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authorspiderpig86 <slim679975@gmail.com>2018-06-24 14:55:47 -0400
committerspiderpig86 <slim679975@gmail.com>2018-06-24 14:55:47 -0400
commit254879a3be6829fa13d984a73dcda994aa3cd83d (patch)
tree11c0eb0bc3f0b6d3a42fb43fa29383b431bcbd35
parent86b8304bc28abab2c1565710deaced66e7a72606 (diff)
feat(mips.html.markdown): Added basics of loading and storing instructions
-rw-r--r--mips.html.markdown49
1 files changed, 39 insertions, 10 deletions
diff --git a/mips.html.markdown b/mips.html.markdown
index 952cc551..1c857ba4 100644
--- a/mips.html.markdown
+++ b/mips.html.markdown
@@ -19,18 +19,47 @@ The MIPS (Microprocessor without Interlocked Pipeline Stages) Assembly language
.data # Section where data is stored in memory (allocated in RAM), similar to variables in higher level languages
# Declarations follow a ( label: .type value(s) ) form of declaration
- hello_world .asciiz "Hello World\n" # Declare a null terminated string
- num1: .word 42 # Integers are referred to as words (32 bit value)
- arr1: .word 1, 2, 3, 4, 5 # Array of words
- arr2: .byte 'a', 'b' # Array of chars (1 byte each)
- buffer: .space 60 # Allocates space in the RAM (not cleared to 0)
+hello_world .asciiz "Hello World\n" # Declare a null terminated string
+ num1: .word 42 # Integers are referred to as words (32 bit value)
+ arr1: .word 1, 2, 3, 4, 5 # Array of words
+ arr2: .byte 'a', 'b' # Array of chars (1 byte each)
+ buffer: .space 60 # Allocates space in the RAM (not cleared to 0)
# Datatype sizes
- _byte: .byte 'a' # 1 byte
- _halfword: .half 53 # 2 bytes
- _word: .word 3 # 4 bytes
- _float: .float 3.14 # 4 bytes
- _double: .double 7.0 # 8 bytes
+ _byte: .byte 'a' # 1 byte
+ _halfword: .half 53 # 2 bytes
+ _word: .word 3 # 4 bytes
+ _float: .float 3.14 # 4 bytes
+ _double: .double 7.0 # 8 bytes
+ .align 2 # Memory alignment of data, where number indicates byte alignment in powers of 2. (.align 2 represents word alignment since 2^2 = 4 bytes)
+
+.text # Section that contains instructions and program logic
+.globl _main # Declares an instruction label as global, making it accessible to other files
+
+ _main: # MIPS programs execute instructions sequentially, where this will be executed first
+
+ # Let's print "hello world"
+ la $a0, hello_world # Load address of string stored in memory
+ li $v0, 4 # Load the syscall value (indicating type of functionality)
+ syscall # Perform the specified syscall with the given argument ($a0)
+
+ # Registers (used to hold data during program execution)
+ # $t0 - $t9 # Temporary registers used for intermediate calculations inside subroutines (not saved across function calls)
+ # $s0 - $s7 # Saved registers where values are saved across subroutine calls. Typically saved in stack
+ # $a0 - $a3 # Argument registers for passing in arguments for subroutines
+ # $v0 - $v1 # Return registers for returning values to caller function
+
+ # Types of load/store instructions
+ la $t0, label # Copy the address of a value in memory specified by the label into register $t0
+ lw $t0, label # Copy a word value from memory
+ lw $t1, 4($s0) # Copy a word value from an address stored in a register with an offset of 4 bytes (addr + 4)
+ lb $t2, label # Copy a byte value to the lower order portion of the register $t2
+ lb $t2, 0($s0) # Copy a byte value from the source address in $s0 with offset 0
+ # Same idea with 'lh' for halfwords
+
+ sw $t0, label # Store word value into memory address mapped by label
+ sw $t0, 8($s0) # Store word value into address specified in $s0 and offset of 8 bytes
+ # Same idea using 'sb' and 'sh' for bytes and halfwords. 'sa' does not exist
``` \ No newline at end of file