6502: optimize bitops on words

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

@@ -288,6 +288,7 @@ object PseudoregisterBuiltIns {
   private def compileFastWordBitOpsToAX(reads: List[List[AssemblyLine]], op: Opcode.Value): Option[List[AssemblyLine]] = {
     val resultLo = mutable.ListBuffer[AssemblyLine]()
     val resultHi = mutable.ListBuffer[AssemblyLine]()
+    var complex = Option.empty[List[AssemblyLine]]
     for(read <- reads) {
       read match {
         case List(l@AssemblyLine0(LDA, Immediate | Absolute | ZeroPage, _), h@AssemblyLine0(LDX, Immediate | Absolute | ZeroPage, _)) =>
@@ -298,12 +299,43 @@ object PseudoregisterBuiltIns {
             resultHi += h.copy(opcode = op)
             resultLo += l.copy(opcode = op)
           }
-        case _ => return None
+        case _ =>
+          if (complex.isDefined) return None
+          else complex = Some(read)
       }
     }
-    resultHi += AssemblyLine.implied(TAX)
-    resultHi ++= resultLo
-    Some(resultHi.toList)
+    complex match {
+      case Some(x) =>
+        if (resultHi.isEmpty) {
+          if (resultLo.isEmpty) return Some(x)
+          else return None
+        } else {
+          if (resultLo.isEmpty) return None
+          if (resultHi.exists(_.concernsX)) return None
+          if (resultLo.exists(_.concernsX)) return None
+          if (resultHi.head.opcode != LDA) return None
+          if (resultLo.head.opcode != LDA) return None
+          resultHi(0) = resultHi.head.copy(opcode = op)
+          resultLo(0) = resultLo.head.copy(opcode = op)
+        }
+        val index = x.lastIndexWhere(_.opcode.==(TAX))
+        if (index < 0) return None
+        val (handleHigh, taxAndHandleLo) = x.splitAt(index)
+        if (taxAndHandleLo.tail.exists(l => l.concernsX || (l.opcode match {
+          case TAX | CLC | SEC | CLD | SED => false
+          case LDA | ADC | SBC | AND | ORA | EOR => false
+          case ASL | LSR | ROL | ROR => false
+          case ANC | ALR | ARR => false
+          case NOP => false
+          case INC | DEC => l.addrMode != Implied
+          case _ => true
+        }))) return None
+        Some(handleHigh ++ resultHi ++ taxAndHandleLo ++ resultLo)
+      case None =>
+        resultHi += AssemblyLine.implied(TAX)
+        resultHi ++= resultLo
+        Some(resultHi.toList)
+    }
   }
 
   def compileWordBitOpsToAX(ctx: CompilationContext, params: List[Expression], op: Opcode.Value): List[AssemblyLine] = {

src/test/scala/millfork/test/BitOpSuite.scala

@@ -89,4 +89,17 @@ class BitOpSuite extends FunSuite with Matchers {
       """.stripMargin
     EmuCrossPlatformBenchmarkRun(Cpu.Mos, Cpu.Z80)(code)(_.readByte(0xc000) should equal(2))
   }
+
+  test("Multiple words") {
+    EmuCrossPlatformBenchmarkRun(Cpu.Mos, Cpu.Z80, Cpu.Intel8080, Cpu.Sharp, Cpu.Intel8086)("""
+        | word output @$c000
+        | void main () {
+        |   word v, w
+        |   v = $ee0e
+        |   barrier()
+        |   output = (v & $F0F0) | $0303
+        | }
+        | noinline void barrier(){}
+      """.stripMargin)(_.readWord(0xc000) should equal(0xE303))
+  }
 }