[SOLVED] Cse505 assignment 1 – object oriented parsing

Consider the following grammar for a simple programming language, TinyPL:
program -> decls stmts end
decls -> int idlist ‘;’
idlist -> id [‘,’ idlist ]
stmts -> stmt [ stmts ]
stmt -> assign ‘;’| cmpd | cond | loop
assign -> id ‘=’ expr
cmpd -> ‘{‘ stmts ‘}’
cond -> if ‘(‘ rexp ‘)’ stmt [ else stmt ]
loop -> for ‘(‘ [assign] ‘;’ [rexp] ‘;’ [assign] ‘)’ stmt

rexp -> expr (‘<‘ | ‘>’ | ‘==’ | ‘!= ‘) expr
expr -> term [ (‘+’ | ‘-‘) expr ]
term -> factor [ (‘*’ | ‘/’) term ]
factor -> int_lit | id | ‘(‘ expr ‘)’
Write an object-oriented top-down parser in Java that translates every TinyPL program into an
equivalent sequence of byte-codes for a Java Virtual Machine.
It would be helpful if you develop your program in three stages, as follows, but you only need to
submit the result of Stage 3:
Stage 1: Assume that stmt is of the form: stmt -> assign | cmpd
Stage 2: Assume that stmt is of the form: stmt -> assign | cmpd | cond
Stage 3: Assume that stmt is of the form: stmt -> assign | cmpd | cond | loop
Assumptions:
1. All input test cases will be syntactically correct; syntax error-checking is not necessary.
2. The lexical analyzer only accepts an id with a single letter, and an int_lit that is an
unsigned integer.
3. Follow Java byte-code naming convention for all opcodes.

Program Structure:
1. There should be one Java class definition for each nonterminal of the grammar. Place
the code for the top-down procedure in the class constructor itself.
2. There should be a top-level driver class called Parser and another class, called
Code, which has methods for code generation.
3. The code for the lexical analyzer will be given to you.
Output:
1. For each test case, show the byte code generated, as well as the object diagram
produced by JIVE at the end of execution: In generating the object diagram, choose
the “Stacked” (i.e., without tables) option while saving the object diagram.
2. Sample test cases and their outputs will be posted on Piazza. File naming convention
will also be posted. Please follow them carefully.
Clarifications:
1. Generate iconst, bipush, or sipush depending upon the numeric value of the literal:
o For small constants, in the range 0..5, the constant is implicit in the name of the instruction:
iconst_0 … iconst_5
o In generating code for integers in the range 6..127, the actual value comes immediately after
the opcode bipush We are not dealing with negative numbers in TinyPL, but Java
encodes numbers from -128 to +127 using 8 bits (one byte). Therefore, Java leaves one byte
after the instruction for bipush.
o For short integers greater than 127, the generated opcode is sipush. Now we need two
bytes to encode the value and hence Java leaves two bytes after the instruction for sipush.
Unike opcodes such as iadd, imul, isub, etc., for which the operands come before
the opcode, in the case of bipush and sipush the operand has to come after the opcode
because that is how the JVM will know how many bytes to push on the stack.
2. The iload and istore instructions have two variations each:
o For the first three variables declared, the load and store instructions are, respectively,
iload_1, iload_2, iload_3 and istore_1, istore_2, and istore_3.
o For the fourth and subsequent variables, the load and store instructions are,
respectively, iload n and istore n respectively, where n > 3. The number n is
encoded in one byte and placed after the iload and istore instructions.
3. Note that the initialization, test, and increment components of a for-loop are all optional, and
the simplest loop is of the form for ( ; ; ) … Your byte-code generation should work
correctly whether or not a particular component of the for-loop is present.
4. Optimizations are not required:
For programs in the TinyPL, the Java compiler would perform two types of optimizations:
a. Expressions such as 3 + (15 – 2 * 3) will be simplified to an integer value, namely, 12.
This is part of a more general process called “constant folding” and this is typically
done in the (machine-independent) optimization phase.
b. When there is a chain of goto’s, each one transferring control to the next, the Java
compiler will optimize each of them by generating “goto x”, where x is the location of
the final destination.
You are not required to make the above optimizations.
End of Assignment 1
Extra Credit (10%), only for those who have the assignment working fully:
Extend the grammar with type bool (for boolean). Support boolean expressions with operators
‘&&’, ‘||’, and “!’ which have their usual meaning. Finally, perform byte-code generation for
boolean expressions that appear in an assignment statement as well as if-else and for-loops.