allow asmsub routines with multiple return values to be called (special case for return values in status register)

compiler/src/prog8/ast/expressions/AstExpressions.kt

@@ -872,6 +872,12 @@ class FunctionCall(override var target: IdentifierReference,
                     return InferredTypes.void()     // no return value
                 if(stmt.returntypes.size==1)
                     return InferredTypes.knownFor(stmt.returntypes[0])
+
+                // multiple return values. Can occur for asmsub routines. If there is exactly one register return value, take that.
+                val numRegisterReturns = stmt.asmReturnvaluesRegisters.count { it.registerOrPair!=null }
+                if(numRegisterReturns==1)
+                    return InferredTypes.InferredType.known(DataType.UBYTE)
+
                 return InferredTypes.unknown()     // has multiple return types... so not a single resulting datatype possible
             }
             else -> return InferredTypes.unknown()

compiler/src/prog8/ast/processing/AstChecker.kt

@@ -346,17 +346,15 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(assignment: Assignment) {
-        // assigning from a functioncall COULD return multiple values (from an asm subroutine)
         if(assignment.value is FunctionCall) {
             val stmt = (assignment.value as FunctionCall).target.targetStatement(program.namespace)
-            if (stmt is Subroutine && stmt.isAsmSubroutine) {
+            if (stmt is Subroutine) {
-                if(stmt.returntypes.size>1)
-                    errors.err("It's not possible to store the multiple results of this asmsub call; you should use a small block of custom inline assembly for this.", assignment.value.position)
-                else {
                 val idt = assignment.target.inferType(program, assignment)
-                    if(!idt.isKnown || stmt.returntypes.single()!=idt.typeOrElse(DataType.BYTE)) {
+                if(!idt.isKnown) {
                      errors.err("return type mismatch", assignment.value.position)
                 }
+                if(stmt.returntypes.size <= 1 && stmt.returntypes.single()!=idt.typeOrElse(DataType.BYTE)) {
+                    errors.err("return type mismatch", assignment.value.position)
                 }
             }
         }
@@ -386,7 +384,8 @@ internal class AstChecker(private val program: Program,
         }
 
         val targetDt = assignment.target.inferType(program, assignment)
-        if(assignment.value.inferType(program) != targetDt) {
+        val valueDt = assignment.value.inferType(program)
+        if(valueDt.isKnown && valueDt != targetDt) {
             if(targetDt.typeOrElse(DataType.STRUCT) in IterableDatatypes)
                 errors.err("cannot assign value to string or array", assignment.value.position)
             else
@@ -446,12 +445,8 @@ internal class AstChecker(private val program: Program,
                     checkValueTypeAndRange(targetDatatype.typeOrElse(DataType.BYTE), constVal)
                 } else {
                     val sourceDatatype = assignment.value.inferType(program)
-                    if (!sourceDatatype.isKnown) {
+                    if (sourceDatatype.isUnknown) {
-                        if (assignment.value is FunctionCall) {
+                        if (assignment.value !is FunctionCall)
-                            val targetStmt = (assignment.value as FunctionCall).target.targetStatement(program.namespace)
-                            if (targetStmt != null)
-                                errors.err("function call doesn't return a suitable value to use in assignment", assignment.value.position)
-                        } else
                             errors.err("assignment value is invalid or has no proper datatype", assignment.value.position)
                     } else {
                         checkAssignmentCompatible(targetDatatype.typeOrElse(DataType.BYTE), assignTarget,
@@ -791,6 +786,8 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(expr: BinaryExpression) {
+        super.visit(expr)
+
         val leftIDt = expr.left.inferType(program)
         val rightIDt = expr.right.inferType(program)
         if(!leftIDt.isKnown || !rightIDt.isKnown)
@@ -836,7 +833,6 @@ internal class AstChecker(private val program: Program,
             errors.err("right operand is not numeric", expr.right.position)
         if(leftDt!=rightDt)
             errors.err("left and right operands aren't the same type", expr.left.position)
-        super.visit(expr)
     }
 
     override fun visit(typecast: TypecastExpression) {
@@ -898,6 +894,28 @@ internal class AstChecker(private val program: Program,
         if(error!=null)
             errors.err(error, functionCall.position)
 
