codegen.java

java中比较著名的js引擎当属mozilla开源的rhino

            cfw.addDLoad(5 + (i * 3));
        }
        cfw.addALoad(4 + argCount * 3);
        cfw.addInvoke(ByteCode.INVOKESTATIC,
                      mainClassName,
                      getBodyMethodName(ofn.fnode),
                      getBodyMethodSignature(ofn.fnode));
        int exitLabel = cfw.acquireLabel();
        cfw.add(ByteCode.DUP); // make a copy of direct call result
        cfw.add(ByteCode.INSTANCEOF, "org/mozilla/javascript/Scriptable");
        cfw.add(ByteCode.IFEQ, exitLabel);
        // cast direct call result
        cfw.add(ByteCode.CHECKCAST, "org/mozilla/javascript/Scriptable");
        cfw.add(ByteCode.ARETURN);
        cfw.markLabel(exitLabel);

        cfw.addALoad(firstLocal);
        cfw.add(ByteCode.ARETURN);

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

    private void generateCallMethod(ClassFileWriter cfw)
    {
        cfw.startMethod("call",
                        "(Lorg/mozilla/javascript/Context;" +
                        "Lorg/mozilla/javascript/Scriptable;" +
                        "Lorg/mozilla/javascript/Scriptable;" +
                        "[Ljava/lang/Object;)Ljava/lang/Object;",
                        (short)(ClassFileWriter.ACC_PUBLIC
                                | ClassFileWriter.ACC_FINAL));

        // Generate code for:
        // if (!ScriptRuntime.hasTopCall(cx)) {
        //     return ScriptRuntime.doTopCall(this, cx, scope, thisObj, args);
        // }

        int nonTopCallLabel = cfw.acquireLabel();
        cfw.addALoad(1); //cx
        cfw.addInvoke(ByteCode.INVOKESTATIC,
                      "org/mozilla/javascript/ScriptRuntime",
                      "hasTopCall",
                      "(Lorg/mozilla/javascript/Context;"
                      +")Z");
        cfw.add(ByteCode.IFNE, nonTopCallLabel);
        cfw.addALoad(0);
        cfw.addALoad(1);
        cfw.addALoad(2);
        cfw.addALoad(3);
        cfw.addALoad(4);
        cfw.addInvoke(ByteCode.INVOKESTATIC,
                      "org/mozilla/javascript/ScriptRuntime",
                      "doTopCall",
                      "(Lorg/mozilla/javascript/Callable;"
                      +"Lorg/mozilla/javascript/Context;"
                      +"Lorg/mozilla/javascript/Scriptable;"
                      +"Lorg/mozilla/javascript/Scriptable;"
                      +"[Ljava/lang/Object;"
                      +")Ljava/lang/Object;");
        cfw.add(ByteCode.ARETURN);
        cfw.markLabel(nonTopCallLabel);

        // No generate switch to call the real methods

        cfw.addALoad(0);
        cfw.addALoad(1);
        cfw.addALoad(2);
        cfw.addALoad(3);
        cfw.addALoad(4);

        int end = scriptOrFnNodes.length;
        boolean generateSwitch = (2 <= end);

        int switchStart = 0;
        int switchStackTop = 0;
        if (generateSwitch) {
            cfw.addLoadThis();
            cfw.add(ByteCode.GETFIELD, cfw.getClassName(), ID_FIELD_NAME, "I");
            // do switch from (1,  end - 1) mapping 0 to
            // the default case
            switchStart = cfw.addTableSwitch(1, end - 1);
        }

        for (int i = 0; i != end; ++i) {
            ScriptOrFnNode n = scriptOrFnNodes[i];
            if (generateSwitch) {
                if (i == 0) {
                    cfw.markTableSwitchDefault(switchStart);
                    switchStackTop = cfw.getStackTop();
                } else {
                    cfw.markTableSwitchCase(switchStart, i - 1,
                                            switchStackTop);
                }
            }
            if (n.getType() == Token.FUNCTION) {
                OptFunctionNode ofn = OptFunctionNode.get(n);
                if (ofn.isTargetOfDirectCall()) {
                    int pcount = ofn.fnode.getParamCount();
                    if (pcount != 0) {
                        // loop invariant:
                        // stack top == arguments array from addALoad4()
                        for (int p = 0; p != pcount; ++p) {
                            cfw.add(ByteCode.ARRAYLENGTH);
                            cfw.addPush(p);
                            int undefArg = cfw.acquireLabel();
                            int beyond = cfw.acquireLabel();
                            cfw.add(ByteCode.IF_ICMPLE, undefArg);
                            // get array[p]
                            cfw.addALoad(4);
                            cfw.addPush(p);
                            cfw.add(ByteCode.AALOAD);
                            cfw.add(ByteCode.GOTO, beyond);
                            cfw.markLabel(undefArg);
                            pushUndefined(cfw);
                            cfw.markLabel(beyond);
                            // Only one push
                            cfw.adjustStackTop(-1);
                            cfw.addPush(0.0);
                            // restore invariant
                            cfw.addALoad(4);
                        }
                    }
                }
            }
            cfw.addInvoke(ByteCode.INVOKESTATIC,
                          mainClassName,
                          getBodyMethodName(n),
                          getBodyMethodSignature(n));
            cfw.add(ByteCode.ARETURN);
        }
        cfw.stopMethod((short)5);
        // 5: this, cx, scope, js this, args[]
    }

