Function pointers – initial version

2024-12-23 08:29:35 +00:00 · 2019-07-27 00:58:10 +02:00 · 2019-07-27 00:58:10 +02:00 · 35ba36ce11
commit 35ba36ce11
parent be9d27e2ee
21 changed files with 399 additions and 26 deletions
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -8,6 +8,8 @@

 * Added `bool` type.

+* Added function pointers – so far quite limited.
+
 * Added arrays of elements of size greater than byte.

 * Improved passing of register parameters to assembly functions.
--- a/docs/lang/operators.md
+++ b/docs/lang/operators.md
@ -264,12 +264,10 @@ Note that you cannot access a whole array element if it's bigger than 2 bytes, b
 Other kinds of expressions than the above (even `nonet(byte + byte + byte)`) will not work as expected.

 * `hi`, `lo`: most/least significant byte of a word  
-`hi(word)`
-
+`hi(word)`  
 Furthermore, any type that can be assigned to a variable can be used to convert
 either from one type either to another type of the same size,
-or from a 1-byte integer type to a compatible 2-byte integer type.
-
+or from a 1-byte integer type to a compatible 2-byte integer type.  
 `byte` → `word`  
 `word` → `pointer`  
 some enum → `byte`  
@ -281,4 +279,12 @@ some enum → `word`
 * `sizeof`: size of the argument in bytes; the argument can be an expression or a type,
 and the result is a constant of either `byte` or `word` type, depending on situation

+* `call`: calls a function via a pointer;  
+the first argument is the pointer to the function;  
+the second argument, if present, is the argument to the called function.  
+The function can have max one parameter, of size max 1 byte, and may return a value of size max 2 bytes.
+You can't create typed pointers to other kinds of functions anyway.  
+If the pointed-to function returns a value, then the result of `call(...)` is the result of the function.  
+Using `call` on 6502 targets requires at least 4 bytes of zeropage pseudoregister. 
+

--- a/docs/lang/types.md
+++ b/docs/lang/types.md
@ -75,6 +75,25 @@ Its actual value is defined using the feature `NULLPTR`, by default it's 0.

 `nullptr` isn't directly assignable to non-pointer types. 

+## Function pointers
+
+For every type `A` of size 1 (or `void`) and every type `B` of size 1 or 2 (or `void`),
+there is a pointer type defined called `function.A.to.B`, which represents functions with a signature like this:
+
+    B function_name(A parameter)
+    B function_name()  // if A is void
+    
+Examples:
+
+    word i
+    function.void.to.word p1 = f1.pointer
+    i = call(p1)
+    function.byte.to.byte p2 = f2.pointer
+    i += call(p2, 7)
+    
+Using `call` on 6502 requires at least 4 bytes of zeropage pseudoregister. 
+
+
 ## Boolean types

 TODO
--- a/examples/README.md
+++ b/examples/README.md
@ -6,6 +6,8 @@

 * [Fizzbuzz](crossplatform/fizzbuzz.mfk) (C64/C16/PET/VIC-20/PET/Atari/Apple II/BBC Micro/ZX Spectrum/PC-88/Armstrad CPC/MSX) – everyone's favourite programming task

+* [Fizzbuzz 2](crossplatform/fizzbuzz2.mfk) (C64/C16/PET/VIC-20/PET/Atari/Apple II/BBC Micro/ZX Spectrum/PC-88/Armstrad CPC/MSX) – an alternative, more extensible implemententation of fizzbuzz
+
 * [Text encodings](crossplatform/text_encodings.mfk) (C64/ZX Spectrum) – examples of text encoding features

 * [Echo](crossplatform/echo.mfk) (C64/C16/ZX Spectrum/PC-88/MSX)– simple text input and output
--- a/examples/crossplatform/fizzbuzz2.mfk
+++ b/examples/crossplatform/fizzbuzz2.mfk
@ -0,0 +1,38 @@
+
+import stdio
+
+bool divisible3(byte x) = x %% 3 == 0
+bool divisible5(byte x) = x %% 5 == 0
+
+struct stage {
+    function.byte.to.bool predicate
+    pointer text
+}
+
+// can't put text literals directly in struct constructors yet
+array fizz = "fizz"z
+array buzz = "buzz"z
+
+array(stage) stages = [
+    stage(divisible3.pointer, fizz),
+    stage(divisible5.pointer, buzz)
+]
+
+void main() {
+    byte i, s
+    bool printed
+    for i,1,to,100 {
+        printed = false
+        for s,0,until,stages.length {
+            if call(stages[s].predicate, i) {
+                printed = true
+                putstrz(stages[js].text)
+            }
+        }
+        if not(printed) {
+            putword(i)
+        }
+        putchar(' ')
+    }
+}
+
--- a/include/stdlib_6502.mfk
+++ b/include/stdlib_6502.mfk
@ -47,4 +47,8 @@ macro asm void panic() {
    ? JSR _panic
 }

