Local optimisations

compiler/src/dotty/tools/backend/jvm/LabelDefs.scala

@@ -75,8 +75,11 @@ import StdNames.nme
  * Unreachable jumps will be eliminated by local dead code analysis.
  * After JVM is smart enough to remove next-line jumps
  *
- * Note that Label DefDefs can be only nested in Block, otherwise no one would
- * be able to call them Other DefDefs are eliminated
+ * Note that his phase Ychecking this phase required softening scoping rules
+ * as it intentionally allowed to break scoping rules inside methods for labels.
+ * This is modified by setting `labelsReordered` flag in Phases.
+ *
+ * @author Dmitry Petrashko
  */
 class LabelDefs extends MiniPhaseTransform {
   def phaseName: String = "labelDef"
@@ -90,76 +93,24 @@ class LabelDefs extends MiniPhaseTransform {
     else {
       collectLabelDefs.clear
       val newRhs = collectLabelDefs.transform(tree.rhs)
-      val labelCalls = collectLabelDefs.labelCalls
-      var entryPoints = collectLabelDefs.parentLabelCalls
       var labelDefs = collectLabelDefs.labelDefs
-      var callCounts = collectLabelDefs.callCounts
-
-      // make sure that for every label there's a single location it should return and single entry point
-      // if theres already a location that it returns to that's a failure
-      val disallowed = new mutable.HashMap[Symbol, Tree]()
-      queue.sizeHint(labelCalls.size + entryPoints.size)
 
       def putLabelDefsNearCallees = new TreeMap() {
 
         override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = {
           tree match {
-            case t: Apply if (entryPoints.contains(t)) =>
-              entryPoints = entryPoints - t
-              labelLevel = labelLevel + 1
-              val r = Block(moveLabels(t), t)
-              labelLevel = labelLevel - 1
-              if (labelLevel == 0) beingAppended.clear()
-              r
-            case _ => if (entryPoints.nonEmpty && labelDefs.nonEmpty) super.transform(tree) else tree
-          }
+            case t: Apply if labelDefs.contains(t.symbol) =>
+              val labelDef = labelDefs(t.symbol)
+              labelDefs -= t.symbol
 
-        }
-      }
+              val labelDef2 = transform(labelDef)
+              Block(labelDef2:: Nil, t)
 
-      def moveLabels(entryPoint: Apply): List[Tree] = {
-        val entrySym = entryPoint.symbol
-        if ((entrySym is Flags.Label) && labelDefs.contains(entrySym)) {
-          val visitedNow = new mutable.HashMap[Symbol, Tree]()
-          val treesToAppend = new ArrayBuffer[Tree]() // order matters. parents should go first
-          treesToAppend += labelDefs(entrySym)
-          queue.clear()
-
-          var visited = 0
-          queue += entryPoint
-          while (visited < queue.size) {
-            val owningLabelDefSym = queue(visited).symbol
-            for (call <- labelCalls(owningLabelDefSym)) {
-              val callSym = call.symbol
-              if (!beingAppended.contains(callSym)) {
-                if (disallowed.contains(callSym)) {
-                  val oldCall = disallowed(callSym)
-                  ctx.error(s"Multiple return locations for Label $oldCall and $call", callSym.pos)
-                } else {
-                  if ((!visitedNow.contains(callSym)) && labelDefs.contains(callSym)) {
-                    val defTree = labelDefs(callSym)
-                    visitedNow.put(callSym, defTree)
-                    val callCount = callCounts(callSym)
-                    if (callCount > 1) {
-                      if (!treesToAppend.contains(defTree)) {
-                        treesToAppend += defTree
-                        queue += call
-
-                      }
-                    } else if (entryPoint.symbol ne callSym) entryPoints += call
-                  }
-                }
-              }
-            }
-
-            visited += 1
+            case _ => if (labelDefs.nonEmpty) super.transform(tree) else tree
           }
-          beingAppended ++= treesToAppend.map(_.symbol)
-          treesToAppend.toList.map(putLabelDefsNearCallees.transform)
-        } else Nil
+        }
       }
 
