1 /*
   2  * Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.javac.jvm;
  27 
  28 import java.util.HashMap;
  29 import java.util.Map;
  30 import java.util.Set;
  31 
  32 import com.sun.tools.javac.jvm.PoolConstant.LoadableConstant;
  33 import com.sun.tools.javac.tree.TreeInfo.PosKind;
  34 import com.sun.tools.javac.util.*;
  35 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
  36 import com.sun.tools.javac.util.List;
  37 import com.sun.tools.javac.code.*;
  38 import com.sun.tools.javac.code.Attribute.TypeCompound;
  39 import com.sun.tools.javac.code.Symbol.VarSymbol;
  40 import com.sun.tools.javac.comp.*;
  41 import com.sun.tools.javac.tree.*;
  42 
  43 import com.sun.tools.javac.code.Symbol.*;
  44 import com.sun.tools.javac.code.Type.*;
  45 import com.sun.tools.javac.jvm.Code.*;
  46 import com.sun.tools.javac.jvm.Items.*;
  47 import com.sun.tools.javac.resources.CompilerProperties.Errors;
  48 import com.sun.tools.javac.tree.EndPosTable;
  49 import com.sun.tools.javac.tree.JCTree.*;
  50 
  51 import static com.sun.tools.javac.code.Flags.*;
  52 import static com.sun.tools.javac.code.Kinds.Kind.*;
  53 import static com.sun.tools.javac.code.TypeTag.*;
  54 import static com.sun.tools.javac.jvm.ByteCodes.*;
  55 import static com.sun.tools.javac.jvm.CRTFlags.*;
  56 import static com.sun.tools.javac.main.Option.*;
  57 import static com.sun.tools.javac.tree.JCTree.Tag.*;
  58 
  59 /** This pass maps flat Java (i.e. without inner classes) to bytecodes.
  60  *
  61  *  <p><b>This is NOT part of any supported API.
  62  *  If you write code that depends on this, you do so at your own risk.
  63  *  This code and its internal interfaces are subject to change or
  64  *  deletion without notice.</b>
  65  */
  66 public class Gen extends JCTree.Visitor {
  67     protected static final Context.Key<Gen> genKey = new Context.Key<>();
  68 
  69     private final Log log;
  70     private final Symtab syms;
  71     private final Check chk;
  72     private final Resolve rs;
  73     private final TreeMaker make;
  74     private final Names names;
  75     private final Target target;
  76     private final String accessDollar;
  77     private final Types types;
  78     private final Lower lower;
  79     private final Annotate annotate;
  80     private final StringConcat concat;
  81 
  82     /** Format of stackmap tables to be generated. */
  83     private final Code.StackMapFormat stackMap;
  84 
  85     /** A type that serves as the expected type for all method expressions.
  86      */
  87     private final Type methodType;
  88 
  89     public static Gen instance(Context context) {
  90         Gen instance = context.get(genKey);
  91         if (instance == null)
  92             instance = new Gen(context);
  93         return instance;
  94     }
  95 
  96     /** Constant pool writer, set by genClass.
  97      */
  98     final PoolWriter poolWriter;
  99 
 100     @SuppressWarnings("this-escape")
 101     protected Gen(Context context) {
 102         context.put(genKey, this);
 103 
 104         names = Names.instance(context);
 105         log = Log.instance(context);
 106         syms = Symtab.instance(context);
 107         chk = Check.instance(context);
 108         rs = Resolve.instance(context);
 109         make = TreeMaker.instance(context);
 110         target = Target.instance(context);
 111         types = Types.instance(context);
 112         concat = StringConcat.instance(context);
 113 
 114         methodType = new MethodType(null, null, null, syms.methodClass);
 115         accessDollar = "access" + target.syntheticNameChar();
 116         lower = Lower.instance(context);
 117 
 118         Options options = Options.instance(context);
 119         lineDebugInfo =
 120             options.isUnset(G_CUSTOM) ||
 121             options.isSet(G_CUSTOM, "lines");
 122         varDebugInfo =
 123             options.isUnset(G_CUSTOM)
 124             ? options.isSet(G)
 125             : options.isSet(G_CUSTOM, "vars");
 126         genCrt = options.isSet(XJCOV);
 127         debugCode = options.isSet("debug.code");
 128         disableVirtualizedPrivateInvoke = options.isSet("disableVirtualizedPrivateInvoke");
 129         poolWriter = new PoolWriter(types, names);
 130 
 131         // ignore cldc because we cannot have both stackmap formats
 132         this.stackMap = StackMapFormat.JSR202;
 133         annotate = Annotate.instance(context);
 134         qualifiedSymbolCache = new HashMap<>();
 135     }
 136 
 137     /** Switches
 138      */
 139     private final boolean lineDebugInfo;
 140     private final boolean varDebugInfo;
 141     private final boolean genCrt;
 142     private final boolean debugCode;
 143     private boolean disableVirtualizedPrivateInvoke;
 144 
 145     /** Code buffer, set by genMethod.
 146      */
 147     private Code code;
 148 
 149     /** Items structure, set by genMethod.
 150      */
 151     private Items items;
 152 
 153     /** Environment for symbol lookup, set by genClass
 154      */
 155     private Env<AttrContext> attrEnv;
 156 
 157     /** The top level tree.
 158      */
 159     private JCCompilationUnit toplevel;
 160 
 161     /** The number of code-gen errors in this class.
 162      */
 163     private int nerrs = 0;
 164 
 165     /** An object containing mappings of syntax trees to their
 166      *  ending source positions.
 167      */
 168     EndPosTable endPosTable;
 169 
 170     boolean inCondSwitchExpression;
 171     Chain switchExpressionTrueChain;
 172     Chain switchExpressionFalseChain;
 173     List<LocalItem> stackBeforeSwitchExpression;
 174     LocalItem switchResult;
 175     PatternMatchingCatchConfiguration patternMatchingCatchConfiguration =
 176             new PatternMatchingCatchConfiguration(Set.of(), null, null, null);
 177 
 178     /** Cache the symbol to reflect the qualifying type.
 179      *  key: corresponding type
 180      *  value: qualified symbol
 181      */
 182     Map<Type, Symbol> qualifiedSymbolCache;
 183 
 184     /** Generate code to load an integer constant.
 185      *  @param n     The integer to be loaded.
 186      */
 187     void loadIntConst(int n) {
 188         items.makeImmediateItem(syms.intType, n).load();
 189     }
 190 
 191     /** The opcode that loads a zero constant of a given type code.
 192      *  @param tc   The given type code (@see ByteCode).
 193      */
 194     public static int zero(int tc) {
 195         switch(tc) {
 196         case INTcode: case BYTEcode: case SHORTcode: case CHARcode:
 197             return iconst_0;
 198         case LONGcode:
 199             return lconst_0;
 200         case FLOATcode:
 201             return fconst_0;
 202         case DOUBLEcode:
 203             return dconst_0;
 204         default:
 205             throw new AssertionError("zero");
 206         }
 207     }
 208 
 209     /** The opcode that loads a one constant of a given type code.
 210      *  @param tc   The given type code (@see ByteCode).
 211      */
 212     public static int one(int tc) {
 213         return zero(tc) + 1;
 214     }
 215 
 216     /** Generate code to load -1 of the given type code (either int or long).
 217      *  @param tc   The given type code (@see ByteCode).
 218      */
 219     void emitMinusOne(int tc) {
 220         if (tc == LONGcode) {
 221             items.makeImmediateItem(syms.longType, Long.valueOf(-1)).load();
 222         } else {
 223             code.emitop0(iconst_m1);
 224         }
 225     }
 226 
 227     /** Construct a symbol to reflect the qualifying type that should
 228      *  appear in the byte code as per JLS 13.1.
 229      *
 230      *  For {@literal target >= 1.2}: Clone a method with the qualifier as owner (except
 231      *  for those cases where we need to work around VM bugs).
 232      *
 233      *  For {@literal target <= 1.1}: If qualified variable or method is defined in a
 234      *  non-accessible class, clone it with the qualifier class as owner.
 235      *
 236      *  @param sym    The accessed symbol
 237      *  @param site   The qualifier's type.
 238      */
 239     Symbol binaryQualifier(Symbol sym, Type site) {
 240 
 241         if (site.hasTag(ARRAY)) {
 242             if (sym == syms.lengthVar ||
 243                 sym.owner != syms.arrayClass)
 244                 return sym;
 245             // array clone can be qualified by the array type in later targets
 246             Symbol qualifier;
 247             if ((qualifier = qualifiedSymbolCache.get(site)) == null) {
 248                 qualifier = new ClassSymbol(Flags.PUBLIC, site.tsym.name, site, syms.noSymbol);
 249                 qualifiedSymbolCache.put(site, qualifier);
 250             }
 251             return sym.clone(qualifier);
 252         }
 253 
 254         if (sym.owner == site.tsym ||
 255             (sym.flags() & (STATIC | SYNTHETIC)) == (STATIC | SYNTHETIC)) {
 256             return sym;
 257         }
 258 
 259         // leave alone methods inherited from Object
 260         // JLS 13.1.
 261         if (sym.owner == syms.objectType.tsym)
 262             return sym;
 263 
 264         return sym.clone(site.tsym);
 265     }
 266 
 267     /** Insert a reference to given type in the constant pool,
 268      *  checking for an array with too many dimensions;
 269      *  return the reference's index.
 270      *  @param type   The type for which a reference is inserted.
 271      */
 272     int makeRef(DiagnosticPosition pos, Type type) {
 273         return poolWriter.putClass(checkDimension(pos, type));
 274     }
 275 
 276     /** Check if the given type is an array with too many dimensions.
 277      */
 278     private Type checkDimension(DiagnosticPosition pos, Type t) {
 279         checkDimensionInternal(pos, t);
 280         return t;
 281     }
 282 
 283     private void checkDimensionInternal(DiagnosticPosition pos, Type t) {
 284         switch (t.getTag()) {
 285         case METHOD:
 286             checkDimension(pos, t.getReturnType());
 287             for (List<Type> args = t.getParameterTypes(); args.nonEmpty(); args = args.tail)
 288                 checkDimension(pos, args.head);
 289             break;
 290         case ARRAY:
 291             if (types.dimensions(t) > ClassFile.MAX_DIMENSIONS) {
 292                 log.error(pos, Errors.LimitDimensions);
 293                 nerrs++;
 294             }
 295             break;
 296         default:
 297             break;
 298         }
 299     }
 300 
 301     /** Create a temporary variable.
 302      *  @param type   The variable's type.
 303      */
 304     LocalItem makeTemp(Type type) {
 305         VarSymbol v = new VarSymbol(Flags.SYNTHETIC,
 306                                     names.empty,
 307                                     type,
 308                                     env.enclMethod.sym);
 309         code.newLocal(v);
 310         return items.makeLocalItem(v);
 311     }
 312 
 313     /** Generate code to call a non-private method or constructor.
 314      *  @param pos         Position to be used for error reporting.
 315      *  @param site        The type of which the method is a member.
 316      *  @param name        The method's name.
 317      *  @param argtypes    The method's argument types.
 318      *  @param isStatic    A flag that indicates whether we call a
 319      *                     static or instance method.
 320      */
 321     void callMethod(DiagnosticPosition pos,
 322                     Type site, Name name, List<Type> argtypes,
 323                     boolean isStatic) {
 324         Symbol msym = rs.
 325             resolveInternalMethod(pos, attrEnv, site, name, argtypes, null);
 326         if (isStatic) items.makeStaticItem(msym).invoke();
 327         else items.makeMemberItem(msym, name == names.init).invoke();
 328     }
 329 
 330     /** Is the given method definition an access method
 331      *  resulting from a qualified super? This is signified by an odd
 332      *  access code.
 333      */
 334     private boolean isAccessSuper(JCMethodDecl enclMethod) {
 335         return
 336             (enclMethod.mods.flags & SYNTHETIC) != 0 &&
 337             isOddAccessName(enclMethod.name);
 338     }
 339 
 340     /** Does given name start with "access$" and end in an odd digit?
 341      */
 342     private boolean isOddAccessName(Name name) {
 343         final String string = name.toString();
 344         return
 345             string.startsWith(accessDollar) &&
 346             (string.charAt(string.length() - 1) & 1) != 0;
 347     }
 348 
 349 /* ************************************************************************
 350  * Non-local exits
 351  *************************************************************************/
 352 
 353     /** Generate code to invoke the finalizer associated with given
 354      *  environment.
 355      *  Any calls to finalizers are appended to the environments `cont' chain.
 356      *  Mark beginning of gap in catch all range for finalizer.
 357      */
 358     void genFinalizer(Env<GenContext> env) {
 359         if (code.isAlive() && env.info.finalize != null)
 360             env.info.finalize.gen();
 361     }
 362 
 363     /** Generate code to call all finalizers of structures aborted by
 364      *  a non-local
 365      *  exit.  Return target environment of the non-local exit.
 366      *  @param target      The tree representing the structure that's aborted
 367      *  @param env         The environment current at the non-local exit.
