codegen.java

java中比较著名的js引擎当属mozilla开源的rhino

    int getIndex(ScriptOrFnNode n)
    {
        return scriptOrFnIndexes.getExisting(n);
    }

    static String getDirectTargetFieldName(int i)
    {
        return "_dt" + i;
    }

    String getDirectCtorName(ScriptOrFnNode n)
    {
        return "_n"+getIndex(n);
    }

    String getBodyMethodName(ScriptOrFnNode n)
    {
        return "_c"+getIndex(n);
    }

    String getBodyMethodSignature(ScriptOrFnNode n)
    {
        StringBuffer sb = new StringBuffer();
        sb.append('(');
        sb.append(mainClassSignature);
        sb.append("Lorg/mozilla/javascript/Context;"
                  +"Lorg/mozilla/javascript/Scriptable;"
                  +"Lorg/mozilla/javascript/Scriptable;");
        if (n.getType() == Token.FUNCTION) {
            OptFunctionNode ofn = OptFunctionNode.get(n);
            if (ofn.isTargetOfDirectCall()) {
                int pCount = ofn.fnode.getParamCount();
                for (int i = 0; i != pCount; i++) {
                    sb.append("Ljava/lang/Object;D");
                }
            }
        }
        sb.append("[Ljava/lang/Object;)Ljava/lang/Object;");
        return sb.toString();
    }

    String getFunctionInitMethodName(OptFunctionNode ofn)
    {
        return "_i"+getIndex(ofn.fnode);
    }

    String getCompiledRegexpName(ScriptOrFnNode n, int regexpIndex)
    {
        return "_re"+getIndex(n)+"_"+regexpIndex;
    }

    static RuntimeException badTree()
    {
        throw new RuntimeException("Bad tree in codegen");
    }

     void setMainMethodClass(String className)
     {
         mainMethodClass = className;
     }

     static final String DEFAULT_MAIN_METHOD_CLASS
        = "org.mozilla.javascript.optimizer.OptRuntime";

    private static final String SUPER_CLASS_NAME
        = "org.mozilla.javascript.NativeFunction";

    static final String DIRECT_CALL_PARENT_FIELD = "_dcp";

    private static final String ID_FIELD_NAME = "_id";

    private static final String REGEXP_INIT_METHOD_NAME = "_reInit";
    private static final String REGEXP_INIT_METHOD_SIGNATURE
        =  "(Lorg/mozilla/javascript/RegExpProxy;"
           +"Lorg/mozilla/javascript/Context;"
           +")V";
    static final String REGEXP_ARRAY_FIELD_NAME = "_re";
    static final String REGEXP_ARRAY_FIELD_TYPE = "[Ljava/lang/Object;";

    static final String FUNCTION_INIT_SIGNATURE
        =  "(Lorg/mozilla/javascript/Context;"
           +"Lorg/mozilla/javascript/Scriptable;"
           +")V";

   static final String FUNCTION_CONSTRUCTOR_SIGNATURE
        = "(Lorg/mozilla/javascript/Scriptable;"
          +"Lorg/mozilla/javascript/Context;I)V";

    private static final Object globalLock = new Object();
    private static int globalSerialClassCounter;

    private CompilerEnvirons compilerEnv;

    private ObjArray directCallTargets;
    ScriptOrFnNode[] scriptOrFnNodes;
    private ObjToIntMap scriptOrFnIndexes;

    private String mainMethodClass = DEFAULT_MAIN_METHOD_CLASS;

    String mainClassName;
    String mainClassSignature;

    boolean itsUseDynamicScope;
    int languageVersion;

    private double[] itsConstantList;
    private int itsConstantListSize;
}


class BodyCodegen
{
    void generateBodyCode()
    {
        initBodyGeneration();

        cfw.startMethod(codegen.getBodyMethodName(scriptOrFn),
                        codegen.getBodyMethodSignature(scriptOrFn),
                        (short)(ClassFileWriter.ACC_STATIC
                                | ClassFileWriter.ACC_PRIVATE));

        generatePrologue();