-
       val res = cpy.DefDef(tree)(rhs = putLabelDefsNearCallees.transform(newRhs))
 
       res
@@ -168,22 +119,11 @@ class LabelDefs extends MiniPhaseTransform {
 
   object collectLabelDefs extends TreeMap() {
 
-    // label calls from this DefDef
-    var parentLabelCalls: mutable.Set[Tree] = new mutable.HashSet[Tree]()
-    var callCounts: mutable.Map[Symbol, Int] = new mutable.HashMap[Symbol, Int]().withDefaultValue(0)
-
-    def shouldMoveLabel = true
-
     // labelSymbol -> Defining tree
     val labelDefs = new mutable.HashMap[Symbol, Tree]()
-    // owner -> all calls by this owner
-    val labelCalls = new mutable.HashMap[Symbol, mutable.Set[Tree]]()
-    var owner: Symbol = null
 
     def clear = {
-      parentLabelCalls.clear()
       labelDefs.clear()
-      labelCalls.clear()
     }
 
     override def transform(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = tree match {
@@ -196,30 +136,14 @@ class LabelDefs extends MiniPhaseTransform {
         }
       case t: DefDef =>
         assert(t.symbol is Flags.Label)
-
-        val st = parentLabelCalls
-        parentLabelCalls = new mutable.HashSet[Tree]()
-        val symt = owner
-        owner = t.symbol
-
         val r = super.transform(tree)
-
-        owner = symt
-        labelCalls(r.symbol) = parentLabelCalls
-        parentLabelCalls = st
-
-        if (shouldMoveLabel) {
-          labelDefs(r.symbol) = r
-          EmptyTree
-        } else r
+        labelDefs(r.symbol) = r
+        EmptyTree
       case t: Apply if t.symbol is Flags.Label =>
         val sym = t.symbol
-        parentLabelCalls = parentLabelCalls + t
-        if (owner != sym) callCounts(sym) = callCounts(sym) + 1
         super.transform(tree)
       case _ =>
         super.transform(tree)
-
     }
   }
 }

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -17,6 +17,7 @@ import core.DenotTransformers.DenotTransformer
 import core.Denotations.SingleDenotation
 
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode, CollectSuperCalls}
+import dotty.tools.dotc.transform.linker.Simplify
 
 /** The central class of the dotc compiler. The job of a compiler is to create
  *  runs, which process given `phases` in a given `rootContext`.
@@ -74,6 +75,7 @@ class Compiler {
            new ElimByName,          // Expand by-name parameter references
            new AugmentScala2Traits, // Expand traits defined in Scala 2.11 to simulate old-style rewritings
            new ResolveSuper,        // Implement super accessors and add forwarders to trait methods
+           new Simplify,            // Perform local optimizations, simplified versions of what linker does.
            new PrimitiveForwarders, // Add forwarders to trait methods that have a mismatch between generic and primitives
            new ArrayConstructors),  // Intercept creation of (non-generic) arrays and intrinsify.
       List(new Erasure),            // Rewrite types to JVM model, erasing all type parameters, abstract types and refinements.
@@ -86,9 +88,10 @@ class Compiler {
            new NonLocalReturns,     // Expand non-local returns
            new CapturedVars,        // Represent vars captured by closures as heap objects
            new Constructors,        // Collect initialization code in primary constructors
-                                       // Note: constructors changes decls in transformTemplate, no InfoTransformers should be added after it
+                                    // Note: constructors changes decls in transformTemplate, no InfoTransformers should be added after it
            new FunctionalInterfaces, // Rewrites closures to implement @specialized types of Functions.
-           new GetClass),           // Rewrites getClass calls on primitive types.
+           new GetClass,            // Rewrites getClass calls on primitive types.
+           new Simplify),           // Perform local optimizations, simplified versions of what linker does.
       List(new LambdaLift,          // Lifts out nested functions to class scope, storing free variables in environments
                                        // Note: in this mini-phase block scopes are incorrect. No phases that rely on scopes should be here
            new ElimStaticThis,      // Replace `this` references to static objects by global identifiers