-array __constant8 = [8]
+const array __constant8 = [8]
+
+#if ZPREG_SIZE < 4
+const array call = [2]
+#endif
--- a/include/stdlib_i80.mfk
+++ b/include/stdlib_i80.mfk
@ -53,3 +53,8 @@ _lo_nibble_to_hex_lbl:
 macro asm void panic() {
    ? CALL _panic
 }
+
+noinline asm word call(word de) {
+    PUSH DE
+    RET
+}
--- a/include/zp_reg.mfk
+++ b/include/zp_reg.mfk
@ -96,3 +96,11 @@ asm word __div_u16u8u16u8() {
 }

 #endif
+
+#if ZPREG_SIZE >= 4
+
+noinline asm word call(word ax) {
+    JMP ((__reg + 2))
+}
+
+#endif
--- a/src/main/scala/millfork/assembly/mos/opt/ZeropageRegisterOptimizations.scala
+++ b/src/main/scala/millfork/assembly/mos/opt/ZeropageRegisterOptimizations.scala
@ -13,6 +13,7 @@ import millfork.error.FatalErrorReporting
 object ZeropageRegisterOptimizations {

  val functionsThatUsePseudoregisterAsInput: Map[String, Set[Int]] = Map(
+    "call" -> Set(2, 3),
    "__mul_u8u8u8" -> Set(0, 1),
    "__mod_u8u8u8u8" -> Set(0, 1),
    "__div_u8u8u8u8" -> Set(0, 1),
--- a/src/main/scala/millfork/assembly/z80/opt/ReverseFlowAnalyzer.scala
+++ b/src/main/scala/millfork/assembly/z80/opt/ReverseFlowAnalyzer.scala
@ -183,13 +183,13 @@ object ReverseFlowAnalyzer {

  val cache = new FlowCache[ZLine, CpuImportance]("z80 reverse")

-  val readsA: Set[String] = Set("__mul_u8u8u8", "__mul_u16u8u16")
+  val readsA: Set[String] = Set("__mul_u8u8u8", "__mul_u16u8u16", "call")
  val readsB: Set[String] = Set("")
  val readsC: Set[String] = Set("")
-  val readsD: Set[String] = Set("__mul_u8u8u8","__mul_u16u8u16", "__divmod_u16u8u16u8")
-  val readsE: Set[String] = Set("__mul_u16u8u16")
-  val readsH: Set[String] = Set("__divmod_u16u8u16u8")
-  val readsL: Set[String] = Set("__divmod_u16u8u16u8")
+  val readsD: Set[String] = Set("__mul_u8u8u8","__mul_u16u8u16", "__divmod_u16u8u16u8", "call")
+  val readsE: Set[String] = Set("__mul_u16u8u16", "call")
+  val readsH: Set[String] = Set("__divmod_u16u8u16u8", "call")
+  val readsL: Set[String] = Set("__divmod_u16u8u16u8", "call")

  //noinspection RedundantNewCaseClass
  def analyze(f: NormalFunction, code: List[ZLine]): List[CpuImportance] = {
--- a/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/AbstractExpressionCompiler.scala
@ -260,7 +260,7 @@ object AbstractExpressionCompiler {

    val v = env.get[Type]("void")
    val w = env.get[Type]("word")
-    val t = expr match {
+    val t: Type = expr match {
      case LiteralExpression(_, size) =>
        size match {
          case 1 => b
@ -372,6 +372,34 @@ object AbstractExpressionCompiler {
          case Some(List(x)) => toType(!x)
          case _ => bool
        }
+      case f@FunctionCallExpression("call", params) =>
+        params match {
+          case List(fp) =>
+            getExpressionType(env, log, fp) match {
+              case fpt@FunctionPointerType(_, _, _, Some(v), Some(r)) =>
+                if (v.name != "void"){
+                  log.error(s"Invalid function pointer type: $fpt", fp.position)
+                }
+                r
+              case fpt =>
+                log.error(s"Not a function pointer type: $fpt", fp.position)
+                v
+            }
+          case List(fp, pp) =>
+            getExpressionType(env, log, fp) match {
+              case fpt@FunctionPointerType(_, _, _, Some(p), Some(r)) =>
+                if (!getExpressionType(env, log, pp).isAssignableTo(p)){
+                  log.error(s"Invalid function pointer type: $fpt", fp.position)
+                }
+                r
+              case fpt =>
+                log.error(s"Not a function pointer type: $fpt", fp.position)
+                v
+            }
+          case _ =>
+            log.error("Invalid call(...) syntax; use either 1 or 2 arguments", f.position)
+            v
+        }
      case FunctionCallExpression("hi", _) => b
      case FunctionCallExpression("lo", _) => b
      case FunctionCallExpression("sin", params) => if (params.size < 2) b else getExpressionType(env, log, params(1))
--- a/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/mos/MosExpressionCompiler.scala
@ -514,6 +514,12 @@ object MosExpressionCompiler extends AbstractExpressionCompiler[AssemblyLine] {
    compile(ctx, expr, Some(p -> env.get[Variable]("__reg.loword")), BranchSpec.None)
  }

