Dijkstra wept

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Current version
 
+* Added goto.
+
 * Added arrays of elements of size greater than byte.
 
 * Improved passing of register parameters to assembly functions.

docs/abi/undefined-behaviour.md

@@ -39,4 +39,6 @@ Currently, such functions may be evaluated either once or twice. This might be f
 
 * when using modifying operators: calling functions on the right-hand-side index expression than modify any of the variables used on the left hand side
 
+* jumping across the scope of for loop that uses a fixed list or across functions
+
 The above list is not exhaustive.

docs/lang/syntax.md

@@ -328,6 +328,7 @@ for <variable> : [ <comma separated expressions> ]  {
 * `<comma separated expressions>` – traverse every value in the list, in the given order.
 Values do not have to be constant.
 If a value is not a constant and its value changes while executing the loop, the behaviour is undefined.
+Jumps using `goto` across the scope of this kind of loop are disallowed.
 
 ### `break` and `continue` statements
 
@@ -345,6 +346,31 @@ continue while
 continue do
 continue <variable>
 ```
+
+### `goto` and `label`
+
+Syntax:
+
+```
+goto <expression>
+label <name>
+```
+
+The `label` statement defines a constant pointer that refers to the current position in the code.
+Such labels are only visible in the scope of the local function.
+
+The `goto` expression jumps to the pointer value of the expression.
+
+Jumping using `goto` across the scope of for loop that uses a fixed list or across functions is not allowed.
+
+Computed gotos are supported:
+
+```
+pointer p
+p = x
+goto p
+label x
+```
     
 ### `asm` statements
 

millfork-udl.xml

@@ -25,7 +25,7 @@
             <Keywords name="Folders in comment, middle"></Keywords>
             <Keywords name="Folders in comment, close"></Keywords>
             <Keywords name="Keywords1">void byte sbyte ubyte array word farword pointer farpointer long word_be word_le long_be long_le file int8 int16 int24 int32 int40 int48 int56 int64 signed8 fast</Keywords>
-            <Keywords name="Keywords2">if else for return while do asm extern import segment break continue default alias enum struct union</Keywords>
+            <Keywords name="Keywords2">if else for return while do asm extern import segment break continue default alias enum struct union goto label</Keywords>
             <Keywords name="Keywords3">defaultz petscii ascii scr petscr pet atascii atari bbc sinclair apple2 jis jisx iso_de iso_yu iso_no iso_dk iso_se iso_fi petsciiz asciiz scrz petscrz petz atasciiz atariz bbcz sinclairz apple2z jisz jisxz iso_dez iso_yuz iso_noz iso_dkz iso_sez iso_fiz until to downto parallelto static stack ref const volatile paralleluntil inline noinline macro register kernal_interrupt interrupt reentrant hi lo sin cos tan nonet align false true nullptr</Keywords>
