codegen.java

java中比较著名的js引擎当属mozilla开源的rhino

        for (int i = 0; i != functionCount; i++) {
            OptFunctionNode ofn = OptFunctionNode.get(scriptOrFn, i);
            if (ofn.fnode.getFunctionType()
                    == FunctionNode.FUNCTION_STATEMENT)
            {
                visitFunction(ofn, FunctionNode.FUNCTION_STATEMENT);
            }
        }

        // default is to generate debug info
        if (compilerEnv.isGenerateDebugInfo()) {
            cfw.addVariableDescriptor(debugVariableName, "Lorg/mozilla/javascript/Scriptable;", cfw.getCurrentCodeOffset(), variableObjectLocal);
        }

        if (fnCurrent == null) {
            // OPT: use dataflow to prove that this assignment is dead
            popvLocal = getNewWordLocal();
            Codegen.pushUndefined(cfw);
            cfw.addAStore(popvLocal);

            int linenum = scriptOrFn.getEndLineno();
            if (linenum != -1)
              cfw.addLineNumberEntry((short)linenum);

        } else {
            if (fnCurrent.itsContainsCalls0) {
                itsZeroArgArray = getNewWordLocal();
                cfw.add(ByteCode.GETSTATIC,
                        "org/mozilla/javascript/ScriptRuntime",
                        "emptyArgs", "[Ljava/lang/Object;");
                cfw.addAStore(itsZeroArgArray);
            }
            if (fnCurrent.itsContainsCalls1) {
                itsOneArgArray = getNewWordLocal();
                cfw.addPush(1);
                cfw.add(ByteCode.ANEWARRAY, "java/lang/Object");
                cfw.addAStore(itsOneArgArray);
            }
        }

    }

    private void generateEpilogue()
    {
        if (hasVarsInRegs) {
            if (epilogueLabel != -1) {
                cfw.markLabel(epilogueLabel);
            }
            cfw.add(ByteCode.ARETURN);
            return;
        }

        cfw.markLabel(epilogueLabel);
        if (fnCurrent == null) {
            cfw.addALoad(popvLocal);
            cfw.add(ByteCode.ARETURN);
        } else {
            generateActivationExit();
            cfw.add(ByteCode.ARETURN);

            // Generate catch block to catch all and rethrow to call exit code
            // under exception propagation as well.

            int finallyHandler = cfw.acquireLabel();
            cfw.markHandler(finallyHandler);
            short exceptionObject = getNewWordLocal();
            cfw.addAStore(exceptionObject);

            // Duplicate generateActivationExit() in the catch block since it
            // takes less space then full-fetured ByteCode.JSR/ByteCode.RET
            generateActivationExit();

            cfw.addALoad(exceptionObject);
            releaseWordLocal(exceptionObject);
            // rethrow
            cfw.add(ByteCode.ATHROW);

            // mark the handler
            cfw.addExceptionHandler(enterAreaStartLabel, epilogueLabel,
                                    finallyHandler, null); // catch any
        }
    }

    private void generateActivationExit()
    {
        if (fnCurrent == null || hasVarsInRegs) throw Kit.codeBug();
        cfw.addALoad(contextLocal);
        addScriptRuntimeInvoke("exitActivationFunction",
                               "(Lorg/mozilla/javascript/Context;)V");
    }

    private void generateStatement(Node node, Node parent)
    {
        // System.out.println("gen code for " + node.toString());

        updateLineNumber(node);
        int type = node.getType();
        Node child = node.getFirstChild();
        switch (type) {
              case Token.LOOP:
              case Token.LABEL:
              case Token.WITH:
              case Token.SCRIPT:
              case Token.BLOCK:
              case Token.EMPTY:
                // no-ops.
                while (child != null) {
                    generateStatement(child, node);
                    child = child.getNext();
                }
                break;

