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Fix #2903: Reduce the depth of trees generated in PatternMatcher #3575

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Merged
merged 2 commits into from
Dec 23, 2017
Merged

Fix #2903: Reduce the depth of trees generated in PatternMatcher #3575

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b3389ea
Fix #2903: Reduce the depth of trees generated in PatternMatcher
nicolasstucki Nov 28, 2017
90c09a1
Add documentation
nicolasstucki Dec 11, 2017
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82 changes: 72 additions & 10 deletions compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -212,14 +212,39 @@ object PatternMatcher {
private def patternPlan(scrutinee: Symbol, tree: Tree, onSuccess: Plan, onFailure: Plan): Plan = {

/** Plan for matching `selectors` against argument patterns `args` */
def matchArgsPlan(selectors: List[Tree], args: List[Tree], onSuccess: Plan): Plan =
args match {
case arg :: args1 =>
val selector :: selectors1 = selectors
letAbstract(selector)(
patternPlan(_, arg, matchArgsPlan(selectors1, args1, onSuccess), onFailure))
case Nil => onSuccess
}
def matchArgsPlan(selectors: List[Tree], args: List[Tree], onSuccess: Plan): Plan = {
/* For a case with arguments that have some test on them such as
* ```
* case Foo(1, 2) => someCode
* ```
* all arguments values are extracted before the checks are performed. This shape is expected by `emit`
* to avoid generating deep trees.
* ```
* val x1: Foo = ...
* val x2: Int = x1._1
* val x3: Int = x1._2
* if (x2 == 1) {
* if (x3 == 2) someCode
* else label$1()
* } else label$1()
* ```
*/
def matchArgsSelectorsPlan(selectors: List[Tree], syms: List[Symbol]): Plan =
selectors match {
case selector :: selectors1 => letAbstract(selector)(sym => matchArgsSelectorsPlan(selectors1, sym :: syms))
case Nil => matchArgsPatternPlan(args, syms.reverse)
}
def matchArgsPatternPlan(args: List[Tree], syms: List[Symbol]): Plan =
args match {
case arg :: args1 =>
val sym :: syms1 = syms
patternPlan(sym, arg, matchArgsPatternPlan(args1, syms1), onFailure)
case Nil =>
assert(syms.isEmpty)
onSuccess
}
matchArgsSelectorsPlan(selectors, Nil)
}

/** Plan for matching the sequence in `seqSym` against sequence elements `args`.
* If `exact` is true, the sequence is not permitted to have any elements following `args`.
Expand Down Expand Up @@ -838,8 +863,45 @@ object PatternMatcher {
val switchCases = collectSwitchCases(plan)
if (switchCases.lengthCompare(4) >= 0) // at least 3 cases + default
Match(plan.scrutinee, emitSwitchCases(switchCases))
else
If(emitCondition(plan).withPos(plan.pos), emit(plan.onSuccess), emit(plan.onFailure))
else {
/** Merge nested `if`s that have the same `else` branch into a single `if`.
* This optimization targets calls to label defs for case failure jumps to next case.
*
* Plan for
* ```
* val x1: Int = ...
* val x2: Int = ...
* if (x1 == y1) {
* if (x2 == y2) someCode
* else label$1()
* } else label$1()
* ```
* is emitted as
* ```
* val x1: Int = ...
* val x2: Int = ...
* if (x1 == y1 && x2 == y2) someCode
* else label$1()
* ```
*/
def emitWithMashedConditions(plans: List[TestPlan]): Tree = {
val plan = plans.head
plan.onSuccess match {
case plan2: TestPlan if plan.onFailure == plan2.onFailure =>
emitWithMashedConditions(plan2 :: plans)
case _ =>
def emitCondWithPos(plan: TestPlan) = emitCondition(plan).withPos(plan.pos)
val conditions =
plans.foldRight[Tree](EmptyTree) { (otherPlan, acc) =>
if (acc.isEmpty) emitCondWithPos(otherPlan)
else acc.select(nme.ZAND).appliedTo(emitCondWithPos(otherPlan))
}
If(conditions, emit(plan.onSuccess), emit(plan.onFailure))
}

}
emitWithMashedConditions(plan :: Nil)
}
case LetPlan(sym, body) =>
seq(ValDef(sym, initializer(sym).ensureConforms(sym.info)) :: Nil, emit(body))
case LabelledPlan(label, body, params) =>
Expand Down
87 changes: 87 additions & 0 deletions tests/pos/i2903.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,87 @@
case class Foo1(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo2(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo3(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo4(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo5(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo6(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo7(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo8(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo9(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo10(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo11(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo12(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo13(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo14(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo15(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo16(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo17(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo18(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo19(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo20(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo21(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo22(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo23(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo24(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo25(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo26(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo27(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo28(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo29(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo30(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo31(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo32(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo33(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo34(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo35(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo36(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo37(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo38(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo39(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)
case class Foo40(x1: Int, x2: Int, x3: Int, x4: Int, x5: Int, x6: Int, x7: Int, x8: Int, x9: Int, x10: Int)

object Test {
def stuff() = {}

def test(x: Any): Unit = x match {
case Foo1(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo2(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo3(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo4(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo5(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo6(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo7(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo8(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo9(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo10(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo11(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo12(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo13(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo14(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo15(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo16(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo17(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo18(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo19(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo20(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo21(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo22(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo23(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo24(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo25(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo26(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo27(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo28(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo29(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo30(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo31(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo32(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo33(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo34(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo35(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo36(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo37(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo38(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo39(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
case Foo40(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) => stuff()
}
}