Merge pull request #653 from boriel/bugfix/USR_preserve_IX

fix: preserve IX reg in USR

Author: boriel

src/arch/zx48k/library-asm/usr.asm

@@ -11,10 +11,11 @@
     push namespace core
 
 USR:
+    push ix       ; must preserve IX
     call CALL_HL
+    pop ix
     ld h, b
     ld l, c
     ret
 
     pop namespace
-

src/arch/zxnext/library-asm/usr.asm

@@ -11,10 +11,11 @@
     push namespace core
 
 USR:
+    push ix       ; must preserve IX
     call CALL_HL
+    pop ix
     ld h, b
     ld l, c
     ret
 
     pop namespace
-

tests/functional/zx48k/opt1_usr.asm

@@ -70,10 +70,12 @@ CALL_HL:
 #line 10 "/zxbasic/src/arch/zx48k/library-asm/usr.asm"
 	    push namespace core
 USR:
+	    push ix       ; must preserve IX
 	    call CALL_HL
+	    pop ix
 	    ld h, b
 	    ld l, c
 	    ret
 	    pop namespace
-#line 23 "opt1_usr.bas"
+#line 23 "zx48k/opt1_usr.bas"
 	END