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Commit1501c94

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Merge pull request#5210 from tanishiking/asinstanceof-linktimeif
Removes spurious js.AsInstanceOf around the js.LinkTimeIf
2 parents849495b +9bb267c commit1501c94

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3 files changed

+115
-1
lines changed

3 files changed

+115
-1
lines changed

‎compiler/src/main/scala/org/scalajs/nscplugin/GenJSCode.scala

Lines changed: 24 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3207,7 +3207,30 @@ abstract class GenJSCode[G <: Global with Singleton](val global: G)
32073207
caseObject_isInstanceOf=>
32083208
genIsAsInstanceOf(obj, targs, cast=false)
32093209
caseObject_asInstanceOf=>
3210-
genIsAsInstanceOf(obj, targs, cast=true)
3210+
valtargetTpe= targs.head.tpe
3211+
objmatch {
3212+
/* This is an optimization for `linkTimeIf(cond)(thenp)(elsep).asInstanceOf[T]`.
3213+
* If both `thenp` and `elsep` are subtypes of `T`, the `asInstanceOf`
3214+
* is redundant and can be removed. The optimizer already routinely performs
3215+
* this optimization. However, that comes too late for the module instance
3216+
* field alias analysis performed by `IncOptimizer`. In that case, while the
3217+
* desugarer removes the `LinkTimeIf`, the extra `AsInstanceOf` prevents
3218+
* aliasing the field. Removing the cast ahead of time in the compiler allows
3219+
* field aliases to be recognized in the presence of `LinkTimeIf`s.
3220+
*/
3221+
caseApply(fun,List(cond, thenp, elsep))
3222+
if fun.symbol== jsDefinitions.LinkingInfo_linkTimeIf&&
3223+
thenp.tpe<:< targetTpe&& elsep.tpe<:< targetTpe=>
3224+
valgenObj= genExpr(obj)match {
3225+
caset: js.LinkTimeIf=> t
3226+
case t=>
3227+
abort("Unexpected tree"+ t+
3228+
" is generated for"+ fun+" at:"+ tree.pos)
3229+
}
3230+
js.LinkTimeIf(genObj.cond, genObj.thenp, genObj.elsep)(toIRType(targetTpe))(genObj.pos)
3231+
case _=>
3232+
genIsAsInstanceOf(obj, targs, cast=true)
3233+
}
32113234
caseObject_synchronized=>
32123235
genSynchronized(obj, args.head, isStat)
32133236
case _=>

‎compiler/src/test/scala/org/scalajs/nscplugin/test/OptimizationTest.scala

Lines changed: 44 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -648,6 +648,50 @@ class OptimizationTest extends JSASTTest {
648648
}
649649
}
650650
}
651+
652+
@Test
653+
deflinkTimeIf:Unit= {
654+
/* Make sure the cast in
655+
* `linkTimeIf(cond)(thenp)(elsep).asInstanceOf[T]``
656+
* is optimized away if `thenp` and `elsep` are subtypes of `T`.
657+
*/
658+
"""
659+
import scala.scalajs.js
660+
import scala.scalajs.LinkingInfo._
661+
662+
class LinkTimeIfTest {
663+
import LinkTimeIfTest._
664+
private val impl = linkTimeIf[ArrayImpl](productionMode) {
665+
JSArrayImpl
666+
} {
667+
ScalaArrayImpl
668+
}
669+
def implPattern(): Int = {
670+
impl.length(impl.empty())
671+
}
672+
}
673+
object LinkTimeIfTest {
674+
sealed private abstract class ArrayImpl {
675+
type Repr
676+
def empty(): Repr
677+
def length(v: Repr): Int
678+
}
679+
private object JSArrayImpl extends ArrayImpl {
680+
type Repr = js.Array[AnyRef]
681+
def empty(): Repr = js.Array[AnyRef]()
682+
def length(v: Repr): Int = v.length
683+
}
684+
private object ScalaArrayImpl extends ArrayImpl {
685+
type Repr = Array[AnyRef]
686+
def empty(): Repr = new Array[AnyRef](0)
687+
def length(v: Repr): Int = v.length
688+
}
689+
}
690+
""".
691+
hasNot("linkTimeIf[A](...).asInstanceOf[A]") {
692+
case js.AsInstanceOf(_:js.LinkTimeIf, _)=>
693+
}
694+
}
651695
}
652696

653697
objectOptimizationTest {

‎test-suite/js/src/test/scala/org/scalajs/testsuite/library/LinkTimeIfTest.scala

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -92,4 +92,51 @@ class LinkTimeIfTest {
9292
}
9393
assertEquals(pow(2.0,8.0),256.0,0)
9494
}
95+
96+
// This test verifies that the compiler can safely compile surrounding
97+
// implicit asInstanceOf casts to a supertype.
98+
@Testdefsubtyping():Unit= {
99+
traitA {defvalue:Int }
100+
classB(valvalue:Int)extendsA
101+
classC(valvalue:Int)extendsA
102+
103+
valb=newB(1)
104+
valc=newC(2)
105+
106+
valresult1= linkTimeIf[A](productionMode) { b } { c }
107+
assertEquals(if (Platform.isInProductionMode) b.valueelse c.value, result1.value)
108+
109+
valresult2= linkTimeIf[A](productionMode) { c } { b }
110+
assertEquals(if (Platform.isInProductionMode) c.valueelse b.value, result2.value)
111+
}
112+
113+
@TestdefimplPattern():Unit= {
114+
importLinkTimeIfTest._
115+
valimpl= linkTimeIf[ArrayImpl](productionMode) {
116+
JSArrayImpl
117+
} {
118+
ScalaArrayImpl
119+
}
120+
assertEquals(0, impl.length(impl.empty()))
121+
}
122+
}
123+
124+
objectLinkTimeIfTest {
125+
sealedprivateabstractclassArrayImpl {
126+
typeRepr
127+
defempty():Repr
128+
deflength(v:Repr):Int
129+
}
130+
131+
privateobjectJSArrayImplextendsArrayImpl {
132+
typeRepr= js.Array[AnyRef]
133+
defempty():Repr= js.Array[AnyRef]()
134+
deflength(v:Repr):Int= v.length
135+
}
136+
137+
privateobjectScalaArrayImplextendsArrayImpl {
138+
typeRepr=Array[AnyRef]
139+
defempty():Repr=newArray[AnyRef](0)
140+
deflength(v:Repr):Int= v.length
141+
}
95142
}

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