+  def compileToZReg2(ctx: CompilationContext, expr: Expression): List[AssemblyLine] = {
+    val env = ctx.env
+    val p = env.get[Type]("pointer")
+    compile(ctx, expr, Some(p -> env.get[Variable]("__reg.b2b3")), BranchSpec.None)
+  }
+
  def getPhysicalPointerForDeref(ctx: CompilationContext, pointerExpression: Expression): (List[AssemblyLine], Constant, AddrMode.Value) = {
    pointerExpression match {
      case VariableExpression(name) =>
@ -1162,6 +1168,36 @@ object MosExpressionCompiler extends AbstractExpressionCompiler[AssemblyLine] {
        var zeroExtend = false
        var resultVariable = ""
        val calculate: List[AssemblyLine] = name match {
+          case "call" =>
+            params match {
+              case List(fp) =>
+                getExpressionType(ctx, fp) match {
+                  case FunctionPointerType(_, _, _, _, Some(v)) if (v.name == "void") =>
+                    compileToZReg2(ctx, fp) :+ AssemblyLine.absolute(JSR, env.get[ThingInMemory]("call"))
+                  case _ =>
+                    ctx.log.error("Not a function pointer", fp.position)
+                    compile(ctx, fp, None, BranchSpec.None)
+                }
+              case List(fp, param) =>
+                getExpressionType(ctx, fp) match {
+                  case FunctionPointerType(_, _, _, Some(pt), Some(v)) =>
+                    if (pt.size != 1) {
+                      ctx.log.error("Invalid parameter type", param.position)
+                      compile(ctx, fp, None, BranchSpec.None) ++ compile(ctx, param, None, BranchSpec.None)
+                    } else if (getExpressionType(ctx, param).isAssignableTo(pt)) {
+                      compileToA(ctx, param) ++ preserveRegisterIfNeeded(ctx, MosRegister.A, compileToZReg2(ctx, fp)) :+ AssemblyLine.absolute(JSR, env.get[ThingInMemory]("call"))
+                    } else {
+                      ctx.log.error("Invalid parameter type", param.position)
+                      compile(ctx, fp, None, BranchSpec.None) ++ compile(ctx, param, None, BranchSpec.None)
+                    }
+                  case _ =>
+                    ctx.log.error("Not a function pointer", fp.position)
+                    compile(ctx, fp, None, BranchSpec.None) ++ compile(ctx, param, None, BranchSpec.None)
+                }
+              case _ =>
+                ctx.log.error("Invalid call syntax", f.position)
+                Nil
+            }
          case "not" =>
            assertBool(ctx, "not", params, 1)
            compile(ctx, params.head, exprTypeAndVariable, branches.flip)
@ -2062,7 +2098,7 @@ object MosExpressionCompiler extends AbstractExpressionCompiler[AssemblyLine] {
                    val reg = env.get[ThingInMemory]("__reg.loword")
                    (addr, addrSource) match {
                      case (MemoryAddressConstant(th1: Thing), MemoryAddressConstant(th2: Thing))
-                        if (th1.name == "__reg.loword" || th1.name == "__reg") && (th2.name == "__reg.loword" || th2.name == "__reg") =>
+                        if (th1.name == "__reg.loword" || th1.name == "__reg.b2b3" || th1.name == "__reg") && (th2.name == "__reg.loword" || th2.name == "__reg.b2b3" || th2.name == "__reg") =>
                        (MosExpressionCompiler.changesZpreg(prepareSource, 2) || MosExpressionCompiler.changesZpreg(prepareSource, 3),
                          MosExpressionCompiler.changesZpreg(prepareSource, 2) || MosExpressionCompiler.changesZpreg(prepareSource, 3)) match {
                          case (_, false) =>
--- a/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala
+++ b/src/main/scala/millfork/compiler/z80/Z80ExpressionCompiler.scala
@ -738,6 +738,37 @@ object Z80ExpressionCompiler extends AbstractExpressionCompiler[ZLine] {
            })
          case f@FunctionCallExpression(name, params) =>
            name match {
+              case "call" =>
+                val callLine = ZLine(CALL, NoRegisters, env.get[ThingInMemory]("call").toAddress)
+                params match {
+                  case List(fp) =>
+                    getExpressionType(ctx, fp) match {
+                      case FunctionPointerType(_, _, _, _, Some(v)) if (v.name == "void") =>
+                        compileToDE(ctx, fp) :+ callLine
+                      case _ =>
+                        ctx.log.error("Not a function pointer", fp.position)
+                        compile(ctx, fp, ZExpressionTarget.NOTHING, BranchSpec.None)
+                    }
+                  case List(fp, param) =>
+                    getExpressionType(ctx, fp) match {
+                      case FunctionPointerType(_, _, _, Some(pt), Some(v)) =>
+                        if (pt.size != 1) {
+                          ctx.log.error("Invalid parameter type", param.position)
+                          compileToHL(ctx, fp) ++ compile(ctx, param, ZExpressionTarget.NOTHING)
+                        } else if (getExpressionType(ctx, param).isAssignableTo(pt)) {
+                          compileToDE(ctx, fp) ++ stashDEIfChanged(ctx, compileToA(ctx, param)) :+ callLine
+                        } else {
+                          ctx.log.error("Invalid parameter type", param.position)
+                          compileToHL(ctx, fp) ++ compile(ctx, param, ZExpressionTarget.NOTHING)
+                        }
+                      case _ =>
+                        ctx.log.error("Not a function pointer", fp.position)
+                        compile(ctx, fp, ZExpressionTarget.NOTHING) ++ compile(ctx, param, ZExpressionTarget.NOTHING)
+                    }
+                  case _ =>
+                    ctx.log.error("Invalid call syntax", f.position)
+                    Nil
+                }
              case "not" =>
                assertBool(ctx, "not", params, 1)
                compile(ctx, params.head, target, branches.flip)
--- a/src/main/scala/millfork/env/Environment.scala
+++ b/src/main/scala/millfork/env/Environment.scala
@ -284,6 +284,12 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
  }

