diff options
| -rw-r--r-- | mips.html.markdown | 64 |
1 files changed, 62 insertions, 2 deletions
diff --git a/mips.html.markdown b/mips.html.markdown index 27a11e2f..9b176842 100644 --- a/mips.html.markdown +++ b/mips.html.markdown @@ -200,7 +200,8 @@ hello_world .asciiz "Hello World\n" # Declare a null terminated string ## LOOPS ## _loops: - # The basic structure of loops is having an exit condition and a jump instruction to continue its execution + # The basic structure of loops is having an exit condition and a jump + instruction to continue its execution li $t0, 0 while: bgt $t0, 10, end_while # While $t0 is less than 10, keep iterating @@ -220,7 +221,7 @@ hello_world .asciiz "Hello World\n" # Declare a null terminated string # Do stuff - addi $t1, $t1, 1 # Increment the col counter + addi $t1, $t1, 1 # Increment the col counter matrix_col_end: # Do stuff @@ -228,4 +229,63 @@ hello_world .asciiz "Hello World\n" # Declare a null terminated string addi $t0, $t0, 1 matrix_row_end: +## FUNCTIONS ## + _functions: + # Functions are callable procedures that can accept arguments and return + values all denoted with labels, like above + + main: # Programs begin with main func + jal return_1 # jal will store the current PC in $ra + # and then jump to return_1 + + # What if we want to pass in args? + # First we must pass in our parameters to the argument registers + li $a0, 1 + li $a1, 2 + jal sum # Now we can call the function + + # How about recursion? + # This is a bit more work since we need to make sure we save and restore + # the previous PC in $ra since jal will automatically overwrite on each call + li $a0, 3 + jal fact + + li $v0, 10 + syscall + + # This function returns 1 + return_1: + li $v0, 1 # Load val in return register $v0 + jr $ra # Jump back to old PC to continue exec + + + # Function with 2 args + sum: + add $v0, $a0, $a1 + jr $ra # Return + + # Recursive function to find factorial + fact: + addi $sp, $sp, -8 # Allocate space in stack + sw $s0, ($sp) # Store reg that holds current num + sw $ra, 4($sp) # Store previous PC + + li $v0, 1 # Init return value + beq $a0, 0, fact_done # Finish if param is 0 + + # Otherwise, continue recursion + move $s0, $a0 # Copy $a0 to $s0 + sub $a0, $a0, 1 + jal fact + + mul $v0, $s0, $v0 # Multiplication is done + + fact_done: + lw $s0, ($sp) + lw $ra, ($sp) # Restore the PC + addi $sp, $sp, 8 + + jr $ra + + ``` |