              case Token.LOCAL_BLOCK: {
                int local = getNewWordLocal();
                node.putIntProp(Node.LOCAL_PROP, local);
                while (child != null) {
                    generateStatement(child, node);
                    child = child.getNext();
                }
                releaseWordLocal((short)local);
                node.removeProp(Node.LOCAL_PROP);
                break;
              }

              case Token.FUNCTION: {
                int fnIndex = node.getExistingIntProp(Node.FUNCTION_PROP);
                OptFunctionNode ofn = OptFunctionNode.get(scriptOrFn, fnIndex);
                int t = ofn.fnode.getFunctionType();
                if (t == FunctionNode.FUNCTION_EXPRESSION_STATEMENT) {
                    visitFunction(ofn, t);
                } else {
                    if (t != FunctionNode.FUNCTION_STATEMENT) {
                        throw Codegen.badTree();
                    }
                }
                break;
              }

              case Token.TRY:
                visitTryCatchFinally((Node.Jump)node, child);
                break;

              case Token.CATCH_SCOPE:
                {
                    int local = getLocalBlockRegister(node);
                    int scopeIndex
                        = node.getExistingIntProp(Node.CATCH_SCOPE_PROP);

                    String name = child.getString(); // name of exception
                    child = child.getNext();
                    generateExpression(child, node); // load expression object
                    if (scopeIndex == 0) {
                        cfw.add(ByteCode.ACONST_NULL);
                    } else {
                        // Load previous catch scope object
                        cfw.addALoad(local);
                    }
                    cfw.addPush(name);
                    cfw.addALoad(contextLocal);
                    cfw.addALoad(variableObjectLocal);

                    addScriptRuntimeInvoke(
                        "newCatchScope",
                        "(Ljava/lang/Throwable;"
                        +"Lorg/mozilla/javascript/Scriptable;"
                        +"Ljava/lang/String;"
                        +"Lorg/mozilla/javascript/Context;"
                        +"Lorg/mozilla/javascript/Scriptable;"
                        +")Lorg/mozilla/javascript/Scriptable;");
                    cfw.addAStore(local);
                }
                break;

              case Token.THROW:
                generateExpression(child, node);
                cfw.add(ByteCode.NEW,
                        "org/mozilla/javascript/JavaScriptException");
                cfw.add(ByteCode.DUP_X1);
                cfw.add(ByteCode.SWAP);
                cfw.addPush(scriptOrFn.getSourceName());
                cfw.addPush(itsLineNumber);
                cfw.addInvoke(
                    ByteCode.INVOKESPECIAL,
                    "org/mozilla/javascript/JavaScriptException",
                    "<init>",
                    "(Ljava/lang/Object;Ljava/lang/String;I)V");
                cfw.add(ByteCode.ATHROW);
                break;

              case Token.RETHROW:
                cfw.addALoad(getLocalBlockRegister(node));
                cfw.add(ByteCode.ATHROW);
                break;

              case Token.RETURN_RESULT:
              case Token.RETURN:
                if (child != null) {
                    generateExpression(child, node);
                } else if (type == Token.RETURN) {
                    Codegen.pushUndefined(cfw);
                } else {
                    if (popvLocal < 0) throw Codegen.badTree();
                    cfw.addALoad(popvLocal);
                }
                if (epilogueLabel == -1) {
                    if (!hasVarsInRegs) throw Codegen.badTree();
                    epilogueLabel = cfw.acquireLabel();
                }
                cfw.add(ByteCode.GOTO, epilogueLabel);
                break;

              case Token.SWITCH:
                visitSwitch((Node.Jump)node, child);
                break;

              case Token.ENTERWITH:
                generateExpression(child, node);
                cfw.addALoad(contextLocal);
                cfw.addALoad(variableObjectLocal);
                addScriptRuntimeInvoke(
                    "enterWith",
                    "(Ljava/lang/Object;"
                    +"Lorg/mozilla/javascript/Context;"
                    +"Lorg/mozilla/javascript/Scriptable;"
                    +")Lorg/mozilla/javascript/Scriptable;");
                cfw.addAStore(variableObjectLocal);
                break;