  def get[T <: Thing : Manifest](name: String, position: Option[Position] = None): T = {
+    if (name.startsWith("function.") && implicitly[Manifest[T]].runtimeClass.isAssignableFrom(classOf[PointerType])) {
+      val tokens = name.stripPrefix("function.").split("\\.to\\.", 2)
+      if (tokens.length == 2) {
+        return FunctionPointerType(name, tokens(0), tokens(1), maybeGet[Type](tokens(0)), maybeGet[Type](tokens(1))).asInstanceOf[T]
+      }
+    }
    if (name.startsWith("pointer.") && implicitly[Manifest[T]].runtimeClass.isAssignableFrom(classOf[PointerType])) {
      val targetName = name.stripPrefix("pointer.")
      val target = maybeGet[VariableType](targetName)
@ -1147,9 +1153,16 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
    }
  }

+  private def getFunctionPointerType(f: FunctionInMemory) = f.params.types match {
+    case List() =>
+      get[Type]("function.void.to." + f.returnType.name)
+    case p :: _ => // TODO: this only handles one type though!
+      get[Type]("function." + p.name + ".to." + f.returnType.name)
+  }
+
  private def registerAddressConstant(thing: ThingInMemory, position: Option[Position], options: CompilationOptions, targetType: Option[Type]): Unit = {
+    val b = get[Type]("byte")
    if (!thing.zeropage && options.flag(CompilationFlag.LUnixRelocatableCode)) {
-      val b = get[Type]("byte")
      val w = get[Type]("word")
      val relocatable = UninitializedMemoryVariable(thing.name + ".addr", w, VariableAllocationMethod.Static, None, defaultVariableAlignment(options, 2), isVolatile = false)
      val addr = relocatable.toAddress
@ -1166,20 +1179,36 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
      addThing(ConstantThing(thing.name + ".rawaddr", rawaddr, get[Type]("pointer")), position)
      addThing(ConstantThing(thing.name + ".rawaddr.hi", rawaddr.hiByte, get[Type]("byte")), position)
      addThing(ConstantThing(thing.name + ".rawaddr.lo", rawaddr.loByte, get[Type]("byte")), position)
+      thing match {
+        case f: FunctionInMemory if f.canBePointedTo =>
+          val typedPointer = RelativeVariable(thing.name + ".pointer", addr, getFunctionPointerType(f), zeropage = false, None, isVolatile = false)
+          addThing(typedPointer, position)
+          addThing(RelativeVariable(thing.name + ".pointer.hi", addr + 1, b, zeropage = false, None, isVolatile = false), position)
+          addThing(RelativeVariable(thing.name + ".pointer.lo", addr, b, zeropage = false, None, isVolatile = false), position)
+        case _ =>
+      }
    } else {
      val addr = thing.toAddress
      addThing(ConstantThing(thing.name + ".addr", addr, get[Type]("pointer")), position)
-      addThing(ConstantThing(thing.name + ".addr.hi", addr.hiByte, get[Type]("byte")), position)
-      addThing(ConstantThing(thing.name + ".addr.lo", addr.loByte, get[Type]("byte")), position)
+      addThing(ConstantThing(thing.name + ".addr.hi", addr.hiByte, b), position)
+      addThing(ConstantThing(thing.name + ".addr.lo", addr.loByte, b), position)
