Several SBC optimizations suggested by Piotr Fusik

git-svn-id: svn://svn.cc65.org/cc65/trunk@1121 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/runtime/ldec.s

@@ -5,13 +5,13 @@
 ;
 
        	.export	       	deceaxy
-	.importzp	ptr4, sreg
+	.importzp	sreg, tmp1
 
 deceaxy:
-	sty	ptr4
+	sty	tmp1
 	sec
-	sbc	ptr4
-	sta	ptr4
+	sbc	tmp1
+	sta	tmp1
 	txa
 	sbc	#0
 	tax
@@ -21,6 +21,6 @@ deceaxy:
 	lda	sreg+1
 	sbc	#0
 	sta	sreg+1
-	lda	ptr4
+	lda	tmp1
 	rts
 

libsrc/runtime/lsub.s

@@ -9,19 +9,18 @@
 ;
 	.export		tossubeax
 	.import		addysp1
-	.importzp	sp, sreg, tmp1, tmp2
+	.importzp   	sp, sreg
 
 tossubeax:
       	ldy	#0
        	sec
-	sta	tmp1
-	lda	(sp),y
-	sbc	tmp1	      	; byte 0
-	sta	tmp2	      	; use as temp storage
+	eor	#$FF
+       	adc	(sp),y		; byte 0
+       	pha			; Save low byte
 	iny
-	stx	tmp1
-	lda	(sp),y
-	sbc	tmp1	      	; byte 1
+	txa
+	eor	#$FF
+	adc	(sp),y		; byte 1
 	tax
 	iny
 	lda	(sp),y
@@ -31,6 +30,6 @@ tossubeax:
 	lda	(sp),y
 	sbc	sreg+1	      	; byte 3
 	sta	sreg+1
-	lda	tmp2	      	; load byte 0
-       	jmp    	addysp1	      	; drop TOS
+	pla	      		; Restore byte 0
+       	jmp    	addysp1	      	; Drop TOS
 

libsrc/runtime/lsubeq.s

@@ -8,7 +8,7 @@
 ;
 
        	.export	       	lsubeq1, lsubeqa, lsubeq
-       	.importzp   	sreg, ptr1, tmp1
+       	.importzp   	sreg, ptr1
 
 
 lsubeq1:
@@ -23,16 +23,15 @@ lsubeq:	sty	ptr1+1		    	; Store high byte of address
 	ldy	#$00		    	; Address low byte
 	sec
 
-	sta	tmp1
-	lda	(ptr1),y	    	; Load byte 0
-	sbc	tmp1
+	eor	#$FF
+	adc	(ptr1),y	    	; Subtract byte 0
 	sta	(ptr1),y
        	pha			    	; Save byte 0 of result for later
 
 	iny			    	; Address byte 1
-	stx	tmp1
-	lda	(ptr1),y	    	; Load byte 1
-	sbc	tmp1
+	txa
+	eor	#$FF
+	adc	(ptr1),y	  	; Subtract byte 1
 	sta	(ptr1),y
 	tax
 
@@ -48,9 +47,9 @@ lsubeq:	sty	ptr1+1		    	; Store high byte of address
 	sta	(ptr1),y
 	sta	sreg+1
 
-	pla				; Retrieve byte 0 of result
+	pla			  	; Retrieve byte 0 of result
 
-	rts				; Done
+	rts			  	; Done
 
 
 

libsrc/runtime/lsubeqsp.s

@@ -5,21 +5,20 @@
 ;
 
        	.export	       	lsubeq0sp, lsubeqysp
-	.importzp   	sp, sreg, tmp1, tmp2
+	.importzp      	sp, sreg
 
 lsubeq0sp:
       	ldy	#0
 lsubeqysp:
     	sec
-	sta	tmp1
-	stx	tmp2
-       	lda	(sp),y
-	sbc	tmp1
+	eor	#$FF
+       	adc	(sp),y
 	sta	(sp),y
-	pha
+	pha	      		; Save low byte
 	iny
-       	lda	(sp),y
-	sbc	tmp2
+	txa
+	eor	#$FF
+       	adc	(sp),y
 	sta	(sp),y
 	tax
 	iny

libsrc/runtime/sub.s

@@ -6,7 +6,7 @@
 
        	.export		tossuba0, tossubax
 	.import		addysp1
-	.importzp	sp, ptr1
+	.importzp	sp
 
 ;
 ; AX = TOS - AX
@@ -15,22 +15,21 @@
 tossuba0:
 	ldx	#0
 tossubax:
-	sta	ptr1
-	stx	ptr1+1
+      	sec
+      	eor	#$FF
 .ifpc02
-       	lda    	(sp)		; Get lo byte
-      	ldy	#1		; Hi index
+        adc	(sp)
+	ldy	#1
 .else
       	ldy	#0
-      	lda	(sp),y		; Lo byte
-      	iny			; Hi index
+      	adc	(sp),y		; Subtract low byte
+	iny
 .endif
-	sec
-	sbc	ptr1
-	sta	ptr1		; save lo byte
-	lda	(sp),y
-	sbc	ptr1+1
-	tax
-	lda	ptr1
-	jmp	addysp1		; drop TOS, set condition codes
+	pha			; Save high byte
+        txa
+	eor	#$FF
+	adc	(sp),y		; Subtract high byte
+	tax			; High byte into X
+	pla			; Restore low byte
+	jmp	addysp1		; drop TOS
 

libsrc/runtime/subeqsp.s

@@ -5,23 +5,22 @@
 ;
 
        	.export	       	subeq0sp, subeqysp
-   	.importzp	sp, tmp1, tmp2
+   	.importzp	sp
 
 subeq0sp:
    	ldy	#0
 subeqysp:
 	sec
-	sta	tmp1
-	stx	tmp2
-	lda    	(sp),y
-	sbc	tmp1
+	eor	#$FF
+	adc    	(sp),y
 	sta	(sp),y
-	pha
+	pha	      		; Save low byte
 	iny
-       	lda	(sp),y
-	sbc	tmp2
+	txa
+	eor	#$FF
+       	adc	(sp),y
 	sta	(sp),y
 	tax
-	pla
+	pla			; Restore low byte
 	rts