tsym) == null) {
             code.emitop2(checkcast, makeRef(tree.pos(), tree.clazz.type));
         }
     }
     public void visitWildcard(JCWildcard tree) {
         throw new AssertionError(this.getClass().getName());
     }
     public void visitTypeTest(JCInstanceOf tree) {
         setTypeAnnotationPositions(tree.pos);
         genExpr(tree.expr, tree.expr.type).load();
         code.emitop2(instanceof_, makeRef(tree.pos(), tree.clazz.type));
         result = items.makeStackItem(syms.booleanType);
     }
     public void visitIndexed(JCArrayAccess tree) {
         genExpr(tree.indexed, tree.indexed.type).load();
         genExpr(tree.index, syms.intType).load();
         result = items.makeIndexedItem(tree.type);
     }
     public void visitIdent(JCIdent tree) {
         Symbol sym = tree.sym;
         if (tree.name == names._this || tree.name == names._super) {
             Item res = tree.name == names._this
                 ? items.makeThisItem()
                 : items.makeSuperItem();
             if (sym.kind == MTH) {
                 // Generate code to address the constructor.
                 res.load();
                 res = items.makeMemberItem(sym, true);
             }
             result = res;
         } else if (sym.kind == VAR && sym.owner.kind == MTH) {
             result = items.makeLocalItem((VarSymbol)sym);
         } else if (isInvokeDynamic(sym)) {
             result = items.makeDynamicItem(sym);
         } else if ((sym.flags() & STATIC) != 0) {
             if (!isAccessSuper(env.enclMethod))
                 sym = binaryQualifier(sym, env.enclClass.type);
             result = items.makeStaticItem(sym);
         } else {
             items.makeThisItem().load();
             sym = binaryQualifier(sym, env.enclClass.type);
             result = items.makeMemberItem(sym, (sym.flags() & PRIVATE) != 0);
         }
     }
     public void visitSelect(JCFieldAccess tree) {
         Symbol sym = tree.sym;
         if (tree.name == names._class) {
             Assert.check(target.hasClassLiterals());
             code.emitLdc(makeRef(tree.pos(), tree.selected.type));
             result = items.makeStackItem(pt);
             return;
        }
         Symbol ssym = TreeInfo.symbol(tree.selected);
         // Are we selecting via super?
         boolean selectSuper =
             ssym != null && (ssym.kind == TYP || ssym.name == names._super);
         // Are we accessing a member of the superclass in an access method
         // resulting from a qualified super?
         boolean accessSuper = isAccessSuper(env.enclMethod);
         Item base = (selectSuper)
             ? items.makeSuperItem()
             : genExpr(tree.selected, tree.selected.type);
         if (sym.kind == VAR && ((VarSymbol) sym).getConstValue() != null) {
             // We are seeing a variable that is constant but its selecting
             // expression is not.
             if ((sym.flags() & STATIC) != 0) {
                 if (!selectSuper && (ssym == null || ssym.kind != TYP))
                     base = base.load();
                 base.drop();
             } else {
                 base.load();
                 genNullCheck(tree.selected.pos());
             }
             result = items.
                 makeImmediateItem(sym.type, ((VarSymbol) sym).getConstValue());
         } else {
             if (isInvokeDynamic(sym)) {
                 result = items.makeDynamicItem(sym);
                 return;
             } else {
                 sym = binaryQualifier(sym, tree.selected.type);
             }
             if ((sym.flags() & STATIC) != 0) {
                 if (!selectSuper && (ssym == null || ssym.kind != TYP))
                     base = base.load();
                 base.drop();
                 result = items.makeStaticItem(sym);
             } else {
                 base.load();
                 if (sym == syms.lengthVar) {
                     code.emitop0(arraylength);
                     result = items.makeStackItem(syms.intType);
                 } else {
                     result = items.