 368      */
 369     Env<GenContext> unwind(JCTree target, Env<GenContext> env) {
 370         Env<GenContext> env1 = env;
 371         while (true) {
 372             genFinalizer(env1);
 373             if (env1.tree == target) break;
 374             env1 = env1.next;
 375         }
 376         return env1;
 377     }
 378 
 379     /** Mark end of gap in catch-all range for finalizer.
 380      *  @param env   the environment which might contain the finalizer
 381      *               (if it does, env.info.gaps != null).
 382      */
 383     void endFinalizerGap(Env<GenContext> env) {
 384         if (env.info.gaps != null && env.info.gaps.length() % 2 == 1)
 385             env.info.gaps.append(code.curCP());
 386     }
 387 
 388     /** Mark end of all gaps in catch-all ranges for finalizers of environments
 389      *  lying between, and including to two environments.
 390      *  @param from    the most deeply nested environment to mark
 391      *  @param to      the least deeply nested environment to mark
 392      */
 393     void endFinalizerGaps(Env<GenContext> from, Env<GenContext> to) {
 394         Env<GenContext> last = null;
 395         while (last != to) {
 396             endFinalizerGap(from);
 397             last = from;
 398             from = from.next;
 399         }
 400     }
 401 
 402     /** Do any of the structures aborted by a non-local exit have
 403      *  finalizers that require an empty stack?
 404      *  @param target      The tree representing the structure that's aborted
 405      *  @param env         The environment current at the non-local exit.
 406      */
 407     boolean hasFinally(JCTree target, Env<GenContext> env) {
 408         while (env.tree != target) {
 409             if (env.tree.hasTag(TRY) && env.info.finalize.hasFinalizer())
 410                 return true;
 411             env = env.next;
 412         }
 413         return false;
 414     }
 415 
 416 /* ************************************************************************
 417  * Normalizing class-members.
 418  *************************************************************************/
 419 
 420     /** Distribute member initializer code into constructors and {@code <clinit>}
 421      *  method.
 422      *  @param defs         The list of class member declarations.
 423      *  @param c            The enclosing class.
 424      */
 425     List<JCTree> normalizeDefs(List<JCTree> defs, ClassSymbol c) {
 426         ListBuffer<JCStatement> initCode = new ListBuffer<>();


 427         ListBuffer<Attribute.TypeCompound> initTAs = new ListBuffer<>();
 428         ListBuffer<JCStatement> clinitCode = new ListBuffer<>();
 429         ListBuffer<Attribute.TypeCompound> clinitTAs = new ListBuffer<>();
 430         ListBuffer<JCTree> methodDefs = new ListBuffer<>();
 431         // Sort definitions into three listbuffers:
 432         //  - initCode for instance initializers
 433         //  - clinitCode for class initializers
 434         //  - methodDefs for method definitions
 435         for (List<JCTree> l = defs; l.nonEmpty(); l = l.tail) {
 436             JCTree def = l.head;
 437             switch (def.getTag()) {
 438             case BLOCK:
 439                 JCBlock block = (JCBlock)def;
 440                 if ((block.flags & STATIC) != 0)
 441                     clinitCode.append(block);
 442                 else if ((block.flags & SYNTHETIC) == 0)
 443                     initCode.append(block);





 444                 break;
 445             case METHODDEF:
 446                 methodDefs.append(def);
 447                 break;
 448             case VARDEF:
 449                 JCVariableDecl vdef = (JCVariableDecl) def;
 450                 VarSymbol sym = vdef.sym;
 451                 checkDimension(vdef.pos(), sym.type);
 452                 if (vdef.init != null) {
 453                     if ((sym.flags() & STATIC) == 0) {
 454                         // Always initialize instance variables.
 455                         JCStatement init = make.at(vdef.pos()).
 456                             Assignment(sym, vdef.init);
 457                         initCode.append(init);
 458                         endPosTable.replaceTree(vdef, init);
 459                         initTAs.addAll(getAndRemoveNonFieldTAs(sym));
 460                     } else if (sym.getConstValue() == null) {
 461                         // Initialize class (static) variables only if
 462                         // they are not compile-time constants.
 463                         JCStatement init = make.at(vdef.pos).
 464                             Assignment(sym, vdef.init);
 465                         clinitCode.append(init);
 466                         endPosTable.replaceTree(vdef, init);
 467                         clinitTAs.addAll(getAndRemoveNonFieldTAs(sym));
 468                     } else {
 469                         checkStringConstant(vdef.init.pos(), sym.getConstValue());
 470                         /* if the init contains a reference to an external class, add it to the
 471                          * constant's pool
 472                          */
 473                         vdef.init.accept(classReferenceVisitor);
 474                     }
 475                 }
 476                 break;
 477             default:
 478                 Assert.error();
 479             }
 480         }
 481         // Insert any instance initializers into all constructors.
 482         if (initCode.length() != 0) {
 483             List<JCStatement> inits = initCode.toList();
 484             initTAs.addAll(c.getInitTypeAttributes());
 485             List<Attribute.TypeCompound> initTAlist = initTAs.toList();
 486             for (JCTree t : methodDefs) {
 487                 normalizeMethod((JCMethodDecl)t, inits, initTAlist);
 488             }
 489         }
 490         // If there are class initializers, create a <clinit> method
 491         // that contains them as its body.
 492         if (clinitCode.length() != 0) {
 493             MethodSymbol clinit = new MethodSymbol(
 494                 STATIC | (c.flags() & STRICTFP),
 495                 names.clinit,
 496                 new MethodType(
 497                     List.nil(), syms.voidType,
 498                     List.nil(), syms.methodClass),
 499                 c);
 500             c.members().enter(clinit);
 501             List<JCStatement> clinitStats = clinitCode.toList();
 502             JCBlock block = make.at(clinitStats.head.pos()).Block(0, clinitStats);
 503             block.endpos = TreeInfo.endPos(clinitStats.last());
 504             methodDefs.append(make.MethodDef(clinit, block));
 505 
 506             if (!clinitTAs.isEmpty())
 507                 clinit.appendUniqueTypeAttributes(clinitTAs.toList());
 508             if (!c.getClassInitTypeAttributes().isEmpty())
 509                 clinit.appendUniqueTypeAttributes(c.getClassInitTypeAttributes());
 510         }
 511         // Return all method definitions.
 512         return methodDefs.toList();
 513     }
 514 
 515     private List<Attribute.TypeCompound> getAndRemoveNonFieldTAs(VarSymbol sym) {
 516         List<TypeCompound> tas = sym.getRawTypeAttributes();
 517         ListBuffer<Attribute.TypeCompound> fieldTAs = new ListBuffer<>();
 518         ListBuffer<Attribute.TypeCompound> nonfieldTAs = new ListBuffer<>();
 519         for (TypeCompound ta : tas) {
 520             Assert.check(ta.getPosition().type != TargetType.UNKNOWN);
 521             if (ta.getPosition().type == TargetType.FIELD) {
 522                 fieldTAs.add(ta);
 523             } else {
 524                 nonfieldTAs.add(ta);
 525             }
 526         }
 527         sym.setTypeAttributes(fieldTAs.toList());
 528         return nonfieldTAs.toList();
 529     }
 530 
 531     /** Check a constant value and report if it is a string that is
 532      *  too large.
 533      */
 534     private void checkStringConstant(DiagnosticPosition pos, Object constValue) {
 535         if (nerrs != 0 || // only complain about a long string once
 536             constValue == null ||
 537             !(constValue instanceof String str) ||
 538             str.length() < PoolWriter.MAX_STRING_LENGTH)
 539             return;
 540         log.error(pos, Errors.LimitString);
 541         nerrs++;
 542     }
 543 
 544     /** Insert instance initializer code into constructors prior to the super() call.
 545      *  @param md        The tree potentially representing a
 546      *                   constructor's definition.
 547      *  @param initCode  The list of instance initializer statements.
 548      *  @param initTAs  Type annotations from the initializer expression.
 549      */
 550     void normalizeMethod(JCMethodDecl md, List<JCStatement> initCode, List<TypeCompound> initTAs) {
 551         if (TreeInfo.isConstructor(md) && TreeInfo.hasConstructorCall(md, names._super)) {
 552             // We are seeing a constructor that has a super() call.
 553             // Find the super() invocation and append the given initializer code.
 554             TreeInfo.mapSuperCalls(md.body, supercall -> make.Block(0, initCode.prepend(supercall)));





 555 
 556             if (md.body.endpos == Position.NOPOS)
 557                 md.body.endpos = TreeInfo.endPos(md.body.stats.last());
 558 
 559             md.sym.appendUniqueTypeAttributes(initTAs);
 560         }
 561     }
 562 


































 563 /* ************************************************************************
 564  * Traversal methods
 565  *************************************************************************/
 566 
 567     /** Visitor argument: The current environment.
 568      */
 569     Env<GenContext> env;
 570 
 571     /** Visitor argument: The expected type (prototype).
 572      */
 573     Type pt;
 574 
 575     /** Visitor result: The item representing the computed value.
 576      */
 577     Item result;
 578 
 579     /** Visitor method: generate code for a definition, catching and reporting
 580      *  any completion failures.
 581      *  @param tree    The definition to be visited.
 582      *  @param env     The environment current at the definition.
 583      */
 584     public void genDef(JCTree tree, Env<GenContext> env) {
 585         Env<GenContext> prevEnv = this.env;
 586         try {
 587             this.env = env;
 588             tree.accept(this);
 589         } catch (CompletionFailure ex) {
 590             chk.completionError(tree.pos(), ex);
 591         } finally {
 592             this.env = prevEnv;
 593         }
 594     }
 595 
 596     /** Derived visitor method: check whether CharacterRangeTable
 597      *  should be emitted, if so, put a new entry into CRTable
 598      *  and call method to generate bytecode.
 599      *  If not, just call method to generate bytecode.
 600      *  @see    #genStat(JCTree, Env)
 601      *
 602      *  @param  tree     The tree to be visited.
 603      *  @param  env      The environment to use.
 604      *  @param  crtFlags The CharacterRangeTable flags
 605      *                   indicating type of the entry.
 606      */
 607     public void genStat(JCTree tree, Env<GenContext> env, int crtFlags) {
 608         if (!genCrt) {
 609             genStat(tree, env);
 610             return;
 611         }
 612         int startpc = code.curCP();
 613         genStat(tree, env);
 614         if (tree.hasTag(Tag.BLOCK)) crtFlags |= CRT_BLOCK;
 615         code.crt.put(tree, crtFlags, startpc, code.curCP());
 616     }
 617 
 618     /** Derived visitor method: generate code for a statement.
 619      */
 620     public void genStat(JCTree tree, Env<GenContext> env) {
 621         if (code.isAlive()) {
 622             code.statBegin(tree.pos);
 623             genDef(tree, env);
 624         } else if (env.info.isSwitch && tree.hasTag(VARDEF)) {
 625             // variables whose declarations are in a switch
 626             // can be used even if the decl is unreachable.
 627             code.newLocal(((JCVariableDecl) tree).sym);
 628         }
 629     }
 630 
 631     /** Derived visitor method: check whether CharacterRangeTable
 632      *  should be emitted, if so, put a new entry into CRTable
 633      *  and call method to generate bytecode.
 634      *  If not, just call method to generate bytecode.
 635      *  @see    #genStats(List, Env)
 636      *
 637      *  @param  trees    The list of trees to be visited.
 638      *  @param  env      The environment to use.
 639      *  @param  crtFlags The CharacterRangeTable flags
 640      *                   indicating type of the entry.
 641      */
 642     public void genStats(List<JCStatement> trees, Env<GenContext> env, int crtFlags) {
 643         if (!genCrt) {
 644             genStats(trees, env);
 645             return;
 646         }
 647         if (trees.length() == 1) {        // mark one statement with the flags
 648             genStat(trees.head, env, crtFlags | CRT_STATEMENT);
 649         } else {
 650             int startpc = code.curCP();
 651             genStats(trees, env);
 652             code.crt.put(trees, crtFlags, startpc, code.curCP());
 653         }
 654     }
 655 
 656     /** Derived visitor method: generate code for a list of statements.
 657      */
 658     public void genStats(List<? extends JCTree> trees, Env<GenContext> env) {
 659         for (List<? extends JCTree> l = trees; l.nonEmpty(); l = l.tail)
 660             genStat(l.head, env, CRT_STATEMENT);
 661     }
 662 
 663     /** Derived visitor method: check whether CharacterRangeTable
 664      *  should be emitted, if so, put a new entry into CRTable
 665      *  and call method to generate bytecode.
 666      *  If not, just call method to generate bytecode.
 667      *  @see    #genCond(JCTree,boolean)
 668      *
 669      *  @param  tree     The tree to be visited.
 670      *  @param  crtFlags The CharacterRangeTable flags
 671      *                   indicating type of the entry.
 672      */
 673     public CondItem genCond(JCTree tree, int crtFlags) {
 674         if (!genCrt) return genCond(tree, false);
 675         int startpc = code.curCP();
 676         CondItem item = genCond(tree, (crtFlags & CRT_FLOW_CONTROLLER) != 0);
 677         code.crt.put(tree, crtFlags, startpc, code.curCP());
 678         return item;
 679     }
 680 
 681     /** Derived visitor method: generate code for a boolean
 682      *  expression in a control-flow context.