      addThing(ConstantThing(thing.name + ".rawaddr", addr, get[Type]("pointer")), position)
-      addThing(ConstantThing(thing.name + ".rawaddr.hi", addr.hiByte, get[Type]("byte")), position)
-      addThing(ConstantThing(thing.name + ".rawaddr.lo", addr.loByte, get[Type]("byte")), position)
+      addThing(ConstantThing(thing.name + ".rawaddr.hi", addr.hiByte, b), position)
+      addThing(ConstantThing(thing.name + ".rawaddr.lo", addr.loByte, b), position)
      targetType.foreach { tt =>
        val pointerType = PointerType("pointer." + tt.name, tt.name, Some(tt))
        val typedPointer = RelativeVariable(thing.name + ".pointer", addr, pointerType, zeropage = false, None, isVolatile = false)
        addThing(ConstantThing(thing.name + ".pointer", addr, pointerType), position)
-        addThing(ConstantThing(thing.name + ".pointer.hi", addr.hiByte, get[Type]("byte")), position)
-        addThing(ConstantThing(thing.name + ".pointer.lo", addr.loByte, get[Type]("byte")), position)
+        addThing(ConstantThing(thing.name + ".pointer.hi", addr.hiByte, b), position)
+        addThing(ConstantThing(thing.name + ".pointer.lo", addr.loByte, b), position)
+      }
+      thing match {
+        case f: FunctionInMemory if f.canBePointedTo =>
+          val pointerType = getFunctionPointerType(f)
+          addThing(ConstantThing(thing.name + ".pointer", addr, pointerType), position)
+          addThing(ConstantThing(thing.name + ".pointer.hi", addr.hiByte, b), position)
+          addThing(ConstantThing(thing.name + ".pointer.lo", addr.loByte, b), position)
+        case _ =>
      }
    }
  }
@ -1698,6 +1727,7 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
      if (function.params.length != actualParams.length) {
        log.error(s"Invalid number of parameters for function `$name`", actualParams.headOption.flatMap(_._2.position))
      }
+      if (name == "call") return Some(function)
      function.params match {
        case NormalParamSignature(params) =>
          function.params.types.zip(actualParams).zip(params).foreach { case ((required, (actual, expr)), m) =>
--- a/src/main/scala/millfork/env/Thing.scala
+++ b/src/main/scala/millfork/env/Thing.scala
@ -82,6 +82,14 @@ case class PointerType(name: String, targetName: String, var target: Option[Type
  override def pointerTargetName: String = targetName
 }

+case class FunctionPointerType(name: String, paramTypeName:String, returnTypeName: String, var paramType: Option[Type], var returnType: Option[Type]) extends VariableType {
+  def size = 2
+
+  override def isSigned: Boolean = false
+
+  override def isPointy: Boolean = false
+}
+
 case object NullType extends VariableType {
  override def size: Int = 2

@ -91,9 +99,9 @@ case object NullType extends VariableType {

  override def isPointy: Boolean = true

-  override def isSubtypeOf(other: Type): Boolean = this == other || other.isPointy && other.size == 2
+  override def isSubtypeOf(other: Type): Boolean = this == other || (other.isPointy || other.isInstanceOf[FunctionPointerType]) && other.size == 2