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -1190,7 +1190,9 @@ object Trees {
     }
 
     abstract class TreeAccumulator[X] {
+      // Ties the knot of the traversal: call `foldOver(x, tree))` to dive in the `tree` node.
       def apply(x: X, tree: Tree)(implicit ctx: Context): X
+
       def apply(x: X, trees: Traversable[Tree])(implicit ctx: Context): X = (x /: trees)(apply)
       def foldOver(x: X, tree: Tree)(implicit ctx: Context): X = {
         def localCtx =
@@ -1301,7 +1303,7 @@ object Trees {
     class ShallowFolder[X](f: (X, Tree) => X) extends TreeAccumulator[X] {
       def apply(x: X, tree: Tree)(implicit ctx: Context): X = {
         val x1 = f(x, tree)
-        if (x1.asInstanceOf[AnyRef] ne x1.asInstanceOf[AnyRef]) x1
+        if (x1.asInstanceOf[AnyRef] ne x.asInstanceOf[AnyRef]) x1
         else foldOver(x1, tree)
       }
     }

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -454,6 +454,8 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   override val cpy: TypedTreeCopier = // Type ascription needed to pick up any new members in TreeCopier (currently there are none)
     new TypedTreeCopier
 
+  val cpyBetweenPhases = new TimeTravellingTreeCopier
+
   class TypedTreeCopier extends TreeCopier {
     def postProcess(tree: Tree, copied: untpd.Tree): copied.ThisTree[Type] =
       copied.withTypeUnchecked(tree.tpe)
@@ -472,16 +474,25 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
     }
 
-    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply =
-      ta.assignType(untpd.cpy.Apply(tree)(fun, args), fun, args)
-      // Note: Reassigning the original type if `fun` and `args` have the same types as before
-      // does not work here: The computed type depends on the widened function type, not
-      // the function type itself. A treetransform may keep the function type the
-      // same but its widened type might change.
+    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply = {
+      val tree1 = untpd.cpy.Apply(tree)(fun, args)
+      tree match {
+        case tree: Apply
+        if (fun.tpe eq tree.fun.tpe) && sameTypes(args, tree.args) =>
+          tree1.withTypeUnchecked(tree.tpe)
+        case _ => ta.assignType(tree1, fun, args)
+      }
+    }
 
-    override def TypeApply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): TypeApply =
-      ta.assignType(untpd.cpy.TypeApply(tree)(fun, args), fun, args)
-      // Same remark as for Apply
+    override def TypeApply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): TypeApply = {
+      val tree1 = untpd.cpy.TypeApply(tree)(fun, args)
+      tree match {
+        case tree: TypeApply
+        if (fun.tpe eq tree.fun.tpe) && sameTypes(args, tree.args) =>
+          tree1.withTypeUnchecked(tree.tpe)
+        case _ => ta.assignType(tree1, fun, args)
+      }
+    }
 
     override def Literal(tree: Tree)(const: Constant)(implicit ctx: Context): Literal =
       ta.assignType(untpd.cpy.Literal(tree)(const))
@@ -514,10 +525,15 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
     }
 
-    override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure =
-      ta.assignType(untpd.cpy.Closure(tree)(env, meth, tpt), meth, tpt)
-      // Same remark as for Apply
 
+    override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure = {
+      val tree1 = untpd.cpy.Closure(tree)(env, meth, tpt)
+      tree match {
+        case tree: Closure if sameTypes(env, tree.env) && (meth.tpe eq tree.meth.tpe) && (tpt.tpe eq tree.tpt.tpe) =>
+          tree1.withTypeUnchecked(tree.tpe)
+        case _ => ta.assignType(tree1, meth, tpt)
+      }
+    }
     override def Match(tree: Tree)(selector: Tree, cases: List[CaseDef])(implicit ctx: Context): Match = {
       val tree1 = untpd.cpy.Match(tree)(selector, cases)
       tree match {
@@ -574,6 +590,25 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       Try(tree: Tree)(expr, cases, finalizer)
   }
 
