SimpLanPlus

Repository for the course "Compilatori e interpreti" (Compilers and Interpreters) at the University of Bologna, A.Y. 2020/21.

Addendum post submission

Feel free to take a cue from this project. The evaluation was good but this project is not without errors (i.e. some edge cases are not considerated).

Instructions for compiling

mvn clean compile assembly:single

Instructions for running (after compiling)

java -jar target/SimpLanPlus.jar fileName.ext [additional args]

with fileName.ext the name of a source code file written in SimpLanPlus language or in the SVM Assembly language (read the next section for more information). The file name cannot start with a dash (-).

Additional arguments

One might add different arguments to print out additional information or change the behaviour of the program while compiling or interpreting:

• --ast prints out the information available in the nodes of the Abstract Syntax Tree (AST) after the semantic and type checks. This will be skipped if argument -mode=run is present;
• --mode=compile only compiles the code and saves it in a file named fileName.asm;
• --mode=run only runs the Assembly code for the SimpLanPlus Virtual Machine (SVM) which is present in the file given as parameter;
• --mode=all compiles the code and runs it;
• --debugcpu shows the content of the memory and registers of the SVM at each instruction available in the compiled (or read) Assembly code. This will be skipped if argument -mode=compile is present;
• --codesize=c requires the memory size for hosting the code to be of size c (i.e. c Assembly instructions can be processed). c must be a positive integer otherwise 1000 is set. This will be skipped if argument -mode=compile is present;
• --memsize=m requires the memory size for executing the program to be of size m (both stack and heap). m must be a positive integer otherwise 1000 is set. This will be skipped if argument -mode=compile is present;

By default:

• the AST is not printed in the console;
• the file given as a parameter contains SimpLanPlus code to be both compiled and interpreted by the SVM;
• the CPU debug is disabled;
• both codesize and memsize are set to 1000.

Registers in the SVM

Available registers in the SVM:

• $sp: Stack Pointer points to the top of the stack
• $bsp: Base Stack Pointer points to the address where is stored the stack pointer prior a function call
• $hp: Heap Pointer points to the top of the heap
• $fp: Frame Pointer points to the current Access Link relative to the active frame
• $al: Access Link is used to go through the static chain (i.e. scopes)
• $ra: Return address stores the return address
• $a0: Accumulator is used to store the computed value of expressions
• $t1: General purpose register is used to store temporary values

Activation Record structure in the SVM

Activation Record
Dec M
Dec M-1
...
Dec 1
Par N
Par N-1
...
Par 1
AL (Access Link)
RA (Return Address)
Previous SP (Stack Pointer)
Previous FP (Frame Pointer)