text: "use strict";
  /*
   * Copyright (c) 2014-2020 Vanessa Freudenberg
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  Object.subclass('Squeak.Compiler',
  
  /****************************************************************************
  
  VM and Compiler
  ===============
  
  The VM has an interpreter, it will work fine (and much more memory-efficient)
  without loading a compiler. The compiler plugs into the VM by providing the
  Squeak.Compiler global. It can be easily replaced by just loading a different
  script providing Squeak.Compiler.
  
  The VM creates the compiler instance after an image has been loaded and the VM
  been initialized. Whenever a method is activated that was not compiled yet, the
  compiler gets a chance to compile it. The compiler may decide to wait for a couple
  of activations before actually compiling it. This might prevent do-its from ever
  getting compiled, because they are only activated once. Therefore, the compiler
  is also called when a long-running non-optimized loop calls checkForInterrupts.
  Finally, whenever the interpreter is about to execute a bytecode, it calls the
  compiled method instead (which typically will execute many bytecodes):
  
      initialize:
          compiler = new Squeak.Compiler(vm);
  
      executeNewMethod, checkForInterrupts:
          if (!method.compiled && compiler)
              compiler.compile(method);
  
      interpret:
          if (method.compiled) method.compiled(vm);
  
  Note that a compiler could hook itself into a compiled method by dispatching
  to vm.compiler in the generated code. This would allow gathering statistics,
  recompiling with optimized code etc.
  
  
  About This Compiler
  ===================
  
  The compiler in this file is meant to be simple, fast-compiling, and general.
  It transcribes bytecodes 1-to-1 into equivalent JavaScript code using
  templates (and thus can even support single-stepping). It uses the
  interpreter's stack pointer (SP) and program counter (PC), actual context
  objects just like the interpreter, no register mapping, it does not optimize
  sends, etc.
  
  Jumps are handled by wrapping the whole method in a loop and switch. This also
  enables continuing in the middle of a compiled method: whenever another context
  is activated, the method returns to the main loop, and is entered again later
  with a different PC. Here is an example method, its bytecodes, and a simplified
  version of the generated JavaScript code:
  
      method
          [value selector] whileFalse.
          ^ 42
  
      0 <00> pushInstVar: 0
      1 <D0> send: #selector
      2 <A8 02> jumpIfTrue: 6
      4 <A3 FA> jumpTo: 0
      6 <21> pushConst: 42
      7 <7C> return: topOfStack
  
      context = vm.activeContext
      while (true) switch (vm.pc) {
      case 0:
          stack[++vm.sp] = inst[0];
          vm.pc = 2; vm.send(#selector); // activate new method
          return; // return to main loop
          // Main loop will execute the activated method. When
          // that method returns, this method will be called
          // again with vm.pc == 2 and jump directly to case 2
      case 2:
          if (stack[vm.sp--] === vm.trueObj) {
              vm.pc = 6;
              continue; // jump to case 6
          }
          // otherwise fall through to next case
      case 4:
          vm.pc = 0;
          continue; // jump to case 0
      case 6:
          stack[++vm.sp] = 42;
          vm.pc = 7; vm.doReturn(stack[vm.sp]);
          return;
      }
  
  Debugging support
  =================
  
  This compiler supports generating single-stepping code and comments, which are
  rather helpful during debugging.
  
  Normally, only bytecodes that can be a jump target are given a label. Also,
  bytecodes following a send operation need a label, to enable returning to that
  spot after the context switch. All other bytecodes are executed continuously.
  
  When compiling for single-stepping, each bytecode gets a label, and after each
  bytecode a flag is checked and the method returns if needed. Because this is
  a performance penalty, methods are first compiled without single-step support,
  and recompiled for single-stepping on demand.
  
  This is optional, another compiler can answer false from enableSingleStepping().
  In that case the VM will delete the compiled method and invoke the interpreter
  to single-step.
  