+  class TimeTravellingTreeCopier extends TypedTreeCopier {
+    override def Apply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): Apply =
+      ta.assignType(untpd.cpy.Apply(tree)(fun, args), fun, args)
+      // Note: Reassigning the original type if `fun` and `args` have the same types as before
+      // does not work here: The computed type depends on the widened function type, not
+      // the function type itself. A treetransform may keep the function type the
+      // same but its widened type might change.
+
+    override def TypeApply(tree: Tree)(fun: Tree, args: List[Tree])(implicit ctx: Context): TypeApply =
+      ta.assignType(untpd.cpy.TypeApply(tree)(fun, args), fun, args)
+      // Same remark as for Apply
+
+    override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure =
+            ta.assignType(untpd.cpy.Closure(tree)(env, meth, tpt), meth, tpt)
+
+    override def Closure(tree: Closure)(env: List[Tree] = tree.env, meth: Tree = tree.meth, tpt: Tree = tree.tpt)(implicit ctx: Context): Closure =
+      Closure(tree: Tree)(env, meth, tpt)
+  }
+
   override def skipTransform(tree: Tree)(implicit ctx: Context) = tree.tpe.isError
 
   implicit class TreeOps[ThisTree <: tpd.Tree](val tree: ThisTree) extends AnyVal {

compiler/src/dotty/tools/dotc/config/CompilerCommand.scala

@@ -1,4 +1,3 @@
-
 package dotty.tools.dotc
 package config
 

compiler/src/dotty/tools/dotc/config/Printers.scala

@@ -32,4 +32,5 @@ object Printers {
   val pickling: Printer = noPrinter
   val inlining: Printer = noPrinter
   val exhaustivity: Printer = noPrinter
+  val simplify: Printer = noPrinter
 }

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -399,6 +399,16 @@ class Definitions {
     def Boolean_&& = Boolean_andR.symbol
     lazy val Boolean_orR  = BooleanClass.requiredMethodRef(nme.ZOR)
     def Boolean_|| = Boolean_orR.symbol
+    lazy val Boolean_eqeqR = BooleanClass.info.member(nme.EQ).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef BooleanClass)
+      case _ => false
+    })
+    def Boolean_== = Boolean_eqeqR.symbol
+    lazy val Boolean_neqeqR = BooleanClass.info.member(nme.NE).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef BooleanClass)
+      case _ => false
+    })
+    def Boolean_!= = Boolean_neqeqR.symbol
 
   lazy val ByteType: TypeRef = valueTypeRef("scala.Byte", BoxedByteType, java.lang.Byte.TYPE, ByteEnc)
   def ByteClass(implicit ctx: Context) = ByteType.symbol.asClass
@@ -430,6 +440,13 @@ class Definitions {
     lazy val Long_LSR_Int = LongType.member(nme.LSR).requiredSymbol(
       x => (x is Method) && (x.info.firstParamTypes.head isRef defn.IntClass)
     )
+    lazy val Long_plusR   = LongClass.requiredMethodRef(nme.PLUS, List(LongType))
+    def Long_+ = Long_plusR.symbol
+    lazy val Long_mulR   = LongClass.requiredMethodRef(nme.MUL, List(LongType))
+    def Long_* = Long_mulR.symbol
+    lazy val Long_divR   = LongClass.requiredMethodRef(nme.DIV, List(LongType))
+    def Long_/ = Long_divR.symbol
+
   lazy val FloatType: TypeRef = valueTypeRef("scala.Float", BoxedFloatType, java.lang.Float.TYPE, FloatEnc)
   def FloatClass(implicit ctx: Context) = FloatType.symbol.asClass
   lazy val DoubleType: TypeRef = valueTypeRef("scala.Double", BoxedDoubleType, java.lang.Double.TYPE, DoubleEnc)
@@ -490,6 +507,11 @@ class Definitions {
   lazy val BoxedNumberClass          = ctx.requiredClass("java.lang.Number")
   lazy val ThrowableClass            = ctx.requiredClass("java.lang.Throwable")
   lazy val ClassCastExceptionClass   = ctx.requiredClass("java.lang.ClassCastException")
+  lazy val ArithmeticExceptionClass  = ctx.requiredClass("java.lang.ArithmeticException")
+    lazy val ArithmeticExceptionClass_stringConstructor  = ArithmeticExceptionClass.info.member(nme.CONSTRUCTOR).suchThat(_.info.firstParamTypes match {
+      case List(pt) => (pt isRef StringClass)
+      case _ => false
+    }).symbol.asTerm
   lazy val JavaSerializableClass     = ctx.requiredClass("java.io.Serializable")
   lazy val ComparableClass           = ctx.requiredClass("java.lang.Comparable")
 
