Mercurial > jdk8-mips64-public > langtools / file revision

 /*

  * Copyright (c) 1999, 2015, 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.tree.TreeInfo.PosKind;

 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;

     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");

         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 if ((block.flags & SYNTHETIC) == 0)

                     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());

                         /* if the init contains a reference to an external class, add it to the

                          * constant's pool

                          */

                         vdef.init.accept(classReferenceVisitor);

                     }

                 }

                 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);

             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);

                 code.resolve(loopEnv.info.cont);

                 genStats(step, loopEnv);

                 code.resolve(code.branch(goto_), startpc);

                 code.resolve(loopDone);

             } else {

                 genStat(body, loopEnv, CRT_STATEMENT | CRT_FLOW_TARGET);

                 code.resolve(loopEnv.info.cont);

                 genStats(step, loopEnv);

                 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);

             }

         }

     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);

             }

             // 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_);

             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, PosKind.FIRST_STAT_POS));

                 code.markStatBegin();

                 Item excVar = makeTemp(syms.throwableType);

                 excVar.store();

                 genFinalizer(env);

                 code.resolvePending();

                 code.statBegin(TreeInfo.finalizerPos(env.tree, PosKind.END_POS));

                 code.markStatBegin();

                 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, PosKind.FIRST_STAT_POS));

                     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 (elseChain != null) {

             code.resolve(elseChain);

             if (tree.elsepart != null) {

                 genStat(tree.elsepart, env,CRT_STATEMENT | CRT_FLOW_TARGET);

             }

         }

         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;

         /* Save and then restore the location of the return in case a finally

          * is expanded (with unwind()) in the middle of our bytecodes.

          */

         int tmpPos = code.pendingStatPos;

         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);

             code.pendingStatPos = tmpPos;

             r.load();

             code.emitop0(ireturn + Code.truncate(Code.typecode(pt)));

         } else {

             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);

             c.pool = pool;

             pool.reset();

             /* method normalizeDefs() can add references to external classes into the constant pool

              * so it should be called after pool.reset()

              */

             cdef.defs = normalizeDefs(cdef.defs, c);

             generateReferencesToPrunedTree(c, pool);

             Env<GenContext> localEnv =

                 new Env<GenContext>(cdef, new GenContext());

             localEnv.toplevel = env.toplevel;

             localEnv.enclClass = cdef;

             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);

         }

     }

 }