  *****************************************************************************/
  
  'initialization', {
      initialize: function(vm) {
          this.vm = vm;
          this.comments = !!Squeak.Compiler.comments, // generate comments
          // for debug-printing only
          this.specialSelectors = ['+', '-', '<', '>', '<=', '>=', '=', '~=', '*', '/', '\\', '@',
              'bitShift:', '//', 'bitAnd:', 'bitOr:', 'at:', 'at:put:', 'size', 'next', 'nextPut:',
              'atEnd', '==', 'class', 'blockCopy:', 'value', 'value:', 'do:', 'new', 'new:', 'x', 'y'];
      },
  },
  'accessing', {
      compile: function(method, optClass, optSel) {
          if (method.compiled === undefined) {
              // 1st time
              method.compiled = false;
          } else {
              // 2nd time
              this.singleStep = false;
              this.debug = this.comments;
              var clsName = optClass && optClass.className(),
                  sel = optSel && optSel.bytesAsString();
              method.compiled = this.generate(method, clsName, sel);
          }
      },
      enableSingleStepping: function(method, optClass, optSel) {
          // recompile method for single-stepping
          if (!method.compiled || !method.compiled.canSingleStep) {
              this.singleStep = true; // generate breakpoint support
              this.debug = true;
              if (!optClass) {
                  this.vm.allMethodsDo(function(classObj, methodObj, selectorObj) {
                      if (methodObj === method) {
                          optClass = classObj;
                          optSel = selectorObj;
                          return true;
                      }
                  });
              }
              var cls = optClass && optClass.className();
              var sel = optSel && optSel.bytesAsString();
              var instVars = optClass && optClass.allInstVarNames();
              method.compiled = this.generate(method, cls, sel, instVars);
              method.compiled.canSingleStep = true;
          }
          // if a compiler does not support single-stepping, return false
          return true;
      },
      functionNameFor: function(cls, sel) {
          if (cls === undefined || cls === '?') return "Squeak_DOIT";
          if (!/[^a-zA-Z0-9:_]/.test(sel))
              return (cls + "_" + sel).replace(/[: ]/g, "_");
          var op = sel.replace(/./g, function(char) {
              var repl = {'|': "OR", '~': "NOT", '<': "LT", '=': "EQ", '>': "GT",
                      '&': "AND", '@': "AT", '*': "TIMES", '+': "PLUS", '\\': "MOD",
                      '-': "MINUS", ',': "COMMA", '/': "DIV", '?': "IF"}[char];
              return repl || 'OPERATOR';
          });
          return cls.replace(/[ ]/, "_") + "__" + op + "__";
      },
  },
  'generating', {
      generate: function(method, optClass, optSel, optInstVarNames) {
          this.method = method;
          this.pc = 0;                // next bytecode
          this.endPC = 0;             // pc of furthest jump target
          this.prevPC = 0;            // pc at start of current instruction
          this.source = [];           // snippets will be joined in the end
          this.sourceLabels = {};     // source pos of generated labels
          this.needsLabel = {};       // jump targets
          this.sourcePos = {};        // source pos of optional vars / statements
          this.needsVar = {};         // true if var was used
          this.needsBreak = false;    // insert break check for previous bytecode
          if (optClass && optSel)
              this.source.push("// ", optClass, ">>", optSel, "\n");
          this.instVarNames = optInstVarNames;
          this.allVars = ['context', 'stack', 'rcvr', 'inst[', 'temp[', 'lit['];
          this.sourcePos['context']    = this.source.length; this.source.push("var context = vm.activeContext;\n");
          this.sourcePos['stack']      = this.source.length; this.source.push("var stack = context.pointers;\n");
          this.sourcePos['rcvr']       = this.source.length; this.source.push("var rcvr = vm.receiver;\n");
          this.sourcePos['inst[']      = this.source.length; this.source.push("var inst = rcvr.pointers;\n");
          this.sourcePos['temp[']      = this.source.length; this.source.push("var temp = vm.homeContext.pointers;\n");
          this.sourcePos['lit[']       = this.source.length; this.source.push("var lit = vm.method.pointers;\n");
          this.sourcePos['loop-start'] = this.source.length; this.source.push("while (true) switch (vm.pc) {\ncase 0:\n");
          this.done = false;
          while (!this.done) {
              var byte = method.bytes[this.pc++],
                  byte2 = 0;
              switch (byte & 0xF8) {
                  // load inst var
                  case 0x00: case 0x08:
                      this.generatePush("inst[", byte & 0x0F, "]");
                      break;
                  // load temp var
                  case 0x10: case 0x18:
                      this.generatePush("temp[", 6 + (byte & 0xF), "]");
                      break;
                  // loadLiteral
                  case 0x20: case 0x28: case 0x30: case 0x38:
                      this.generatePush("lit[", 1 + (byte & 0x1F), "]");
                      break;
                  // loadLiteralIndirect
                  case 0x40: case 0x48: case 0x50: case 0x58:
                      this.generatePush("lit[", 1 + (byte & 0x1F), "].pointers[1]");
                      break;
                  // storeAndPop inst var
                  case 0x60:
                      this.generatePopInto("inst[", byte & 0x07, "]");
                      break;
                  // storeAndPop temp var
                  case 0x68:
                      this.generatePopInto("temp[", 6 + (byte & 0x07), "]");
                      break;
                  // Quick push
                  case 0x70:
                      switch (byte) {
                          case 0x70: this.generatePush("rcvr"); break;
                          case 0x71: this.generatePush("vm.trueObj"); break;
                          case 0x72: this.generatePush("vm.falseObj"); break;
                          case 0x73: this.generatePush("vm.nilObj"); break;
                          case 0x74: this.generatePush("-1"); break;
                          case 0x75: this.generatePush("0"); break;
                          case 0x76: this.generatePush("1"); break;
                          case 0x77: this.generatePush("2"); break;
                      }
                      break;
                  // Quick return
                  case 0x78:
                      switch (byte) {
                          case 0x78: this.generateReturn("rcvr"); break;
                          case 0x79: this.generateReturn("vm.trueObj"); break;
                          case 0x7A: this.generateReturn("vm.falseObj"); break;
                          case 0x7B: this.generateReturn("vm.nilObj"); break;
                          case 0x7C: this.generateReturn("stack[vm.sp]"); break;
                          case 0x7D: this.generateBlockReturn(); break;
                          default: throw Error("unusedBytecode");
                      }
                      break;
                  // Extended bytecodes
                  case 0x80: case 0x88:
                      this.generateExtended(byte);
                      break;
                  // short jump
                  case 0x90:
                      this.generateJump((byte & 0x07) + 1);
                      break;
                  // short conditional jump
                  case 0x98:
                      this.generateJumpIf(false, (byte & 0x07) + 1);
                      break;
                  // long jump, forward and back
                  case 0xA0:
                      byte2 = method.bytes[this.pc++];
                      this.generateJump(((byte&7)-4) * 256 + byte2);
                      break;
                  // long conditional jump
                  case 0xA8:
                      byte2 = method.bytes[this.pc++];
                      this.generateJumpIf(byte < 0xAC, (byte & 3) * 256 + byte2);
                      break;
                  // SmallInteger ops: + - < > <= >= = ~= * /  @ lshift: lxor: land: lor:
                  case 0xB0: case 0xB8:
                      this.generateNumericOp(byte);
                      break;
                  // quick primitives: // at:, at:put:, size, next, nextPut:, ...
                  case 0xC0: case 0xC8:
                      this.generateQuickPrim(byte);
                      break;
                  // send literal selector
                  case 0xD0: case 0xD8:
                      this.generateSend("lit[", 1 + (byte & 0x0F), "]", 0, false);
                      break;
                  case 0xE0: case 0xE8:
                      this.generateSend("lit[", 1 + (byte & 0x0F), "]", 1, false);
                      break;
                  case 0xF0: case 0xF8:
                      this.generateSend("lit[", 1 + (byte & 0x0F), "]", 2, false);
                      break;
              }
          }
          var funcName = this.functionNameFor(optClass, optSel);
          if (this.singleStep) {
              if (this.debug) this.source.push("// all valid PCs have a label;\n");
              this.source.push("default: throw Error('invalid PC');\n}"); // all PCs handled
          } else {
              this.sourcePos['loop-end'] = this.source.length; this.source.push("default: vm.interpretOne(true); return;\n}");
              this.deleteUnneededLabels();
          }
          this.deleteUnneededVariables();
          return new Function("'use strict';\nreturn function " + funcName + "(vm) {\n" + this.source.join("") + "}")();
      },
      generateExtended: function(bytecode) {
          var byte2, byte3;
          switch (bytecode) {
              // extended push
              case 0x80:
                  byte2 = this.method.bytes[this.pc++];