-  override def isAssignableTo(targetType: Type): Boolean = this == targetType || targetType.isPointy && targetType.size == 2
+  override def isAssignableTo(targetType: Type): Boolean = this == targetType || (targetType.isPointy || targetType.isInstanceOf[FunctionPointerType]) && targetType.size == 2
 }

 case class EnumType(name: String, count: Option[Int]) extends VariableType {
@ -340,6 +348,8 @@ sealed trait MangledFunction extends CallableThing {
  def params: ParamSignature

  def interrupt: Boolean
+
+  def canBePointedTo: Boolean
 }

 case class EmptyFunction(name: String,
@ -348,6 +358,8 @@ case class EmptyFunction(name: String,
  override def params = EmptyFunctionParamSignature(paramType)

  override def interrupt = false
+
+  override def canBePointedTo: Boolean = false
 }

 case class MacroFunction(name: String,
@ -356,6 +368,8 @@ case class MacroFunction(name: String,
                         environment: Environment,
                         code: List[ExecutableStatement]) extends MangledFunction {
  override def interrupt = false
+
+  override def canBePointedTo: Boolean = false
 }

 sealed trait FunctionInMemory extends MangledFunction with ThingInMemory {
@ -381,6 +395,8 @@ case class ExternFunction(name: String,
  override def zeropage: Boolean = false

  override def isVolatile: Boolean = false
+
+  override def canBePointedTo: Boolean = !interrupt && returnType.size <= 2 && params.canBePointedTo && name !="call"
 }

 case class NormalFunction(name: String,
@ -402,6 +418,8 @@ case class NormalFunction(name: String,
  override def zeropage: Boolean = false

  override def isVolatile: Boolean = false
+
+  override def canBePointedTo: Boolean = !interrupt && returnType.size <= 2 && params.canBePointedTo && name !="call"
 }

 case class ConstantThing(name: String, value: Constant, typ: Type) extends TypedThing with VariableLikeThing with IndexableThing {
@ -416,12 +434,16 @@ trait ParamSignature {
  def types: List[Type]

  def length: Int
+
+  def canBePointedTo: Boolean
 }

 case class NormalParamSignature(params: List[VariableInMemory]) extends ParamSignature {
  override def length: Int = params.length

  override def types: List[Type] = params.map(_.typ)
+
+  def canBePointedTo: Boolean = params.size <= 1 && params.forall(_.typ.size.<=(1))
 }

 sealed trait ParamPassingConvention {
@ -464,17 +486,27 @@ object AssemblyParameterPassingBehaviour extends Enumeration {
  val Copy, ByReference, ByConstant = Value
 }

-case class AssemblyParam(typ: Type, variable: TypedThing, behaviour: AssemblyParameterPassingBehaviour.Value)
+case class AssemblyParam(typ: Type, variable: TypedThing, behaviour: AssemblyParameterPassingBehaviour.Value) {
+  def canBePointedTo: Boolean = behaviour == AssemblyParameterPassingBehaviour.Copy && (variable match {
+    case RegisterVariable(MosRegister.A | MosRegister.AX, _) => true
+    case ZRegisterVariable(ZRegister.A | ZRegister.HL, _) => true
+    case _ => false
+  })
+}


 case class AssemblyParamSignature(params: List[AssemblyParam]) extends ParamSignature {
  override def length: Int = params.length

  override def types: List[Type] = params.map(_.typ)
+
+  def canBePointedTo: Boolean = params.size <= 1 && params.forall(_.canBePointedTo)
 }

 case class EmptyFunctionParamSignature(paramType: Type) extends ParamSignature {
  override def length: Int = 1