@@ -521,6 +543,10 @@ class Definitions {
   def DynamicClass(implicit ctx: Context) = DynamicType.symbol.asClass
   lazy val OptionType: TypeRef                  = ctx.requiredClassRef("scala.Option")
   def OptionClass(implicit ctx: Context) = OptionType.symbol.asClass
+  lazy val SomeType: TypeRef                  = ctx.requiredClassRef("scala.Some")
+  def SomeClass(implicit ctx: Context) = SomeType.symbol.asClass
+  lazy val NoneModuleRef: TermRef                  = ctx.requiredModuleRef("scala.None")
+  def NoneClass(implicit ctx: Context) = NoneModuleRef.symbol.moduleClass.asClass
   lazy val EnumType: TypeRef                    = ctx.requiredClassRef("scala.Enum")
   def EnumClass(implicit ctx: Context) = EnumType.symbol.asClass
   lazy val EnumValuesType: TypeRef              = ctx.requiredClassRef("scala.runtime.EnumValues")

compiler/src/dotty/tools/dotc/core/NameKinds.scala

@@ -308,6 +308,9 @@ object NameKinds {
   val PatMatCaseName          = new UniqueNameKind("case")
   val PatMatMatchFailName     = new UniqueNameKind("matchFail")
   val PatMatSelectorName      = new UniqueNameKind("selector")
+  val LocalOptFact            = new UniqueNameKind("fact")
+  val LocalOptSelector        = new UniqueNameKind("selector")
+  val LocalOptFallback        = new UniqueNameKind("fallback")
 
   /** The kind of names of default argument getters */
   val DefaultGetterName = new NumberedNameKind(DEFAULTGETTER, "DefaultGetter") {
@@ -384,4 +387,4 @@ object NameKinds {
   def qualifiedNameKindOfTag   : collection.Map[Int, QualifiedNameKind]  = qualifiedNameKinds
   def numberedNameKindOfTag    : collection.Map[Int, NumberedNameKind]   = numberedNameKinds
   def uniqueNameKindOfSeparator: collection.Map[String, UniqueNameKind]  = uniqueNameKinds
-}
+}

compiler/src/dotty/tools/dotc/core/Scopes.scala

@@ -91,8 +91,10 @@ object Scopes {
     /** Is the scope empty? */
     def isEmpty: Boolean = lastEntry eq null
 
-    def foreach[U](p: Symbol => U)(implicit ctx: Context): Unit = toList foreach p
+    /** Applies a function f to all Symbols of this Scope. */
+    def foreach[U](f: Symbol => U)(implicit ctx: Context): Unit = toList.foreach(f)
 
+    /** Selects all Symbols of this Scope which satisfy a predicate. */
     def filter(p: Symbol => Boolean)(implicit ctx: Context): List[Symbol] = {
       ensureComplete()
       var syms: List[Symbol] = Nil
@@ -105,6 +107,10 @@ object Scopes {
       syms
     }
 
+    /** Tests whether a predicate holds for at least one Symbol of this Scope. */
+    def exists(p: Symbol => Boolean)(implicit ctx: Context): Boolean = filter(p).isEmpty
+
+    /** Finds the first Symbol of this Scope satisfying a predicate, if any. */
     def find(p: Symbol => Boolean)(implicit ctx: Context): Symbol = filter(p) match {
       case sym :: _ => sym
       case _ => NoSymbol