                         makeMemberItem(sym,
                                        (sym.flags() & PRIVATE) != 0 ||
                                        selectSuper || accessSuper);
                 }
             }
         }
     }
     public boolean isInvokeDynamic(Symbol sym) {
         return sym.kind == MTH && ((MethodSymbol)sym).isDynamic();
     }
     public void visitLiteral(JCLiteral tree) {
         if (tree.type.hasTag(BOT)) {
             code.emitop0(aconst_null);
             if (types.dimensions(pt) > 1) {
                 code.emitop2(checkcast, makeRef(tree.pos(), pt));
                 result = items.makeStackItem(pt);
             } else {
                 result = items.makeStackItem(tree.type);
             }
         }
         else
             result = items.makeImmediateItem(tree.type, tree.value);
     }
     public void visitLetExpr(LetExpr tree) {
         int limit = code.nextreg;
         genStats(tree.defs, env);
         result = genExpr(tree.expr, tree.expr.type).load();
         code.endScopes(limit);
     }
     private void generateReferencesToPrunedTree(ClassSymbol classSymbol, Pool pool) {
         List<JCTree> prunedInfo = lower.prunedTree.get(classSymbol);
         if (prunedInfo != null) {
             for (JCTree prunedTree: prunedInfo) {
                 prunedTree.accept(classReferenceVisitor);
             }
         }
     }
 /* ************************************************************************
  * main method
  *************************************************************************/
     /** Generate code for a class definition.
      *  @param env   The attribution environment that belongs to the
      *               outermost class containing this class definition.
      *               We need this for resolving some additional symbols.
      *  @param cdef  The tree representing the class definition.
      *  @return      True if code is generated with no errors.
      */
     public boolean genClass(Env<AttrContext> env, JCClassDecl cdef) {
         try {
             attrEnv = env;
             ClassSymbol c = cdef.sym;
             this.toplevel = env.toplevel;
             this.endPosTable = toplevel.endPositions;
             // If this is a class definition requiring Miranda methods,
             // add them.
             if (generateIproxies &&
                 (c.flags() & (INTERFACE|ABSTRACT)) == ABSTRACT
                 && !allowGenerics // no Miranda methods available with generics
                 )
                 implementInterfaceMethods(c);
             cdef.defs = normalizeDefs(cdef.defs, c);
             c.pool = pool;
             pool.reset();
             generateReferencesToPrunedTree(c, pool);
             Env<GenContext> localEnv =
                 new Env<GenContext>(cdef, new GenContext());
             localEnv.toplevel = env.toplevel;
             localEnv.enclClass = cdef;
             /*  We must not analyze synthetic methods
              */
             if (varDebugInfo && (cdef.sym.flags() & SYNTHETIC) == 0) {
                 try {
                     new LVTAssignAnalyzer().analyzeTree(localEnv);
                 } catch (Throwable e) {
                     throw e;
                 }
             }
             for (List<JCTree> l = cdef.defs; l.nonEmpty(); l = l.tail) {
                 genDef(l.head, localEnv);
             }
             if (pool.numEntries() > Pool.MAX_ENTRIES) {
                 log.error(cdef.pos(), "limit.pool");
                 nerrs++;
             }
             if (nerrs != 0) {
                 // if errors, discard code
                 for (List<JCTree> l = cdef.defs; l.nonEmpty(); l = l.tail) {
                     if (l.head.hasTag(METHODDEF))
                         ((JCMethodDecl) l.head).sym.code = null;
                 }
             }
             cdef.defs = List.nil(); // discard trees
             return nerrs == 0;
         } finally {
             // note: this method does NOT support recursion.
             attrEnv = null;
             this.env = null;
             toplevel = null;
             endPosTable = null;
             nerrs = 0;
         }
     }
 /* ************************************************************************
  * Auxiliary classes
  *************************************************************************/
     /** An abstract class for finalizer generation.
      */
     abstract class GenFinalizer {
         /** Generate code to clean up when unwinding. */
         abstract void gen();
         /** Generate code to clean up at last. */
         abstract void genLast();
         /** Does this finalizer have some nontrivial cleanup to perform? */
         boolean hasFinalizer() { return true; }
     }
     /** code generation contexts,
      *  to be used as type parameter for environments.
      */
     static class GenContext {
         /** A chain for all unresolved jumps that exit the current environment.
          */
         Chain exit = null;
         /** A chain for all unresolved jumps that continue in the
          *  current environment.
          */
         Chain cont = null;
         /** A closure that generates the finalizer of the current environment.
          *  Only set for Synchronized and Try contexts.
          */
         GenFinalizer finalize = null;
         /** Is this a switch statement?  If so, allocate registers
          * even when the variable declaration is unreachable.