             <Keywords name="Keywords4">&quot;sta &quot; &quot;lda &quot; &quot;jmp &quot; &quot;bit &quot; &quot;eor &quot; &quot;adc &quot; &quot;sbc &quot; &quot;ora &quot; &quot;and &quot; &quot;ldx &quot; &quot;ldy &quot; &quot;stx &quot; &quot;sty &quot; &quot;tax&quot; &quot;tay&quot; &quot;tya&quot; &quot;txa&quot; &quot;txs&quot; &quot;tsx&quot; &quot;sei&quot; &quot;cli&quot; &quot;clv&quot; &quot;clc&quot; &quot;cld&quot; &quot;sed&quot; &quot;sec&quot; &quot;bra &quot; &quot;beq &quot; &quot;bne &quot; &quot;bmi &quot; &quot;bpl &quot; &quot;bcc &quot; &quot;bcs &quot; &quot;bvs &quot; bvc &quot;  &quot;jsr &quot; rts&quot;  &quot;rti&quot; &quot;brk&quot; &quot;rol&quot; &quot;ror&quot; &quot;asl&quot; &quot;lsr&quot; &quot;inc &quot; &quot;dec &quot; &quot;cmp &quot; &quot;cpx &quot; &quot;cpy &quot; inx iny dex dey pla pha plp  hp phx plx phy ply &quot;stz &quot; &quot;ldz &quot; tza taz &quot;tsb &quot; &quot;trb &quot; ra   txy tyx pld plb phb phd phk xce&#x000D;&#x000A;&#x000D;&#x000A;&quot;STA &quot; &quot;LDA &quot; &quot;JMP &quot; &quot;BIT &quot; &quot;EOR &quot; &quot;ADC &quot; &quot;SBC &quot; &quot;ORA &quot; &quot;AND &quot; &quot;LDX &quot; &quot;LDY &quot; &quot;STX &quot; &quot;STY &quot; &quot;TAX&quot; &quot;TAY&quot; &quot;TYA&quot; &quot;TXA&quot; &quot;TXS&quot; &quot;TSX&quot; &quot;SEI&quot; &quot;CLI&quot; &quot;CLV&quot; &quot;CLC&quot; &quot;CLD&quot; &quot;SED&quot; &quot;SEC&quot;   &quot;BEQ &quot; &quot;BRA &quot; &quot;BNE &quot; &quot;BMI &quot; &quot;BPL &quot; &quot;BCC &quot; &quot;BCS &quot; &quot;BVS &quot; BVC &quot;  &quot;JSR &quot; RTS&quot;  &quot;RTI&quot; &quot;BRK&quot; &quot;ROL&quot; &quot;ROR&quot; &quot;ASL&quot; &quot;LSR&quot; &quot;INC &quot; &quot;DEC &quot; &quot;CMP &quot; &quot;CPX &quot; &quot;CPY &quot; INX INY DEX DEY PLA PHA PLP  HP PHX PLX PHY PLY &quot;STZ &quot; &quot;LDZ &quot; TZA TAZ &quot;TSB &quot; &quot;TRB &quot; RA   TXY TYX PLD PLB PHB PHD PHK XCE</Keywords>
             <Keywords name="Keywords5">&quot;sbx &quot; &quot;isc &quot; &quot;dcp &quot; &quot;lax &quot; &quot;sax &quot; &quot;anc &quot; &quot;alr &quot; &quot;arr &quot; &quot;rra &quot; &quot;rla &quot; &quot;lxa &quot; &quot;ane &quot; &quot;xaa &quot;&#x000D;&#x000A;&quot;SBX &quot; &quot;ISC &quot; &quot;DCP &quot; &quot;LAX &quot; &quot;SAX &quot; &quot;ANC &quot; &quot;ALR &quot; &quot;ARR &quot; &quot;RRA &quot; &quot;RLA &quot; &quot;LXA &quot; &quot;ANE &quot; &quot;XAA &quot;</Keywords>

src/main/scala/millfork/compiler/mos/MosStatementCompiler.scala

@@ -277,6 +277,14 @@ object MosStatementCompiler extends AbstractStatementCompiler[AssemblyLine] {
                 }
             }
         }) -> Nil
+      case s: GotoStatement =>
+        env.eval(s.target) match {
+          case Some(e) => List(AssemblyLine.absolute(JMP, e)) -> Nil
+          case None =>
+            MosExpressionCompiler.compileToZReg(ctx, s.target) ++ List(AssemblyLine(JMP, Indirect, env.get[ThingInMemory]("__reg.loword").toAddress)) -> Nil
+        }
+      case s: LabelStatement =>
+        List(AssemblyLine.label(env.prefix + s.name)) -> Nil
       case s: IfStatement =>
         compileIfStatement(ctx, s)
       case s: WhileStatement =>

src/main/scala/millfork/compiler/z80/Z80StatementCompiler.scala

@@ -83,6 +83,14 @@ object Z80StatementCompiler extends AbstractStatementCompiler[ZLine] {
 
             }
         }) -> Nil
+      case s: GotoStatement =>
+        env.eval(s.target) match {
+          case Some(e) => List(ZLine(JP, NoRegisters, e)) -> Nil
+          case None =>
+            Z80ExpressionCompiler.compileToHL(ctx, s.target) ++ List(ZLine(JP, OneRegister(ZRegister.HL), Constant.Zero)) -> Nil
+        }
+      case s: LabelStatement =>
+        List(ZLine.label(env.prefix + s.name)) -> Nil
       case Assignment(destination, source) =>