 683      *  @param _tree         The expression to be visited.
 684      *  @param markBranches The flag to indicate that the condition is
 685      *                      a flow controller so produced conditions
 686      *                      should contain a proper tree to generate
 687      *                      CharacterRangeTable branches for them.
 688      */
 689     public CondItem genCond(JCTree _tree, boolean markBranches) {
 690         JCTree inner_tree = TreeInfo.skipParens(_tree);
 691         if (inner_tree.hasTag(CONDEXPR)) {
 692             JCConditional tree = (JCConditional)inner_tree;
 693             CondItem cond = genCond(tree.cond, CRT_FLOW_CONTROLLER);
 694             if (cond.isTrue()) {
 695                 code.resolve(cond.trueJumps);
 696                 CondItem result = genCond(tree.truepart, CRT_FLOW_TARGET);
 697                 if (markBranches) result.tree = tree.truepart;
 698                 return result;
 699             }
 700             if (cond.isFalse()) {
 701                 code.resolve(cond.falseJumps);
 702                 CondItem result = genCond(tree.falsepart, CRT_FLOW_TARGET);
 703                 if (markBranches) result.tree = tree.falsepart;
 704                 return result;
 705             }
 706             Chain secondJumps = cond.jumpFalse();
 707             code.resolve(cond.trueJumps);
 708             CondItem first = genCond(tree.truepart, CRT_FLOW_TARGET);
 709             if (markBranches) first.tree = tree.truepart;
 710             Chain falseJumps = first.jumpFalse();
 711             code.resolve(first.trueJumps);
 712             Chain trueJumps = code.branch(goto_);
 713             code.resolve(secondJumps);
 714             CondItem second = genCond(tree.falsepart, CRT_FLOW_TARGET);
 715             CondItem result = items.makeCondItem(second.opcode,
 716                                       Code.mergeChains(trueJumps, second.trueJumps),
 717                                       Code.mergeChains(falseJumps, second.falseJumps));
 718             if (markBranches) result.tree = tree.falsepart;
 719             return result;
 720         } else if (inner_tree.hasTag(SWITCH_EXPRESSION)) {
 721             code.resolvePending();
 722 
 723             boolean prevInCondSwitchExpression = inCondSwitchExpression;
 724             Chain prevSwitchExpressionTrueChain = switchExpressionTrueChain;
 725             Chain prevSwitchExpressionFalseChain = switchExpressionFalseChain;
 726             try {
 727                 inCondSwitchExpression = true;
 728                 switchExpressionTrueChain = null;
 729                 switchExpressionFalseChain = null;
 730                 try {
 731                     doHandleSwitchExpression((JCSwitchExpression) inner_tree);
 732                 } catch (CompletionFailure ex) {
 733                     chk.completionError(_tree.pos(), ex);
 734                     code.state.stacksize = 1;
 735                 }
 736                 CondItem result = items.makeCondItem(goto_,
 737                                                      switchExpressionTrueChain,
 738                                                      switchExpressionFalseChain);
 739                 if (markBranches) result.tree = _tree;
 740                 return result;
 741             } finally {
 742                 inCondSwitchExpression = prevInCondSwitchExpression;
 743                 switchExpressionTrueChain = prevSwitchExpressionTrueChain;
 744                 switchExpressionFalseChain = prevSwitchExpressionFalseChain;
 745             }
 746         } else if (inner_tree.hasTag(LETEXPR) && ((LetExpr) inner_tree).needsCond) {
 747             code.resolvePending();
 748 
 749             LetExpr tree = (LetExpr) inner_tree;
 750             int limit = code.nextreg;
 751             int prevLetExprStart = code.setLetExprStackPos(code.state.stacksize);
 752             try {
 753                 genStats(tree.defs, env);
 754             } finally {
 755                 code.setLetExprStackPos(prevLetExprStart);
 756             }
 757             CondItem result = genCond(tree.expr, markBranches);
 758             code.endScopes(limit);
 759             return result;
 760         } else {
 761             CondItem result = genExpr(_tree, syms.booleanType).mkCond();
 762             if (markBranches) result.tree = _tree;
 763             return result;
 764         }
 765     }
 766 
 767     public Code getCode() {
 768         return code;
 769     }
 770 
 771     public Items getItems() {
 772         return items;
 773     }
 774 
 775     public Env<AttrContext> getAttrEnv() {
 776         return attrEnv;
 777     }
 778 
 779     /** Visitor class for expressions which might be constant expressions.
 780      *  This class is a subset of TreeScanner. Intended to visit trees pruned by
 781      *  Lower as long as constant expressions looking for references to any
 782      *  ClassSymbol. Any such reference will be added to the constant pool so
 783      *  automated tools can detect class dependencies better.
 784      */
 785     class ClassReferenceVisitor extends JCTree.Visitor {
 786 
 787         @Override
 788         public void visitTree(JCTree tree) {}
 789 
 790         @Override
 791         public void visitBinary(JCBinary tree) {
 792             tree.lhs.accept(this);
 793             tree.rhs.accept(this);
 794         }
 795 
 796         @Override
 797         public void visitSelect(JCFieldAccess tree) {
 798             if (tree.selected.type.hasTag(CLASS)) {
 799                 makeRef(tree.selected.pos(), tree.selected.type);
 800             }
 801         }
 802 
 803         @Override
 804         public void visitIdent(JCIdent tree) {
 805             if (tree.sym.owner instanceof ClassSymbol classSymbol) {
 806                 poolWriter.putClass(classSymbol);
 807             }
 808         }
 809 
 810         @Override
 811         public void visitConditional(JCConditional tree) {
 812             tree.cond.accept(this);
 813             tree.truepart.accept(this);
 814             tree.falsepart.accept(this);
 815         }
 816 
 817         @Override
 818         public void visitUnary(JCUnary tree) {
 819             tree.arg.accept(this);
 820         }
 821 
 822         @Override
 823         public void visitParens(JCParens tree) {
 824             tree.expr.accept(this);
 825         }
 826 
 827         @Override
 828         public void visitTypeCast(JCTypeCast tree) {
 829             tree.expr.accept(this);
 830         }
 831     }
 832 
 833     private ClassReferenceVisitor classReferenceVisitor = new ClassReferenceVisitor();
 834 
 835     /** Visitor method: generate code for an expression, catching and reporting
 836      *  any completion failures.
 837      *  @param tree    The expression to be visited.
 838      *  @param pt      The expression's expected type (proto-type).
 839      */
 840     public Item genExpr(JCTree tree, Type pt) {
 841         if (!code.isAlive()) {
 842             return items.makeStackItem(pt);
 843         }
 844 
 845         Type prevPt = this.pt;
 846         try {
 847             if (tree.type.constValue() != null) {
 848                 // Short circuit any expressions which are constants
 849                 tree.accept(classReferenceVisitor);
 850                 checkStringConstant(tree.pos(), tree.type.constValue());
 851                 Symbol sym = TreeInfo.symbol(tree);
 852                 if (sym != null && isConstantDynamic(sym)) {
 853                     result = items.makeDynamicItem(sym);
 854                 } else {
 855                     result = items.makeImmediateItem(tree.type, tree.type.constValue());
 856                 }
 857             } else {
 858                 this.pt = pt;
 859                 tree.accept(this);
 860             }
 861             return result.coerce(pt);
 862         } catch (CompletionFailure ex) {
 863             chk.completionError(tree.pos(), ex);
 864             code.state.stacksize = 1;
 865             return items.makeStackItem(pt);
 866         } finally {
 867             this.pt = prevPt;
 868         }
 869     }
 870 
 871     public boolean isConstantDynamic(Symbol sym) {
 872         return sym.kind == VAR &&
 873                 sym instanceof DynamicVarSymbol dynamicVarSymbol &&
 874                 dynamicVarSymbol.isDynamic();
 875     }
 876 
 877     /** Derived visitor method: generate code for a list of method arguments.
 878      *  @param trees    The argument expressions to be visited.
 879      *  @param pts      The expression's expected types (i.e. the formal parameter
 880      *                  types of the invoked method).
 881      */
 882     public void genArgs(List<JCExpression> trees, List<Type> pts) {
 883         for (List<JCExpression> l = trees; l.nonEmpty(); l = l.tail) {
 884             genExpr(l.head, pts.head).load();
 885             pts = pts.tail;
 886         }
 887         // require lists be of same length
 888         Assert.check(pts.isEmpty());
 889     }
 890 
 891 /* ************************************************************************
 892  * Visitor methods for statements and definitions
 893  *************************************************************************/
 894 
 895     /** Thrown when the byte code size exceeds limit.
 896      */
 897     public static class CodeSizeOverflow extends RuntimeException {
 898         private static final long serialVersionUID = 0;
 899         public CodeSizeOverflow() {}
 900     }
 901 
 902     public void visitMethodDef(JCMethodDecl tree) {
 903         // Create a new local environment that points pack at method
 904         // definition.
 905         Env<GenContext> localEnv = env.dup(tree);
 906         localEnv.enclMethod = tree;
 907         // The expected type of every return statement in this method
 908         // is the method's return type.
 909         this.pt = tree.sym.erasure(types).getReturnType();
 910 
 911         checkDimension(tree.pos(), tree.sym.erasure(types));
 912         genMethod(tree, localEnv, false);
 913     }
 914 //where
 915         /** Generate code for a method.
 916          *  @param tree     The tree representing the method definition.
 917          *  @param env      The environment current for the method body.
 918          *  @param fatcode  A flag that indicates whether all jumps are
 919          *                  within 32K.  We first invoke this method under
 920          *                  the assumption that fatcode == false, i.e. all
 921          *                  jumps are within 32K.  If this fails, fatcode
 922          *                  is set to true and we try again.
 923          */
 924         void genMethod(JCMethodDecl tree, Env<GenContext> env, boolean fatcode) {
 925             MethodSymbol meth = tree.sym;
 926             int extras = 0;
 927             // Count up extra parameters
 928             if (meth.isConstructor()) {
 929                 extras++;
 930                 if (meth.enclClass().isInner() &&
 931                     !meth.enclClass().isStatic()) {
 932                     extras++;
 933                 }
 934             } else if ((tree.mods.flags & STATIC) == 0) {
 935                 extras++;
 936             }
 937             //      System.err.println("Generating " + meth + " in " + meth.owner); //DEBUG
 938             if (Code.width(types.erasure(env.enclMethod.sym.type).getParameterTypes()) + extras >
 939                 ClassFile.MAX_PARAMETERS) {
 940                 log.error(tree.pos(), Errors.LimitParameters);
 941                 nerrs++;
 942             }
 943 
 944             else if (tree.body != null) {
 945                 // Create a new code structure and initialize it.
 946                 int startpcCrt = initCode(tree, env, fatcode);
 947 
 948                 try {
 949                     genStat(tree.body, env);
 950                 } catch (CodeSizeOverflow e) {
 951                     // Failed due to code limit, try again with jsr/ret
 952                     startpcCrt = initCode(tree, env, fatcode);
 953                     genStat(tree.body, env);
 954                 }
 955 
 956                 if (code.state.stacksize != 0) {
 957                     log.error(tree.body.pos(), Errors.StackSimError(tree.sym));
 958                     throw new AssertionError();
 959                 }
 960 
 961                 // If last statement could complete normally, insert a
 962                 // return at the end.
 963                 if (code.isAlive()) {
 964                     code.statBegin(TreeInfo.endPos(tree.body));
 965                     if (env.enclMethod == null ||
 966                         env.enclMethod.sym.type.getReturnType().hasTag(VOID)) {
 967                         code.emitop0(return_);
 968                     } else {
 969                         // sometime dead code seems alive (4415991);
 970                         // generate a small loop instead
 971                         int startpc = code.entryPoint();
 972                         CondItem c = items.makeCondItem(goto_);
 973                         code.resolve(c.jumpTrue(), startpc);
 974                     }
 975                 }
 976                 if (genCrt)
 977                     code.crt.put(tree.body,
 978                                  CRT_BLOCK,
 979                                  startpcCrt,
 980                                  code.curCP());
 981 
 982                 code.endScopes(0);
 983 
 984                 // If we exceeded limits, panic
 985                 if (code.checkLimits(tree.pos(), log)) {
 986                     nerrs++;
 987                     return;
 988                 }
 989 
 990                 // If we generated short code but got a long jump, do it again
 991                 // with fatCode = true.
 992                 if (!fatcode && code.fatcode) genMethod(tree, env, true);
 993 
 994                 // Clean up
 995                 if(stackMap == StackMapFormat.JSR202) {
 996                     code.lastFrame = null;
 997                     code.frameBeforeLast = null;
 998                 }
 999 
1000                 // Compress exception table
1001                 code.compressCatchTable();
1002 
1003                 // Fill in type annotation positions for exception parameters
1004                 code.fillExceptionParameterPositions();
1005             }
1006         }
1007 
1008         private int initCode(JCMethodDecl tree, Env<GenContext> env, boolean fatcode) {
1009             MethodSymbol meth = tree.sym;
1010 
1011             // Create a new code structure.
