mirror of
https://github.com/cc65/cc65.git
synced 2024-12-27 15:29:46 +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
186 lines
3.0 KiB
ArmAsm
186 lines
3.0 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 20.09.1998
|
|
;
|
|
; CC65 runtime: right shift support for longs
|
|
;
|
|
|
|
|
|
.export tosasreax, tosshreax
|
|
.import addysp1
|
|
.importzp sp, sreg, ptr1, ptr2
|
|
|
|
; --------------------------------------------------------------------
|
|
; signed shift
|
|
|
|
.proc tosasreax
|
|
|
|
jsr getlhs ; Get the lhs from the stack
|
|
|
|
jsr checkovf ; Check for overflow
|
|
bcs L6 ; Jump if shift count too large
|
|
|
|
cpy #0 ; Shift count zero?
|
|
beq L5
|
|
|
|
; We must shift. Shift by multiples of eight if possible
|
|
|
|
tya
|
|
L1: cmp #8
|
|
bcc L3
|
|
sbc #8
|
|
ldx ptr1+1
|
|
stx ptr1
|
|
ldx ptr2
|
|
stx ptr1+1
|
|
ldy #0
|
|
ldx ptr2+1
|
|
stx ptr2
|
|
bpl L2
|
|
dey ; Get sign
|
|
L2: sty ptr2+1
|
|
jmp L1
|
|
|
|
; Shift count is now less than eight. Do a real shift.
|
|
|
|
L3: tay ; Shift count to Y
|
|
lda ptr2+1 ; Get one byte into A for speed
|
|
cpy #0
|
|
beq L4a ; Jump if done
|
|
L4: cmp #$80 ; Get sign bit into C
|
|
ror a
|
|
ror ptr2
|
|
ror ptr1+1
|
|
ror ptr1
|
|
dey
|
|
bne L4
|
|
|
|
; Put the result in place
|
|
|
|
L4a: sta sreg+1
|
|
lda ptr2
|
|
sta sreg
|
|
ldx ptr1+1
|
|
lda ptr1
|
|
L5: rts
|
|
|
|
; Jump here if shift count overflow
|
|
|
|
L6: ldx #0
|
|
lda ptr2+1 ; Check sign
|
|
bpl L7
|
|
dex
|
|
L7: stx sreg+1
|
|
stx sreg
|
|
txa
|
|
rts
|
|
|
|
.endproc
|
|
|
|
; --------------------------------------------------------------------
|
|
; unsigned shift
|
|
|
|
.proc tosshreax
|
|
|
|
jsr getlhs ; Get the lhs from the stack
|
|
|
|
jsr checkovf ; Check for overflow
|
|
bcs L6 ; Jump if shift count too large
|
|
|
|
cpy #0 ; Shift count zero?
|
|
beq L5
|
|
|
|
; We must shift. Shift by multiples of eight if possible
|
|
|
|
tya
|
|
L1: cmp #8
|
|
bcc L3
|
|
sbc #8
|
|
ldx ptr1+1
|
|
stx ptr1
|
|
ldx ptr2
|
|
stx ptr1+1
|
|
ldx ptr2+1
|
|
stx ptr2
|
|
ldx #0
|
|
stx ptr2+1
|
|
beq L1
|
|
|
|
; Shift count is now less than eight. Do a real shift.
|
|
|
|
L3: tay ; Shift count to Y
|
|
lda ptr2+1 ; Get one byte into A for speed
|
|
cpy #0
|
|
beq L4a ; Jump if done
|
|
L4: lsr a
|
|
ror ptr2
|
|
ror ptr1+1
|
|
ror ptr1
|
|
dey
|
|
bne L4
|
|
|
|
; Put the result in place
|
|
|
|
L4a: sta sreg+1
|
|
lda ptr2
|
|
sta sreg
|
|
ldx ptr1+1
|
|
lda ptr1
|
|
L5: rts
|
|
|
|
; Jump here if shift count overflow
|
|
|
|
L6: lda #0
|
|
sta sreg+1
|
|
sta sreg
|
|
tax
|
|
rts
|
|
|
|
.endproc
|
|
|
|
; --------------------------------------------------------------------
|
|
; Helpers
|
|
|
|
.proc getlhs ; Get the lhs from stack into ptr1/ptr2
|
|
|
|
pha
|
|
ldy #0
|
|
lda (sp),y
|
|
sta ptr1
|
|
iny
|
|
lda (sp),y
|
|
sta ptr1+1
|
|
iny
|
|
lda (sp),y
|
|
sta ptr2
|
|
iny
|
|
lda (sp),y
|
|
sta ptr2+1
|
|
pla
|
|
jmp addysp1
|
|
|
|
.endproc
|
|
|
|
|
|
.proc checkovf ; Check for shift overflow
|
|
|
|
tay ; Low byte of shift count into y
|
|
txa ; Get byte 2
|
|
ora sreg
|
|
ora sreg+1 ; Check high 24 bit
|
|
bne TooLarge ; Shift count too large
|
|
cpy #32
|
|
bcc Ok
|
|
TooLarge:
|
|
sec
|
|
Ok: rts
|
|
|
|
.endproc
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|