ECE 0142 Recitation #5

SPIM Simulator Official website: Versions http://pages.cs.wisc.edu/~larus/spim.html Versions Unix, Linux, Mac: spim, xspim Windows: PCSpim

Register Pane Program Pane Memory & stack Program input/output Memory address of instructions Instructions Correspondent line in source file Program Pane Encoded instruction Memory & stack Program input/output Message Pane

SPIM Basics Must have a label “main” – entrance of your program Data segment Starts with “.data” directive Memory locations, constants, string literals Text segment Your program

System Calls Simple I/O functions in your program Example How to use? print_int: print an integer on console print_string: print a zero-ended string on console read_int ...... How to use? Load $v0 with service number (e.g. 1 for print_int) Load arguments (if any) to $a0, $a1 or $f12 syscall

Example: Swap Words .data value1: .word 1111 value2: .word 2222 msg_v1: .asciiz "v1=" msg_v2: .asciiz "v2=" newline: .asciiz "\n" .text .globl main main: # Load value1, value2 into $s0, $s1 la $t0, value1 lw $s0, 0($t0) la $t1, value2 lw $s1, 0($t1) # swap $s0, $s1 move $s2, $s0 move $s0, $s1 move $s1, $s2 # Save $s0, $s1 back to value1, value2 sw $s0, 0($t0) sw $s1, 0($t1)

Example (cont.) # print value1 li $v0, 4 la $a0, msg_v1 syscall li $v0, 1 la $t0, value1 lw $a0, 0($t0) la $a0, newline # print value2 li $v0, 4 la $a0, msg_v2 syscall li $v0, 1 la $t0, value2 lw $a0, 0($t0) la $a0, newline # exit li $v0, 10