Optimize ldax?sp/sta/stx to ldptr1?sp

2025-07-20 12:24:24 +02:00
parent 5fc300b987
commit 17b8645360
5 changed files with 103 additions and 0 deletions
--- a/libsrc/runtime/ldptr1sp.s
+++ b/libsrc/runtime/ldptr1sp.s
@@ -0,0 +1,20 @@
+;
+; Ullrich von Bassewitz, 31.08.1998
+;
+; CC65 runtime: Load ptr1 from offset in stack
+;
+
+        .export         ldptr10sp, ldptr1ysp
+        .importzp       c_sp, ptr1
+
+; Beware: The optimizer knows about the value in Y after return!
+
+ldptr10sp:
+        ldy     #1
+ldptr1ysp:
+        lda     (c_sp),y        ; get high byte
+        sta     ptr1+1          ; and save it
+        dey                     ; point to lo byte
+        lda     (c_sp),y        ; load low byte
+        sta     ptr1
+        rts