mirror of
https://github.com/cc65/cc65.git
synced 2024-12-23 19:29:37 +00:00
53dd513176
which included commits to RCS files with non-trunk default branches. git-svn-id: svn://svn.cc65.org/cc65/trunk@3 b7a2c559-68d2-44c3-8de9-860c34a00d81
70 lines
1.0 KiB
ArmAsm
70 lines
1.0 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 05.08.1998
|
|
;
|
|
; CC65 runtime: left shift support for ints
|
|
;
|
|
|
|
.export tosasla0, tosaslax, tosshla0, tosshlax
|
|
.import popsreg, return0
|
|
.importzp sreg
|
|
|
|
tosshla0:
|
|
tosasla0:
|
|
ldx #0
|
|
tosshlax:
|
|
tosaslax:
|
|
jsr popsreg ; get TOS into sreg
|
|
cpx #0
|
|
bne TooLarge
|
|
cmp #16
|
|
bcs TooLarge
|
|
|
|
cmp #8 ; Shift count greater 8?
|
|
beq L3 ; Jump if exactly 8
|
|
bcc L1 ; Jump if no
|
|
|
|
; Shift count is greater 8. Do the first 8 bits the fast way
|
|
|
|
ldy sreg
|
|
sty sreg+1
|
|
stx sreg ; Low byte = 0
|
|
sec
|
|
sbc #8
|
|
|
|
; Shift count less than 8 if we come here
|
|
|
|
L1: tay ; Shift count --> Y
|
|
beq Zero ; Done if shift count zero
|
|
|
|
lda sreg ; get low byte for faster shift
|
|
|
|
; Do the actual shift
|
|
|
|
L2: asl a
|
|
rol sreg+1
|
|
dey
|
|
bne L2
|
|
|
|
; Done with shift
|
|
|
|
ldx sreg+1
|
|
rts
|
|
|
|
; Shift count == 8
|
|
|
|
L3: txa ; X == 0, now A == 0
|
|
ldx sreg
|
|
rts
|
|
|
|
; Shift count was zero
|
|
|
|
Zero: lda sreg
|
|
ldx sreg+1
|
|
rts
|
|
|
|
; Shift count too large, result is zero
|
|
|
|
TooLarge:
|
|
jmp return0
|
|
|