codegen.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

        if (k >= 0) {
            expr.oprand1().accept(this);
            ASTree right = expr.oprand2();
            if (right == null)
                return;     // see TypeChecker.atBinExpr().

            int type1 = exprType;
            int dim1 = arrayDim;
            String cname1 = className;
            right.accept(this);
            if (dim1 != arrayDim)
                throw new CompileError("incompatible array types");

            if (token == '+' && dim1 == 0
                && (type1 == CLASS || exprType == CLASS))
                atStringConcatExpr(expr, type1, dim1, cname1);
            else
                atArithBinExpr(expr, token, k, type1);
        }
        else {
            /* equation: &&, ||, ==, !=, <=, >=, <, >
            */
            booleanExpr(true, expr);
            bytecode.addIndex(7);
            bytecode.addIconst(0);  // false
            bytecode.addOpcode(Opcode.GOTO);
            bytecode.addIndex(4);
            bytecode.addIconst(1);  // true
        }
    }

    /* arrayDim values of the two oprands must be equal.
     * If an oprand type is not a numeric type, this method
     * throws an exception.
     */
    private void atArithBinExpr(Expr expr, int token,
                                int index, int type1) throws CompileError
    {
        if (arrayDim != 0)
            badTypes(expr);

        int type2 = exprType;
        if (token == LSHIFT || token == RSHIFT || token == ARSHIFT)
            if (type2 == INT || type2 == SHORT
                || type2 == CHAR || type2 == BYTE)
                exprType = type1;
            else
                badTypes(expr);
        else
            convertOprandTypes(type1, type2, expr);

        int p = typePrecedence(exprType);
        if (p >= 0) {
            int op = binOp[index + p + 1];
            if (op != NOP) {
                if (p == P_INT && exprType != BOOLEAN)
                    exprType = INT;     // type1 may be BYTE, ...

                bytecode.addOpcode(op);
                return;
            }
        }

        badTypes(expr);
    }

    private void atStringConcatExpr(Expr expr, int type1, int dim1,
                                    String cname1) throws CompileError
    {
        int type2 = exprType;
        int dim2 = arrayDim;
        boolean type2Is2 = is2word(type2, dim2);
        boolean type2IsString
            = (type2 == CLASS && jvmJavaLangString.equals(className));

        if (type2Is2)
            convToString(type2, dim2);

        if (is2word(type1, dim1)) {
            bytecode.addOpcode(DUP_X2);
            bytecode.addOpcode(POP);
        }
        else
            bytecode.addOpcode(SWAP);

        // even if type1 is String, the left operand might be null.
        convToString(type1, dim1);
        bytecode.addOpcode(SWAP);

        if (!type2Is2 && !type2IsString)
            convToString(type2, dim2);

        bytecode.addInvokevirtual(javaLangString, "concat",
                                "(Ljava/lang/String;)Ljava/lang/String;");
        exprType = CLASS;
        arrayDim = 0;
        className = jvmJavaLangString;
    }

    private void convToString(int type, int dim) throws CompileError {
        final String method = "valueOf";

        if (isRefType(type) || dim > 0)
            bytecode.addInvokestatic(javaLangString, method,
                                "(Ljava/lang/Object;)Ljava/lang/String;");
        else if (type == DOUBLE)
            bytecode.addInvokestatic(javaLangString, method,
                                     "(D)Ljava/lang/String;");
        else if (type == FLOAT)
            bytecode.addInvokestatic(javaLangString, method,
                                     "(F)Ljava/lang/String;");
        else if (type == LONG)
            bytecode.addInvokestatic(javaLangString, method,
                                     "(J)Ljava/lang/String;");
        else if (type == BOOLEAN)
            bytecode.addInvokestatic(javaLangString, method,
                                     "(Z)Ljava/lang/String;");
        else if (type == CHAR)
            bytecode.addInvokestatic(javaLangString, method,
                                     "(C)Ljava/lang/String;");
        else if (type == VOID)
            throw new CompileError("void type expression");
        else /* INT, BYTE, SHORT */
            bytecode.addInvokestatic(javaLangString, method,
                                     "(I)Ljava/lang/String;");
    }

    /* Produces the opcode to branch if the condition is true.
     * The oprand is not produced.
     *
     * @return	true if the compiled code is GOTO (always branch).
     */
    private boolean booleanExpr(boolean branchIf, ASTree expr)
        throws CompileError
    {
        boolean isAndAnd;
        int op = getCompOperator(expr);
        if (op == EQ) {         // ==, !=, ...
            BinExpr bexpr = (BinExpr)expr;
            int type1 = compileOprands(bexpr);
            // here, arrayDim might represent the array dim. of the left oprand
            // if the right oprand is NULL.
            compareExpr(branchIf, bexpr.getOperator(), type1, bexpr);
        }
        else if (op == '!')
            booleanExpr(!branchIf, ((Expr)expr).oprand1());
        else if ((isAndAnd = (op == ANDAND)) || op == OROR) {
            BinExpr bexpr = (BinExpr)expr;
            booleanExpr(!isAndAnd, bexpr.oprand1());
            int pc = bytecode.currentPc();
            bytecode.addIndex(0);       // correct later