    private void generateMain(ClassFileWriter cfw)
    {
        cfw.startMethod("main", "([Ljava/lang/String;)V",
                        (short)(ClassFileWriter.ACC_PUBLIC
                                | ClassFileWriter.ACC_STATIC));

        // load new ScriptImpl()
        cfw.add(ByteCode.NEW, cfw.getClassName());
        cfw.add(ByteCode.DUP);
        cfw.addInvoke(ByteCode.INVOKESPECIAL, cfw.getClassName(),
                      "<init>", "()V");
         // load 'args'
        cfw.add(ByteCode.ALOAD_0);
        // Call mainMethodClass.main(Script script, String[] args)
        cfw.addInvoke(ByteCode.INVOKESTATIC,
                      mainMethodClass,
                      "main",
                      "(Lorg/mozilla/javascript/Script;[Ljava/lang/String;)V");
        cfw.add(ByteCode.RETURN);
        // 1 = String[] args
        cfw.stopMethod((short)1);
    }

    private void generateExecute(ClassFileWriter cfw, ScriptOrFnNode script)
    {
        cfw.startMethod("exec",
                        "(Lorg/mozilla/javascript/Context;"
                        +"Lorg/mozilla/javascript/Scriptable;"
                        +")Ljava/lang/Object;",
                        (short)(ClassFileWriter.ACC_PUBLIC
                                | ClassFileWriter.ACC_FINAL));

        final int CONTEXT_ARG = 1;
        final int SCOPE_ARG = 2;

        cfw.addLoadThis();
        cfw.addALoad(CONTEXT_ARG);
        cfw.addALoad(SCOPE_ARG);
        cfw.add(ByteCode.DUP);
        cfw.add(ByteCode.ACONST_NULL);
        cfw.addInvoke(ByteCode.INVOKEVIRTUAL,
                      cfw.getClassName(),
                      "call",
                      "(Lorg/mozilla/javascript/Context;"
                      +"Lorg/mozilla/javascript/Scriptable;"
                      +"Lorg/mozilla/javascript/Scriptable;"
                      +"[Ljava/lang/Object;"
                      +")Ljava/lang/Object;");

        cfw.add(ByteCode.ARETURN);
        // 3 = this + context + scope
        cfw.stopMethod((short)3);
    }

    private void generateScriptCtor(ClassFileWriter cfw,
                                    ScriptOrFnNode script)
    {
        cfw.startMethod("<init>", "()V", ClassFileWriter.ACC_PUBLIC);

        cfw.addLoadThis();
        cfw.addInvoke(ByteCode.INVOKESPECIAL, SUPER_CLASS_NAME,
                      "<init>", "()V");
        // set id to 0
        cfw.addLoadThis();
        cfw.addPush(0);
        cfw.add(ByteCode.PUTFIELD, cfw.getClassName(), ID_FIELD_NAME, "I");

        cfw.add(ByteCode.RETURN);
        // 1 parameter = this
        cfw.stopMethod((short)1);
    }

    private void generateFunctionConstructor(ClassFileWriter cfw)
    {
        final int SCOPE_ARG = 1;
        final int CONTEXT_ARG = 2;
        final int ID_ARG = 3;

        cfw.startMethod("<init>", FUNCTION_CONSTRUCTOR_SIGNATURE,
                        ClassFileWriter.ACC_PUBLIC);
        cfw.addALoad(0);
        cfw.addInvoke(ByteCode.INVOKESPECIAL, SUPER_CLASS_NAME,
                      "<init>", "()V");

        cfw.addLoadThis();
        cfw.addILoad(ID_ARG);
        cfw.add(ByteCode.PUTFIELD, cfw.getClassName(), ID_FIELD_NAME, "I");

        cfw.addLoadThis();
        cfw.addALoad(CONTEXT_ARG);
        cfw.addALoad(SCOPE_ARG);

        int start = (scriptOrFnNodes[0].getType() == Token.SCRIPT) ? 1 : 0;
        int end = scriptOrFnNodes.length;
        if (start == end) throw badTree();
        boolean generateSwitch = (2 <= end - start);

