Sharing backend between scalac and dotty.

Due to a lot of error and workarounds required for backend not regress in terms of speed, I guess the original idea was to high to be reached..
Nevertheless it was good to try.

Author: DarkDimius

src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -0,0 +1,381 @@
+package dotty.tools.backend.jvm
+
+import dotty.tools.dotc.CompilationUnit
+import dotty.tools.dotc.ast.Trees.PackageDef
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Phases.Phase
+
+import scala.tools.nsc.Settings
+import scala.tools.nsc.backend.jvm.{FileConflictException, BCodeSyncAndTry, BackendInterface, AsmUtils}
+import dotty.tools.dotc
+import dotty.tools.dotc.backend.jvm.DottyPrimitives
+import dotty.tools.dotc.transform.Erasure
+
+import scala.reflect.ClassTag
+import dotty.tools.dotc.core._
+import Periods._
+import SymDenotations._
+import Contexts._
+import Types._
+import Symbols._
+import Denotations._
+import Phases._
+import java.lang.AssertionError
+import scala.tools.asm
+import scala.tools.asm.tree._
+import dotty.tools.dotc.util.{Positions, DotClass}
+import tpd._
+
+import scala.tools.nsc.backend.jvm.opt.LocalOpt
+
+/**
+ * Created by dark on 24/11/14.
+ */
+abstract class GenBCode extends Phase with BCodeSyncAndTry{
+
+  val int: DottyBackendInterface
+  implicit val ctx: Context
+
+  def entryPoints: List[Symbol] = ???
+  def tree: Tree = ???
+  def toTypeKind(t: Type)(implicit ctx: Context): bTypes.BType = ???
+  val phaseName = "jvm"
+
+  final class PlainClassBuilder(cunit: CompilationUnit) extends SyncAndTryBuilder(cunit)
+
+  class BCodePhase() {
+
+    private var bytecodeWriter  : BytecodeWriter   = null
+    private var mirrorCodeGen   : JMirrorBuilder   = null
+    private var beanInfoCodeGen : JBeanInfoBuilder = null
+
+    /* ---------------- q1 ---------------- */
+
+    case class Item1(arrivalPos: Int, cd: TypeDef, cunit: CompilationUnit) {
+      def isPoison = { arrivalPos == Int.MaxValue }
+    }
+    private val poison1 = Item1(Int.MaxValue, null, ???)
+    private val q1 = new java.util.LinkedList[Item1]
+
+    /* ---------------- q2 ---------------- */
+
+    case class Item2(arrivalPos:   Int,
+                     mirror:       asm.tree.ClassNode,
+                     plain:        asm.tree.ClassNode,
+                     bean:         asm.tree.ClassNode,
+                     outFolder:    scala.tools.nsc.io.AbstractFile) {
+      def isPoison = { arrivalPos == Int.MaxValue }
+    }
+
+    private val poison2 = Item2(Int.MaxValue, null, null, null, null)
+    private val q2 = new _root_.java.util.LinkedList[Item2]
+
+    /* ---------------- q3 ---------------- */
+
+    /*
+     *  An item of queue-3 (the last queue before serializing to disk) contains three of these
+     *  (one for each of mirror, plain, and bean classes).
+     *
+     *  @param jclassName  internal name of the class
+     *  @param jclassBytes bytecode emitted for the class SubItem3 represents
+     */
+    case class SubItem3(
+                         jclassName:  String,
+                         jclassBytes: Array[Byte]
+                         )
+
+    case class Item3(arrivalPos: Int,
+                     mirror:     SubItem3,
+                     plain:      SubItem3,
+                     bean:       SubItem3,
+                     outFolder:  scala.tools.nsc.io.AbstractFile) {
+
+      def isPoison  = { arrivalPos == Int.MaxValue }
+    }
+    private val i3comparator = new java.util.Comparator[Item3] {
+      override def compare(a: Item3, b: Item3) = {
+        if (a.arrivalPos < b.arrivalPos) -1
+        else if (a.arrivalPos == b.arrivalPos) 0
+        else 1
+      }
+    }
+    private val poison3 = Item3(Int.MaxValue, null, null, null, null)
+    private val q3 = new java.util.PriorityQueue[Item3](1000, i3comparator)
+
+    /*
+     *  Pipeline that takes ClassDefs from queue-1, lowers them into an intermediate form, placing them on queue-2
+     */
+    class Worker1(needsOutFolder: Boolean) {
+
+      val caseInsensitively = scala.collection.mutable.Map.empty[String, Symbol]
+
+      def run() {
+        while (true) {
+          val item = q1.poll
+          if (item.isPoison) {
+            q2 add poison2
+            return
+          }
+          else {
+            try   { /*withCurrentUnit(item.cunit)*/(visit(item)) }
+            catch {
+              case ex: Throwable =>
+                ex.printStackTrace()
+                error(s"Error while emitting ${int.sourceFileFor(item.cunit)}\n${ex.getMessage}")
+            }
+          }
+        }
+      }
+
+      /*
+       *  Checks for duplicate internal names case-insensitively,
+       *  builds ASM ClassNodes for mirror, plain, and bean classes;
+       *  enqueues them in queue-2.
