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cc65/libsrc/runtime/lsub.s
cuz c413c5feeb Several SBC optimizations suggested by Piotr Fusik
git-svn-id: svn://svn.cc65.org/cc65/trunk@1121 b7a2c559-68d2-44c3-8de9-860c34a00d81
2001-11-17 11:25:12 +00:00

36 lines
488 B
ArmAsm

;
; Ullrich von Bassewitz, 05.08.1998
;
; CC65 runtime: long sub
;
;
; EAX = TOS - EAX
;
.export tossubeax
.import addysp1
.importzp sp, sreg
tossubeax:
ldy #0
sec
eor #$FF
adc (sp),y ; byte 0
pha ; Save low byte
iny
txa
eor #$FF
adc (sp),y ; byte 1
tax
iny
lda (sp),y
sbc sreg ; byte 2
sta sreg
iny
lda (sp),y
sbc sreg+1 ; byte 3
sta sreg+1
pla ; Restore byte 0
jmp addysp1 ; Drop TOS