1. Keith Carolus and Dr. Alphonce
Smallpond Simulator
Keith Carolus and Dr. Alphonce

2. Keith Carolus Senior computer engineering student
keithcarolus.com
linkedin.com/in/keithcarolus
Previous CSE115/116, CSE341 TA
Current CSE379 TA

3. Simulator
Developed as a framework for simulating RISC, non-pipelined ISAs
Targeting Smallpond ISA, providing assembler and simulator
~2000 lines of code
Verbose assembly error reporting
Front end interface with view of memory, registers, and current instruction

4. Smallpond Simulator From Linux terminal (Bash): Notes:
> java -jar SmallpondSimulator.jar input_assembly.s mem_cap output_exec
Notes:
mem_cap: memory capacity in bytes (optional, default 500)
output_exec: output executable (optional)
May run jar in Eclipse, demo to come

5. Smallpond Assembly Syntax
C/Java-like single line comments, i.e., prefaced by “//”
Mnemonics, operands separated by whitespace and/or commas
Registers, mnemonics, flags, condition codes all uppercase
Labels expected on line of assembly
Instructions described in reference manual

6. Registers and Register Aliases
32 registers, R0-R31
Aliases:
A0-A3
T0-T7
S0-S5
+ and -
C+ and C-
HP, FP, SP
LR0-LR3 PC
CPSR

7. Structure of Assembly File
DATA block, optional
MAIN subroutine, required
e.g.
DATA my_block BLOCK 50
MAIN ADDI T0, T0, #1
Demo later

8. Data Section For defining constants 6 types: BLOCK INT HEX BINARY REAL
STRING
*** all constants are padded to multiple of 4 bytes

9. Data Section Example
my_block BLOCK 50 // a block of memory 50 bytes in size
my_block INT 2 // a 32 bit integer of value 2
my_block HEX 0xF // a 32 bit integer of value 15
my_block BINARY 0b1 // a 32 bit integer of value 1
my_block REAL 2.5 // a 64 IEEE-754 standard floating point number of value 2.5
my_block STRING “this is a string” // a variable length string
// STRING prefaced by 32 bit integer length in memory

10. How to Load a Data’s Address
2 instructions, ADDI and LUI
e.g.
ADDI T0, T0, my_data
LUI T0, my_data
This is very RISC-like

11. End of Execution Denoted by a “NOP” instruction Reason:
We have no operating system to return to :)
Suggested:
Place NOP at end of MAIN subroutine and always return back to the MAIN subroutine at the end of your program

12. Layout in Memory Low addresses Set SP (end of code segment)
Set HP (end of memory, grows backwards)
Set CPSR (jump to code segment)
Data segment
Code segment (starting with MAIN)
Stack ↓
High addresses
Heap ↑

13. Beta Release This simulator is ~2000 lines of code Many moving parts
Let me know if you encounter an issue or have any later questions
Piazza

14. Questions?

15. Importing JAR as Eclipse project
Main method located in package model.driver, class Driver.java
Arguments may be set in “Run configurations...”

16. Immediates Immediate values are prefaced by ‘#’ and may be:
Integer, e.g., #1
Hexadecimal (prefaced by 0x), e.g., #0xF
Binary (prefaced by 0b), e.g., #0b1010
Example of usage:
ADDI T0, 0, #0xAB

17. STRING Data Type Note that strings are interpretted literally
i.e. there are no escaped characters