              case Token.LEAVEWITH:
                cfw.addALoad(variableObjectLocal);
                addScriptRuntimeInvoke(
                    "leaveWith",
                    "(Lorg/mozilla/javascript/Scriptable;"
                    +")Lorg/mozilla/javascript/Scriptable;");
                cfw.addAStore(variableObjectLocal);
                break;

              case Token.ENUM_INIT_KEYS:
              case Token.ENUM_INIT_VALUES:
                generateExpression(child, node);
                cfw.addALoad(contextLocal);
                cfw.addPush(type == Token.ENUM_INIT_VALUES);
                addScriptRuntimeInvoke("enumInit",
                                       "(Ljava/lang/Object;"
                                       +"Lorg/mozilla/javascript/Context;"
                                       +"Z"
                                       +")Ljava/lang/Object;");
                cfw.addAStore(getLocalBlockRegister(node));
                break;

              case Token.EXPR_VOID:
                if (child.getType() == Token.SETVAR) {
                    /* special case this so as to avoid unnecessary
                    load's & pop's */
                    visitSetVar(child, child.getFirstChild(), false);
                }
                else {
                    generateExpression(child, node);
                    if (node.getIntProp(Node.ISNUMBER_PROP, -1) != -1)
                        cfw.add(ByteCode.POP2);
                    else
                        cfw.add(ByteCode.POP);
                }
                break;

              case Token.EXPR_RESULT:
                generateExpression(child, node);
                if (popvLocal < 0) {
                    popvLocal = getNewWordLocal();
                }
                cfw.addAStore(popvLocal);
                break;

              case Token.TARGET:
                {
                    int label = getTargetLabel(node);
                    cfw.markLabel(label);
                }
                break;

              case Token.JSR:
              case Token.GOTO:
              case Token.IFEQ:
              case Token.IFNE:
                visitGOTO((Node.Jump)node, type, child);
                break;

              case Token.FINALLY:
                {
                    //Save return address in a new local where
                    int finallyRegister = getNewWordLocal();
                    cfw.addAStore(finallyRegister);
                    while (child != null) {
                        generateStatement(child, node);
                        child = child.getNext();
                    }
                    cfw.add(ByteCode.RET, finallyRegister);
                    releaseWordLocal((short)finallyRegister);
                }
                break;

              default:
                throw Codegen.badTree();
        }

    }

    private void generateExpression(Node node, Node parent)
    {
        int type = node.getType();
        Node child = node.getFirstChild();
        switch (type) {
              case Token.USE_STACK:
                break;

              case Token.FUNCTION:
                if (fnCurrent != null || parent.getType() != Token.SCRIPT) {
                    int fnIndex = node.getExistingIntProp(Node.FUNCTION_PROP);
                    OptFunctionNode ofn = OptFunctionNode.get(scriptOrFn,
                                                             fnIndex);
                    int t = ofn.fnode.getFunctionType();
                    if (t != FunctionNode.FUNCTION_EXPRESSION) {
                        throw Codegen.badTree();
                    }
                    visitFunction(ofn, t);
                }
                break;

              case Token.NAME:
                {
                    cfw.addALoad(contextLocal);
                    cfw.addALoad(variableObjectLocal);
                    cfw.addPush(node.getString());
                    addScriptRuntimeInvoke(
                        "name",
                        "(Lorg/mozilla/javascript/Context;"
                        +"Lorg/mozilla/javascript/Scriptable;"
                        +"Ljava/lang/String;"
                        +")Ljava/lang/Object;");
                }
                break;

              case Token.CALL:
              case Token.NEW:
                {
                    int specialType = node.getIntProp(Node.SPECIALCALL_PROP,
                                                      Node.NON_SPECIALCALL);