1012             meth.code = code = new Code(meth,
1013                                         fatcode,
1014                                         lineDebugInfo ? toplevel.lineMap : null,
1015                                         varDebugInfo,
1016                                         stackMap,
1017                                         debugCode,
1018                                         genCrt ? new CRTable(tree, env.toplevel.endPositions)
1019                                                : null,
1020                                         syms,
1021                                         types,
1022                                         poolWriter);
1023             items = new Items(poolWriter, code, syms, types);
1024             if (code.debugCode) {
1025                 System.err.println(meth + " for body " + tree);
1026             }
1027 
1028             // If method is not static, create a new local variable address
1029             // for `this'.
1030             if ((tree.mods.flags & STATIC) == 0) {
1031                 Type selfType = meth.owner.type;
1032                 if (meth.isConstructor() && selfType != syms.objectType)
1033                     selfType = UninitializedType.uninitializedThis(selfType);
1034                 code.setDefined(
1035                         code.newLocal(
1036                             new VarSymbol(FINAL, names._this, selfType, meth.owner)));
1037             }
1038 
1039             // Mark all parameters as defined from the beginning of
1040             // the method.
1041             for (List<JCVariableDecl> l = tree.params; l.nonEmpty(); l = l.tail) {
1042                 checkDimension(l.head.pos(), l.head.sym.type);
1043                 code.setDefined(code.newLocal(l.head.sym));
1044             }
1045 
1046             // Get ready to generate code for method body.
1047             int startpcCrt = genCrt ? code.curCP() : 0;
1048             code.entryPoint();
1049 
1050             // Suppress initial stackmap
1051             code.pendingStackMap = false;
1052 
1053             return startpcCrt;
1054         }
1055 
1056     public void visitVarDef(JCVariableDecl tree) {
1057         VarSymbol v = tree.sym;
1058         if (tree.init != null) {
1059             checkStringConstant(tree.init.pos(), v.getConstValue());
1060             if (v.getConstValue() == null || varDebugInfo) {
1061                 Assert.check(code.isStatementStart());
1062                 code.newLocal(v);
1063                 genExpr(tree.init, v.erasure(types)).load();
1064                 items.makeLocalItem(v).store();
1065                 Assert.check(code.isStatementStart());
1066             }
1067         } else {
1068             code.newLocal(v);
1069         }
1070         checkDimension(tree.pos(), v.type);
1071     }
1072 
1073     public void visitSkip(JCSkip tree) {
1074     }
1075 
1076     public void visitBlock(JCBlock tree) {
1077         /* this method is heavily invoked, as expected, for deeply nested blocks, if blocks doesn't happen to have
1078          * patterns there will be an unnecessary tax on memory consumption every time this method is executed, for this
1079          * reason we have created helper methods and here at a higher level we just discriminate depending on the
1080          * presence, or not, of patterns in a given block
1081          */
1082         if (tree.patternMatchingCatch != null) {
1083             visitBlockWithPatterns(tree);
1084         } else {
1085             internalVisitBlock(tree);
1086         }
1087     }
1088 
1089     private void visitBlockWithPatterns(JCBlock tree) {
1090         PatternMatchingCatchConfiguration prevConfiguration = patternMatchingCatchConfiguration;
1091         try {
1092             patternMatchingCatchConfiguration =
1093                     new PatternMatchingCatchConfiguration(tree.patternMatchingCatch.calls2Handle(),
1094                                                          new ListBuffer<int[]>(),
1095                                                          tree.patternMatchingCatch.handler(),
1096                                                          code.state.dup());
1097             internalVisitBlock(tree);
1098         } finally {
1099             generatePatternMatchingCatch(env);
1100             patternMatchingCatchConfiguration = prevConfiguration;
1101         }
1102     }
1103 
1104     private void generatePatternMatchingCatch(Env<GenContext> env) {
1105         if (patternMatchingCatchConfiguration.handler != null &&
1106             !patternMatchingCatchConfiguration.ranges.isEmpty()) {
1107             Chain skipCatch = code.branch(goto_);
1108             JCCatch handler = patternMatchingCatchConfiguration.handler();
1109             code.entryPoint(patternMatchingCatchConfiguration.startState(),
1110                             handler.param.sym.type);
1111             genPatternMatchingCatch(handler,
1112                                     env,
1113                                     patternMatchingCatchConfiguration.ranges.toList());
1114             code.resolve(skipCatch);
1115         }
1116     }
1117 
1118     private void internalVisitBlock(JCBlock tree) {
1119         int limit = code.nextreg;
1120         Env<GenContext> localEnv = env.dup(tree, new GenContext());
1121         genStats(tree.stats, localEnv);
1122         // End the scope of all block-local variables in variable info.
1123         if (!env.tree.hasTag(METHODDEF)) {
1124             code.statBegin(tree.endpos);
1125             code.endScopes(limit);
1126             code.pendingStatPos = Position.NOPOS;
1127         }
1128     }
1129 
1130     public void visitDoLoop(JCDoWhileLoop tree) {
1131         genLoop(tree, tree.body, tree.cond, List.nil(), false);
1132     }
1133 
1134     public void visitWhileLoop(JCWhileLoop tree) {
1135         genLoop(tree, tree.body, tree.cond, List.nil(), true);
1136     }
1137 
1138     public void visitForLoop(JCForLoop tree) {
1139         int limit = code.nextreg;
1140         genStats(tree.init, env);
1141         genLoop(tree, tree.body, tree.cond, tree.step, true);
1142         code.endScopes(limit);
1143     }
1144     //where
1145         /** Generate code for a loop.
1146          *  @param loop       The tree representing the loop.
1147          *  @param body       The loop's body.
1148          *  @param cond       The loop's controlling condition.
1149          *  @param step       "Step" statements to be inserted at end of
1150          *                    each iteration.
1151          *  @param testFirst  True if the loop test belongs before the body.
1152          */
1153         private void genLoop(JCStatement loop,
1154                              JCStatement body,
1155                              JCExpression cond,
1156                              List<JCExpressionStatement> step,
1157                              boolean testFirst) {
1158             Env<GenContext> loopEnv = env.dup(loop, new GenContext());
1159             int startpc = code.entryPoint();
1160             if (testFirst) { //while or for loop
1161                 CondItem c;
1162                 if (cond != null) {
1163                     code.statBegin(cond.pos);
1164                     Assert.check(code.isStatementStart());
1165                     c = genCond(TreeInfo.skipParens(cond), CRT_FLOW_CONTROLLER);
1166                 } else {
1167                     c = items.makeCondItem(goto_);
1168                 }
1169                 Chain loopDone = c.jumpFalse();
1170                 code.resolve(c.trueJumps);
1171                 Assert.check(code.isStatementStart());
1172                 genStat(body, loopEnv, CRT_STATEMENT | CRT_FLOW_TARGET);
1173                 code.resolve(loopEnv.info.cont);
1174                 genStats(step, loopEnv);
1175                 code.resolve(code.branch(goto_), startpc);
1176                 code.resolve(loopDone);
1177             } else {
1178                 genStat(body, loopEnv, CRT_STATEMENT | CRT_FLOW_TARGET);
1179                 code.resolve(loopEnv.info.cont);
1180                 genStats(step, loopEnv);
1181                 if (code.isAlive()) {
1182                     CondItem c;
1183                     if (cond != null) {
1184                         code.statBegin(cond.pos);
1185                         Assert.check(code.isStatementStart());
1186                         c = genCond(TreeInfo.skipParens(cond), CRT_FLOW_CONTROLLER);
1187                     } else {
1188                         c = items.makeCondItem(goto_);
1189                     }
1190                     code.resolve(c.jumpTrue(), startpc);
1191                     Assert.check(code.isStatementStart());
1192                     code.resolve(c.falseJumps);
1193                 }
1194             }
1195             Chain exit = loopEnv.info.exit;
1196             if (exit != null) {
1197                 code.resolve(exit);
1198                 exit.state.defined.excludeFrom(code.nextreg);
1199             }
1200         }
1201 
1202     public void visitForeachLoop(JCEnhancedForLoop tree) {
1203         throw new AssertionError(); // should have been removed by Lower.
1204     }
1205 
1206     public void visitLabelled(JCLabeledStatement tree) {
1207         Env<GenContext> localEnv = env.dup(tree, new GenContext());
1208         genStat(tree.body, localEnv, CRT_STATEMENT);
1209         Chain exit = localEnv.info.exit;
1210         if (exit != null) {
1211             code.resolve(exit);
1212             exit.state.defined.excludeFrom(code.nextreg);
1213         }
1214     }
1215 
1216     public void visitSwitch(JCSwitch tree) {
1217         handleSwitch(tree, tree.selector, tree.cases, tree.patternSwitch);
1218     }
1219 
1220     @Override
1221     public void visitSwitchExpression(JCSwitchExpression tree) {
1222         code.resolvePending();
1223         boolean prevInCondSwitchExpression = inCondSwitchExpression;
1224         try {
1225             inCondSwitchExpression = false;
1226             doHandleSwitchExpression(tree);
1227         } finally {
1228             inCondSwitchExpression = prevInCondSwitchExpression;
1229         }
1230         result = items.makeStackItem(pt);
1231     }
1232 
1233     private void doHandleSwitchExpression(JCSwitchExpression tree) {
1234         List<LocalItem> prevStackBeforeSwitchExpression = stackBeforeSwitchExpression;
1235         LocalItem prevSwitchResult = switchResult;
1236         int limit = code.nextreg;
1237         try {
1238             stackBeforeSwitchExpression = List.nil();
1239             switchResult = null;
1240             if (hasTry(tree)) {
1241                 //if the switch expression contains try-catch, the catch handlers need to have
1242                 //an empty stack. So stash whole stack to local variables, and restore it before
1243                 //breaks:
1244                 while (code.state.stacksize > 0) {
1245                     Type type = code.state.peek();
1246                     Name varName = names.fromString(target.syntheticNameChar() +
1247                                                     "stack" +
1248                                                     target.syntheticNameChar() +
1249                                                     tree.pos +
1250                                                     target.syntheticNameChar() +
1251                                                     code.state.stacksize);
1252                     VarSymbol var = new VarSymbol(Flags.SYNTHETIC, varName, type,
1253                                                   this.env.enclMethod.sym);
1254                     LocalItem item = items.new LocalItem(type, code.newLocal(var));
1255                     stackBeforeSwitchExpression = stackBeforeSwitchExpression.prepend(item);
1256                     item.store();
1257                 }
1258                 switchResult = makeTemp(tree.type);
1259             }
1260             int prevLetExprStart = code.setLetExprStackPos(code.state.stacksize);
1261             try {
1262                 handleSwitch(tree, tree.selector, tree.cases, tree.patternSwitch);
1263             } finally {
1264                 code.setLetExprStackPos(prevLetExprStart);
1265             }
1266         } finally {
1267             stackBeforeSwitchExpression = prevStackBeforeSwitchExpression;
1268             switchResult = prevSwitchResult;
1269             code.endScopes(limit);
1270         }
1271     }
1272     //where:
1273         private boolean hasTry(JCSwitchExpression tree) {
1274             class HasTryScanner extends TreeScanner {
1275                 private boolean hasTry;
1276 
1277                 @Override
1278                 public void visitTry(JCTry tree) {
1279                     hasTry = true;
1280                 }
1281 
1282                 @Override
1283                 public void visitSynchronized(JCSynchronized tree) {
1284                     hasTry = true;
1285                 }
1286 
1287                 @Override
1288                 public void visitClassDef(JCClassDecl tree) {
1289                 }
1290 
1291                 @Override
1292                 public void visitLambda(JCLambda tree) {
1293                 }
1294             };
1295 
1296             HasTryScanner hasTryScanner = new HasTryScanner();
1297 
1298             hasTryScanner.scan(tree);
1299             return hasTryScanner.hasTry;
1300         }
1301 
1302     private void handleSwitch(JCTree swtch, JCExpression selector, List<JCCase> cases,
1303                               boolean patternSwitch) {
1304         int limit = code.nextreg;
1305         Assert.check(!selector.type.hasTag(CLASS));
1306         int switchStart = patternSwitch ? code.entryPoint() : -1;
1307         int startpcCrt = genCrt ? code.curCP() : 0;
1308         Assert.check(code.isStatementStart());
1309         Item sel = genExpr(selector, syms.intType);
1310         if (cases.isEmpty()) {
1311             // We are seeing:  switch <sel> {}
1312             sel.load().drop();
1313             if (genCrt)
1314                 code.crt.put(TreeInfo.skipParens(selector),
1315                              CRT_FLOW_CONTROLLER, startpcCrt, code.curCP());
1316         } else {
1317             // We are seeing a nonempty switch.
1318             sel.load();
1319             if (genCrt)
1320                 code.crt.put(TreeInfo.skipParens(selector),
1321                              CRT_FLOW_CONTROLLER, startpcCrt, code.curCP());
1322             Env<GenContext> switchEnv = env.dup(swtch, new GenContext());
1323             switchEnv.info.isSwitch = true;
1324 
1325             // Compute number of labels and minimum and maximum label values.