+        // check the functions that return multiple returnvalues.
+        val stmt = functionCall.target.targetStatement(program.namespace)
+        if (stmt is Subroutine) {
+            if (stmt.returntypes.size > 1) {
+                // Currently, it's only possible to handle ONE (or zero) return values from a subroutine.
+                // asmsub routines can have multiple return values, for instance in 2 different registers.
+                // It's not (yet) possible to handle these multiple return values because assignments
+                // are only to a single unique target at the same time.
+                //   EXCEPTION:
+                // if the asmsub returns multiple values and one of them is via a status register bit,
+                // it *is* possible to handle them by just actually assigning the register value and
+                // dealing with the status bit as just being that, the status bit after the call.
+                val (returnRegisters, returnStatusflags) = stmt.asmReturnvaluesRegisters.partition { rr -> rr.registerOrPair != null }
+                if (returnRegisters.isEmpty() || returnRegisters.size == 1) {
+                    if (returnStatusflags.any())
+                        errors.warn("this asmsub also has one or more return 'values' in one of the status flags", functionCall.position)
+                } else {
+                    errors.err("It's not possible to store the multiple result values of this asmsub call; you should use a small block of custom inline assembly for this.", functionCall.position)
+                }
+            }
+        }
+
         super.visit(functionCall)
     }
 

compiler/src/prog8/ast/processing/VerifyFunctionArgTypes.kt

@@ -4,10 +4,9 @@ import prog8.ast.IFunctionCall
 import prog8.ast.INameScope
 import prog8.ast.Program
 import prog8.ast.base.DataType
+import prog8.ast.expressions.Expression
 import prog8.ast.expressions.FunctionCall
-import prog8.ast.statements.BuiltinFunctionStatementPlaceholder
+import prog8.ast.statements.*
-import prog8.ast.statements.FunctionCallStatement
-import prog8.ast.statements.Subroutine
 import prog8.compiler.CompilerException
 import prog8.functions.BuiltinFunctions
 
@@ -43,7 +42,6 @@ class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
             val argtypes = call.args.map { it.inferType(program).typeOrElse(DataType.STRUCT) }
             val target = call.target.targetStatement(scope)
             if (target is Subroutine) {
-                // asmsub types are not checked specifically at this time
                 if(call.args.size != target.parameters.size)
                     return "invalid number of arguments"
                 val paramtypes = target.parameters.map { it.type }
@@ -53,6 +51,16 @@ class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
                     val expected = paramtypes[mismatch].toString()
                     return "argument ${mismatch + 1} type mismatch, was: $actual expected: $expected"
                 }
+                if(target.isAsmSubroutine) {
+                    if(target.asmReturnvaluesRegisters.size>1) {
+                        // multiple return values will NOT work inside an expression.
+                        // they MIGHT work in a regular assignment or just a function call statement.
+                        val parent = if(call is Statement) call.parent else if(call is Expression) call.parent else null
+                        if(call !is FunctionCallStatement && parent !is Assignment && parent !is VarDecl) {
+                            return "can't use multiple return values here"
+                        }
+                    }
+                }
             }
             else if (target is BuiltinFunctionStatementPlaceholder) {
                 val func = BuiltinFunctions.getValue(target.name)

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

@@ -416,7 +416,7 @@ data class AssignTarget(var identifier: IdentifierReference?,
         }
     }
 
-    fun inferType(program: Program, stmt: Statement): InferredTypes.InferredType {
+    fun inferType(program: Program, stmt: Statement): InferredTypes.InferredType {  // TODO why does this have the extra 'stmt' scope parameter???
         if (identifier != null) {
             val symbol = program.namespace.lookup(identifier!!.nameInSource, stmt) ?: return InferredTypes.unknown()
             if (symbol is VarDecl) return InferredTypes.knownFor(symbol.datatype)

compiler/src/prog8/compiler/Main.kt

@@ -56,7 +56,7 @@ fun compileProgram(filepath: Path,
                 optimizeAst(programAst, errors)
             postprocessAst(programAst, errors, compilationOptions)
 
-            printAst(programAst) // TODO
+            // printAst(programAst)
 
             if(writeAssembly)
                 programName = writeAssembly(programAst, errors, outputDir, optimize, compilationOptions)
@@ -219,7 +219,7 @@ private fun writeAssembly(programAst: Program, errors: ErrorReporter, outputDir:
     programAst.processAstBeforeAsmGeneration(errors)
     errors.handle()
 
-    printAst(programAst) // TODO
+    // printAst(programAst)
 
     CompilationTarget.instance.machine.initializeZeropage(compilerOptions)
     val assembly = CompilationTarget.instance.asmGenerator(