+       *
+       */
+      def visit(item: Item1) {
+        val Item1(arrivalPos, cd, cunit) = item
+        val claszSymbol = cd.symbol
+
+        // GenASM checks this before classfiles are emitted, https://github.com/scala/scala/commit/e4d1d930693ac75d8eb64c2c3c69f2fc22bec739
+        // todo: add back those checks
+        /*val lowercaseJavaClassName = claszSymbol.javaClassName.toLowerCase
+        caseInsensitively.get(lowercaseJavaClassName) match {
+          case None =>
+            caseInsensitively.put(lowercaseJavaClassName, claszSymbol)
+          case Some(dupClassSym) =>
+            reporter.warning(
+              claszSymbol.pos,
+              s"Class ${claszSymbol.javaClassName} differs only in case from ${dupClassSym.javaClassName}. " +
+                "Such classes will overwrite one another on case-insensitive filesystems."
+            )
+        }*/
+
+        // -------------- mirror class, if needed --------------
+        val mirrorC =
+          if (int.symHelper(claszSymbol).isTopLevelModuleClass) {
+            if (claszSymbol.companionClass == NoSymbol) {
+              mirrorCodeGen.genMirrorClass(claszSymbol, cunit)
+            } else {
+              ctx.log(s"No mirror class for module with linked class: ${claszSymbol.fullName}")
+              null
+            }
+          } else null
+
+        // -------------- "plain" class --------------
+        val pcb = new PlainClassBuilder(cunit)
+        pcb.genPlainClass(cd)
+        val outF = if (needsOutFolder) getOutFolder(claszSymbol, pcb.thisName) else null;
+        val plainC = pcb.cnode
+
+        // -------------- bean info class, if needed --------------
+        val beanC =
+          if (claszSymbol hasAnnotation int.BeanInfoAttr) {
+            beanInfoCodeGen.genBeanInfoClass(
+              claszSymbol, cunit,
+              int.symHelper(claszSymbol).fieldSymbols,
+              int.symHelper(claszSymbol).methodSymbols
+            )
+          } else null
+
+        // ----------- hand over to pipeline-2
+
+        val item2 =
+          Item2(arrivalPos,
+            mirrorC, plainC, beanC,
+            outF)
+
+        q2 add item2 // at the very end of this method so that no Worker2 thread starts mutating before we're done.
+
+      } // end of method visit(Item1)
+
+    } // end of class BCodePhase.Worker1
+
+    /*
+     *  Pipeline that takes ClassNodes from queue-2. The unit of work depends on the optimization level:
+     *
+     *    (a) no optimization involves:
+     *          - converting the plain ClassNode to byte array and placing it on queue-3
+     */
+    class Worker2 {
+      lazy val localOpt = new LocalOpt(new Settings())
+
+      def localOptimizations(classNode: ClassNode): Unit = {
+        /*BackendStats.timed(BackendStats.methodOptTimer)*/(localOpt.methodOptimizations(classNode))
+      }
+
+      def run() {
+        while (true) {
+          val item = q2.poll
+          if (item.isPoison) {
+            q3 add poison3
+            return
+          }
+          else {
+            try {
+              localOptimizations(item.plain)
+              addToQ3(item)
+            } catch {
+              case ex: Throwable =>
+                ex.printStackTrace()
+                error(s"Error while emitting ${item.plain.name}\n${ex.getMessage}")
+            }
+          }
+        }
+      }
+
+      private def addToQ3(item: Item2) {
+
+        def getByteArray(cn: asm.tree.ClassNode): Array[Byte] = {
+          val cw = new CClassWriter(extraProc)
+          cn.accept(cw)
+          cw.toByteArray
+        }
+
+        val Item2(arrivalPos, mirror, plain, bean, outFolder) = item
+
+        val mirrorC = if (mirror == null) null else SubItem3(mirror.name, getByteArray(mirror))
+        val plainC  = SubItem3(plain.name, getByteArray(plain))
+        val beanC   = if (bean == null)   null else SubItem3(bean.name, getByteArray(bean))
+
+        if (AsmUtils.traceSerializedClassEnabled && plain.name.contains(AsmUtils.traceSerializedClassPattern)) {
+          if (mirrorC != null) AsmUtils.traceClass(mirrorC.jclassBytes)
+          AsmUtils.traceClass(plainC.jclassBytes)
+          if (beanC != null) AsmUtils.traceClass(beanC.jclassBytes)
+        }
+
+        q3 add Item3(arrivalPos, mirrorC, plainC, beanC, outFolder)
+
+      }
+
+    } // end of class BCodePhase.Worker2
+
+    var arrivalPos = 0
+
+    /*
+     *  A run of the BCodePhase phase comprises:
+     *
+     *    (a) set-up steps (most notably supporting maps in `BCodeTypes`,
+     *        but also "the" writer where class files in byte-array form go)
+     *
+     *    (b) building of ASM ClassNodes, their optimization and serialization.
