Interrupt handler optimization

src/main/scala/millfork/OptimizationPresets.scala

@@ -32,6 +32,7 @@ object OptimizationPresets {
     VariableToRegisterOptimization,
     AlwaysGoodOptimizations.PoinlessLoadBeforeAnotherLoad,
     AlwaysGoodOptimizations.PointlessOperationPairRemoval,
+    AlwaysGoodOptimizations.PointlessOperationPairRemoval2,
     AlwaysGoodOptimizations.PoinlessLoadBeforeAnotherLoad,
     LaterOptimizations.PointlessLoadAfterStore,
     AlwaysGoodOptimizations.PointlessOperationAfterLoad,
@@ -146,6 +147,7 @@ object OptimizationPresets {
     AlwaysGoodOptimizations.PointlessMathFromFlow,
     AlwaysGoodOptimizations.PointlessOperationAfterLoad,
     AlwaysGoodOptimizations.PointlessOperationPairRemoval,
+    AlwaysGoodOptimizations.PointlessOperationPairRemoval2,
     AlwaysGoodOptimizations.PointlessRegisterTransfers,
     AlwaysGoodOptimizations.PointlessRegisterTransfersBeforeCompare,
     AlwaysGoodOptimizations.PointlessRegisterTransfersBeforeReturn,

src/main/scala/millfork/assembly/opt/AlwaysGoodOptimizations.scala

@@ -194,6 +194,47 @@ object AlwaysGoodOptimizations {
     operationPairBuilder(DEY, INY, Not(ConcernsX) & Not(ReadsNOrZ)),
   )
 
+
+  private def operationPairBuilder2(op1: Opcode.Value, op1extra: AssemblyLinePattern, middle: AssemblyLinePattern,op2: Opcode.Value,  op2extra: AssemblyLinePattern) = {
+    (HasOpcode(op1) & Elidable & op1extra) ~
+      (Linear & middle).*.capture(1) ~
+      (HasOpcode(op2) & Elidable & op2extra) ~~> { (_, ctx) =>
+      ctx.get[List[AssemblyLine]](1)
+    }
+  }
+
+  val PointlessOperationPairRemoval2 = new RuleBasedAssemblyOptimization("Pointless operation pair 2",
+    needsFlowInfo = FlowInfoRequirement.BackwardFlow,
+    operationPairBuilder2(
+      PHA, Anything,
+      Not(ConcernsStack),
+      PLA, DoesntMatterWhatItDoesWith(State.A, State.N, State.Z)),
+    operationPairBuilder2(
+      PHX, Anything,
+      Not(ConcernsStack),
+      PLX, DoesntMatterWhatItDoesWith(State.X, State.N, State.Z)),
+    operationPairBuilder2(
+      PHY, Anything,
+      Not(ConcernsStack),
+      PLY, DoesntMatterWhatItDoesWith(State.Y, State.N, State.Z)),
+    operationPairBuilder2(
+      INX, DoesntMatterWhatItDoesWith(State.X, State.N, State.Z),
+      Anything,
+      DEX, DoesntMatterWhatItDoesWith(State.X, State.N, State.Z)),
+    operationPairBuilder2(
+      DEX, DoesntMatterWhatItDoesWith(State.X, State.N, State.Z),
+      Anything,
+      INX, DoesntMatterWhatItDoesWith(State.X, State.N, State.Z)),
+    operationPairBuilder2(
+      INY, DoesntMatterWhatItDoesWith(State.Y, State.N, State.Z),
+      Anything,
+      DEY, DoesntMatterWhatItDoesWith(State.Y, State.N, State.Z)),
+    operationPairBuilder2(
+      DEY, DoesntMatterWhatItDoesWith(State.Y, State.N, State.Z),
+      Anything,
+      INY, DoesntMatterWhatItDoesWith(State.Y, State.N, State.Z)),
+  )
+
   val PointlessStackStashing = new RuleBasedAssemblyOptimization("Pointless stack stashing",
     needsFlowInfo = FlowInfoRequirement.NoRequirement,
     (Elidable & HasOpcode(LDA) & MatchAddrMode(0) & MatchParameter(1)) ~

src/main/scala/millfork/assembly/opt/ReverseFlowAnalyzer.scala

@@ -145,8 +145,10 @@ object ReverseFlowAnalyzer {
             currentImportance = currentImportance.copy(n = Important)
           case AssemblyLine(SED | CLD, _, _, _) =>
             currentImportance = currentImportance.copy(d = Unimportant)
-          case AssemblyLine(RTS | RTI, _, _, _) =>
+          case AssemblyLine(RTS, _, _, _) =>
             currentImportance = finalImportance
+          case AssemblyLine(RTI, _, _, _) =>
+            currentImportance = new CpuImportance(a = Unimportant, x = Unimportant, y = Unimportant, z = Unimportant, n = Unimportant, c = Unimportant, v = Unimportant, d = Unimportant)
           case AssemblyLine(DISCARD_XF, _, _, _) =>
             currentImportance = currentImportance.copy(x = Unimportant, n = Unimportant, z = Unimportant, c = Unimportant, v = Unimportant)
           case AssemblyLine(DISCARD_YF, _, _, _) =>

src/test/scala/millfork/test/AssemblyOptimizationSuite.scala

@@ -2,7 +2,7 @@ package millfork.test
 
 import millfork.{Cpu, OptimizationPresets}
 import millfork.assembly.opt.{AlwaysGoodOptimizations, LaterOptimizations, VariableToRegisterOptimization}
-import millfork.test.emu.{EmuBenchmarkRun, EmuUltraBenchmarkRun, EmuRun}
+import millfork.test.emu.{EmuBenchmarkRun, EmuRun, EmuSuperOptimizedRun, EmuUltraBenchmarkRun}
 import org.scalatest.{FunSuite, Matchers}
 
 /**
@@ -292,4 +292,14 @@ class AssemblyOptimizationSuite extends FunSuite with Matchers {
       m.readWord(0xc00c) should equal(0x201)
     }
   }
+
+  test("Empty interrupt"){
+    EmuSuperOptimizedRun(
+      """
+        | void main () {
+        | }
+        | interrupt void i (){}
+        |
+      """.stripMargin)
+  }
 }