         val sourceType = AbstractExpressionCompiler.getExpressionType(ctx, source)
         val targetType = AbstractExpressionCompiler.getExpressionType(ctx, destination)

src/main/scala/millfork/env/Environment.scala

@@ -210,6 +210,7 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
   val things: mutable.Map[String, Thing] = mutable.Map()
   val pointiesUsed: mutable.Map[String, Set[String]] = mutable.Map()
   val removedThings: mutable.Set[String] = mutable.Set()
+  val knownLocalLabels: mutable.Set[(String, Option[Position])] = mutable.Set()
 
   private def addThing(t: Thing, position: Option[Position]): Unit = {
     if (assertNotDefined(t.name, position)) {
@@ -938,6 +939,7 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
     val pointies = collectPointies(stmt.statements.getOrElse(Seq.empty))
     pointiesUsed(stmt.name) = pointies
     val w = get[Type]("word")
+    val p = get[Type]("pointer")
     val name = stmt.name
     val resultType = get[Type](stmt.resultType)
     if (stmt.name == "main") {
@@ -1022,6 +1024,50 @@ class Environment(val parent: Option[Environment], val prefix: String, val cpuFa
           case a: ArrayDeclarationStatement => env.registerArray(a, options)
           case _ => ()
         }
+        def scanForLabels(statement: Statement): Unit = statement match {
+          case c: CompoundStatement => c.getChildStatements.foreach(scanForLabels)
+          case LabelStatement(labelName) => env.knownLocalLabels += (labelName -> statement.position)
+          case _ => ()
+        }
+        statements.foreach(scanForLabels)
+        for ((knownLabel, position) <- env.knownLocalLabels) {
+          env.addThing(knownLabel, ConstantThing(env.prefix + knownLabel, Label(env.prefix + knownLabel).toAddress, p), position)
+        }
+
+        // not all in-function gotos are allowed; warn about the provably wrong ones:
+        def checkLabels(statements: Seq[Statement]) = {
+          def getAllSafeLabels(statements: Seq[Statement]): Seq[String] = statements.flatMap {
+            case _: ForEachStatement => Nil
+            case c: CompoundStatement => getAllSafeLabels(c.getChildStatements)
+            case LabelStatement(labelName) => Seq(labelName)
+            case _ => Nil
+          }
+          def getAllSafeGotos(statements: Seq[Statement]):Seq[String] = statements.flatMap {
+            case _: ForEachStatement => Nil
+            case c: CompoundStatement => getAllSafeGotos(c.getChildStatements)
+            case GotoStatement(VariableExpression(labelName)) if env.knownLocalLabels.exists(_._1.==(labelName)) => Seq(labelName)
+            case _ => Nil
+          }
+          def doOnlyCheck(position: Option[Position], statements: Seq[Statement]): Unit = {
+            val l = getAllSafeLabels(statements).toSet
+            val g = getAllSafeGotos(statements).toSet
+            val bad = g.&(env.knownLocalLabels.map(_._1)).--(l)
+            if (bad.nonEmpty) {
+              log.warn("Detected cross-loop gotos to labels " + bad.mkString(", "), position)
+            }
+          }
+          def recurse(statements: Seq[Statement]):Unit = statements.foreach {
+            case c: ForEachStatement =>
+              doOnlyCheck(c.position, c.body)
+              recurse(c.body)
+            case c: CompoundStatement => recurse(c.getChildStatements)
+            case _ => Nil
+          }
+          doOnlyCheck(stmt.position, statements)