            booleanExpr(isAndAnd, bexpr.oprand2());
            bytecode.write16bit(pc, bytecode.currentPc() - pc + 3);
            if (branchIf != isAndAnd) {
                bytecode.addIndex(6);   // skip GOTO instruction
                bytecode.addOpcode(Opcode.GOTO);
            }
        }
        else if (isAlwaysBranch(expr, branchIf)) {
            bytecode.addOpcode(Opcode.GOTO);
            return true;	// always branch
        }
        else {                          // others
            expr.accept(this);
            if (exprType != BOOLEAN || arrayDim != 0)
                throw new CompileError("boolean expr is required");

            bytecode.addOpcode(branchIf ? IFNE : IFEQ);
        }

        exprType = BOOLEAN;
        arrayDim = 0;
        return false;
    }


    private static boolean isAlwaysBranch(ASTree expr, boolean branchIf) {
        if (expr instanceof Keyword) {
            int t = ((Keyword)expr).get();
            return branchIf ? t == TRUE : t == FALSE;
        }

        return false;
    }

    static int getCompOperator(ASTree expr) throws CompileError {
        if (expr instanceof Expr) {
            Expr bexpr = (Expr)expr;
            int token = bexpr.getOperator();
            if (token == '!')
                return '!';
            else if ((bexpr instanceof BinExpr)
                     && token != OROR && token != ANDAND
                     && token != '&' && token != '|')
                return EQ;      // ==, !=, ...
            else
                return token;
        }

        return ' ';     // others
    }

    private int compileOprands(BinExpr expr) throws CompileError {
        expr.oprand1().accept(this);
        int type1 = exprType;
        int dim1 = arrayDim;
        expr.oprand2().accept(this);
        if (dim1 != arrayDim)
            if (type1 != NULL && exprType != NULL)
                throw new CompileError("incompatible array types");
            else if (exprType == NULL)
                arrayDim = dim1;

        if (type1 == NULL)
            return exprType;
        else
            return type1;
    }

    private static final int ifOp[] = { EQ, IF_ICMPEQ, IF_ICMPNE,
                                        NEQ, IF_ICMPNE, IF_ICMPEQ,
                                        LE, IF_ICMPLE, IF_ICMPGT,
                                        GE, IF_ICMPGE, IF_ICMPLT,
                                        '<', IF_ICMPLT, IF_ICMPGE,
                                        '>', IF_ICMPGT, IF_ICMPLE };

    private static final int ifOp2[] = { EQ, IFEQ, IFNE,
                                         NEQ, IFNE, IFEQ,
                                         LE, IFLE, IFGT,
                                         GE, IFGE, IFLT,
                                         '<', IFLT, IFGE,
                                         '>', IFGT, IFLE };

    /* Produces the opcode to branch if the condition is true.
     * The oprands are not produced.
     *
     * Parameter expr - compare expression ==, !=, <=, >=, <, >
     */
    private void compareExpr(boolean branchIf,
                             int token, int type1, BinExpr expr)
        throws CompileError
    {
        if (arrayDim == 0)
            convertOprandTypes(type1, exprType, expr);

        int p = typePrecedence(exprType);
        if (p == P_OTHER || arrayDim > 0)
            if (token == EQ)
                bytecode.addOpcode(branchIf ? IF_ACMPEQ : IF_ACMPNE);
            else if (token == NEQ)
                bytecode.addOpcode(branchIf ? IF_ACMPNE : IF_ACMPEQ);
            else
                badTypes(expr);
        else
            if (p == P_INT) {
                int op[] = ifOp;
                for (int i = 0; i < op.length; i += 3)
                    if (op[i] == token) {
                        bytecode.addOpcode(op[i + (branchIf ? 1 : 2)]);
                        return;
                    }

                badTypes(expr);
            }
            else {
                if (p == P_DOUBLE)
                    if (token == '<' || token == LE)
                        bytecode.addOpcode(DCMPG);
                    else
                        bytecode.addOpcode(DCMPL);
                else if (p == P_FLOAT)
                    if (token == '<' || token == LE)
                        bytecode.addOpcode(FCMPG);
                    else
                        bytecode.addOpcode(FCMPL);
                else if (p == P_LONG)
                    bytecode.addOpcode(LCMP); // 1: >, 0: =, -1: <
                else
                    fatal();

                int[] op = ifOp2;
                for (int i = 0; i < op.length; i += 3)
                    if (op[i] == token) {
                        bytecode.addOpcode(op[i + (branchIf ? 1 : 2)]);
                        return;
                    }

                badTypes(expr);
            }
    }

    protected static void badTypes(Expr expr) throws CompileError {
        throw new CompileError("invalid types for " + expr.getName());
    }

    private static final int P_DOUBLE = 0;
    private static final int P_FLOAT = 1;
    private static final int P_LONG = 2;
    private static final int P_INT = 3;
    private static final int P_OTHER = -1;

    protected static boolean isRefType(int type) {
        return type == CLASS || type == NULL;
    }

    private static int typePrecedence(int type) {
        if (type == DOUBLE)
            return P_DOUBLE;
        else if (type == FLOAT)
            return P_FLOAT;
        else if (type == LONG)
            return P_LONG;
        else if (isRefType(type))
            return P_OTHER;
        else if (type == VOID)
            return P_OTHER;     // this is wrong, but ...
        else
            return P_INT;       // BOOLEAN, BYTE, CHAR, SHORT, INT
    }