  override def types: List[Type] = List(paramType)
+
+  def canBePointedTo: Boolean = false
 }
--- a/src/main/scala/millfork/node/CallGraph.scala
+++ b/src/main/scala/millfork/node/CallGraph.scala
@ -59,12 +59,16 @@ abstract class CallGraph(program: Program, log: Logger) {
      case s: SumExpression =>
        s.expressions.foreach(expr => add(currentFunction, callingFunctions, expr._2))
      case x: VariableExpression =>
-        val varName = x.name.stripSuffix(".hi").stripSuffix(".lo").stripSuffix(".addr")
+        val varName = x.name.stripSuffix(".hi").stripSuffix(".lo").stripSuffix(".addr").stripSuffix(".pointer")
        everCalledFunctions += varName
+        entryPoints += varName // TODO: figure out how to interpret pointed-to functions
      case i: IndexedExpression =>
-        val varName = i.name.stripSuffix(".hi").stripSuffix(".lo").stripSuffix(".addr")
+        val varName = i.name.stripSuffix(".hi").stripSuffix(".lo").stripSuffix(".addr").stripSuffix(".pointer")
        everCalledFunctions += varName
+        entryPoints += varName
        add(currentFunction, callingFunctions, i.index)
+      case i: DerefExpression =>
+        add(currentFunction, callingFunctions, i.inner)
      case i: DerefDebuggingExpression =>
        add(currentFunction, callingFunctions, i.inner)
      case IndirectFieldExpression(root, firstIndices, fields) =>
--- a/src/main/scala/millfork/output/AbstractInliningCalculator.scala
+++ b/src/main/scala/millfork/output/AbstractInliningCalculator.scala
@ -77,6 +77,9 @@ abstract class AbstractInliningCalculator[T <: AbstractCode] {
    case s: Statement => getAllCalledFunctions(s.getAllExpressions)
    case s: VariableExpression => Set(
          s.name,
+          s.name.stripSuffix(".pointer"),
+          s.name.stripSuffix(".pointer.lo"),
+          s.name.stripSuffix(".pointer.hi"),
          s.name.stripSuffix(".addr"),
          s.name.stripSuffix(".hi"),
          s.name.stripSuffix(".lo"),
--- a/src/test/scala/millfork/test/FunctionPointerSuite.scala
+++ b/src/test/scala/millfork/test/FunctionPointerSuite.scala
@ -0,0 +1,102 @@
+package millfork.test
+
+import millfork.Cpu
+import millfork.test.emu.{EmuCrossPlatformBenchmarkRun, EmuUnoptimizedCrossPlatformRun, ShouldNotCompile}
+import org.scalatest.{AppendedClues, FunSuite, Matchers}
+
+/**
+  * @author Karol Stasiak
+  */
+class FunctionPointerSuite extends FunSuite with Matchers with AppendedClues{
+
+  test("Function pointers 1") {
+    EmuCrossPlatformBenchmarkRun(Cpu.Mos, Cpu.Cmos, Cpu.Z80, Cpu.Intel8080, Cpu.Sharp)(
+      """
+        |
+        | byte output @$c000
+        | void f1() {
+        |   output = 100
+        | }
+        |
+        | void main() {
+        |   function.void.to.void p1
+        |   p1 = f1.pointer
+        |   call(p1)
+        | }
+        |
+      """.stripMargin) { m =>
+      m.readByte(0xc000) should equal(100)
+    }
+  }
+
+  test("Function pointers 2") {
+    EmuUnoptimizedCrossPlatformRun (Cpu.Mos, Cpu.Cmos, Cpu.Z80, Cpu.Intel8080, Cpu.Sharp)(
+      """
+        | const byte COUNT = 128
+        | array output0[COUNT] @$c000
+        | array output1[COUNT] @$c100
+        | array output2[COUNT] @$c200
+        | array output3[COUNT] @$c300
+        |
+        | void tabulate(pointer target, function.byte.to.byte f) {
+        |   byte i
+        |   for i,0,until,COUNT {
+        |     target[i] = call(f, i)
+        |   }
+        | }
+        |
+        | byte double(byte x) = x*2
+        | byte negate(byte x) = 0-x
+        | byte zero(byte x)   = 0
+        | byte id(byte x)     = x
+        |
+        | void main() {
+        |   tabulate(output0, zero.pointer)
+        |   tabulate(output1, id.pointer)
+        |   tabulate(output2, double.pointer)
+        |   tabulate(output3, negate.pointer)
+        | }
+        |
+      """.stripMargin) { m =>
+      for (i <- 0 until 0x80) {
+        m.readByte(0xc000 + i) should equal(0) withClue ("zero " + i)
+        m.readByte(0xc100 + i) should equal(i) withClue ("id " + i)
+        m.readByte(0xc200 + i) should equal(i * 2) withClue ("double " + i)
+        m.readByte(0xc300 + i) should equal((256 - i) & 0xff) withClue ("negate " + i)
+      }
+    }
+  }
+
+  test("Function pointers: invalid types") {
+    ShouldNotCompile(