          */
         boolean isSwitch = false;
         /** A list buffer containing all gaps in the finalizer range,
          *  where a catch all exception should not apply.
          */
         ListBuffer<Integer> gaps = null;
         /** Add given chain to exit chain.
          */
         void addExit(Chain c)  {
             exit = Code.mergeChains(c, exit);
         }
         /** Add given chain to cont chain.
          */
         void addCont(Chain c) {
             cont = Code.mergeChains(c, cont);
         }
     }
     class LVTAssignAnalyzer
         extends Flow.AbstractAssignAnalyzer<LVTAssignAnalyzer.LVTAssignPendingExit> {
         final LVTBits lvtInits;
         /*  This class is anchored to a context dependent tree. The tree can
          *  vary inside the same instruction for example in the switch instruction
          *  the same FlowBits instance can be anchored to the whole tree, or
          *  to a given case. The aim is to always anchor the bits to the tree
          *  capable of closing a DA range.
          */
         class LVTBits extends Bits {
             JCTree currentTree;
             private int[] oldBits = null;
             BitsState stateBeforeOp;
             @Override
             public void clear() {
                 generalOp(null, -1, BitsOpKind.CLEAR);
             }
             @Override
             protected void internalReset() {
                 super.internalReset();
                 oldBits = null;
             }
             @Override
             public Bits assign(Bits someBits) {
                 // bits can be null
                 oldBits = bits;
                 stateBeforeOp = currentState;
                 super.assign(someBits);
                 changed();
                 return this;
             }
             @Override
             public void excludeFrom(int start) {
                 generalOp(null, start, BitsOpKind.EXCL_RANGE);
             }
             @Override
             public void excl(int x) {
                 Assert.check(x >= 0);
                 generalOp(null, x, BitsOpKind.EXCL_BIT);
             }
             @Override
             public Bits andSet(Bits xs) {
                return generalOp(xs, -1, BitsOpKind.AND_SET);
             }
             @Override
             public Bits orSet(Bits xs) {
                 return generalOp(xs, -1, BitsOpKind.OR_SET);
             }
             @Override
             public Bits diffSet(Bits xs) {
                 return generalOp(xs, -1, BitsOpKind.DIFF_SET);
             }
             @Override
             public Bits xorSet(Bits xs) {
                 return generalOp(xs, -1, BitsOpKind.XOR_SET);
             }
             private Bits generalOp(Bits xs, int i, BitsOpKind opKind) {
                 Assert.check(currentState != BitsState.UNKNOWN);
                 oldBits = dupBits();
                 stateBeforeOp = currentState;
                 switch (opKind) {
                     case AND_SET:
                         super.andSet(xs);
                         break;
                     case OR_SET:
                         super.orSet(xs);
                         break;
                     case XOR_SET:
                         super.xorSet(xs);
                         break;
                     case DIFF_SET:
                         super.diffSet(xs);
                         break;
                     case CLEAR:
                         super.clear();
                         break;
                     case EXCL_BIT:
                         super.excl(i);
                         break;
                     case EXCL_RANGE:
                         super.excludeFrom(i);
                         break;
                 }
                 changed();
                 return this;
             }
             /*  The tree we need to anchor the bits instance to.
              */
             LVTBits at(JCTree tree) {
                 this.currentTree = tree;
                 return this;
             }
             /*  If the instance should be changed but the tree is not a closing
              *  tree then a reset is needed or the former tree can mistakingly be
              *  used.
              */
             LVTBits resetTree() {
                 this.currentTree = null;
                 return this;
             }
             /** This method will be called after any operation that causes a change to
              *  the bits. Subclasses can thus override it in order to extract information
              *  from the changes produced to the bits by the given operation.
              */
             public void changed() {
                 if (currentTree != null &&
                         stateBeforeOp != BitsState.UNKNOWN &&
                         trackTree(currentTree)) {
                     List<VarSymbol> locals = lvtRanges
                             .getVars(currentMethod, currentTree);
                     locals = locals != null ?
                             locals : List.<VarSymbol>nil();
                     for (JCVariableDecl vardecl : vardecls) {
                         //once the first is null, the rest will be so.
