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
parent 834eff684f
commit c413c5feeb
6 changed files with 53 additions and 58 deletions
--- a/libsrc/runtime/subeqsp.s
+++ b/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