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137 lines
7.1 KiB
Markdown
137 lines
7.1 KiB
Markdown
---
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language: "MIPS"
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filename: MIPS.mips
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contributors:
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- ["Stanley Lim", "https://github.com/Spiderpig86"]
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---
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The MIPS (Microprocessor without Interlocked Pipeline Stages) Assembly language
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is designed to work with the MIPS microprocessor paradigm designed by J. L.
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Hennessy in 1981. These RISC processors are used in embedded systems such as
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gateways and routers.
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[Read More](https://en.wikipedia.org/wiki/MIPS_architecture)
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```assembly
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# Comments are denoted with a '#'
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# Everything that occurs after a '#' will be ignored by the assembler's lexer.
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# Programs typically contain a .data and .text sections
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.data # Section where data is stored in memory (allocated in RAM), similar to
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variables in higher level languages
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# Declarations follow a ( label: .type value(s) ) form of declaration
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hello_world .asciiz "Hello World\n" # Declare a null terminated string
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num1: .word 42 # Integers are referred to as words
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# (32 bit value)
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arr1: .word 1, 2, 3, 4, 5 # Array of words
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arr2: .byte 'a', 'b' # Array of chars (1 byte each)
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buffer: .space 60 # Allocates space in the RAM
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# (not cleared to 0)
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# Datatype sizes
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_byte: .byte 'a' # 1 byte
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_halfword: .half 53 # 2 bytes
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_word: .word 3 # 4 bytes
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_float: .float 3.14 # 4 bytes
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_double: .double 7.0 # 8 bytes
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.align 2 # Memory alignment of data, where
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# number indicates byte alignment in
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# powers of 2. (.align 2 represents
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#word alignment since 2^2 = 4 bytes)
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.text # Section that contains instructions
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# and program logic
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.globl _main # Declares an instruction label as
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# global, making it accessible to
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# other files
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_main: # MIPS programs execute instructions
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# sequentially, where the code under
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# this label will be executed firsts
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# Let's print "hello world"
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la $a0, hello_world # Load address of string stored in
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# memory
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li $v0, 4 # Load the syscall value (indicating
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# type of functionality)
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syscall # Perform the specified syscall with
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# the given argument ($a0)
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# Registers (used to hold data during program execution)
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# $t0 - $t9 # Temporary registers used for
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# intermediate calculations inside
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# subroutines (not saved across
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# function calls)
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# $s0 - $s7 # Saved registers where values are
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# saved across subroutine calls.
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# Typically saved in stack
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# $a0 - $a3 # Argument registers for passing in
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# arguments for subroutines
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# $v0 - $v1 # Return registers for returning
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# values to caller function
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# Types of load/store instructions
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la $t0, label # Copy the address of a value in
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# memory specified by the label into
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# register $t0
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lw $t0, label # Copy a word value from memory
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lw $t1, 4($s0) # Copy a word value from an address
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# stored in a register with an offset
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# of 4 bytes (addr + 4)
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lb $t2, label # Copy a byte value to the lower order
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# portion of the register $t2
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lb $t2, 0($s0) # Copy a byte value from the source
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# address in $s0 with offset 0
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# Same idea with 'lh' for halfwords
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sw $t0, label # Store word value into memory address
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# mapped by label
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sw $t0, 8($s0) # Store word value into address
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# specified in $s0 and offset of 8 bytes
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# Same idea using 'sb' and 'sh' for bytes and halfwords. 'sa' does not exist
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### Math ###
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_math:
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# Remember to load your values into a register
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lw $t0, num # From the data section
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li $t0, 5 # Or from an immediate (constant)
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li $t1, 6
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add $t2, $t0, $t1 # $t2 = $t0 + $t1
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sub $t2, $t0, $t1 # $t2 = $t0 - $t1
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mul $t2, $t0, $t1 # $t2 = $t0 * $t1
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div $t2, $t0, $t1 # $t2 = $t0 / $t1 (Might not be
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# supported in some versons of MARS)
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div $t0, $t1 # Performs $t0 / $t1. Get the quotient
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# using 'mflo' and remainder using 'mfhi'
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# Bitwise Shifting
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sll $t0, $t0, 2 # Bitwise shift to the left with
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# immediate (constant value) of 2
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sllv $t0, $t1, $t2 # Shift left by a variable amount in
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# register
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srl $t0, $t0, 5 # Bitwise shift to the right (does
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# not sign preserve, sign-extends with 0)
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srlv $t0, $t1, $t2 # Shift right by a variable amount in
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# a register
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sra $t0, $t0, 7 # Bitwise arithmetic shift to the right
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# (preserves sign)
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srav $t0, $t1, $t2 # Shift right by a variable amount
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# in a register
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# Bitwise operators
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and $t0, $t1, $t2 # Bitwise AND
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andi $t0, $t1, 0xFFF # Bitwise AND with immediate
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or $t0, $t1, $t2 # Bitwise OR
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ori $t0, $t1, 0xFFF # Bitwise OR with immediate
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xor $t0, $t1, $t2 # Bitwise XOR
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xori $t0, $t1, 0xFFF # Bitwise XOR with immediate
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nor $t0, $t1, $t2 # Bitwise NOR
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``` |