1326             // For each case, store its label in an array.
1327             int lo = Integer.MAX_VALUE;  // minimum label.
1328             int hi = Integer.MIN_VALUE;  // maximum label.
1329             int nlabels = 0;               // number of labels.
1330 
1331             int[] labels = new int[cases.length()];  // the label array.
1332             int defaultIndex = -1;     // the index of the default clause.
1333 
1334             List<JCCase> l = cases;
1335             for (int i = 0; i < labels.length; i++) {
1336                 if (l.head.labels.head instanceof JCConstantCaseLabel constLabel) {
1337                     Assert.check(l.head.labels.size() == 1);
1338                     int val = ((Number) constLabel.expr.type.constValue()).intValue();
1339                     labels[i] = val;
1340                     if (val < lo) lo = val;
1341                     if (hi < val) hi = val;
1342                     nlabels++;
1343                 } else {
1344                     Assert.check(defaultIndex == -1);
1345                     defaultIndex = i;
1346                 }
1347                 l = l.tail;
1348             }
1349 
1350             // Determine whether to issue a tableswitch or a lookupswitch
1351             // instruction.
1352             long table_space_cost = 4 + ((long) hi - lo + 1); // words
1353             long table_time_cost = 3; // comparisons
1354             long lookup_space_cost = 3 + 2 * (long) nlabels;
1355             long lookup_time_cost = nlabels;
1356             int opcode =
1357                 nlabels > 0 &&
1358                 table_space_cost + 3 * table_time_cost <=
1359                 lookup_space_cost + 3 * lookup_time_cost
1360                 ?
1361                 tableswitch : lookupswitch;
1362 
1363             int startpc = code.curCP();    // the position of the selector operation
1364             code.emitop0(opcode);
1365             code.align(4);
1366             int tableBase = code.curCP();  // the start of the jump table
1367             int[] offsets = null;          // a table of offsets for a lookupswitch
1368             code.emit4(-1);                // leave space for default offset
1369             if (opcode == tableswitch) {
1370                 code.emit4(lo);            // minimum label
1371                 code.emit4(hi);            // maximum label
1372                 for (long i = lo; i <= hi; i++) {  // leave space for jump table
1373                     code.emit4(-1);
1374                 }
1375             } else {
1376                 code.emit4(nlabels);    // number of labels
1377                 for (int i = 0; i < nlabels; i++) {
1378                     code.emit4(-1); code.emit4(-1); // leave space for lookup table
1379                 }
1380                 offsets = new int[labels.length];
1381             }
1382             Code.State stateSwitch = code.state.dup();
1383             code.markDead();
1384 
1385             // For each case do:
1386             l = cases;
1387             for (int i = 0; i < labels.length; i++) {
1388                 JCCase c = l.head;
1389                 l = l.tail;
1390 
1391                 int pc = code.entryPoint(stateSwitch);
1392                 // Insert offset directly into code or else into the
1393                 // offsets table.
1394                 if (i != defaultIndex) {
1395                     if (opcode == tableswitch) {
1396                         code.put4(
1397                             tableBase + 4 * (labels[i] - lo + 3),
1398                             pc - startpc);
1399                     } else {
1400                         offsets[i] = pc - startpc;
1401                     }
1402                 } else {
1403                     code.put4(tableBase, pc - startpc);
1404                 }
1405 
1406                 // Generate code for the statements in this case.
1407                 genStats(c.stats, switchEnv, CRT_FLOW_TARGET);
1408             }
1409 
1410             if (switchEnv.info.cont != null) {
1411                 Assert.check(patternSwitch);
1412                 code.resolve(switchEnv.info.cont, switchStart);
1413             }
1414 
1415             // Resolve all breaks.
1416             Chain exit = switchEnv.info.exit;
1417             if  (exit != null) {
1418                 code.resolve(exit);
1419                 exit.state.defined.excludeFrom(limit);
1420             }
1421 
1422             // If we have not set the default offset, we do so now.
1423             if (code.get4(tableBase) == -1) {
1424                 code.put4(tableBase, code.entryPoint(stateSwitch) - startpc);
1425             }
1426 
1427             if (opcode == tableswitch) {
1428                 // Let any unfilled slots point to the default case.
1429                 int defaultOffset = code.get4(tableBase);
1430                 for (long i = lo; i <= hi; i++) {
1431                     int t = (int)(tableBase + 4 * (i - lo + 3));
1432                     if (code.get4(t) == -1)
1433                         code.put4(t, defaultOffset);
1434                 }
1435             } else {
1436                 // Sort non-default offsets and copy into lookup table.
1437                 if (defaultIndex >= 0)
1438                     for (int i = defaultIndex; i < labels.length - 1; i++) {
1439                         labels[i] = labels[i+1];
1440                         offsets[i] = offsets[i+1];
1441                     }
1442                 if (nlabels > 0)
1443                     qsort2(labels, offsets, 0, nlabels - 1);
1444                 for (int i = 0; i < nlabels; i++) {
1445                     int caseidx = tableBase + 8 * (i + 1);
1446                     code.put4(caseidx, labels[i]);
1447                     code.put4(caseidx + 4, offsets[i]);
1448                 }
1449             }
1450 
1451             if (swtch instanceof JCSwitchExpression) {
1452                  // Emit line position for the end of a switch expression
1453                  code.statBegin(TreeInfo.endPos(swtch));
1454             }
1455         }
1456         code.endScopes(limit);
1457     }
1458 //where
1459         /** Sort (int) arrays of keys and values
1460          */
1461        static void qsort2(int[] keys, int[] values, int lo, int hi) {
1462             int i = lo;
1463             int j = hi;
1464             int pivot = keys[(i+j)/2];
1465             do {
1466                 while (keys[i] < pivot) i++;
1467                 while (pivot < keys[j]) j--;
1468                 if (i <= j) {
1469                     int temp1 = keys[i];
1470                     keys[i] = keys[j];
1471                     keys[j] = temp1;
1472                     int temp2 = values[i];
1473                     values[i] = values[j];
1474                     values[j] = temp2;
1475                     i++;
1476                     j--;
1477                 }
1478             } while (i <= j);
1479             if (lo < j) qsort2(keys, values, lo, j);
1480             if (i < hi) qsort2(keys, values, i, hi);
1481         }
1482 
1483     public void visitSynchronized(JCSynchronized tree) {
1484         int limit = code.nextreg;
1485         // Generate code to evaluate lock and save in temporary variable.
1486         final LocalItem lockVar = makeTemp(syms.objectType);
1487         Assert.check(code.isStatementStart());
1488         genExpr(tree.lock, tree.lock.type).load().duplicate();
1489         lockVar.store();
1490 
1491         // Generate code to enter monitor.
1492         code.emitop0(monitorenter);
1493         code.state.lock(lockVar.reg);
1494 
1495         // Generate code for a try statement with given body, no catch clauses
1496         // in a new environment with the "exit-monitor" operation as finalizer.
1497         final Env<GenContext> syncEnv = env.dup(tree, new GenContext());
1498         syncEnv.info.finalize = new GenFinalizer() {
1499             void gen() {
1500                 genLast();
1501                 Assert.check(syncEnv.info.gaps.length() % 2 == 0);
1502                 syncEnv.info.gaps.append(code.curCP());
1503             }
1504             void genLast() {
1505                 if (code.isAlive()) {
1506                     lockVar.load();
1507                     code.emitop0(monitorexit);
1508                     code.state.unlock(lockVar.reg);
1509                 }
1510             }
1511         };
1512         syncEnv.info.gaps = new ListBuffer<>();
1513         genTry(tree.body, List.nil(), syncEnv);
1514         code.endScopes(limit);
1515     }
1516 
1517     public void visitTry(final JCTry tree) {
1518         // Generate code for a try statement with given body and catch clauses,
1519         // in a new environment which calls the finally block if there is one.
1520         final Env<GenContext> tryEnv = env.dup(tree, new GenContext());
1521         final Env<GenContext> oldEnv = env;
1522         tryEnv.info.finalize = new GenFinalizer() {
1523             void gen() {
1524                 Assert.check(tryEnv.info.gaps.length() % 2 == 0);
1525                 tryEnv.info.gaps.append(code.curCP());
1526                 genLast();
1527             }
1528             void genLast() {
1529                 if (tree.finalizer != null)
1530                     genStat(tree.finalizer, oldEnv, CRT_BLOCK);
1531             }
1532             boolean hasFinalizer() {
1533                 return tree.finalizer != null;
1534             }
1535 
1536             @Override
1537             void afterBody() {
1538                 if (tree.finalizer != null && (tree.finalizer.flags & BODY_ONLY_FINALIZE) != 0) {
1539                     //for body-only finally, remove the GenFinalizer after try body
1540                     //so that the finally is not generated to catch bodies:
1541                     tryEnv.info.finalize = null;
1542                 }
1543             }
1544 
1545         };
1546         tryEnv.info.gaps = new ListBuffer<>();
1547         genTry(tree.body, tree.catchers, tryEnv);
1548     }
1549     //where
1550         /** Generate code for a try or synchronized statement
1551          *  @param body      The body of the try or synchronized statement.
1552          *  @param catchers  The list of catch clauses.
1553          *  @param env       The current environment of the body.
1554          */
1555         void genTry(JCTree body, List<JCCatch> catchers, Env<GenContext> env) {
1556             int limit = code.nextreg;
1557             int startpc = code.curCP();
1558             Code.State stateTry = code.state.dup();
1559             genStat(body, env, CRT_BLOCK);
1560             int endpc = code.curCP();
1561             List<Integer> gaps = env.info.gaps.toList();
1562             code.statBegin(TreeInfo.endPos(body));
1563             genFinalizer(env);
1564             code.statBegin(TreeInfo.endPos(env.tree));
1565             Chain exitChain;
1566             boolean actualTry = env.tree.hasTag(TRY);
1567             if (startpc == endpc && actualTry) {
1568                 exitChain = code.branch(dontgoto);
1569             } else {
1570                 exitChain = code.branch(goto_);
1571             }
1572             endFinalizerGap(env);
1573             env.info.finalize.afterBody();
1574             boolean hasFinalizer =
1575                 env.info.finalize != null &&
1576                 env.info.finalize.hasFinalizer();
1577             if (startpc != endpc) for (List<JCCatch> l = catchers; l.nonEmpty(); l = l.tail) {
1578                 // start off with exception on stack
1579                 code.entryPoint(stateTry, l.head.param.sym.type);
1580                 genCatch(l.head, env, startpc, endpc, gaps);
1581                 genFinalizer(env);
1582                 if (hasFinalizer || l.tail.nonEmpty()) {
1583                     code.statBegin(TreeInfo.endPos(env.tree));
1584                     exitChain = Code.mergeChains(exitChain,
1585                                                  code.branch(goto_));
1586                 }
1587                 endFinalizerGap(env);
1588             }
1589             if (hasFinalizer && (startpc != endpc || !actualTry)) {
1590                 // Create a new register segment to avoid allocating
1591                 // the same variables in finalizers and other statements.
1592                 code.newRegSegment();
1593 
1594                 // Add a catch-all clause.
1595 
1596                 // start off with exception on stack
1597                 int catchallpc = code.entryPoint(stateTry, syms.throwableType);
1598 
1599                 // Register all exception ranges for catch all clause.
1600                 // The range of the catch all clause is from the beginning
1601                 // of the try or synchronized block until the present
1602                 // code pointer excluding all gaps in the current
1603                 // environment's GenContext.
1604                 int startseg = startpc;
1605                 while (env.info.gaps.nonEmpty()) {
1606                     int endseg = env.info.gaps.next().intValue();
1607                     registerCatch(body.pos(), startseg, endseg,
1608                                   catchallpc, 0);
1609                     startseg = env.info.gaps.next().intValue();
1610                 }
1611                 code.statBegin(TreeInfo.finalizerPos(env.tree, PosKind.FIRST_STAT_POS));
1612                 code.markStatBegin();
1613 
1614                 Item excVar = makeTemp(syms.throwableType);
1615                 excVar.store();
1616                 genFinalizer(env);
1617                 code.resolvePending();
1618                 code.statBegin(TreeInfo.finalizerPos(env.tree, PosKind.END_POS));
1619                 code.markStatBegin();
1620 
1621                 excVar.load();
1622                 registerCatch(body.pos(), startseg,
1623                               env.info.gaps.next().intValue(),
1624                               catchallpc, 0);
1625                 code.emitop0(athrow);
1626                 code.markDead();
1627 
1628                 // If there are jsr's to this finalizer, ...
1629                 if (env.info.cont != null) {
1630                     // Resolve all jsr's.
1631                     code.resolve(env.info.cont);
1632 
1633                     // Mark statement line number
1634                     code.statBegin(TreeInfo.finalizerPos(env.tree, PosKind.FIRST_STAT_POS));
1635                     code.markStatBegin();
1636 
1637                     // Save return address.
1638                     LocalItem retVar = makeTemp(syms.throwableType);
1639                     retVar.store();
1640 
1641                     // Generate finalizer code.
1642                     env.info.finalize.genLast();
1643 
1644                     // Return.