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

@@ -588,9 +588,10 @@ internal class AsmGen(private val program: Program,
                 if (builtinFunc != null) {
                     builtinFunctionsAsmGen.translateFunctioncallStatement(stmt, builtinFunc)
                 } else {
-                    functioncallAsmGen.translateFunctionCall(stmt)
-                    // discard any results from the stack:
                     val sub = stmt.target.targetSubroutine(program.namespace)!!
+                    val preserveStatusRegisterAfterCall = sub.asmReturnvaluesRegisters.any {it.statusflag!=null}
+                    functioncallAsmGen.translateFunctionCall(stmt, preserveStatusRegisterAfterCall)
+                    // discard any results from the stack:
                     val returns = sub.returntypes.zip(sub.asmReturnvaluesRegisters)
                     for ((t, reg) in returns) {
                         if (reg.stack) {
@@ -598,6 +599,8 @@ internal class AsmGen(private val program: Program,
                             else if (t == DataType.FLOAT) out("  inx |  inx |  inx")
                         }
                     }
+                    if(preserveStatusRegisterAfterCall)
+                        out("  plp\t; restore status flags from call")
                 }
             }
             is Assignment -> assignmentAsmGen.translate(stmt)
@@ -763,8 +766,8 @@ internal class AsmGen(private val program: Program,
     internal fun translateFunctioncallExpression(functionCall: FunctionCall, signature: FSignature) =
             builtinFunctionsAsmGen.translateFunctioncallExpression(functionCall, signature)
 
-    internal fun translateFunctionCall(functionCall: FunctionCall) =
+    internal fun translateFunctionCall(functionCall: FunctionCall, preserveStatusRegisterAfterCall: Boolean) =
-            functioncallAsmGen.translateFunctionCall(functionCall)
+            functioncallAsmGen.translateFunctionCall(functionCall, preserveStatusRegisterAfterCall)
 
     internal fun translateNormalAssignment(assign: AsmAssignment) =
             assignmentAsmGen.translateNormalAssignment(assign)

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

@@ -949,7 +949,8 @@ internal class ExpressionsAsmGen(private val program: Program, private val asmge
             asmgen.translateFunctioncallExpression(expression, builtinFunc)
         } else {
             val sub = expression.target.targetSubroutine(program.namespace)!!
-            asmgen.translateFunctionCall(expression)
+            val preserveStatusRegisterAfterCall = sub.asmReturnvaluesRegisters.any {it.statusflag!=null}
+            asmgen.translateFunctionCall(expression, preserveStatusRegisterAfterCall)
             val returns = sub.returntypes.zip(sub.asmReturnvaluesRegisters)
             for ((_, reg) in returns) {
                 if (!reg.stack) {

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

@@ -13,7 +13,7 @@ import prog8.compiler.target.c64.codegen.assignment.*
 
 internal class FunctionCallAsmGen(private val program: Program, private val asmgen: AsmGen) {
 
-    internal fun translateFunctionCall(stmt: IFunctionCall) {
+    internal fun translateFunctionCall(stmt: IFunctionCall, preserveStatusRegisterAfterCall: Boolean) {
         // 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}")
@@ -57,6 +57,12 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
         }
         asmgen.out("  jsr  $subName")
 
+        if(preserveStatusRegisterAfterCall) {
+            asmgen.out("  php\t; save status flags from call")
+            // note: the containing statement (such as the FunctionCallStatement or the Assignment or the Expression)
+            //       must take care of popping this value again at the end!
+        }
+
         if(saveX)
             asmgen.restoreRegister(CpuRegister.X)
     }

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

@@ -6,6 +6,7 @@ import prog8.ast.expressions.*
 import prog8.ast.statements.AssignTarget
 import prog8.ast.statements.Assignment
 import prog8.ast.statements.DirectMemoryWrite
+import prog8.ast.statements.Subroutine
 import prog8.compiler.AssemblyError
 import prog8.compiler.target.c64.codegen.AsmGen
 
@@ -118,8 +119,23 @@ internal class AsmAssignSource(val kind: SourceStorageKind,
                     AsmAssignSource(SourceStorageKind.ARRAY, program, dt, array = value)
                 }
                 else -> {
+                    if(value is FunctionCall) {
+                        // functioncall.
+                        val asmSub = value.target.targetStatement(program.namespace)
+                        if(asmSub is Subroutine && asmSub.isAsmSubroutine) {
+                            when (asmSub.asmReturnvaluesRegisters.count { rr -> rr.registerOrPair!=null }) {
+                                0 -> throw AssemblyError("can't translate zero return values in assignment")
+                                1 -> {
+                                    // assignment generation itself must make sure the status register is correct after the subroutine call, if status register is involved!
+                                    return AsmAssignSource(SourceStorageKind.EXPRESSION, program, DataType.UBYTE, expression = value)
+                                }
+                                else -> throw AssemblyError("can't translate multiple return values in assignment")
+                            }
+                        }
+                    }
+
                     val dt = value.inferType(program).typeOrElse(DataType.STRUCT)
-                    AsmAssignSource(SourceStorageKind.EXPRESSION, program, dt, expression = value)
+                    return AsmAssignSource(SourceStorageKind.EXPRESSION, program, dt, expression = value)
                 }
             }
         }
@@ -160,6 +176,7 @@ internal class AsmAssignment(val source: AsmAssignSource,
 
     init {
         if(target.register !in setOf(RegisterOrPair.XY, RegisterOrPair.AX, RegisterOrPair.AY))
+            require(source.datatype != DataType.STRUCT) { "must not be placeholder datatype" }
             require(source.datatype.memorySize() == target.datatype.memorySize()) { "source and target datatype must be same storage class" }
     }
 }

