2009-11-03 13:40:03 +00:00
|
|
|
;
|
|
|
|
|
; Ullrich von Bassewitz, 2010-11-03
|
|
|
|
|
;
|
|
|
|
|
; CC65 runtime: 16x16 => 32 multiplication
|
|
|
|
|
;
|
|
|
|
|
|
2009-11-03 17:43:57 +00:00
|
|
|
.export umul16x16r32, _cc65_umul16x16r32
|
2009-11-03 13:40:03 +00:00
|
|
|
.export mul16x16r32 := umul16x16r32
|
2009-11-03 17:43:57 +00:00
|
|
|
.import popax
|
2009-11-03 13:40:03 +00:00
|
|
|
.importzp ptr1, ptr2, ptr3, ptr4, sreg
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
;---------------------------------------------------------------------------
|
|
|
|
|
; 16x16 => 32 multiplication routine.
|
|
|
|
|
;
|
|
|
|
|
; lhs rhs result result also in
|
|
|
|
|
; -------------------------------------------------------------
|
2009-11-03 17:43:57 +00:00
|
|
|
; ptr1 ax ax:sreg ptr1:sreg
|
2009-11-03 13:40:03 +00:00
|
|
|
;
|
|
|
|
|
|
2009-11-03 17:43:57 +00:00
|
|
|
_cc65_umul16x16r32:
|
|
|
|
|
sta ptr1
|
|
|
|
|
stx ptr1+1
|
|
|
|
|
jsr popax
|
|
|
|
|
|
2009-11-03 13:40:03 +00:00
|
|
|
umul16x16r32:
|
2009-11-03 17:43:57 +00:00
|
|
|
sta ptr3
|
|
|
|
|
stx ptr3+1
|
2009-11-03 13:40:03 +00:00
|
|
|
lda #0
|
|
|
|
|
sta sreg+1
|
|
|
|
|
ldy #16 ; Number of bits
|
|
|
|
|
|
|
|
|
|
lsr ptr1+1
|
|
|
|
|
ror ptr1 ; Get first bit into carry
|
|
|
|
|
@L0: bcc @L1
|
|
|
|
|
|
|
|
|
|
clc
|
|
|
|
|
adc ptr3
|
|
|
|
|
pha
|
|
|
|
|
txa ; hi byte of left op
|
|
|
|
|
adc sreg+1
|
|
|
|
|
sta sreg+1
|
|
|
|
|
pla
|
|
|
|
|
|
|
|
|
|
@L1: ror sreg+1
|
|
|
|
|
ror a
|
|
|
|
|
ror ptr1+1
|
|
|
|
|
ror ptr1
|
|
|
|
|
dey
|
|
|
|
|
bne @L0
|
|
|
|
|
|
|
|
|
|
sta sreg ; Save byte 3
|
|
|
|
|
lda ptr1 ; Load the result
|
|
|
|
|
ldx ptr1+1
|
|
|
|
|
rts ; Done
|
|
|
|
|
|
