status condition couldn't properly be tested because restoring the X register clobbers the status flag

compiler/res/prog8lib/diskio.p8

@@ -134,11 +134,9 @@ io_error:
 
             @(nameptr) = 0
 
+            while c64.CHRIN() {
                 ; read the rest of the entry until the end
-            do {
+            }
-                ubyte char2 = c64.CHRIN()
-                char2++              ; TODO fix condition test problem with ldx
-            } until char2==1
 
             void c64.CHRIN()     ; skip 2 bytes
             void c64.CHRIN()

compiler/src/prog8/ast/statements/AstStatements.kt

@@ -757,6 +757,8 @@ class Subroutine(override val name: String,
 
     fun regXasResult() = asmReturnvaluesRegisters.any { it.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY) }
     fun regXasParam() = asmParameterRegisters.any { it.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY) }
+    fun shouldPreserveStatusRegisterAfterCall() = asmReturnvaluesRegisters.any { it.statusflag != null } || shouldSaveX()
+    fun shouldSaveX() = CpuRegister.X in asmClobbers || regXasResult() || regXasParam()
 
     fun amountOfRtsInAsm(): Int = statements
             .asSequence()

compiler/src/prog8/compiler/target/c64/codegen/ExpressionsAsmGen.kt

@@ -1329,7 +1329,7 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
             asmgen.translateBuiltinFunctionCallExpression(expression, builtinFunc, true)
         } else {
             sub as Subroutine
-            val preserveStatusRegisterAfterCall = sub.asmReturnvaluesRegisters.any {it.statusflag!=null}
+            val preserveStatusRegisterAfterCall = sub.shouldPreserveStatusRegisterAfterCall()
             asmgen.translateFunctionCall(expression, preserveStatusRegisterAfterCall)
             val returns = sub.returntypes.zip(sub.asmReturnvaluesRegisters)
             for ((_, reg) in returns) {

compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt

@@ -16,7 +16,7 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
 
     internal fun translateFunctionCallStatement(stmt: IFunctionCall) {
         val sub = stmt.target.targetSubroutine(program.namespace)!!
-        val preserveStatusRegisterAfterCall = sub.asmReturnvaluesRegisters.any {it.statusflag!=null}
+        val preserveStatusRegisterAfterCall = sub.shouldPreserveStatusRegisterAfterCall()
         translateFunctionCall(stmt, preserveStatusRegisterAfterCall)
         // functioncalls no longer return results on the stack, so simply ignore the results in the registers
         if(preserveStatusRegisterAfterCall)
@@ -28,7 +28,7 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
         // output the code to setup the parameters and perform the actual call
         // does NOT output the code to deal with the result values!
         val sub = stmt.target.targetSubroutine(program.namespace) ?: throw AssemblyError("undefined subroutine ${stmt.target}")
-        val saveX = CpuRegister.X in sub.asmClobbers || sub.regXasResult() || sub.regXasParam()
+        val saveX = sub.shouldSaveX()
         if(saveX)
             asmgen.saveRegister(CpuRegister.X, preserveStatusRegisterAfterCall, (stmt as Node).definingSubroutine()!!)
 

compiler/src/prog8/compiler/target/c64/codegen/assignment/AssignmentAsmGen.kt

@@ -142,7 +142,7 @@ internal class AssignmentAsmGen(private val program: Program, private val asmgen
                     is FunctionCall -> {
                         when (val sub = value.target.targetStatement(program.namespace)) {
                             is Subroutine -> {
-                                val preserveStatusRegisterAfterCall = sub.asmReturnvaluesRegisters.any { it.statusflag != null }
+                                val preserveStatusRegisterAfterCall = sub.shouldPreserveStatusRegisterAfterCall()
                                 asmgen.translateFunctionCall(value, preserveStatusRegisterAfterCall)
                                 val returnValue = sub.returntypes.zip(sub.asmReturnvaluesRegisters).single { it.second.registerOrPair!=null }
                                 when (returnValue.first) {

examples/test.p8

@@ -8,36 +8,12 @@
 errors {
     sub tofix() {
 
-        repeat {
-            ubyte char3 = c64.CHRIN()
-            if_cc
-                break
 
-            if_z
+;        ; TODO fix undefined symbol:
-                char3 ++
+;        repeat {
-            else
+;            ubyte char = c64.CHRIN()
-                break
+;            ; ...
-
+;        }
-            char3--
-        }
-labeltje:
-
-
-        while c64.CHRIN() {
-            ; TODO: the loop condition isn't properly tested because a ldx is in the way before the beq
-        }
-
-        repeat {
-            ubyte char2 = c64.CHRIN()
-            if char2==0         ; TODO condition not properly tested after optimizing because there's only a sta char2 before it (works without optimizing)
-                break
-        }
-
-        ; TODO fix undefined symbol:
-        repeat {
-            ubyte char = c64.CHRIN()
-            ; ...
-        }
 ;        do {
 ;            char = c64.CHRIN()      ; TODO fix undefined symbol error, should refer to 'char' above in the subroutine's scope
 ;        } until char==0