+      """
+        |void main() {
+        | call(main.pointer, 1)
+        |}
+        |""".stripMargin)
+    ShouldNotCompile(
+      """
+        |void f(byte a) = 0
+        |void main() {
+        | call(f.pointer)
+        |}
+        |""".stripMargin)
+    ShouldNotCompile(
+      """
+        |enum e {}
+        |void f(e a) = 0
+        |void main() {
+        | call(f.pointer, 0)
+        |}
+        |""".stripMargin)
+    ShouldNotCompile(
+      """
+        |enum e {}
+        |void f(byte a) = 0
+        |void main() {
+        | call(f.pointer, e(7))
+        |}
+        |""".stripMargin)
+  }
+
+}
--- a/src/test/scala/millfork/test/emu/EmuRun.scala
+++ b/src/test/scala/millfork/test/emu/EmuRun.scala
@ -156,6 +156,7 @@ class EmuRun(cpu: millfork.Cpu.Value, nodeOptimizations: List[NodeOptimization],
    if (native16 && platform.cpu != millfork.Cpu.Sixteen) throw new IllegalStateException
    var effectiveSource = source
    if (!source.contains("_panic")) effectiveSource += "\n void _panic(){while(true){}}"
+    if (source.contains("call(")) effectiveSource += "\nnoinline asm word call(word ax) {\nJMP ((__reg.b2b3))\n}\n"
    if (native16) effectiveSource +=
      """
        |
--- a/src/test/scala/millfork/test/emu/EmuZ80Run.scala
+++ b/src/test/scala/millfork/test/emu/EmuZ80Run.scala
@ -92,6 +92,11 @@ class EmuZ80Run(cpu: millfork.Cpu.Value, nodeOptimizations: List[NodeOptimizatio
    log.verbosity = 999
    var effectiveSource = source
    if (!source.contains("_panic")) effectiveSource += "\n void _panic(){while(true){}}"
+    if (source.contains("call(")) {
+      if (options.flag(CompilationFlag.UseIntelSyntaxForInput))
+        effectiveSource += "\nnoinline asm word call(word de) {\npush d\nret\n}\n"
+      else effectiveSource += "\nnoinline asm word call(word de) {\npush de\nret\n}\n"
+    }
    log.setSource(Some(effectiveSource.linesIterator.toIndexedSeq))
    val PreprocessingResult(preprocessedSource, features, pragmas) = Preprocessor.preprocessForTest(options, effectiveSource)
    // tests use Intel syntax only when forced to:
--- a/src/test/scala/millfork/test/emu/ShouldNotCompile.scala
+++ b/src/test/scala/millfork/test/emu/ShouldNotCompile.scala
@ -8,7 +8,7 @@ import millfork.compiler.{CompilationContext, LabelGenerator}
 import millfork.compiler.mos.MosCompiler
 import millfork.env.{Environment, InitializedArray, InitializedMemoryVariable, NormalFunction}
 import millfork.node.StandardCallGraph
-import millfork.parser.{MosParser, PreprocessingResult, Preprocessor}
+import millfork.parser.{MosParser, PreprocessingResult, Preprocessor, Z80Parser}
 import millfork._
 import millfork.compiler.m6809.M6809Compiler
 import millfork.compiler.z80.Z80Compiler
@ -36,11 +36,27 @@ object ShouldNotCompile extends Matchers {
    log.verbosity = 999
    var effectiveSource = source
    if (!source.contains("_panic")) effectiveSource += "\n void _panic(){while(true){}}"
+    if (source.contains("call(")) {
+      platform.cpuFamily match {
+        case CpuFamily.M6502 =>
+          effectiveSource += "\nnoinline asm word call(word ax) {\nJMP ((__reg.b2b3))\n}\n"
+        case CpuFamily.I80 =>
+          if (options.flag(CompilationFlag.UseIntelSyntaxForInput))
+            effectiveSource += "\nnoinline asm word call(word de) {\npush d\nret\n}\n"
+          else effectiveSource += "\nnoinline asm word call(word de) {\npush de\nret\n}\n"
+      }
+    }
    if (source.contains("import zp_reg"))
      effectiveSource += Files.readAllLines(Paths.get("include/zp_reg.mfk"), StandardCharsets.US_ASCII).asScala.mkString("\n", "\n", "")
    log.setSource(Some(effectiveSource.linesIterator.toIndexedSeq))
    val PreprocessingResult(preprocessedSource, features, _) = Preprocessor.preprocessForTest(options, effectiveSource)
-    val parserF = MosParser("", preprocessedSource, "", options, features)
+    val parserF =
+      platform.cpuFamily match {
+        case CpuFamily.M6502 =>
+          MosParser("", preprocessedSource, "", options, features)
+        case CpuFamily.I80 =>
+          Z80Parser("", preprocessedSource, "", options, features, options.flag(CompilationFlag.UseIntelSyntaxForInput))
+      }
    parserF.toAst match {
      case Success(program, _) =>
        log.assertNoErrors("Parse failed")