        Node treeTop;
        if (fnCurrent != null) {
            treeTop = scriptOrFn.getLastChild();
        } else {
            treeTop = scriptOrFn;
        }
        generateStatement(treeTop, null);

        generateEpilogue();

        cfw.stopMethod((short)(localsMax + 1));
    }

    private void initBodyGeneration()
    {
        isTopLevel = (scriptOrFn == codegen.scriptOrFnNodes[0]);

        varRegisters = null;
        if (scriptOrFn.getType() == Token.FUNCTION) {
            fnCurrent = OptFunctionNode.get(scriptOrFn);
            hasVarsInRegs = !fnCurrent.fnode.requiresActivation();
            if (hasVarsInRegs) {
                int n = fnCurrent.fnode.getParamAndVarCount();
                if (n != 0) {
                    varRegisters = new short[n];
                }
            }
            inDirectCallFunction = fnCurrent.isTargetOfDirectCall();
            if (inDirectCallFunction && !hasVarsInRegs) Codegen.badTree();
        } else {
            fnCurrent = null;
            hasVarsInRegs = false;
            inDirectCallFunction = false;
        }

        locals = new boolean[MAX_LOCALS];

        funObjLocal = 0;
        contextLocal = 1;
        variableObjectLocal = 2;
        thisObjLocal = 3;
        localsMax = (short) 4;  // number of parms + "this"
        firstFreeLocal = 4;

        popvLocal = -1;
        argsLocal = -1;
        itsZeroArgArray = -1;
        itsOneArgArray = -1;
        scriptRegexpLocal = -1;
        epilogueLabel = -1;
        enterAreaStartLabel = -1;
    }

    /**
     * Generate the prologue for a function or script.
     */
    private void generatePrologue()
    {
        if (inDirectCallFunction) {
            int directParameterCount = scriptOrFn.getParamCount();
            // 0 is reserved for function Object 'this'
            // 1 is reserved for context
            // 2 is reserved for parentScope
            // 3 is reserved for script 'this'
            if (firstFreeLocal != 4) Kit.codeBug();
            for (int i = 0; i != directParameterCount; ++i) {
                varRegisters[i] = firstFreeLocal;
                // 3 is 1 for Object parm and 2 for double parm
                firstFreeLocal += 3;
            }
            if (!fnCurrent.getParameterNumberContext()) {
                // make sure that all parameters are objects
                itsForcedObjectParameters = true;
                for (int i = 0; i != directParameterCount; ++i) {
                    short reg = varRegisters[i];
                    cfw.addALoad(reg);
                    cfw.add(ByteCode.GETSTATIC,
                            "java/lang/Void",
                            "TYPE",
                            "Ljava/lang/Class;");
                    int isObjectLabel = cfw.acquireLabel();
                    cfw.add(ByteCode.IF_ACMPNE, isObjectLabel);
                    cfw.addDLoad(reg + 1);
                    addDoubleWrap();
                    cfw.addAStore(reg);
                    cfw.markLabel(isObjectLabel);
                }
            }
        }

        if (fnCurrent != null && !inDirectCallFunction
            && (!compilerEnv.isUseDynamicScope()
                || fnCurrent.fnode.getIgnoreDynamicScope()))
        {
            // Unless we're either in a direct call or using dynamic scope,
            // use the enclosing scope of the function as our variable object.
            cfw.addALoad(funObjLocal);
            cfw.addInvoke(ByteCode.INVOKEINTERFACE,
                          "org/mozilla/javascript/Scriptable",
                          "getParentScope",
                          "()Lorg/mozilla/javascript/Scriptable;");
            cfw.addAStore(variableObjectLocal);
        }

        // reserve 'args[]'
        argsLocal = firstFreeLocal++;
        localsMax = firstFreeLocal;

        if (fnCurrent == null) {
            // See comments in case Token.REGEXP
            if (scriptOrFn.getRegexpCount() != 0) {
                scriptRegexpLocal = getNewWordLocal();
                codegen.pushRegExpArray(cfw, scriptOrFn, contextLocal,
                                        variableObjectLocal);
                cfw.addAStore(scriptRegexpLocal);
            }
        }