1645                     code.emitop1w(ret, retVar.reg);
1646                     code.markDead();
1647                 }
1648             }
1649             // Resolve all breaks.
1650             code.resolve(exitChain);
1651 
1652             code.endScopes(limit);
1653         }
1654 
1655         /** Generate code for a catch clause.
1656          *  @param tree     The catch clause.
1657          *  @param env      The environment current in the enclosing try.
1658          *  @param startpc  Start pc of try-block.
1659          *  @param endpc    End pc of try-block.
1660          */
1661         void genCatch(JCCatch tree,
1662                       Env<GenContext> env,
1663                       int startpc, int endpc,
1664                       List<Integer> gaps) {
1665             if (startpc != endpc) {
1666                 List<Pair<List<Attribute.TypeCompound>, JCExpression>> catchTypeExprs
1667                         = catchTypesWithAnnotations(tree);
1668                 while (gaps.nonEmpty()) {
1669                     for (Pair<List<Attribute.TypeCompound>, JCExpression> subCatch1 : catchTypeExprs) {
1670                         JCExpression subCatch = subCatch1.snd;
1671                         int catchType = makeRef(tree.pos(), subCatch.type);
1672                         int end = gaps.head.intValue();
1673                         registerCatch(tree.pos(),
1674                                       startpc,  end, code.curCP(),
1675                                       catchType);
1676                         for (Attribute.TypeCompound tc :  subCatch1.fst) {
1677                                 tc.position.setCatchInfo(catchType, startpc);
1678                         }
1679                     }
1680                     gaps = gaps.tail;
1681                     startpc = gaps.head.intValue();
1682                     gaps = gaps.tail;
1683                 }
1684                 if (startpc < endpc) {
1685                     for (Pair<List<Attribute.TypeCompound>, JCExpression> subCatch1 : catchTypeExprs) {
1686                         JCExpression subCatch = subCatch1.snd;
1687                         int catchType = makeRef(tree.pos(), subCatch.type);
1688                         registerCatch(tree.pos(),
1689                                       startpc, endpc, code.curCP(),
1690                                       catchType);
1691                         for (Attribute.TypeCompound tc :  subCatch1.fst) {
1692                             tc.position.setCatchInfo(catchType, startpc);
1693                         }
1694                     }
1695                 }
1696                 genCatchBlock(tree, env);
1697             }
1698         }
1699         void genPatternMatchingCatch(JCCatch tree,
1700                                      Env<GenContext> env,
1701                                      List<int[]> ranges) {
1702             for (int[] range : ranges) {
1703                 JCExpression subCatch = tree.param.vartype;
1704                 int catchType = makeRef(tree.pos(), subCatch.type);
1705                 registerCatch(tree.pos(),
1706                               range[0], range[1], code.curCP(),
1707                               catchType);
1708             }
1709             genCatchBlock(tree, env);
1710         }
1711         void genCatchBlock(JCCatch tree, Env<GenContext> env) {
1712             VarSymbol exparam = tree.param.sym;
1713             code.statBegin(tree.pos);
1714             code.markStatBegin();
1715             int limit = code.nextreg;
1716             code.newLocal(exparam);
1717             items.makeLocalItem(exparam).store();
1718             code.statBegin(TreeInfo.firstStatPos(tree.body));
1719             genStat(tree.body, env, CRT_BLOCK);
1720             code.endScopes(limit);
1721             code.statBegin(TreeInfo.endPos(tree.body));
1722         }
1723         // where
1724         List<Pair<List<Attribute.TypeCompound>, JCExpression>> catchTypesWithAnnotations(JCCatch tree) {
1725             return TreeInfo.isMultiCatch(tree) ?
1726                     catchTypesWithAnnotationsFromMulticatch((JCTypeUnion)tree.param.vartype, tree.param.sym.getRawTypeAttributes()) :
1727                     List.of(new Pair<>(tree.param.sym.getRawTypeAttributes(), tree.param.vartype));
1728         }
1729         // where
1730         List<Pair<List<Attribute.TypeCompound>, JCExpression>> catchTypesWithAnnotationsFromMulticatch(JCTypeUnion tree, List<TypeCompound> first) {
1731             List<JCExpression> alts = tree.alternatives;
1732             List<Pair<List<TypeCompound>, JCExpression>> res = List.of(new Pair<>(first, alts.head));
1733             alts = alts.tail;
1734 
1735             while(alts != null && alts.head != null) {
1736                 JCExpression alt = alts.head;
1737                 if (alt instanceof JCAnnotatedType annotatedType) {
1738                     res = res.prepend(new Pair<>(annotate.fromAnnotations(annotatedType.annotations), alt));
1739                 } else {
1740                     res = res.prepend(new Pair<>(List.nil(), alt));
1741                 }
1742                 alts = alts.tail;
1743             }
1744             return res.reverse();
1745         }
1746 
1747         /** Register a catch clause in the "Exceptions" code-attribute.
1748          */
1749         void registerCatch(DiagnosticPosition pos,
1750                            int startpc, int endpc,
1751                            int handler_pc, int catch_type) {
1752             char startpc1 = (char)startpc;
1753             char endpc1 = (char)endpc;
1754             char handler_pc1 = (char)handler_pc;
1755             if (startpc1 == startpc &&
1756                 endpc1 == endpc &&
1757                 handler_pc1 == handler_pc) {
1758                 code.addCatch(startpc1, endpc1, handler_pc1,
1759                               (char)catch_type);
1760             } else {
1761                 log.error(pos, Errors.LimitCodeTooLargeForTryStmt);
1762                 nerrs++;
1763             }
1764         }
1765 
1766     public void visitIf(JCIf tree) {
1767         int limit = code.nextreg;
1768         Chain thenExit = null;
1769         Assert.check(code.isStatementStart());
1770         CondItem c = genCond(TreeInfo.skipParens(tree.cond),
1771                              CRT_FLOW_CONTROLLER);
1772         Chain elseChain = c.jumpFalse();
1773         Assert.check(code.isStatementStart());
1774         if (!c.isFalse()) {
1775             code.resolve(c.trueJumps);
1776             genStat(tree.thenpart, env, CRT_STATEMENT | CRT_FLOW_TARGET);
1777             thenExit = code.branch(goto_);
1778         }
1779         if (elseChain != null) {
1780             code.resolve(elseChain);
1781             if (tree.elsepart != null) {
1782                 genStat(tree.elsepart, env,CRT_STATEMENT | CRT_FLOW_TARGET);
1783             }
1784         }
1785         code.resolve(thenExit);
1786         code.endScopes(limit);
1787         Assert.check(code.isStatementStart());
1788     }
1789 
1790     public void visitExec(JCExpressionStatement tree) {
1791         // Optimize x++ to ++x and x-- to --x.
1792         JCExpression e = tree.expr;
1793         switch (e.getTag()) {
1794             case POSTINC:
1795                 ((JCUnary) e).setTag(PREINC);
1796                 break;
1797             case POSTDEC:
1798                 ((JCUnary) e).setTag(PREDEC);
1799                 break;
1800         }
1801         Assert.check(code.isStatementStart());
1802         genExpr(tree.expr, tree.expr.type).drop();
1803         Assert.check(code.isStatementStart());
1804     }
1805 
1806     public void visitBreak(JCBreak tree) {
1807         Assert.check(code.isStatementStart());
1808         final Env<GenContext> targetEnv = unwindBreak(tree.target);
1809         targetEnv.info.addExit(code.branch(goto_));
1810         endFinalizerGaps(env, targetEnv);
1811     }
1812 
1813     public void visitYield(JCYield tree) {
1814         Assert.check(code.isStatementStart());
1815         final Env<GenContext> targetEnv;
1816         if (inCondSwitchExpression) {
1817             CondItem value = genCond(tree.value, CRT_FLOW_TARGET);
1818             Chain falseJumps = value.jumpFalse();
1819 
1820             code.resolve(value.trueJumps);
1821             Env<GenContext> localEnv = unwindBreak(tree.target);
1822             reloadStackBeforeSwitchExpr();
1823             Chain trueJumps = code.branch(goto_);
1824 
1825             endFinalizerGaps(env, localEnv);
1826 
1827             code.resolve(falseJumps);
1828             targetEnv = unwindBreak(tree.target);
1829             reloadStackBeforeSwitchExpr();
1830             falseJumps = code.branch(goto_);
1831 
1832             if (switchExpressionTrueChain == null) {
1833                 switchExpressionTrueChain = trueJumps;
1834             } else {
1835                 switchExpressionTrueChain =
1836                         Code.mergeChains(switchExpressionTrueChain, trueJumps);
1837             }
1838             if (switchExpressionFalseChain == null) {
1839                 switchExpressionFalseChain = falseJumps;
1840             } else {
1841                 switchExpressionFalseChain =
1842                         Code.mergeChains(switchExpressionFalseChain, falseJumps);
1843             }
1844         } else {
1845             genExpr(tree.value, pt).load();
1846             if (switchResult != null)
1847                 switchResult.store();
1848 
1849             targetEnv = unwindBreak(tree.target);
1850 
1851             if (code.isAlive()) {
1852                 reloadStackBeforeSwitchExpr();
1853                 if (switchResult != null)
1854                     switchResult.load();
1855 
1856                 code.state.forceStackTop(tree.target.type);
1857                 targetEnv.info.addExit(code.branch(goto_));
1858                 code.markDead();
1859             }
1860         }
1861         endFinalizerGaps(env, targetEnv);
1862     }
1863     //where:
1864         /** As side-effect, might mark code as dead disabling any further emission.
1865          */
1866         private Env<GenContext> unwindBreak(JCTree target) {
1867             int tmpPos = code.pendingStatPos;
1868             Env<GenContext> targetEnv = unwind(target, env);
1869             code.pendingStatPos = tmpPos;
1870             return targetEnv;
1871         }
1872 
1873         private void reloadStackBeforeSwitchExpr() {
1874             for (LocalItem li : stackBeforeSwitchExpression)
1875                 li.load();
1876         }
1877 
1878     public void visitContinue(JCContinue tree) {
1879         int tmpPos = code.pendingStatPos;
1880         Env<GenContext> targetEnv = unwind(tree.target, env);
1881         code.pendingStatPos = tmpPos;
1882         Assert.check(code.isStatementStart());
1883         targetEnv.info.addCont(code.branch(goto_));
1884         endFinalizerGaps(env, targetEnv);
1885     }
1886 
1887     public void visitReturn(JCReturn tree) {
1888         int limit = code.nextreg;
1889         final Env<GenContext> targetEnv;
1890 
1891         /* Save and then restore the location of the return in case a finally
1892          * is expanded (with unwind()) in the middle of our bytecodes.
1893          */
1894         int tmpPos = code.pendingStatPos;
1895         if (tree.expr != null) {
1896             Assert.check(code.isStatementStart());
1897             Item r = genExpr(tree.expr, pt).load();
1898             if (hasFinally(env.enclMethod, env)) {
1899                 r = makeTemp(pt);
1900                 r.store();
1901             }
1902             targetEnv = unwind(env.enclMethod, env);
1903             code.pendingStatPos = tmpPos;
1904             r.load();
1905             code.emitop0(ireturn + Code.truncate(Code.typecode(pt)));
1906         } else {
1907             targetEnv = unwind(env.enclMethod, env);
1908             code.pendingStatPos = tmpPos;
1909             code.emitop0(return_);
1910         }
1911         endFinalizerGaps(env, targetEnv);
1912         code.endScopes(limit);
1913     }
1914 
1915     public void visitThrow(JCThrow tree) {
1916         Assert.check(code.isStatementStart());
1917         genExpr(tree.expr, tree.expr.type).load();
1918         code.emitop0(athrow);
1919         Assert.check(code.isStatementStart());
1920     }
1921 
1922 /* ************************************************************************
1923  * Visitor methods for expressions
1924  *************************************************************************/
1925 
1926     public void visitApply(JCMethodInvocation tree) {
1927         setTypeAnnotationPositions(tree.pos);
1928         // Generate code for method.
1929         Item m = genExpr(tree.meth, methodType);
1930         // Generate code for all arguments, where the expected types are
1931         // the parameters of the method's external type (that is, any implicit
1932         // outer instance of a super(...) call appears as first parameter).