                  switch (byte2 >> 6) {
                      case 0: this.generatePush("inst[", byte2 & 0x3F, "]"); return;
                      case 1: this.generatePush("temp[", 6 + (byte2 & 0x3F), "]"); return;
                      case 2: this.generatePush("lit[", 1 + (byte2 & 0x3F), "]"); return;
                      case 3: this.generatePush("lit[", 1 + (byte2 & 0x3F), "].pointers[1]"); return;
                  }
              // extended store
              case 0x81:
                  byte2 = this.method.bytes[this.pc++];
                  switch (byte2 >> 6) {
                      case 0: this.generateStoreInto("inst[", byte2 & 0x3F, "]"); return;
                      case 1: this.generateStoreInto("temp[", 6 + (byte2 & 0x3F), "]"); return;
                      case 2: throw Error("illegal store into literal");
                      case 3: this.generateStoreInto("lit[", 1 + (byte2 & 0x3F), "].pointers[1]"); return;
                  }
                  return;
              // extended pop into
              case 0x82:
                  byte2 = this.method.bytes[this.pc++];
                  switch (byte2 >> 6) {
                      case 0: this.generatePopInto("inst[", byte2 & 0x3F, "]"); return;
                      case 1: this.generatePopInto("temp[", 6 + (byte2 & 0x3F), "]"); return;
                      case 2: throw Error("illegal pop into literal");
                      case 3: this.generatePopInto("lit[", 1 + (byte2 & 0x3F), "].pointers[1]"); return;
                  }
              // Single extended send
              case 0x83:
                  byte2 = this.method.bytes[this.pc++];
                  this.generateSend("lit[", 1 + (byte2 & 0x1F), "]", byte2 >> 5, false);
                  return;
              // Double extended do-anything
              case 0x84:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  switch (byte2 >> 5) {
                      case 0: this.generateSend("lit[", 1 + byte3, "]", byte2 & 31, false); return;
                      case 1: this.generateSend("lit[", 1 + byte3, "]", byte2 & 31, true); return;
                      case 2: this.generatePush("inst[", byte3, "]"); return;
                      case 3: this.generatePush("lit[", 1 + byte3, "]"); return;
                      case 4: this.generatePush("lit[", 1 + byte3, "].pointers[1]"); return;
                      case 5: this.generateStoreInto("inst[", byte3, "]"); return;
                      case 6: this.generatePopInto("inst[", byte3, "]"); return;
                      case 7: this.generateStoreInto("lit[", 1 + byte3, "].pointers[1]"); return;
                  }
              // Single extended send to super
              case 0x85:
                  byte2 = this.method.bytes[this.pc++];
                  this.generateSend("lit[", 1 + (byte2 & 0x1F), "]", byte2 >> 5, true);
                  return;
              // Second extended send
              case 0x86:
                   byte2 = this.method.bytes[this.pc++];
                   this.generateSend("lit[", 1 + (byte2 & 0x3F), "]", byte2 >> 6, false);
                   return;
              // pop
              case 0x87:
                  this.generateInstruction("pop", "vm.sp--");
                  return;
              // dup
              case 0x88:
                  this.needsVar['stack'] = true;
                  this.generateInstruction("dup", "var dup = stack[vm.sp]; stack[++vm.sp] = dup");
                  return;
              // thisContext
              case 0x89:
                  this.needsVar['stack'] = true;
                  this.generateInstruction("push thisContext", "stack[++vm.sp] = vm.exportThisContext()");
                  return;
              // closures
              case 0x8A:
                  byte2 = this.method.bytes[this.pc++];
                  var popValues = byte2 > 127,
                      count = byte2 & 127;
                  this.generateClosureTemps(count, popValues);
                  return;
              // call primitive
              case 0x8B:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  this.generateCallPrimitive(byte2 + 256 * byte3);
                  return
              // remote push from temp vector
              case 0x8C:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  this.generatePush("temp[", 6 + byte3, "].pointers[", byte2, "]");
                  return;
              // remote store into temp vector
              case 0x8D:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  this.generateStoreInto("temp[", 6 + byte3, "].pointers[", byte2, "]");
                  return;
              // remote store and pop into temp vector
              case 0x8E:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  this.generatePopInto("temp[", 6 + byte3, "].pointers[", byte2, "]");
                  return;
              // pushClosureCopy
              case 0x8F:
                  byte2 = this.method.bytes[this.pc++];
                  byte3 = this.method.bytes[this.pc++];