+          recurse(statements)
+        }
+        checkLabels(statements)
+
         val executableStatements = statements.flatMap {
           case e: ExecutableStatement => Some(e)
           case _ => None

src/main/scala/millfork/node/Node.scala

@@ -467,6 +467,14 @@ case class ReturnStatement(value: Option[Expression]) extends ExecutableStatemen
   override def getAllExpressions: List[Expression] = value.toList
 }
 
+case class GotoStatement(target: Expression) extends ExecutableStatement {
+  override def getAllExpressions: List[Expression] = List(target)
+}
+
+case class LabelStatement(name: String) extends ExecutableStatement {
+  override def getAllExpressions: List[Expression] = Nil
+}
+
 case class EmptyStatement(toTypecheck: List[ExecutableStatement]) extends ExecutableStatement {
   override def getAllExpressions: List[Expression] = toTypecheck.flatMap(_.getAllExpressions)
 }

src/main/scala/millfork/parser/MfParser.scala

@@ -380,6 +380,8 @@ abstract class MfParser[T](fileId: String, input: String, currentDirectory: Stri
 
   def keywordStatement: P[Seq[ExecutableStatement]] = P(
     returnOrDispatchStatement |
+      gotoStatement |
+      labelStatement |
       ifStatement |
       whileStatement |
       forStatement |
@@ -437,6 +439,10 @@ abstract class MfParser[T](fileId: String, input: String, currentDirectory: Stri
 
   val returnOrDispatchStatement: P[Seq[ExecutableStatement]] = "return" ~ !letterOrDigit ~/ HWS ~ (dispatchStatementBody | mfExpression(nonStatementLevel, false).?.map(ReturnStatement).map(Seq(_)))
 
+  val gotoStatement: P[Seq[ExecutableStatement]] = "goto" ~ !letterOrDigit ~/ HWS ~ mfExpression(nonStatementLevel, false).map(GotoStatement).map(Seq(_))
+
+  val labelStatement: P[Seq[ExecutableStatement]] = "label" ~ !letterOrDigit ~/ HWS ~ identifier.map(LabelStatement).map(Seq(_))
+
   def ifStatement: P[Seq[ExecutableStatement]] = for {
     condition <- "if" ~ !letterOrDigit ~/ HWS ~/ mfExpression(nonStatementLevel, false)
     thenBranch <- AWS ~/ executableStatements

src/test/scala/millfork/test/GotoSuite.scala

@@ -0,0 +1,57 @@
+package millfork.test
+
+import millfork.Cpu
+import millfork.test.emu.{EmuCrossPlatformBenchmarkRun, EmuUnoptimizedCrossPlatformRun}
+import org.scalatest.{FunSuite, Matchers}
+
+/**
+  * @author Karol Stasiak
+  */
+class GotoSuite extends FunSuite with Matchers {
+
+  test("Goto 1") {
+    EmuCrossPlatformBenchmarkRun(Cpu.Mos, Cpu.Cmos, Cpu.Z80, Cpu.Intel8080, Cpu.Sharp)(
+      """
+        |
+        | byte output @$c000
+        |
+        | void main() {
+        |   byte x
+        |   x = 0
+        |   if x == 0 {
+        |     label a
+        |   }
+        |   x += 1
+        |   if x < 100 {
+        |     goto a
+        |   }
+        |   output = x
+        | }
+        |
+      """.stripMargin){m =>
+      m.readByte(0xc000) should equal(100)
+    }
+  }
+
+  test("Cross-loop goto") {
+    EmuUnoptimizedCrossPlatformRun(Cpu.Mos, Cpu.Z80)(
+      """
+        |
+        | byte output @$c000
+        |
+        | void main() {
+        |   byte x
+        |   label a
+        |   for x : [1,2,3] {
+        |     if x == 0 { goto a }
+        |     goto b
+        |     label b
+        |     output = x
+        |   }
+        | }
+        |
+      """.stripMargin){m =>
+      m.readByte(0xc000) should equal(3)
+    }
+  }
+}