1. Assembler Directives
Example program: .data # DATA segment city: .asciiz “Seattle” .align 2 num: .word , 2341, 26, 0x022ec, 0x byte 65, 79, text # CODE segment .globl main # declaring “main” as global main: li $v0, # syscall for print_string la $a0, city # argument in $a0 syscall la $t0, num # get address of first number lw $s0, 0($t0) # s0 = lw $s1, 4($t0) # s1 = add $s0, $s0, $s1 # s0 = li $v0, # syscall for print_int move $a0, $s # argument in $a0 syscall .end main

2. General format of MIPS programs
Xspim on our machines automatically loads some assembly code that takes care of calling “main”
Need to write code that looks roughly like the following: .data # DATA segment lab1: .byte ……… lab2: .asciiz …… # some static data .float ……… lab3: .double …… text # CODE segment .globl main # declaring “main” as global main: <your part of the code> … end main

3. If-then-else in MIPS
What does the following C code looks like in MIPS assembly language: if (a < b) { a = a + 1; b = b - 1; } else { a = a * 2; b = b / 2; } Assume $s0 contains a, and $s1 contains b.

4. If-then-else (cont.)
# if (a < b) slt $t0, $s0, $s1 beq $t0, $zero, else_label # a = a + 1, b = b - 1 addi $s0, $s0, 1 subi $s1, $s1, 1 j end_label # else a = a * 2, b = b / 2 else_label: sll $s0, $s0, 1 sra $s1, $s1, 1 # end of if-then-else end: <statements following if-then-else>

5. From C Program to Machine Language
Stages in the transformation:
C program
Compiler
Assembly Language program
Assembler
Object : Machine
Language Module
Library routines
Machine Lang
Linker
Executable (Machine Language)
Loader
Memory