                  var byte4 = this.method.bytes[this.pc++];
                  var numArgs = byte2 & 0xF,
                      numCopied = byte2 >> 4,
                      blockSize = byte3 << 8 | byte4;
                  this.generateClosureCopy(numArgs, numCopied, blockSize);
                  return;
          }
      },
      generatePush: function(target, arg1, suffix1, arg2, suffix2) {
          if (this.debug) this.generateDebugCode("push", target, arg1, suffix1, arg2, suffix2);
          this.generateLabel();
          this.needsVar[target] = true;
          this.needsVar['stack'] = true;
          this.source.push("stack[++vm.sp] = ", target);
          if (arg1 !== undefined) {
              this.source.push(arg1, suffix1);
              if (arg2 !== undefined) {
                  this.source.push(arg2, suffix2);
              }
          }
          this.source.push(";\n");
      },
      generateStoreInto: function(target, arg1, suffix1, arg2, suffix2) {
          if (this.debug) this.generateDebugCode("store into", target, arg1, suffix1, arg2, suffix2);
          this.generateLabel();
          this.needsVar[target] = true;
          this.needsVar['stack'] = true;
          this.source.push(target);
          if (arg1 !== undefined) {
              this.source.push(arg1, suffix1);
              if (arg2 !== undefined) {
                  this.source.push(arg2, suffix2);
              }
          }
          this.source.push(" = stack[vm.sp];\n");
          this.generateDirty(target, arg1);
      },
      generatePopInto: function(target, arg1, suffix1, arg2, suffix2) {
          if (this.debug) this.generateDebugCode("pop into", target, arg1, suffix1, arg2, suffix2);
          this.generateLabel();
          this.needsVar[target] = true;
          this.needsVar['stack'] = true;
          this.source.push(target);
          if (arg1 !== undefined) {
              this.source.push(arg1, suffix1);
              if (arg2 !== undefined) {
                  this.source.push(arg2, suffix2);
              }
          }
          this.source.push(" = stack[vm.sp--];\n");
          this.generateDirty(target, arg1);
      },
      generateReturn: function(what) {
          if (this.debug) this.generateDebugCode("return", what);
          this.generateLabel();
          this.needsVar[what] = true;
          this.source.push(
              "vm.pc = ", this.pc, "; vm.doReturn(", what, "); return;\n");
          this.needsBreak = false; // returning anyway
          this.done = this.pc > this.endPC;
      },
      generateBlockReturn: function() {
          if (this.debug) this.generateDebugCode("block return");
          this.generateLabel();
          this.needsVar['stack'] = true;
          // actually stack === context.pointers but that would look weird
          this.source.push(
              "vm.pc = ", this.pc, "; vm.doReturn(stack[vm.sp--], context.pointers[0]); return;\n");
          this.needsBreak = false; // returning anyway
      },
      generateJump: function(distance) {
          var destination = this.pc + distance;
          if (this.debug) this.generateDebugCode("jump to " + destination);
          this.generateLabel();
          this.needsVar['context'] = true;
          this.source.push("vm.pc = ", destination, "; ");
          if (distance < 0) this.source.push(
              "\nif (vm.interruptCheckCounter-- <= 0) {\n",
              "   vm.checkForInterrupts();\n",
              "   if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return;\n",
              "}\n");
          if (this.singleStep) this.source.push("\nif (vm.breakOutOfInterpreter) return;\n");
          this.source.push("continue;\n");
          this.needsBreak = false; // already checked
          this.needsLabel[destination] = true;
          if (destination > this.endPC) this.endPC = destination;
      },
      generateJumpIf: function(condition, distance) {
          var destination = this.pc + distance;
          if (this.debug) this.generateDebugCode("jump if " + condition + " to " + destination);
          this.generateLabel();
          this.needsVar['stack'] = true;
          this.source.push(
              "var cond = stack[vm.sp--]; if (cond === vm.", condition, "Obj) {vm.pc = ", destination, "; ");
          if (this.singleStep) this.source.push("if (vm.breakOutOfInterpreter) return; else ");
          this.source.push("continue}\n",
              "else if (cond !== vm.", !condition, "Obj) {vm.sp++; vm.pc = ", this.pc, "; vm.send(vm.specialObjects[25], 0, false); return}\n");
          this.needsLabel[this.pc] = true; // for coming back after #mustBeBoolean send
          this.needsLabel[destination] = true; // obviously
          if (destination > this.endPC) this.endPC = destination;
      },
      generateQuickPrim: function(byte) {
          if (this.debug) this.generateDebugCode("quick prim " + this.specialSelectors[(byte & 0x0F) + 16]);
          this.generateLabel();
          switch (byte) {
