As with all subroutines, mysub()
starts with a prolog.
mysub()
Of
course, mysub starts with a prolog.
There are two variables so space is assigned to them on the stack.
The subroutine could be written without using $s1.
But here is used to show how linkage works.
# int mysub( int arg )
# {
# int b,c; // b: 0($fp)
# // c: 4($fp)
# b = arg*2;
# c = b + 7;
#
# return c;
# }
.text
.globl
:
# prolog
sub $sp,$sp,4 # 1. Push return address
sw $ra,($sp)
sub $sp,$sp,4 # 2. Push caller's frame pointer
sw $fp,($sp)
, , # 3. Push register $s1
,
sub $fp,$sp, # 4. $fp = $sp - space_for_variables
move $sp,$fp # 5. $sp = $fp
. . . .
# epilog
jr $ra # return to caller
Play compiler:
Fill in those blanks.