65C816: fix behavior of mvn and mvp when C=$FFFF (#314)

X16Community · Dec 24, 2024 · 4b6dd10 · 4b6dd10
1 parent cf50c59
commit 4b6dd10
Showing 1 changed file with 12 additions and 16 deletions.
diff --git a/src/cpu/instructions.h b/src/cpu/instructions.h
@@ -829,27 +829,23 @@ static void tsc() {
 }
 
 static void mvn() {
-    if (regs.c != 0xFFFF) {
-        if (index_16bit()) {
-            write6502(regs.y++, read6502(regs.x++));
-        } else {
-            write6502(regs.yl++, read6502(regs.xl++));
-        }
-
-        regs.c--;
+    if (index_16bit()) {
+        write6502(regs.y++, read6502(regs.x++));
+    } else {
+        write6502(regs.yl++, read6502(regs.xl++));
+    }
+    if (--regs.c != 0xFFFF) {
         regs.pc -= 3;
     }
 }
 
 static void mvp() {
-    if (regs.c != 0xFFFF) {
-        if (index_16bit()) {
-            write6502(regs.y--, read6502(regs.x--));
-        } else {
-            write6502(regs.yl--, read6502(regs.xl--));
-        }
-
-        regs.c--;
+    if (index_16bit()) {
+        write6502(regs.y--, read6502(regs.x--));
+    } else {
+        write6502(regs.yl--, read6502(regs.xl--));
+    }
+    if (--regs.c != 0xFFFF) {
         regs.pc -= 3;
     }
 }