s3c2410a Samsung Semiconductor, Inc., s3c2410a Datasheet - Page 188

• Manufacturer Part Number: s3c2410a
• Description: 16/32-bit Risc Arm Microprocessor
• Manufacturer: Samsung Semiconductor, Inc.

THUMB INSTRUCTION SET
Now fix up the signs of the quotient (R0) and remainder (R1)
ARM Code
signed_divide
;ip bit 31 = sign of result
;ip bit 30 = sign of a2
;Central part is identical code to udiv (without MOV a4, #0 which comes for free as part of signed entry sequence)
just_l
div_l
4-42
POP
EOR
EOR
SUB
EOR
SUB
MOV
ANDS
RSBMI
EORS
RSBCS
MOVS
BEQ
CMP
MOVLS
BLO
CMP
ADC
SUBCS
TEQ
MOVNE
BNE
MOV
MOVS
RSBCS
RSBMI
MOV
{R2, R3}
R3, R2
R0, R3
R0, R3
R1, R2
R1, R2
pc, lr
;
a4, a1, #&80000000
a1, a1, #0
ip, a4, a2, ASR #32
a3, a1
divide_by_zero
a3, a2, LSR #1
a3, a3, LSL #1
s_loop
a2, a3
a4, a4, a4
a2, a2, a3
a3, a1
a3, a3, LSR #1
s_loop2
a1, a4
ip, ip, ASL #1
a1, a1, #0
a2, a2, #0
pc, lr
a2, a2, #0
; Get dividend/divisor signs back
; Result sign
; Negate if result sign = - 1
; Negate remainder if dividend sign = - 1
Effectively zero a4 as top bit will be shifted out later
; Justification stage shifts 1 bit at a time
; NB: LSL #1 is always OK if LS succeeds
S3C2410A