Constant pointer optimization

src/main/scala/millfork/OptimizationPresets.scala

@@ -133,6 +133,7 @@ object OptimizationPresets {
     AlwaysGoodOptimizations.CommonBranchBodyOptimization,
     AlwaysGoodOptimizations.CommonExpressionInConditional,
     AlwaysGoodOptimizations.CommonIndexSubexpressionElimination,
+    AlwaysGoodOptimizations.ConstantPointer,
     AlwaysGoodOptimizations.ConstantFlowAnalysis,
     AlwaysGoodOptimizations.ConstantIndexPropagation,
     AlwaysGoodOptimizations.DoubleJumpSimplification,

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

@@ -1395,4 +1395,53 @@ object AlwaysGoodOptimizations {
     )
   }
 
+  // this grows the code by one byte, but shaves 1 cycle and allows for optimizing some stores away
+  val ConstantPointer = new RuleBasedAssemblyOptimization("Constant pointer optimization",
+    needsFlowInfo = FlowInfoRequirement.ForwardFlow,
+
+    (HasOpcode(STA) & MatchA(0) & HasAddrModeIn(Set(Absolute, ZeroPage)) & MatchParameter(4)) ~
+      Where(ctx => {
+        val lo = ctx.get[Constant](4)
+        ctx.addObject(5, lo + 1)
+        ctx.addObject(3, ZeroPage)
+        true
+      }) ~
+      (Linear & DoesNotConcernMemoryAt(3,4) & DoesNotConcernMemoryAt(3,5)).* ~
+      (HasOpcode(STA) & MatchA(1) & HasAddrModeIn(Set(Absolute, ZeroPage)) & MatchParameter(5)) ~
+      Where(ctx => {
+        val lo = ctx.get[Int](0) & 0xff
+        val hi = ctx.get[Int](1) & 0xff
+        ctx.addObject(2, hi * 256 + lo)
+        true
+      }) ~
+      (Linear & DoesNotConcernMemoryAt(3,4) & DoesNotConcernMemoryAt(3,5)).* ~
+      (Elidable & MatchParameter(6) & HasAddrModeIn(Set(ZeroPageIndirect, IndexedY))) ~~> { (code, ctx) =>
+      val addr = ctx.get[Int](2)
+      val last = code.last
+      code.init :+ last.copy(parameter = NumericConstant(addr, 2), addrMode = if (last.addrMode == ZeroPageIndirect) Absolute else AbsoluteY)
+    },
+
+    (HasOpcode(STA) & MatchA(0) & HasAddrModeIn(Set(Absolute, ZeroPage)) & MatchParameter(4)) ~
+      Where(ctx => {
+        val lo = ctx.get[Constant](4)
+        ctx.addObject(5, lo + 1)
+        ctx.addObject(3, ZeroPage)
+        true
+      }) ~
+      (Linear & DoesNotConcernMemoryAt(3,4) & DoesNotConcernMemoryAt(3,5)).* ~
+      (HasOpcode(STX) & MatchX(1) & HasAddrModeIn(Set(Absolute, ZeroPage)) & MatchParameter(5)) ~
+      Where(ctx => {
+        val lo = ctx.get[Int](0) & 0xff
+        val hi = ctx.get[Int](1) & 0xff
+        ctx.addObject(2, hi * 256 + lo)
+        true
+      }) ~
+      (Linear & DoesNotConcernMemoryAt(3,4) & DoesNotConcernMemoryAt(3,5)).* ~
+      (Elidable & MatchParameter(6) & HasAddrModeIn(Set(ZeroPageIndirect, IndexedY))) ~~> { (code, ctx) =>
+      val addr = ctx.get[Int](2)
+      val last = code.last
+      code.init :+ last.copy(parameter = NumericConstant(addr, 2), addrMode = if (last.addrMode == ZeroPageIndirect) Absolute else AbsoluteY)
+    },
+  )
+
 }

src/main/scala/millfork/env/Constant.scala

@@ -158,6 +158,7 @@ case class CompoundConstant(operator: MathOperator.Value, lhs: Constant, rhs: Co
     val l = lhs.quickSimplify
     val r = rhs.quickSimplify
     (l, r) match {
+      case (CompoundConstant(MathOperator.Shl, HalfWordConstant(c1, true), NumericConstant(8, _)), HalfWordConstant(c2, false)) if operator == MathOperator.Or && c1 == c2 => c1
       case (NumericConstant(lv, ls), NumericConstant(rv, rs)) =>
         var size = ls max rs
         val value = operator match {
@@ -233,6 +234,7 @@ case class CompoundConstant(operator: MathOperator.Value, lhs: Constant, rhs: Co
     val That = that
     val MinusThat = -that
     this match {
+      case CompoundConstant(Plus, CompoundConstant(Shl, HalfWordConstant(c1, true), NumericConstant(8, _)), HalfWordConstant(c2, false)) if c1 == c2 => c1
       case CompoundConstant(Plus, NumericConstant(MinusThat, _), r) => r
       case CompoundConstant(Plus, l, NumericConstant(MinusThat, _)) => l
       case CompoundConstant(Plus, NumericConstant(x, _), r) => CompoundConstant(Plus, r, NumericConstant(x + that, minimumSize(x + that)))

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

@@ -408,4 +408,24 @@ class AssemblyOptimizationSuite extends FunSuite with Matchers {
         | }
       """.stripMargin).readByte(0xc000) should equal(1)
   }
+
+  test("Constant pointers") {
+    EmuBenchmarkRun(
+      """
+        |byte output0 @$c000
+        |byte output1 @$c001
+        |void main() {
+        |   pointer p
+        |   p = output0.addr
+        |   p[0] = 33
+        |   p = op()
+        |   p[0] = 34
+        |}
+        |word op () { return output1.addr }
+      """.stripMargin
+    ){m =>
+      m.readByte(0xc000) should equal(33)
+      m.readByte(0xc001) should equal(34)
+    }
+  }
 }

src/test/scala/millfork/test/emu/EmuOptimizedInlinedRun.scala

@@ -15,7 +15,7 @@ object EmuOptimizedInlinedRun extends EmuRun(
     OptimizationPresets.Good,
   false) {
   override def inline: Boolean = true
-  override def blastProcessing: Boolean = true
+  override def blastProcessing: Boolean = false
 }