1933         MethodSymbol msym = (MethodSymbol)TreeInfo.symbol(tree.meth);
1934         genArgs(tree.args,
1935                 msym.externalType(types).getParameterTypes());
1936         if (!msym.isDynamic()) {
1937             code.statBegin(tree.pos);
1938         }
1939         if (patternMatchingCatchConfiguration.invocations().contains(tree)) {
1940             int start = code.curCP();
1941             result = m.invoke();
1942             patternMatchingCatchConfiguration.ranges().add(new int[] {start, code.curCP()});
1943         } else {
1944             if (msym.isConstructor() && TreeInfo.isConstructorCall(tree)) {
1945                 //if this is a this(...) or super(...) call, there is a pending
1946                 //"uninitialized this" before this call. One catch handler cannot
1947                 //handle exceptions that may come from places with "uninitialized this"
1948                 //and (initialized) this, hence generate one set of handlers here
1949                 //for the "uninitialized this" case, and another set of handlers
1950                 //will be generated at the end of the method for the initialized this,
1951                 //if needed:
1952                 generatePatternMatchingCatch(env);
1953                 result = m.invoke();
1954                 patternMatchingCatchConfiguration =
1955                         patternMatchingCatchConfiguration.restart(code.state.dup());
1956             } else {
1957                 result = m.invoke();
1958             }
1959         }
1960     }
1961 
1962     public void visitConditional(JCConditional tree) {
1963         Chain thenExit = null;
1964         code.statBegin(tree.cond.pos);
1965         CondItem c = genCond(tree.cond, CRT_FLOW_CONTROLLER);
1966         Chain elseChain = c.jumpFalse();
1967         if (!c.isFalse()) {
1968             code.resolve(c.trueJumps);
1969             int startpc = genCrt ? code.curCP() : 0;
1970             code.statBegin(tree.truepart.pos);
1971             genExpr(tree.truepart, pt).load();
1972             code.state.forceStackTop(tree.type);
1973             if (genCrt) code.crt.put(tree.truepart, CRT_FLOW_TARGET,
1974                                      startpc, code.curCP());
1975             thenExit = code.branch(goto_);
1976         }
1977         if (elseChain != null) {
1978             code.resolve(elseChain);
1979             int startpc = genCrt ? code.curCP() : 0;
1980             code.statBegin(tree.falsepart.pos);
1981             genExpr(tree.falsepart, pt).load();
1982             code.state.forceStackTop(tree.type);
1983             if (genCrt) code.crt.put(tree.falsepart, CRT_FLOW_TARGET,
1984                                      startpc, code.curCP());
1985         }
1986         code.resolve(thenExit);
1987         result = items.makeStackItem(pt);
1988     }
1989 
1990     private void setTypeAnnotationPositions(int treePos) {
1991         MethodSymbol meth = code.meth;
1992         boolean initOrClinit = code.meth.getKind() == javax.lang.model.element.ElementKind.CONSTRUCTOR
1993                 || code.meth.getKind() == javax.lang.model.element.ElementKind.STATIC_INIT;
1994 
1995         for (Attribute.TypeCompound ta : meth.getRawTypeAttributes()) {
1996             if (ta.hasUnknownPosition())
1997                 ta.tryFixPosition();
1998 
1999             if (ta.position.matchesPos(treePos))
2000                 ta.position.updatePosOffset(code.cp);
2001         }
2002 
2003         if (!initOrClinit)
2004             return;
2005 
2006         for (Attribute.TypeCompound ta : meth.owner.getRawTypeAttributes()) {
2007             if (ta.hasUnknownPosition())
2008                 ta.tryFixPosition();
2009 
2010             if (ta.position.matchesPos(treePos))
2011                 ta.position.updatePosOffset(code.cp);
2012         }
2013 
2014         ClassSymbol clazz = meth.enclClass();
2015         for (Symbol s : new com.sun.tools.javac.model.FilteredMemberList(clazz.members())) {
2016             if (!s.getKind().isField())
2017                 continue;
2018 
2019             for (Attribute.TypeCompound ta : s.getRawTypeAttributes()) {
2020                 if (ta.hasUnknownPosition())
2021                     ta.tryFixPosition();
2022 
2023                 if (ta.position.matchesPos(treePos))
2024                     ta.position.updatePosOffset(code.cp);
2025             }
2026         }
2027     }
2028 
2029     public void visitNewClass(JCNewClass tree) {
2030         // Enclosing instances or anonymous classes should have been eliminated
2031         // by now.
2032         Assert.check(tree.encl == null && tree.def == null);
2033         setTypeAnnotationPositions(tree.pos);
2034 
2035         code.emitop2(new_, checkDimension(tree.pos(), tree.type), PoolWriter::putClass);
2036         code.emitop0(dup);
2037 
2038         // Generate code for all arguments, where the expected types are
2039         // the parameters of the constructor's external type (that is,
2040         // any implicit outer instance appears as first parameter).
2041         genArgs(tree.args, tree.constructor.externalType(types).getParameterTypes());
2042 
2043         items.makeMemberItem(tree.constructor, true).invoke();
2044         result = items.makeStackItem(tree.type);
2045     }
2046 
2047     public void visitNewArray(JCNewArray tree) {
2048         setTypeAnnotationPositions(tree.pos);
2049 
2050         if (tree.elems != null) {
2051             Type elemtype = types.elemtype(tree.type);
2052             loadIntConst(tree.elems.length());
2053             Item arr = makeNewArray(tree.pos(), tree.type, 1);
2054             int i = 0;
2055             for (List<JCExpression> l = tree.elems; l.nonEmpty(); l = l.tail) {
2056                 arr.duplicate();
2057                 loadIntConst(i);
2058                 i++;
2059                 genExpr(l.head, elemtype).load();
2060                 items.makeIndexedItem(elemtype).store();
2061             }
2062             result = arr;
2063         } else {
2064             for (List<JCExpression> l = tree.dims; l.nonEmpty(); l = l.tail) {
2065                 genExpr(l.head, syms.intType).load();
2066             }
2067             result = makeNewArray(tree.pos(), tree.type, tree.dims.length());
2068         }
2069     }
2070 //where
2071         /** Generate code to create an array with given element type and number
2072          *  of dimensions.
2073          */
2074         Item makeNewArray(DiagnosticPosition pos, Type type, int ndims) {
2075             Type elemtype = types.elemtype(type);
2076             if (types.dimensions(type) > ClassFile.MAX_DIMENSIONS) {
2077                 log.error(pos, Errors.LimitDimensions);
2078                 nerrs++;
2079             }
2080             int elemcode = Code.arraycode(elemtype);
2081             if (elemcode == 0 || (elemcode == 1 && ndims == 1)) {
2082                 code.emitAnewarray(makeRef(pos, elemtype), type);
2083             } else if (elemcode == 1) {
2084                 code.emitMultianewarray(ndims, makeRef(pos, type), type);
2085             } else {
2086                 code.emitNewarray(elemcode, type);
2087             }
2088             return items.makeStackItem(type);
2089         }
2090 
2091     public void visitParens(JCParens tree) {
2092         result = genExpr(tree.expr, tree.expr.type);
2093     }
2094 
2095     public void visitAssign(JCAssign tree) {
2096         Item l = genExpr(tree.lhs, tree.lhs.type);
2097         genExpr(tree.rhs, tree.lhs.type).load();
2098         if (tree.rhs.type.hasTag(BOT)) {
2099             /* This is just a case of widening reference conversion that per 5.1.5 simply calls
2100                for "regarding a reference as having some other type in a manner that can be proved
2101                correct at compile time."
2102             */
2103             code.state.forceStackTop(tree.lhs.type);
2104         }
2105         result = items.makeAssignItem(l);
2106     }
2107 
2108     public void visitAssignop(JCAssignOp tree) {
2109         OperatorSymbol operator = tree.operator;
2110         Item l;
2111         if (operator.opcode == string_add) {
2112             l = concat.makeConcat(tree);
2113         } else {
2114             // Generate code for first expression
2115             l = genExpr(tree.lhs, tree.lhs.type);
2116 
2117             // If we have an increment of -32768 to +32767 of a local
2118             // int variable we can use an incr instruction instead of
2119             // proceeding further.
2120             if ((tree.hasTag(PLUS_ASG) || tree.hasTag(MINUS_ASG)) &&
2121                 l instanceof LocalItem localItem &&
2122                 tree.lhs.type.getTag().isSubRangeOf(INT) &&
2123                 tree.rhs.type.getTag().isSubRangeOf(INT) &&
2124                 tree.rhs.type.constValue() != null) {
2125                 int ival = ((Number) tree.rhs.type.constValue()).intValue();
2126                 if (tree.hasTag(MINUS_ASG)) ival = -ival;
2127                 localItem.incr(ival);
2128                 result = l;
2129                 return;
2130             }
2131             // Otherwise, duplicate expression, load one copy
2132             // and complete binary operation.
2133             l.duplicate();
2134             l.coerce(operator.type.getParameterTypes().head).load();
2135             completeBinop(tree.lhs, tree.rhs, operator).coerce(tree.lhs.type);
2136         }
2137         result = items.makeAssignItem(l);
2138     }
2139 
2140     public void visitUnary(JCUnary tree) {
2141         OperatorSymbol operator = tree.operator;
2142         if (tree.hasTag(NOT)) {
2143             CondItem od = genCond(tree.arg, false);
2144             result = od.negate();
2145         } else {
2146             Item od = genExpr(tree.arg, operator.type.getParameterTypes().head);
2147             switch (tree.getTag()) {
2148             case POS:
2149                 result = od.load();
2150                 break;
2151             case NEG:
2152                 result = od.load();
2153                 code.emitop0(operator.opcode);
2154                 break;
2155             case COMPL:
2156                 result = od.load();
2157                 emitMinusOne(od.typecode);
2158                 code.emitop0(operator.opcode);
2159                 break;
2160             case PREINC: case PREDEC:
2161                 od.duplicate();
2162                 if (od instanceof LocalItem localItem &&
2163                     (operator.opcode == iadd || operator.opcode == isub)) {
2164                     localItem.incr(tree.hasTag(PREINC) ? 1 : -1);
2165                     result = od;
2166                 } else {
2167                     od.load();
2168                     code.emitop0(one(od.typecode));
2169                     code.emitop0(operator.opcode);
2170                     // Perform narrowing primitive conversion if byte,
2171                     // char, or short.  Fix for 4304655.
2172                     if (od.typecode != INTcode &&
2173                         Code.truncate(od.typecode) == INTcode)
2174                       code.emitop0(int2byte + od.typecode - BYTEcode);
2175                     result = items.makeAssignItem(od);
2176                 }
2177                 break;
2178             case POSTINC: case POSTDEC:
2179                 od.duplicate();
2180                 if (od instanceof LocalItem localItem &&
2181                     (operator.opcode == iadd || operator.opcode == isub)) {
2182                     Item res = od.load();
2183                     localItem.incr(tree.hasTag(POSTINC) ? 1 : -1);
2184                     result = res;
2185                 } else {
2186                     Item res = od.load();
2187                     od.stash(od.typecode);
2188                     code.emitop0(one(od.typecode));
2189                     code.emitop0(operator.opcode);
2190                     // Perform narrowing primitive conversion if byte,
2191                     // char, or short.  Fix for 4304655.
2192                     if (od.typecode != INTcode &&
2193                         Code.truncate(od.typecode) == INTcode)
2194                       code.emitop0(int2byte + od.typecode - BYTEcode);
2195                     od.store();
2196                     result = res;
2197                 }
2198                 break;
2199             case NULLCHK:
2200                 result = od.load();
2201                 code.emitop0(dup);
2202                 genNullCheck(tree);
2203                 break;
2204             default:
2205                 Assert.error();
2206             }
2207         }
2208     }
2209 
2210     /** Generate a null check from the object value at stack top. */
2211     private void genNullCheck(JCTree tree) {
2212         code.statBegin(tree.pos);
2213         callMethod(tree.pos(), syms.objectsType, names.requireNonNull,
2214                    List.of(syms.objectType), true);
2215         code.emitop0(pop);
2216     }
2217 
2218     public void visitBinary(JCBinary tree) {
2219         OperatorSymbol operator = tree.operator;
2220         if (operator.opcode == string_add) {
2221             result = concat.makeConcat(tree);
2222         } else if (tree.hasTag(AND)) {
2223             CondItem lcond = genCond(tree.lhs, CRT_FLOW_CONTROLLER);
2224             if (!lcond.isFalse()) {
2225                 Chain falseJumps = lcond.jumpFalse();
2226                 code.resolve(lcond.trueJumps);
2227                 CondItem rcond = genCond(tree.rhs, CRT_FLOW_TARGET);
2228                 result = items.
2229                     makeCondItem(rcond.opcode,
2230                                  rcond.trueJumps,
2231                                  Code.mergeChains(falseJumps,
2232                                                   rcond.falseJumps));
2233             } else {
2234                 result = lcond;
2235             }
2236         } else if (tree.hasTag(OR)) {
2237             CondItem lcond = genCond(tree.lhs, CRT_FLOW_CONTROLLER);
2238             if (!lcond.isTrue()) {
2239                 Chain trueJumps = lcond.jumpTrue();
2240                 code.resolve(lcond.falseJumps);
2241                 CondItem rcond = genCond(tree.rhs, CRT_FLOW_TARGET);
2242                 result = items.
2243                     makeCondItem(rcond.opcode,
2244                                  Code.mergeChains(trueJumps, rcond.trueJumps),
2245                                  rcond.falseJumps);
2246             } else {
2247                 result = lcond;
2248             }
2249         } else {
2250             Item od = genExpr(tree.lhs, operator.type.getParameterTypes().head);
2251             od.load();
2252             result = completeBinop(tree.lhs, tree.rhs, operator);
2253         }
2254     }
2255 
2256 
2257         /** Complete generating code for operation, with left operand
2258          *  already on stack.
2259          *  @param lhs       The tree representing the left operand.
2260          *  @param rhs       The tree representing the right operand.
2261          *  @param operator  The operator symbol.
