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ArmAsm

;
; Ullrich von Bassewitz, 1998-08-05, 2004-06-25
;
; CC65 runtime: left shift support for ints and unsigneds
;
; Note: The standard declares a shift count that is negative or >= the
; bitcount of the shifted type for undefined behaviour.
;
; Note^2: The compiler knowns about the register/zero page usage of this
; function, so you need to change the compiler source if you change it!
;
.export tosaslax, tosshlax
.import popax
.importzp tmp1
tosshlax:
tosaslax:
and #$0F ; Bring the shift count into a valid range
sta tmp1 ; Save it
jsr popax ; Get the left hand operand
ldy tmp1 ; Get shift count
beq L9 ; Bail out if shift count zero
cpy #8 ; Shift count 8 or greater?
bcc L3 ; Jump if not
; Shift count is greater 7. The carry is set when we enter here.
tax
tya
sbc #8
tay
txa
jmp L2
L1: asl a
L2: dey
bpl L1
tax
lda #$00
rts
; Shift count is less than 8.
L3: stx tmp1 ; Save high byte of lhs
L4: asl a
rol tmp1
dey
bne L4
; Done with shift
ldx tmp1
L9: rts