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

@@ -123,20 +123,22 @@ internal class AssignmentAsmGen(private val program: Program, private val asmgen
                     is ArrayIndexedExpression -> throw AssemblyError("source kind should have been array")
                     is DirectMemoryRead -> throw AssemblyError("source kind should have been memory")
                     is TypecastExpression -> assignTypeCastedValue(assign.target, value.type, value.expression, assign)
-//                    is FunctionCall -> {
+                    is FunctionCall -> {
-//                        if (assign.target.kind == TargetStorageKind.STACK) {
+                        if(value.target.targetSubroutine(program.namespace)?.isAsmSubroutine==true) {
-//                            asmgen.translateExpression(value)
+                            // TODO handle asmsub functioncalls specifically, without shoving stuff on the estack
-//                            assignStackValue(assign.target)
+                            asmgen.translateExpression(value)
-//                        } else {
+                            assignStackValue(assign.target)
-//                            val functionName = value.target.nameInSource.last()
+                            val sub = value.target.targetSubroutine(program.namespace)
-//                            val builtinFunc = BuiltinFunctions[functionName]
+                            if(sub!=null && sub.asmReturnvaluesRegisters.any { it.statusflag != null }) {
-//                            if (builtinFunc != null) {
+                                // the expression translation will have generated a 'php' instruction earlier.
-//                                println("!!!!BUILTIN-FUNCCALL target=${assign.target.kind} $value") // TODO optimize certain functions?
+                                asmgen.out("  plp\t; restore status flags from call")
-//                            }
+                            }
-//                            asmgen.translateExpression(value)
+                        } else {
-//                            assignStackValue(assign.target)
+                            // regular subroutine, return values are (for now) always done via the stack...  TODO optimize this
-//                        }
+                            asmgen.translateExpression(value)
-//                    }
+                            assignStackValue(assign.target)
+                        }
+                    }
                     else -> {
                         // everything else just evaluate via the stack.
                         asmgen.translateExpression(value)

docs/source/syntaxreference.rst

@@ -503,6 +503,8 @@ takes no parameters.  If the subroutine returns a value, usually you assign it t
 If you're not interested in the return value, prefix the function call with the ``void`` keyword.
 Otherwise the compiler will warn you about discarding the result of the call.
 
+Multiple return values
+^^^^^^^^^^^^^^^^^^^^^^
 Normal subroutines can only return zero or one return values.
 However, the special ``asmsub`` routines (implemented in assembly code) or ``romsub`` routines
 (referencing a routine in kernel ROM) can return more than one return value.
@@ -510,9 +512,16 @@ For example a status in the carry bit and a number in A, or a 16-bit value in A/
 It is not possible to process the results of a call to these kind of routines
 directly from the language, because only single value assignments are possible.
 You can still call the subroutine and not store the results.
-But if you want to do something with the values it returns, you'll have to write
+
-a small block of custom inline assembly that does the call and stores the values
+**There is an exception:** if there's just one return value in a register, and one or more others that are returned
-appropriately. Don't forget to save/restore the registers if required.
+as bits in the status register (such as the Carry bit), the compiler allows you to call the subroutine.
+It will then store the result value in a variable if required, and *keep the status register untouched
+after the call* so you can use a conditional branch statement for that.
+Note that this makes no sense inside an expression, so the compiler will still give an error for that.
+
+If there really are multiple return values (other than a combined 16 bit return value in 2 registers),
+you'll have to write a small block of custom inline assembly that does the call and stores the values
+appropriately. Don't forget to save/restore any registers that are modified.
 
 
 Subroutine definitions

examples/test.p8

@@ -8,11 +8,20 @@ main {
     str planet_name = "12345678"
     sub start() {
 
-        ; TODO make this work, with a warning about Pc:
+        c64.OPEN()          ; works: function call droppign the value but preserving the statusregister
+        if_cs
+            return
+
         ubyte status
         status = c64.OPEN()          ; open 1,8,0,"$"
-        ; TODO make this work as well, with the same warning:
+        if_cs
-        ubyte status2 = c64.OPEN()          ; open 1,8,0,"$"
+            return
+
+
+;        ; TODO make this work as well, with the same warning:
+;        ubyte status2 = c64.OPEN()          ; open 1,8,0,"$"
+        if_cs
+            return