+     *
+     *    (c) tear down (closing the classfile-writer and clearing maps)
+     *
+     */
+    def run() {
+      // val bcodeStart = Statistics.startTimer(BackendStats.bcodeTimer)
+
+      // val initStart = Statistics.startTimer(BackendStats.bcodeInitTimer)
+      arrivalPos = 0 // just in case
+      // scalaPrimitives.init()
+      bTypes.intializeCoreBTypes()
+      // Statistics.stopTimer(BackendStats.bcodeInitTimer, initStart)
+
+      // initBytecodeWriter invokes fullName, thus we have to run it before the typer-dependent thread is activated.
+      bytecodeWriter  = initBytecodeWriter(entryPoints)
+      mirrorCodeGen   = new JMirrorBuilder
+      beanInfoCodeGen = new JBeanInfoBuilder
+
+      val needsOutfileForSymbol = bytecodeWriter.isInstanceOf[ClassBytecodeWriter]
+      buildAndSendToDisk(needsOutfileForSymbol)
+
+      // closing output files.
+      bytecodeWriter.close()
+      // Statistics.stopTimer(BackendStats.bcodeTimer, bcodeStart)
+
+      /* TODO Bytecode can be verified (now that all classfiles have been written to disk)
+       *
+       * (1) asm.util.CheckAdapter.verify()
+       *       public static void verify(ClassReader cr, ClassLoader loader, boolean dump, PrintWriter pw)
+       *     passing a custom ClassLoader to verify inter-dependent classes.
+       *     Alternatively,
+       *       - an offline-bytecode verifier could be used (e.g. Maxine brings one as separate tool).
+       *       - -Xverify:all
+       *
+       * (2) if requested, check-java-signatures, over and beyond the syntactic checks in `getGenericSignature()`
+       *
+       */
+    }
+
+    /*
+     *  Sequentially:
+     *    (a) place all ClassDefs in queue-1
+     *    (b) dequeue one at a time from queue-1, convert it to ASM ClassNode, place in queue-2
+     *    (c) dequeue one at a time from queue-2, convert it to byte-array,    place in queue-3
+     *    (d) serialize to disk by draining queue-3.
+     */
+    private def buildAndSendToDisk(needsOutFolder: Boolean) {
+
+      feedPipeline1()
+      // val genStart = Statistics.startTimer(BackendStats.bcodeGenStat)
+      (new Worker1(needsOutFolder)).run()
+      // Statistics.stopTimer(BackendStats.bcodeGenStat, genStart)
+
+      (new Worker2).run()
+
+      // val writeStart = Statistics.startTimer(BackendStats.bcodeWriteTimer)
+      drainQ3()
+      // Statistics.stopTimer(BackendStats.bcodeWriteTimer, writeStart)
+
+    }
+
+    /* Feed pipeline-1: place all ClassDefs on q1, recording their arrival position. */
+    private def feedPipeline1() {
+      def gen(tree: Tree) {
+        tree match {
+          case EmptyTree            => ()
+          case PackageDef(_, stats) => stats foreach gen
+          case cd: TypeDef         =>
+            q1 add Item1(arrivalPos, cd, int.currentUnit)
+            arrivalPos += 1
+        }
+      }
+      gen(tree)
+      q1 add poison1
+    }
+
+    /* Pipeline that writes classfile representations to disk. */
+    private def drainQ3() {
+
+      def sendToDisk(cfr: SubItem3, outFolder: scala.tools.nsc.io.AbstractFile) {
+        if (cfr != null){
+          val SubItem3(jclassName, jclassBytes) = cfr
+          try {
+            val outFile =
+              if (outFolder == null) null
+              else getFileForClassfile(outFolder, jclassName, ".class")
+            bytecodeWriter.writeClass(jclassName, jclassName, jclassBytes, outFile)
+          }
+          catch {
+            case e: FileConflictException =>
+              error(s"error writing $jclassName: ${e.getMessage}")
+          }
+        }
+      }
+
+      var moreComing = true
+      // `expected` denotes the arrivalPos whose Item3 should be serialized next
+      var expected = 0
+
+      while (moreComing) {
+        val incoming = q3.poll
+        moreComing   = !incoming.isPoison
+        if (moreComing) {
+          val item = incoming
+          val outFolder = item.outFolder
+          sendToDisk(item.mirror, outFolder)
+          sendToDisk(item.plain,  outFolder)
+          sendToDisk(item.bean,   outFolder)
+          expected += 1
+        }
+      }
+
+      // we're done
+      assert(q1.isEmpty, s"Some ClassDefs remained in the first queue: $q1")
+      assert(q2.isEmpty, s"Some classfiles remained in the second queue: $q2")
+      assert(q3.isEmpty, s"Some classfiles weren't written to disk: $q3")
+
+    }
+  } // end of class BCodePhase
+}