              //case 0xC0: return this.popNandPushIfOK(2, this.objectAt(true,true,false)); // at:
              //case 0xC1: return this.popNandPushIfOK(3, this.objectAtPut(true,true,false)); // at:put:
              case 0xC2: // size
                  this.needsVar['stack'] = true;
                  this.source.push(
                      "if (stack[vm.sp].sqClass === vm.specialObjects[7]) stack[vm.sp] = stack[vm.sp].pointersSize();\n",
                      "else if (stack[vm.sp].sqClass === vm.specialObjects[6]) stack[vm.sp] = stack[vm.sp].bytesSize();\n",
                      "else { vm.pc = ", this.pc, "; vm.sendSpecial(18); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return; }\n");
                  this.needsLabel[this.pc] = true;
                  return;
              //case 0xC3: return false; // next
              //case 0xC4: return false; // nextPut:
              //case 0xC5: return false; // atEnd
              case 0xC6: // ==
                  this.needsVar['stack'] = true;
                  this.source.push("var cond = stack[vm.sp-1] === stack[vm.sp];\nstack[--vm.sp] = cond ? vm.trueObj : vm.falseObj;\n");
                  return;
              case 0xC7: // class
                  this.needsVar['stack'] = true;
                  this.source.push("stack[vm.sp] = typeof stack[vm.sp] === 'number' ? vm.specialObjects[5] : stack[vm.sp].sqClass;\n");
                  return;
              case 0xC8: // blockCopy:
                  this.needsVar['rcvr'] = true;
                  this.source.push(
                      "vm.pc = ", this.pc, "; if (!vm.primHandler.quickSendOther(rcvr, ", (byte & 0x0F), ")) ",
                      "{vm.sendSpecial(", ((byte & 0x0F) + 16), "); return}\n");
                  this.needsLabel[this.pc] = true;        // for send
                  this.needsLabel[this.pc + 2] = true;    // for start of block
                  return;
              case 0xC9: // value
              case 0xCA: // value:
              case 0xCB: // do:
                  this.needsVar['rcvr'] = true;
                  this.source.push(
                      "vm.pc = ", this.pc, "; if (!vm.primHandler.quickSendOther(rcvr, ", (byte & 0x0F), ")) vm.sendSpecial(", ((byte & 0x0F) + 16), "); return;\n");
                  this.needsLabel[this.pc] = true;
                  return;
              //case 0xCC: return false; // new
              //case 0xCD: return false; // new:
              //case 0xCE: return false; // x
              //case 0xCF: return false; // y
          }
          // generic version for the bytecodes not yet handled above
          this.needsVar['rcvr'] = true;
          this.needsVar['context'] = true;
          this.source.push(
              "vm.pc = ", this.pc, "; if (!vm.primHandler.quickSendOther(rcvr, ", (byte & 0x0F), "))",
              " vm.sendSpecial(", ((byte & 0x0F) + 16), ");\n",
              "if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return;\n");
          this.needsBreak = false; // already checked
          // if falling back to a full send we need a label for coming back
          this.needsLabel[this.pc] = true;
      },
      generateNumericOp: function(byte) {
          if (this.debug) this.generateDebugCode("numeric op " + this.specialSelectors[byte & 0x0F]);
          this.generateLabel();
          // if the op cannot be executed here, do a full send and return to main loop
          // we need a label for coming back
          this.needsLabel[this.pc] = true;
          switch (byte) {
              case 0xB0: // PLUS +
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = vm.primHandler.signed32BitIntegerFor(a + b);\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(0); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB1: // MINUS -
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = vm.primHandler.signed32BitIntegerFor(a - b);\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(1); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB2: // LESS <
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a < b ? vm.trueObj : vm.falseObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(2); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB3: // GRTR >
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a > b ? vm.trueObj : vm.falseObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(3); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB4: // LEQ <=
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a <= b ? vm.trueObj : vm.falseObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(4); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB5: // GEQ >=
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a >= b ? vm.trueObj : vm.falseObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(5); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB6: // EQU =
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a === b ? vm.trueObj : vm.falseObj;\n",
                  "} else if (a === b && a.float === a.float) {\n",   // NaN check
