Assignment 3 Solution

Assignment 3 consists of 1) Symbol table handling and




Generating an assembly code for the simplified version of our Grammar from assignment2 (arithmetic expressions and assignment statement for 80% of grade plus documentation(10%).



Or implement a Bottom-Up approach for the Syntax Analyzer. Or add implementation to your Top-Down Syntax Analyzer.




100% of grade for all the production rules for declarative, while and if and assignment.

Extra credit for:




Integration of all the 3 stages.

Separate working iterations using different approaches.







Our Grammar:




The grammar is essentially the same except that the program has NO <Function Definitions



No “real” type is allowed



Some Semantics:




Consider that “true” has an integer value of 1 and “false” has an integer value of 0.
No arithmetic operations are allowed for booleans.
The types must match for arithmetic operations (no conversions)






Part 1) Symbol table Handling (2%): Every identifier declared in the program should be placed in a symbol table and accessed by the symbol table handling procedures.




Each entry in the symbol table should hold the lexeme, and a "memory address" where an identifier is placed within the symbol table. For example, define a global integer variable called "Memory_address" and set initially 5000 and increment it by one when a new identifier is declared and placed into the table.



You need to write a procedure that will check to see if a particular identifier is already in the table, a procedure that will insert into the table and a procedure that will printout all identifiers in the table. If an identifier is used without declaring it, then the parser should provide an error message. Also, if an identifier is already in the table and wants to declare it for the second time, then the parser should provide an error message. Also, you should check the type match.












Part 2) Generating the assembly code (8%):




Modify your parser according to the simplified Rat18F and add code to your parser that will produce the assembly code instructions. The instructions should be kept in an array and at the










1



end, the content of the array is printed out to produce the listing of assembly code. Your array should hold at least 1000 assembly instructions. The instruction starts from 1.




The listing should include an array index for each entry so that it serves as label to jump to. The compiler should also produce a listing of all the identifiers.













Our target machine is a virtual machine based on a stack with the following instructions




PUSHI {Integer Value} Pushes the {Integer Value} onto the Top of the Stack (TOS) PUSHM {ML - Memory Location} Pushes the value stored at {ML} onto TOS POPM {ML} Pops the value from the top of the stack and stores it at {ML}

STDOUT Pops the value from TOS and outputs it to the standard output




STDIN Get the value from the standard input and place in onto the TOS

ADD Pop the first two items from stack and push the sum onto the TOS




SUB Pop the first two items from stack and push the difference onto the TOS

( Second item - First item)




MUL Pop the first two items from stack and push the product onto the TOS

DIV Pop the first two items from stack and push the result onto the TOS




( Second item / First item and ignore the remainder)

GRT Pops two items from the stack and pushes 1 onto TOS if second item is

larger otherwise push 0




LES Pops two items from the stack and pushes 1 onto TOS if the second item is

smaller than first item otherwise push 0




EQU Pops two items from the stack and pushes 1 onto TOS if they are equal

otherwise push 0




NEQ Pops two items from the stack and pushes 1 onto TOS if they are not equal

otherwise push 0




GEQ Pops two items from the stack and pushes 1 onto TOS if second item is

larger or equal, otherwise push 0




LEQ Pops two items from the stack and pushes 1 onto TOS if second item is

less or equal, otherwise push 0




JUMPZ {IL - Instruction Location} Pop the stack and if the value is 0 then jump to {IL}




JUMP {IL} Unconditionally jump to {IL}

LABEL Empty Instruction; Provides the instruction location to jump to.







Sample Source Code



[* this is comment for this sample code for assignment 3 *]







$$




int i, max, sum; [* declarations *]




sum = 0;

i = 1;










2
input ( max);

while (i < max) {




sum = sum + i;

i = i + 1;




}

output (sum + max);




$$







One Possible Assembly Code Listing







1
PUSHI
0
2
POPM
5002
3
PUSHI
1
4
POPM
5000
STDIN



POPM5001
LABEL



PUSHM 5000
PUSHM 5001



LES



JUMPZ21
PUSHM 5002



PUSHM 5000
ADD



POPM5002
PUSHM 5000



PUSHI1
ADD



19 POPM 5000

20 JUMP 7

PUSHM 5002



PUSHM 5001
ADD



STDOUT










Symbol Table
Identifier
MemoryLocation
Type
i
5000
integer
max
5001
integer
sum
5002
integer


















3
NOTE:




DO NOT CREATE YOUR OWN ASSEMBLY INSTRUCTIONS. USE ONLY PROVIDED INSTRUCTIONS.



Turn in your document according to the instructions given in the
project outline.















































































































































































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