    // used in TypeChecker.
    static boolean isP_INT(int type) {
        return typePrecedence(type) == P_INT;
    }

    // used in TypeChecker.
    static boolean rightIsStrong(int type1, int type2) {
        int type1_p = typePrecedence(type1);
        int type2_p = typePrecedence(type2);
        return type1_p >= 0 && type2_p >= 0 && type1_p > type2_p;
    }

    private static final int[] castOp = {
            /*            D    F    L    I */
            /* double */ NOP, D2F, D2L, D2I,
            /* float  */ F2D, NOP, F2L, F2I,
            /* long   */ L2D, L2F, NOP, L2I,
            /* other  */ I2D, I2F, I2L, NOP };

    /* do implicit type conversion.
     * arrayDim values of the two oprands must be zero.
     */
    private void convertOprandTypes(int type1, int type2, Expr expr)
        throws CompileError
    {
        boolean rightStrong;
        int type1_p = typePrecedence(type1);
        int type2_p = typePrecedence(type2);

        if (type2_p < 0 && type1_p < 0) // not primitive types
            return;

        if (type2_p < 0 || type1_p < 0) // either is not a primitive type
            badTypes(expr);

        int op, result_type;
        if (type1_p <= type2_p) {
            rightStrong = false;
            exprType = type1;
            op = castOp[type2_p * 4 + type1_p];
            result_type = type1_p;
        }
        else {
            rightStrong = true;
            op = castOp[type1_p * 4 + type2_p];
            result_type = type2_p;
        }

        if (rightStrong) {
            if (result_type == P_DOUBLE || result_type == P_LONG) {
                if (type1_p == P_DOUBLE || type1_p == P_LONG)
                    bytecode.addOpcode(DUP2_X2);
                else
                    bytecode.addOpcode(DUP2_X1);

                bytecode.addOpcode(POP2);
                bytecode.addOpcode(op);
                bytecode.addOpcode(DUP2_X2);
                bytecode.addOpcode(POP2);
            }
            else if (result_type == P_FLOAT) {
                if (type1_p == P_LONG) {
                    bytecode.addOpcode(DUP_X2);
                    bytecode.addOpcode(POP);
                }
                else
                    bytecode.addOpcode(SWAP);

                bytecode.addOpcode(op);
                bytecode.addOpcode(SWAP);
            }
            else
                fatal();
        }
        else if (op != NOP)
            bytecode.addOpcode(op);
    }

    public void atCastExpr(CastExpr expr) throws CompileError {
        String cname = resolveClassName(expr.getClassName());
        String toClass = checkCastExpr(expr, cname);
        int srcType = exprType;
        exprType = expr.getType();
        arrayDim = expr.getArrayDim();
        className = cname;
        if (toClass == null)
            atNumCastExpr(srcType, exprType);   // built-in type
        else
            bytecode.addCheckcast(toClass);
    }

    public void atInstanceOfExpr(InstanceOfExpr expr) throws CompileError {
        String cname = resolveClassName(expr.getClassName());
        String toClass = checkCastExpr(expr, cname);
        bytecode.addInstanceof(toClass);
        exprType = BOOLEAN;
        arrayDim = 0;
    }

    private String checkCastExpr(CastExpr expr, String name)
        throws CompileError
    {
        final String msg = "invalid cast";
        ASTree oprand = expr.getOprand();
        int dim = expr.getArrayDim();
        int type = expr.getType();
        oprand.accept(this);
        int srcType = exprType;
        if (invalidDim(srcType, arrayDim, className, type, dim, name, true)
            || srcType == VOID || type == VOID)
            throw new CompileError(msg);

        if (type == CLASS) {
            if (!isRefType(srcType))
                throw new CompileError(msg);

            return toJvmArrayName(name, dim);
        }
        else
            if (dim > 0)
                return toJvmTypeName(type, dim);
            else
                return null;    // built-in type
    }

    void atNumCastExpr(int srcType, int destType)
        throws CompileError
    {
        if (srcType == destType)
            return;
        
        int op, op2;
        int stype = typePrecedence(srcType);
        int dtype = typePrecedence(destType);
        if (0 <= stype && stype < 3)
            op = castOp[stype * 4 + dtype];
        else
            op = NOP;

        if (destType == DOUBLE)
            op2 = I2D;
        else if (destType == FLOAT)
            op2 = I2F;
        else if (destType == LONG)
            op2 = I2L;
        else if (destType == SHORT)
            op2 = I2S;
        else if (destType == CHAR)
            op2 = I2C;
        else if (destType == BYTE)
            op2 = I2B;
        else
            op2 = NOP;