                  "   stack[--vm.sp] = vm.trueObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(6); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB7: // NEQ ~=
                  this.needsVar['stack'] = true;
                  this.source.push("var a = stack[vm.sp - 1], b = stack[vm.sp];\n",
                  "if (typeof a === 'number' && typeof b === 'number') {\n",
                  "   stack[--vm.sp] = a !== b ? vm.trueObj : vm.falseObj;\n",
                  "} else if (a === b && a.float === a.float) {\n",   // NaN check
                  "   stack[--vm.sp] = vm.falseObj;\n",
                  "} else { vm.pc = ", this.pc, "; vm.sendSpecial(7); if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return}\n");
                  return;
              case 0xB8: // TIMES *
                  this.source.push("vm.success = true; vm.resultIsFloat = false; if(!vm.pop2AndPushNumResult(vm.stackIntOrFloat(1) * vm.stackIntOrFloat(0))) { vm.pc = ", this.pc, "; vm.sendSpecial(8); return}\n");
                  return;
              case 0xB9: // DIV /
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.quickDivide(vm.stackInteger(1),vm.stackInteger(0)))) { vm.pc = ", this.pc, "; vm.sendSpecial(9); return}\n");
                  return;
              case 0xBA: // MOD \
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.mod(vm.stackInteger(1),vm.stackInteger(0)))) { vm.pc = ", this.pc, "; vm.sendSpecial(10); return}\n");
                  return;
              case 0xBB:  // MakePt int@int
                  this.source.push("vm.success = true; if(!vm.primHandler.primitiveMakePoint(1, true)) { vm.pc = ", this.pc, "; vm.sendSpecial(11); return}\n");
                  return;
              case 0xBC: // bitShift:
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.safeShift(vm.stackInteger(1),vm.stackInteger(0)))) { vm.pc = ", this.pc, "; vm.sendSpecial(12); return}\n");
                  return;
              case 0xBD: // Divide //
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.div(vm.stackInteger(1),vm.stackInteger(0)))) { vm.pc = ", this.pc, "; vm.sendSpecial(13); return}\n");
                  return;
              case 0xBE: // bitAnd:
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.stackInteger(1) & vm.stackInteger(0))) { vm.pc = ", this.pc, "; vm.sendSpecial(14); return}\n");
                  return;
              case 0xBF: // bitOr:
                  this.source.push("vm.success = true; if(!vm.pop2AndPushIntResult(vm.stackInteger(1) | vm.stackInteger(0))) { vm.pc = ", this.pc, "; vm.sendSpecial(15); return}\n");
                  return;
          }
      },
      generateSend: function(prefix, num, suffix, numArgs, superSend) {
          if (this.debug) this.generateDebugCode("send " + (prefix === "lit[" ? this.method.pointers[num].bytesAsString() : "..."));
          this.generateLabel();
          this.needsVar[prefix] = true;
          this.needsVar['context'] = true;
          // set pc, activate new method, and return to main loop
          // unless the method was a successfull primitive call (no context change)
          this.source.push(
              "vm.pc = ", this.pc, "; vm.send(", prefix, num, suffix, ", ", numArgs, ", ", superSend, "); ",
              "if (context !== vm.activeContext || vm.breakOutOfInterpreter !== false) return;\n");
          this.needsBreak = false; // already checked
          // need a label for coming back after send
          this.needsLabel[this.pc] = true;
      },
      generateClosureTemps: function(count, popValues) {
          if (this.debug) this.generateDebugCode("closure temps");
          this.generateLabel();
          this.needsVar['stack'] = true;
          this.source.push("var array = vm.instantiateClass(vm.specialObjects[7], ", count, ");\n");
          if (popValues) {
              for (var i = 0; i < count; i++)
                  this.source.push("array.pointers[", i, "] = stack[vm.sp - ", count - i - 1, "];\n");
              this.source.push("stack[vm.sp -= ", count - 1, "] = array;\n");
          } else {
              this.source.push("stack[++vm.sp] = array;\n");
          }
      },
      generateClosureCopy: function(numArgs, numCopied, blockSize) {
          var from = this.pc,
              to = from + blockSize;
          if (this.debug) this.generateDebugCode("push closure(" + from + "-" + (to-1) + "): " + numCopied + " copied, " + numArgs + " args");
          this.generateLabel();
          this.needsVar['stack'] = true;
          this.source.push(
              "var closure = vm.instantiateClass(vm.specialObjects[36], ", numCopied, ");\n",
              "closure.pointers[0] = context; vm.reclaimableContextCount = 0;\n",
              "closure.pointers[1] = ", from + this.method.pointers.length * 4 + 1, ";\n",  // encodeSqueakPC
              "closure.pointers[2] = ", numArgs, ";\n");
          if (numCopied > 0) {
              for (var i = 0; i < numCopied; i++)
                  this.source.push("closure.pointers[", i + 3, "] = stack[vm.sp - ", numCopied - i - 1,"];\n");
