New functions to swap register variables

git-svn-id: svn://svn.cc65.org/cc65/trunk@1629 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-11-25 12:38:38 +00:00
parent da44e7ae4b
commit e1385c925a
4 changed files with 88 additions and 0 deletions
--- a/libsrc/runtime/regswap1.s
+++ b/libsrc/runtime/regswap1.s
@@ -0,0 +1,22 @@
+;
+; Ullrich von Bassewitz, 25.11.2002
+;
+; CC65 runtime: Swap 1 byte of register variable space
+;
+
+   	.export	  	regswap1
+	.importzp      	sp, regbank
+
+.proc	regswap1
+
+        lda     regbank,x               ; Get old value
+        pha                             ; Save it
+        lda     (sp),y                  ; Get stack loc
+        sta     regbank,x               ; Store new value
+        pla
+        sta     (sp),y                  ; Store old value
+	rts
+
+.endproc
+
+