addcc instruction

[mattyice31]

i am in school taking a machine language class and need helpt writing out the asm code for teh addcc instruction. i have a detailed source code complete taht just needs teh blanks to be filled in.

.global main
main:
save %sp, -96, %sp ! %l1, %l2 will be set in gdb
set_vars:
! set %l1, %l2 NOW

clr %l7 ! init the CC holder to 0

! Here is where you need to start the add loop
! Add %l1 + %l2 = %l0
! See page 116 for the C algorithm for addition

! Store result in %l0
!--------------------------------------------------------------------------

setccs:
!at this point, we know that %l0 holds the result of our addition.
!we also know that %l1 holds our first operand
!and that %l2 holds our second operand
! %l7 will hold cc's (it is set to 0 right now)

zero: !found at bottom of register (0x1) -
!You can use tst for the zero
orcc %l0, %g0, %g0
bne zero_nset
nop
zero_set: !0 is the result
mov 1, %l7
ba zero_set_out ! get out if %l0 is 0
nop
zero_nset:
!--------------------------------------------------------------------------

negative: !found at second bit of register (0x2) -
!Use N = result<31> = 1; N=1 else N=0
srl %o0, 31, %o0 !shift 31 times to get the sign bit
sll %o0, 1, %o0 !shift it over 1 place
or %o0, %l7, %l7 !place it in my CC register
neg_set:

!--------------------------------------------------------------------------
carry: !found at third bit of register (0x4)
!if %l1 + %l2 = %l0
! Check the order of operations
!Use C = %l1<31> & %l2<31> | %l1<31> & !%l0<31> | %l2<31> & !%l0<31>

! CC is set in the lsb of %o0
sll %o0, 2, %o0 !shift it over 2 places
or %o0, %l7, %l7 !place it in my CC register
carry_set:

!--------------------------------------------------------------------------
overflow: !found at forth bit of register (0x8)
! Check the order of operations
!Use V = !%l1<31> & !%l2<31> & %l0<31> | %l1<31> & %l2<31> & !%l0<31>

! CC is set in the lsb of %o0
sll %o0, 3, %o0 !shift it over 3 places
or %o0, %l7, %l7 !place it in my CC register
overflow_set:

!--------------------------------------------------------------------------
! End of condition code setting
zero_set_out: ! As discussed, if we have 0, the rest is pointless to do
dunn:
! Here is where you need to print out %l1, %l2, %l0 and %l7

ret
restore