        if (hasVarsInRegs) {
            // No need to create activation. Pad arguments if need be.
            int parmCount = scriptOrFn.getParamCount();
            if (parmCount > 0 && !inDirectCallFunction) {
                // Set up args array
                // check length of arguments, pad if need be
                cfw.addALoad(argsLocal);
                cfw.add(ByteCode.ARRAYLENGTH);
                cfw.addPush(parmCount);
                int label = cfw.acquireLabel();
                cfw.add(ByteCode.IF_ICMPGE, label);
                cfw.addALoad(argsLocal);
                cfw.addPush(parmCount);
                addScriptRuntimeInvoke("padArguments",
                                       "([Ljava/lang/Object;I"
                                       +")[Ljava/lang/Object;");
                cfw.addAStore(argsLocal);
                cfw.markLabel(label);
            }

            int paramCount = fnCurrent.fnode.getParamCount();
            int varCount = fnCurrent.fnode.getParamAndVarCount();

            // REMIND - only need to initialize the vars that don't get a value
            // before the next call and are used in the function
            short firstUndefVar = -1;
            for (int i = 0; i != varCount; ++i) {
                short reg = -1;
                if (i < paramCount) {
                    if (!inDirectCallFunction) {
                        reg = getNewWordLocal();
                        cfw.addALoad(argsLocal);
                        cfw.addPush(i);
                        cfw.add(ByteCode.AALOAD);
                        cfw.addAStore(reg);
                    }
                } else if (fnCurrent.isNumberVar(i)) {
                    reg = getNewWordPairLocal();
                    cfw.addPush(0.0);
                    cfw.addDStore(reg);
                } else {
                    reg = getNewWordLocal();
                    if (firstUndefVar == -1) {
                        Codegen.pushUndefined(cfw);
                        firstUndefVar = reg;
                    } else {
                        cfw.addALoad(firstUndefVar);
                    }
                    cfw.addAStore(reg);
                }
                if (reg >= 0) {
                    varRegisters[i] = reg;
                }

                // Add debug table enry if we're generating debug info
                if (compilerEnv.isGenerateDebugInfo()) {
                    String name = fnCurrent.fnode.getParamOrVarName(i);
                    String type = fnCurrent.isNumberVar(i)
                                      ? "D" : "Ljava/lang/Object;";
                    int startPC = cfw.getCurrentCodeOffset();
                    if (reg < 0) {
                        reg = varRegisters[i];
                    }
                    cfw.addVariableDescriptor(name, type, startPC, reg);
                }
            }

            // Skip creating activation object.
            return;
        }

        String debugVariableName;
        if (fnCurrent != null) {
            debugVariableName = "activation";
            cfw.addALoad(funObjLocal);
            cfw.addALoad(variableObjectLocal);
            cfw.addALoad(argsLocal);
            addScriptRuntimeInvoke("createFunctionActivation",
                                   "(Lorg/mozilla/javascript/NativeFunction;"
                                   +"Lorg/mozilla/javascript/Scriptable;"
                                   +"[Ljava/lang/Object;"
                                   +")Lorg/mozilla/javascript/Scriptable;");
            cfw.addAStore(variableObjectLocal);
            cfw.addALoad(contextLocal);
            cfw.addALoad(variableObjectLocal);
            addScriptRuntimeInvoke("enterActivationFunction",
                                   "(Lorg/mozilla/javascript/Context;"
                                   +"Lorg/mozilla/javascript/Scriptable;"
                                   +")V");
        } else {
            debugVariableName = "global";
            cfw.addALoad(funObjLocal);
            cfw.addALoad(thisObjLocal);
            cfw.addALoad(contextLocal);
            cfw.addALoad(variableObjectLocal);
            cfw.addPush(0); // false to indicate it is not eval script
            addScriptRuntimeInvoke("initScript",
                                   "(Lorg/mozilla/javascript/NativeFunction;"
                                   +"Lorg/mozilla/javascript/Scriptable;"
                                   +"Lorg/mozilla/javascript/Context;"
                                   +"Lorg/mozilla/javascript/Scriptable;"
                                   +"Z"
                                   +")V");
        }

        enterAreaStartLabel = cfw.acquireLabel();
        epilogueLabel = cfw.acquireLabel();
        cfw.markLabel(enterAreaStartLabel);

        int functionCount = scriptOrFn.getFunctionCount();