2262          */
2263         Item completeBinop(JCTree lhs, JCTree rhs, OperatorSymbol operator) {
2264             MethodType optype = (MethodType)operator.type;
2265             int opcode = operator.opcode;
2266             if (opcode >= if_icmpeq && opcode <= if_icmple &&
2267                     rhs.type.constValue() instanceof Number number &&
2268                     number.intValue() == 0) {
2269                 opcode = opcode + (ifeq - if_icmpeq);
2270             } else if (opcode >= if_acmpeq && opcode <= if_acmpne &&
2271                        TreeInfo.isNull(rhs)) {
2272                 opcode = opcode + (if_acmp_null - if_acmpeq);
2273             } else {
2274                 // The expected type of the right operand is
2275                 // the second parameter type of the operator, except for
2276                 // shifts with long shiftcount, where we convert the opcode
2277                 // to a short shift and the expected type to int.
2278                 Type rtype = operator.erasure(types).getParameterTypes().tail.head;
2279                 if (opcode >= ishll && opcode <= lushrl) {
2280                     opcode = opcode + (ishl - ishll);
2281                     rtype = syms.intType;
2282                 }
2283                 // Generate code for right operand and load.
2284                 genExpr(rhs, rtype).load();
2285                 // If there are two consecutive opcode instructions,
2286                 // emit the first now.
2287                 if (opcode >= (1 << preShift)) {
2288                     code.emitop0(opcode >> preShift);
2289                     opcode = opcode & 0xFF;
2290                 }
2291             }
2292             if (opcode >= ifeq && opcode <= if_acmpne ||
2293                 opcode == if_acmp_null || opcode == if_acmp_nonnull) {
2294                 return items.makeCondItem(opcode);
2295             } else {
2296                 code.emitop0(opcode);
2297                 return items.makeStackItem(optype.restype);
2298             }
2299         }
2300 
2301     public void visitTypeCast(JCTypeCast tree) {
2302         result = genExpr(tree.expr, tree.clazz.type).load();
2303         setTypeAnnotationPositions(tree.pos);
2304         // Additional code is only needed if we cast to a reference type
2305         // which is not statically a supertype of the expression's type.
2306         // For basic types, the coerce(...) in genExpr(...) will do
2307         // the conversion.
2308         if (!tree.clazz.type.isPrimitive() &&
2309            !types.isSameType(tree.expr.type, tree.clazz.type) &&
2310            types.asSuper(tree.expr.type, tree.clazz.type.tsym) == null) {
2311             code.emitop2(checkcast, checkDimension(tree.pos(), tree.clazz.type), PoolWriter::putClass);
2312         }
2313     }
2314 
2315     public void visitWildcard(JCWildcard tree) {
2316         throw new AssertionError(this.getClass().getName());
2317     }
2318 
2319     public void visitTypeTest(JCInstanceOf tree) {
2320         genExpr(tree.expr, tree.expr.type).load();
2321         setTypeAnnotationPositions(tree.pos);
2322         code.emitop2(instanceof_, makeRef(tree.pos(), tree.pattern.type));
2323         result = items.makeStackItem(syms.booleanType);
2324     }
2325 
2326     public void visitIndexed(JCArrayAccess tree) {
2327         genExpr(tree.indexed, tree.indexed.type).load();
2328         genExpr(tree.index, syms.intType).load();
2329         result = items.makeIndexedItem(tree.type);
2330     }
2331 
2332     public void visitIdent(JCIdent tree) {
2333         Symbol sym = tree.sym;
2334         if (tree.name == names._this || tree.name == names._super) {
2335             Item res = tree.name == names._this
2336                 ? items.makeThisItem()
2337                 : items.makeSuperItem();
2338             if (sym.kind == MTH) {
2339                 // Generate code to address the constructor.
2340                 res.load();
2341                 res = items.makeMemberItem(sym, true);
2342             }
2343             result = res;
2344        } else if (isInvokeDynamic(sym) || isConstantDynamic(sym)) {
2345             if (isConstantDynamic(sym)) {
2346                 setTypeAnnotationPositions(tree.pos);
2347             }
2348             result = items.makeDynamicItem(sym);
2349         } else if (sym.kind == VAR && (sym.owner.kind == MTH || sym.owner.kind == VAR)) {
2350             result = items.makeLocalItem((VarSymbol)sym);
2351         } else if ((sym.flags() & STATIC) != 0) {
2352             if (!isAccessSuper(env.enclMethod))
2353                 sym = binaryQualifier(sym, env.enclClass.type);
2354             result = items.makeStaticItem(sym);
2355         } else {
2356             items.makeThisItem().load();
2357             sym = binaryQualifier(sym, env.enclClass.type);
2358             result = items.makeMemberItem(sym, nonVirtualForPrivateAccess(sym));
2359         }
2360     }
2361 
2362     //where
2363     private boolean nonVirtualForPrivateAccess(Symbol sym) {
2364         boolean useVirtual = target.hasVirtualPrivateInvoke() &&
2365                              !disableVirtualizedPrivateInvoke;
2366         return !useVirtual && ((sym.flags() & PRIVATE) != 0);
2367     }
2368 
2369     public void visitSelect(JCFieldAccess tree) {
2370         Symbol sym = tree.sym;
2371 
2372         if (tree.name == names._class) {
2373             code.emitLdc((LoadableConstant)checkDimension(tree.pos(), tree.selected.type));
2374             result = items.makeStackItem(pt);
2375             return;
2376        }
2377 
2378         Symbol ssym = TreeInfo.symbol(tree.selected);
2379 
2380         // Are we selecting via super?
2381         boolean selectSuper =
2382             ssym != null && (ssym.kind == TYP || ssym.name == names._super);
2383 
2384         // Are we accessing a member of the superclass in an access method
2385         // resulting from a qualified super?
2386         boolean accessSuper = isAccessSuper(env.enclMethod);
2387 
2388         Item base = (selectSuper)
2389             ? items.makeSuperItem()
2390             : genExpr(tree.selected, tree.selected.type);
2391 
2392         if (sym.kind == VAR && ((VarSymbol) sym).getConstValue() != null) {
2393             // We are seeing a variable that is constant but its selecting
2394             // expression is not.
2395             if ((sym.flags() & STATIC) != 0) {
2396                 if (!selectSuper && (ssym == null || ssym.kind != TYP))
2397                     base = base.load();
2398                 base.drop();
2399             } else {
2400                 base.load();
2401                 genNullCheck(tree.selected);
2402             }
2403             result = items.
2404                 makeImmediateItem(sym.type, ((VarSymbol) sym).getConstValue());
2405         } else {
2406             if (isInvokeDynamic(sym)) {
2407                 result = items.makeDynamicItem(sym);
2408                 return;
2409             } else {
2410                 sym = binaryQualifier(sym, tree.selected.type);
2411             }
2412             if ((sym.flags() & STATIC) != 0) {
2413                 if (!selectSuper && (ssym == null || ssym.kind != TYP))
2414                     base = base.load();
2415                 base.drop();
2416                 result = items.makeStaticItem(sym);
2417             } else {
2418                 base.load();
2419                 if (sym == syms.lengthVar) {
2420                     code.emitop0(arraylength);
2421                     result = items.makeStackItem(syms.intType);
2422                 } else {
2423                     result = items.
2424                         makeMemberItem(sym,
2425                                        nonVirtualForPrivateAccess(sym) ||
2426                                        selectSuper || accessSuper);
2427                 }
2428             }
2429         }
2430     }
2431 
2432     public boolean isInvokeDynamic(Symbol sym) {
2433         return sym.kind == MTH && ((MethodSymbol)sym).isDynamic();
2434     }
2435 
2436     public void visitLiteral(JCLiteral tree) {
2437         if (tree.type.hasTag(BOT)) {
2438             code.emitop0(aconst_null);
2439             result = items.makeStackItem(tree.type);
2440         }
2441         else
2442             result = items.makeImmediateItem(tree.type, tree.value);
2443     }
2444 
2445     public void visitLetExpr(LetExpr tree) {
2446         code.resolvePending();
2447 
2448         int limit = code.nextreg;
2449         int prevLetExprStart = code.setLetExprStackPos(code.state.stacksize);
2450         try {
2451             genStats(tree.defs, env);
2452         } finally {
2453             code.setLetExprStackPos(prevLetExprStart);
2454         }
2455         result = genExpr(tree.expr, tree.expr.type).load();
2456         code.endScopes(limit);
2457     }
2458 
2459     private void generateReferencesToPrunedTree(ClassSymbol classSymbol) {
2460         List<JCTree> prunedInfo = lower.prunedTree.get(classSymbol);
2461         if (prunedInfo != null) {
2462             for (JCTree prunedTree: prunedInfo) {
2463                 prunedTree.accept(classReferenceVisitor);
2464             }
2465         }
2466     }
2467 
2468 /* ************************************************************************
2469  * main method
2470  *************************************************************************/
2471 
2472     /** Generate code for a class definition.
2473      *  @param env   The attribution environment that belongs to the
2474      *               outermost class containing this class definition.
2475      *               We need this for resolving some additional symbols.
2476      *  @param cdef  The tree representing the class definition.
2477      *  @return      True if code is generated with no errors.
2478      */
2479     public boolean genClass(Env<AttrContext> env, JCClassDecl cdef) {
2480         try {
2481             attrEnv = env;
2482             ClassSymbol c = cdef.sym;
2483             this.toplevel = env.toplevel;
2484             this.endPosTable = toplevel.endPositions;
2485             /* method normalizeDefs() can add references to external classes into the constant pool
2486              */
2487             cdef.defs = normalizeDefs(cdef.defs, c);
2488             generateReferencesToPrunedTree(c);
2489             Env<GenContext> localEnv = new Env<>(cdef, new GenContext());
2490             localEnv.toplevel = env.toplevel;
2491             localEnv.enclClass = cdef;
2492 
2493             for (List<JCTree> l = cdef.defs; l.nonEmpty(); l = l.tail) {
2494                 genDef(l.head, localEnv);
2495             }
2496             if (poolWriter.size() > PoolWriter.MAX_ENTRIES) {
2497                 log.error(cdef.pos(), Errors.LimitPool);
2498                 nerrs++;
2499             }
2500             if (nerrs != 0) {
2501                 // if errors, discard code
2502                 for (List<JCTree> l = cdef.defs; l.nonEmpty(); l = l.tail) {
2503                     if (l.head.hasTag(METHODDEF))
2504                         ((JCMethodDecl) l.head).sym.code = null;
2505                 }
2506             }
2507             cdef.defs = List.nil(); // discard trees
2508             return nerrs == 0;
2509         } finally {
2510             // note: this method does NOT support recursion.
2511             attrEnv = null;
2512             this.env = null;
2513             toplevel = null;
2514             endPosTable = null;
2515             nerrs = 0;
2516             qualifiedSymbolCache.clear();
2517         }
2518     }
2519 
2520 /* ************************************************************************
2521  * Auxiliary classes
2522  *************************************************************************/
2523 
2524     /** An abstract class for finalizer generation.
2525      */
2526     abstract class GenFinalizer {
2527         /** Generate code to clean up when unwinding. */
2528         abstract void gen();
2529 
2530         /** Generate code to clean up at last. */
2531         abstract void genLast();
2532 
2533         /** Does this finalizer have some nontrivial cleanup to perform? */
2534         boolean hasFinalizer() { return true; }
2535 
2536         /** Should be invoked after the try's body has been visited. */
2537         void afterBody() {}
2538     }
2539 
2540     /** code generation contexts,
2541      *  to be used as type parameter for environments.
2542      */
2543     static class GenContext {
2544 
2545         /** A chain for all unresolved jumps that exit the current environment.
2546          */
2547         Chain exit = null;
2548 
2549         /** A chain for all unresolved jumps that continue in the
2550          *  current environment.
2551          */
2552         Chain cont = null;
2553 
2554         /** A closure that generates the finalizer of the current environment.
2555          *  Only set for Synchronized and Try contexts.
2556          */
2557         GenFinalizer finalize = null;
2558 
2559         /** Is this a switch statement?  If so, allocate registers
2560          * even when the variable declaration is unreachable.
2561          */
2562         boolean isSwitch = false;
2563 
2564         /** A list buffer containing all gaps in the finalizer range,
2565          *  where a catch all exception should not apply.
2566          */
2567         ListBuffer<Integer> gaps = null;
2568 
2569         /** Add given chain to exit chain.
2570          */
2571         void addExit(Chain c)  {
2572             exit = Code.mergeChains(c, exit);
2573         }
2574 
2575         /** Add given chain to cont chain.
2576          */
2577         void addCont(Chain c) {
2578             cont = Code.mergeChains(c, cont);
2579         }
2580     }
2581 
2582     record PatternMatchingCatchConfiguration(Set<JCMethodInvocation> invocations,
2583                                             ListBuffer<int[]> ranges,
2584                                             JCCatch handler,
2585                                             State startState) {
2586         public PatternMatchingCatchConfiguration restart(State newState) {
2587             return new PatternMatchingCatchConfiguration(invocations(),
2588                                                         new ListBuffer<int[]>(),
2589                                                         handler(),
2590                                                         newState);
2591         }
2592     }
2593 }
--- EOF ---