diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/transform/LazyVals.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/transform/LazyVals.scala | 95 |
1 files changed, 60 insertions, 35 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/LazyVals.scala b/src/compiler/scala/tools/nsc/transform/LazyVals.scala index b6695efb0b..bc9f70679c 100644 --- a/src/compiler/scala/tools/nsc/transform/LazyVals.scala +++ b/src/compiler/scala/tools/nsc/transform/LazyVals.scala @@ -1,14 +1,14 @@ package scala.tools.nsc package transform -import scala.collection.{ mutable, immutable } +import scala.collection.mutable abstract class LazyVals extends Transform with TypingTransformers with ast.TreeDSL { // inherits abstract value `global` and class `Phase` from Transform import global._ // the global environment import definitions._ // standard classes and methods - import typer.{typed, atOwner} // methods to type trees + import typer.typed // methods to type trees import CODE._ val phaseName: String = "lazyvals" @@ -38,6 +38,7 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD case ClassDef(_, _, _, _) | DefDef(_, _, _, _, _, _) | ModuleDef(_, _, _) => + // Avoid adding bitmaps when they are fully overshadowed by those that are added inside loops case LabelDef(name, _, _) if nme.isLoopHeaderLabel(name) => case _ => @@ -54,9 +55,28 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD private val lazyVals = perRunCaches.newMap[Symbol, Int]() withDefaultValue 0 import symtab.Flags._ + private def flattenThickets(stats: List[Tree]): List[Tree] = stats.flatMap(_ match { + case b @ Block(List(d1@DefDef(_, n1, _, _, _, _)), d2@DefDef(_, n2, _, _, _, _)) if b.tpe == null && n1.endsWith(nme.LAZY_SLOW_SUFFIX) => + List(d1, d2) + case stat => + List(stat) + }) /** Perform the following transformations: * - for a lazy accessor inside a method, make it check the initialization bitmap + * - implement double checked locking of member modules for non-trait owners (trait just have the abstract accessor) + * ``` + * // typer + * class C { object x } + * // refchecks + * class C { var x$module; def x() = { x$module = new x; x$module } + * // lazyvals + * class C { + * var x$module // module var + * def x() = { if (x$module == null) x$lzycompute() else x$module // fast path + * def x$lzycompute() = { synchronized { if (x$module == null) x$module = new x }; x$module } // slow path + * } + * ``` * - for all methods, add enough int vars to allow one flag per lazy local value * - blocks in template bodies behave almost like methods. A single bitmaps section is * added in the first block, for all lazy values defined in such blocks. @@ -72,20 +92,14 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD case Block(_, _) => val block1 = super.transform(tree) val Block(stats, expr) = block1 - val stats1 = stats.flatMap(_ match { - case Block(List(d1@DefDef(_, n1, _, _, _, _)), d2@DefDef(_, n2, _, _, _, _)) if (nme.newLazyValSlowComputeName(n2) == n1) => - List(d1, d2) - case stat => - List(stat) - }) - treeCopy.Block(block1, stats1, expr) + treeCopy.Block(block1, flattenThickets(stats), expr) case DefDef(_, _, _, _, _, rhs) => atOwner(tree.symbol) { val (res, slowPathDef) = if (!sym.owner.isClass && sym.isLazy) { val enclosingClassOrDummyOrMethod = { val enclMethod = sym.enclMethod - if (enclMethod != NoSymbol ) { + if (enclMethod != NoSymbol) { val enclClass = sym.enclClass if (enclClass != NoSymbol && enclMethod == enclClass.enclMethod) enclClass @@ -100,30 +114,39 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD val (rhs1, sDef) = mkLazyDef(enclosingClassOrDummyOrMethod, transform(rhs), idx, sym) sym.resetFlag((if (lazyUnit(sym)) 0 else LAZY) | ACCESSOR) (rhs1, sDef) - } else + } else if (sym.hasAllFlags(MODULE | METHOD) && !sym.owner.isTrait) { + rhs match { + case b @ Block((assign @ Assign(moduleRef, _)) :: Nil, expr) => + def cond = Apply(Select(moduleRef, Object_eq), List(Literal(Constant(null)))) + val (fastPath, slowPath) = mkFastPathBody(sym.owner.enclClass, moduleRef.symbol, cond, transform(assign) :: Nil, Nil, transform(expr)) + (localTyper.typedPos(tree.pos)(fastPath), localTyper.typedPos(tree.pos)(slowPath)) + case rhs => + global.reporter.error(tree.pos, "Unexpected tree on the RHS of a module accessor: " + rhs) + (rhs, EmptyTree) + } + } else { (transform(rhs), EmptyTree) + } val ddef1 = deriveDefDef(tree)(_ => if (LocalLazyValFinder.find(res)) typed(addBitmapDefs(sym, res)) else res) - if (slowPathDef != EmptyTree) Block(slowPathDef, ddef1) else ddef1 + if (slowPathDef != EmptyTree) { + // The contents of this block are flattened into the enclosing statement sequence, see flattenThickets + // This is a poor man's version of dotty's Thicket: https://github.com/lampepfl/dotty/blob/d5280358d1/src/dotty/tools/dotc/ast/Trees.scala#L707 + Block(slowPathDef, ddef1) + } else ddef1 } case Template(_, _, body) => atOwner(currentOwner) { - val body1 = super.transformTrees(body) + // TODO: shady business... can this logic be encapsulated in LocalLazyValFinder? var added = false - val stats = - for (stat <- body1) yield stat match { - case Block(_, _) | Apply(_, _) | If(_, _, _) | Try(_, _, _) if !added => - // Avoid adding bitmaps when they are fully overshadowed by those - // that are added inside loops - if (LocalLazyValFinder.find(stat)) { - added = true - typed(addBitmapDefs(sym, stat)) - } else stat - case ValDef(_, _, _, _) => - typed(deriveValDef(stat)(addBitmapDefs(stat.symbol, _))) - case _ => - stat + val stats = super.transformTrees(body) mapConserve { + case stat: ValDef => typed(deriveValDef(stat)(addBitmapDefs(stat.symbol, _))) + case stat: TermTree if !added && (LocalLazyValFinder find stat) => + added = true + typed(addBitmapDefs(sym, stat)) + case stat => stat } + val innerClassBitmaps = if (!added && currentOwner.isClass && bitmaps.contains(currentOwner)) { // add bitmap to inner class if necessary val toAdd0 = bitmaps(currentOwner).map(s => typed(ValDef(s, ZERO))) @@ -135,7 +158,7 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD }) toAdd0 } else List() - deriveTemplate(tree)(_ => innerClassBitmaps ++ stats) + deriveTemplate(tree)(_ => innerClassBitmaps ++ flattenThickets(stats)) } case ValDef(_, _, _, _) if !sym.owner.isModule && !sym.owner.isClass => @@ -192,21 +215,23 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD def mkSlowPathDef(clazz: Symbol, lzyVal: Symbol, cond: Tree, syncBody: List[Tree], stats: List[Tree], retVal: Tree): Tree = { - // Q: is there a reason to first set owner to `clazz` (by using clazz.newMethod), and then - // changing it to lzyVal.owner very soon after? Could we just do lzyVal.owner.newMethod? - val defSym = clazz.newMethod(nme.newLazyValSlowComputeName(lzyVal.name.toTermName), lzyVal.pos, STABLE | PRIVATE) + val owner = lzyVal.owner + val defSym = owner.newMethod(nme.newLazyValSlowComputeName(lzyVal.name.toTermName), lzyVal.pos, STABLE | PRIVATE) defSym setInfo MethodType(List(), lzyVal.tpe.resultType) - defSym.owner = lzyVal.owner + if (owner.isClass) owner.info.decls.enter(defSym) debuglog(s"crete slow compute path $defSym with owner ${defSym.owner} for lazy val $lzyVal") - if (bitmaps.contains(lzyVal)) - bitmaps(lzyVal).map(_.owner = defSym) + // this is a hack i don't understand for lazy vals nested in a lazy val, introduced in 3769f4d, + // tested in pos/t3670 (add9be64). class A { val n = { lazy val b = { lazy val dd = 3; dd }; b } } + // bitmaps has an entry bMethodSym -> List(bitmap$0), where bitmap$0.owner == bMethodSym. + // now we set bitmap$0.owner = b$lzycomputeMethodSym. + for (bitmap <- bitmaps(lzyVal)) bitmap.owner = defSym val rhs: Tree = gen.mkSynchronizedCheck(clazz, cond, syncBody, stats).changeOwner(currentOwner -> defSym) DefDef(defSym, addBitmapDefs(lzyVal, BLOCK(rhs, retVal))) } - def mkFastPathBody(clazz: Symbol, lzyVal: Symbol, cond: Tree, syncBody: List[Tree], + def mkFastPathBody(clazz: Symbol, lzyVal: Symbol, cond: => Tree, syncBody: List[Tree], stats: List[Tree], retVal: Tree): (Tree, Tree) = { val slowPathDef: Tree = mkSlowPathDef(clazz, lzyVal, cond, syncBody, stats, retVal) (If(cond, Apply(Ident(slowPathDef.symbol), Nil), retVal), slowPathDef) @@ -261,7 +286,7 @@ abstract class LazyVals extends Transform with TypingTransformers with ast.TreeD (mkBlock(rhs), UNIT) } - val cond = (bitmapRef GEN_& (mask, bitmapKind)) GEN_== (ZERO, bitmapKind) + def cond = (bitmapRef GEN_& (mask, bitmapKind)) GEN_== (ZERO, bitmapKind) val lazyDefs = mkFastPathBody(methOrClass.enclClass, lazyVal, cond, List(block), Nil, res) (atPos(tree.pos)(localTyper.typed {lazyDefs._1 }), atPos(tree.pos)(localTyper.typed {lazyDefs._2 })) } |