        int switchStart = 0;
        int switchStackTop = 0;
        if (generateSwitch) {
            cfw.addILoad(ID_ARG);
            // do switch from (start + 1,  end - 1) mapping start to
            // the default case
            switchStart = cfw.addTableSwitch(start + 1, end - 1);
        }

        for (int i = start; i != end; ++i) {
            if (generateSwitch) {
                if (i == start) {
                    cfw.markTableSwitchDefault(switchStart);
                    switchStackTop = cfw.getStackTop();
                } else {
                    cfw.markTableSwitchCase(switchStart, i - 1 - start,
                                            switchStackTop);
                }
            }
            OptFunctionNode ofn = OptFunctionNode.get(scriptOrFnNodes[i]);
            cfw.addInvoke(ByteCode.INVOKEVIRTUAL,
                          mainClassName,
                          getFunctionInitMethodName(ofn),
                          FUNCTION_INIT_SIGNATURE);
            cfw.add(ByteCode.RETURN);
        }

        // 4 = this + scope + context + id
        cfw.stopMethod((short)4);
    }

    private void generateFunctionInit(ClassFileWriter cfw,
                                      OptFunctionNode ofn)
    {
        final int CONTEXT_ARG = 1;
        final int SCOPE_ARG = 2;
        cfw.startMethod(getFunctionInitMethodName(ofn),
                        FUNCTION_INIT_SIGNATURE,
                        (short)(ClassFileWriter.ACC_PRIVATE
                                | ClassFileWriter.ACC_FINAL));

        // Call NativeFunction.initScriptFunction
        cfw.addLoadThis();
        cfw.addALoad(CONTEXT_ARG);
        cfw.addALoad(SCOPE_ARG);
        cfw.addInvoke(ByteCode.INVOKEVIRTUAL,
                      "org/mozilla/javascript/NativeFunction",
                      "initScriptFunction",
                      "(Lorg/mozilla/javascript/Context;"
                      +"Lorg/mozilla/javascript/Scriptable;"
                      +")V");

        // precompile all regexp literals
        int regexpCount = ofn.fnode.getRegexpCount();
        if (regexpCount != 0) {
            cfw.addLoadThis();
            pushRegExpArray(cfw, ofn.fnode, CONTEXT_ARG, SCOPE_ARG);
            cfw.add(ByteCode.PUTFIELD, mainClassName,
                    REGEXP_ARRAY_FIELD_NAME, REGEXP_ARRAY_FIELD_TYPE);
        }

        cfw.add(ByteCode.RETURN);
        // 3 = (scriptThis/functionRef) + scope + context
        cfw.stopMethod((short)3);
    }

    private void generateNativeFunctionOverrides(ClassFileWriter cfw,
                                                 String encodedSource)
    {
        // Override NativeFunction.getLanguageVersion() with
        // public int getLanguageVersion() { return <version-constant>; }

        cfw.startMethod("getLanguageVersion", "()I",
                        ClassFileWriter.ACC_PUBLIC);

        cfw.addPush(compilerEnv.getLanguageVersion());
        cfw.add(ByteCode.IRETURN);

        // 1: this and no argument or locals
        cfw.stopMethod((short)1);

        // The rest of NativeFunction overrides require specific code for each
        // script/function id

        final int Do_getFunctionName      = 0;
        final int Do_getParamCount        = 1;
        final int Do_getParamAndVarCount  = 2;
        final int Do_getParamOrVarName    = 3;
        final int Do_getEncodedSource     = 4;
        final int SWITCH_COUNT            = 5;

        for (int methodIndex = 0; methodIndex != SWITCH_COUNT; ++methodIndex) {
            if (methodIndex == Do_getEncodedSource && encodedSource == null) {
                continue;
            }

            // Generate:
            //   prologue;
            //   switch over function id to implement function-specific action
            //   epilogue

            short metodLocals;
            switch (methodIndex) {
              case Do_getFunctionName:
                metodLocals = 1; // Only this
                cfw.startMethod("getFunctionName", "()Ljava/lang/String;",
                                ClassFileWriter.ACC_PUBLIC);
                break;
              case Do_getParamCount:
                metodLocals = 1; // Only this
                cfw.startMethod("getParamCount", "()I",
                                ClassFileWriter.ACC_PUBLIC);
                break;
              case Do_getParamAndVarCount:
                metodLocals = 1; // Only this
                cfw.startMethod("getParamAndVarCount", "()I",
                                ClassFileWriter.ACC_PUBLIC);
                break;
              case Do_getParamOrVarName:
                metodLocals = 1 + 1; // this + paramOrVarIndex