                         if (vardecl == null) {
                             break;
                         }
                         if (trackVar(vardecl.sym) && bitChanged(vardecl.sym.adr)) {
                             locals = locals.prepend(vardecl.sym);
                         }
                     }
                     if (!locals.isEmpty()) {
                         lvtRanges.setEntry(currentMethod,
                                 currentTree, locals);
                     }
                 }
             }
             boolean bitChanged(int x) {
                 boolean isMemberOfBits = isMember(x);
                 int[] tmp = bits;
                 bits = oldBits;
                 boolean isMemberOfOldBits = isMember(x);
                 bits = tmp;
                 return (!isMemberOfBits && isMemberOfOldBits);
             }
             boolean trackVar(VarSymbol var) {
                 return (var.owner.kind == MTH &&
                         (var.flags() & PARAMETER) == 0 &&
                         trackable(var));
             }
             boolean trackTree(JCTree tree) {
                 switch (tree.getTag()) {
                     // of course a method closes the alive range of a local variable.
                     case METHODDEF:
                     // for while loops we want only the body
                     case WHILELOOP:
                         return false;
                 }
                 return true;
             }
         }
         public class LVTAssignPendingExit extends
                                     Flow.AbstractAssignAnalyzer<LVTAssignPendingExit>.AbstractAssignPendingExit {
             LVTAssignPendingExit(JCTree tree, final Bits inits, final Bits uninits) {
                 super(tree, inits, uninits);
             }
             @Override
             public void resolveJump(JCTree tree) {
                 lvtInits.at(tree);
                 super.resolveJump(tree);
             }
         }
         private LVTAssignAnalyzer() {
             flow.super();
             lvtInits = new LVTBits();
             inits = lvtInits;
         }
         @Override
         protected void markDead(JCTree tree) {
             lvtInits.at(tree).inclRange(returnadr, nextadr);
             super.markDead(tree);
         }
         @Override
         protected void merge(JCTree tree) {
             lvtInits.at(tree);
             super.merge(tree);
         }
         boolean isSyntheticOrMandated(Symbol sym) {
             return (sym.flags() & (SYNTHETIC | MANDATED)) != 0;
         }
         @Override
         protected boolean trackable(VarSymbol sym) {
             if (isSyntheticOrMandated(sym)) {
                 //fast check to avoid tracking synthetic or mandated variables
                 return false;
             }
             return super.trackable(sym);
         }
         @Override
         protected void initParam(JCVariableDecl def) {
             if (!isSyntheticOrMandated(def.sym)) {
                 super.initParam(def);
             }
         }
         @Override
         protected void assignToInits(JCTree tree, Bits bits) {
             lvtInits.at(tree);
             lvtInits.assign(bits);
         }
         @Override
         protected void andSetInits(JCTree tree, Bits bits) {
             lvtInits.at(tree);
             lvtInits.andSet(bits);
         }
         @Override
         protected void orSetInits(JCTree tree, Bits bits) {
             lvtInits.at(tree);
             lvtInits.orSet(bits);
         }
         @Override
         protected void exclVarFromInits(JCTree tree, int adr) {
             lvtInits.at(tree);
             lvtInits.excl(adr);
         }
         @Override
         protected LVTAssignPendingExit createNewPendingExit(JCTree tree, Bits inits, Bits uninits) {
             return new LVTAssignPendingExit(tree, inits, uninits);
         }
         MethodSymbol currentMethod;
         @Override
         public void visitMethodDef(JCMethodDecl tree) {
             if ((tree.sym.flags() & (SYNTHETIC | GENERATEDCONSTR)) != 0
                     && (tree.sym.flags() & LAMBDA_METHOD) == 0) {
                 return;
             }
             if (tree.name.equals(names.clinit)) {
                 return;
             }
             boolean enumClass = (tree.sym.owner.flags() & ENUM) != 0;
             if (enumClass &&
                     (tree.name.equals(names.valueOf) ||
                     tree.name.equals(names.values) ||
                     tree.name.equals(names.init))) {
                 return;
             }
             currentMethod = tree.sym;
             super.visitMethodDef(tree);
         }
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/jvm/Gen.java@9ca8d8713094 (annotated)

src/share/classes/com/sun/tools/javac/jvm/Gen.java