              this.source.push("stack[vm.sp -= ", numCopied - 1,"] = closure;\n");
          } else {
              this.source.push("stack[++vm.sp] = closure;\n");
          }
          this.source.push("vm.pc = ", to, ";\n");
          if (this.singleStep) this.source.push("if (vm.breakOutOfInterpreter) return;\n");
          this.source.push("continue;\n");
          this.needsBreak = false; // already checked
          this.needsLabel[from] = true;   // initial pc when activated
          this.needsLabel[to] = true;     // for jump over closure
          if (to > this.endPC) this.endPC = to;
      },
      generateCallPrimitive: function(index) {
          if (this.debug) this.generateDebugCode("call primitive " + index);
          this.generateLabel();
          if (this.method.bytes[this.pc] === 0x81)  {// extended store
              this.needsVar['stack'] = true;
              this.source.push("if (vm.primFailCode) {stack[vm.sp] = vm.getErrorObjectFromPrimFailCode(); vm.primFailCode = 0;}\n");
          }
      },
      generateDirty: function(target, arg) {
          switch(target) {
              case "inst[": this.source.push("rcvr.dirty = true;\n"); break;
              case "lit[": this.source.push(target, arg, "].dirty = true;\n"); break;
              case "temp[": break;
              default:
                  throw Error("unexpected target " + target);
          }
      },
      generateLabel: function() {
          // remember label position for deleteUnneededLabels()
          if (this.prevPC) {
              this.sourceLabels[this.prevPC] = this.source.length;
              this.source.push("case ", this.prevPC, ":\n");           // must match deleteUnneededLabels
          }
          this.prevPC = this.pc;
      },
      generateDebugCode: function(command, what, arg1, suffix1, arg2, suffix2) {
          // single-step for previous instructiuon
          if (this.needsBreak) {
               this.source.push("if (vm.breakOutOfInterpreter) {vm.pc = ", this.prevPC, "; return}\n");
               this.needsLabel[this.prevPC] = true;
          }
          // comment for this instruction
          var bytecodes = [];
          for (var i = this.prevPC; i < this.pc; i++)
              bytecodes.push((this.method.bytes[i] + 0x100).toString(16).slice(-2).toUpperCase());
          this.source.push("// ", this.prevPC, " <", bytecodes.join(" "), "> ", command);
          // append argument to comment
          if (what) {
              this.source.push(" ");
              switch (what) {
                  case 'vm.nilObj':    this.source.push('nil'); break;
                  case 'vm.trueObj':   this.source.push('true'); break;
                  case 'vm.falseObj':  this.source.push('false'); break;
                  case 'rcvr':         this.source.push('self'); break;
                  case 'stack[vm.sp]': this.source.push('top of stack'); break;
                  case 'inst[':
                      if (!this.instVarNames) this.source.push('inst var ', arg1);
                      else this.source.push(this.instVarNames[arg1]);
                      break;
                  case 'temp[':
                      this.source.push('tmp', arg1 - 6);
                      if (suffix1 !== ']') this.source.push('[', arg2, ']');
                      break;
                  case 'lit[':
                      var lit = this.method.pointers[arg1];
                      if (suffix1 === ']') this.source.push(lit);
                      else this.source.push(lit.pointers[0].bytesAsString());
                      break;
                  default:
                      this.source.push(what);
              }
          }
          this.source.push("\n");
          // enable single-step for next instruction
          this.needsBreak = this.singleStep;
      },
      generateInstruction: function(comment, instr) {
          if (this.debug) this.generateDebugCode(comment);
          this.generateLabel();
          this.source.push(instr, ";\n");
      },
      deleteUnneededLabels: function() {
          // switch statement is more efficient with fewer labels
          var hasAnyLabel = false;
          for (var i in this.sourceLabels)
              if (this.needsLabel[i])
                  hasAnyLabel = true;
              else for (var j = 0; j < 3; j++)
                 this.source[this.sourceLabels[i] + j] = "";
          if (!hasAnyLabel) {
              this.source[this.sourcePos['loop-start']] = "";
              this.source[this.sourcePos['loop-end']] = "";
          }
      },
      deleteUnneededVariables: function() {
          if (this.needsVar['stack']) this.needsVar['context'] = true;
          if (this.needsVar['inst[']) this.needsVar['rcvr'] = true;
          for (var i = 0; i < this.allVars.length; i++) {
              var v = this.allVars[i];
              if (!this.needsVar[v])
                  this.source[this.sourcePos[v]] = "";
          }
      },
  });
  