Optimizer: Make special subtyping checks for RuntimeLong explicit

gzm0 · gzm0 · commit 817018d31261 · 2024-11-24T10:22:38.000+01:00
To enable the IRChecker, we only want to consider RuntimeLong
equivalent to BoxedLong when we'll end up removing that type
information from the IR. In practice, this is during instance checks.

As a result, we can also see that some of the cases were unnecessary:
- The instance checks already handle nullability.
- We never emit an instance check for RuntimeLong, so that direction
  is unnecessary.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -272,27 +272,8 @@ private[optimizer] abstract class OptimizerCore(
 
   private val isSubclassFun = isSubclass _
 
-  private def isSubtype(lhs: Type, rhs: Type): Boolean = {
-    assert(lhs != VoidType)
-    assert(rhs != VoidType)
-
-    Types.isSubtype(lhs, rhs)(isSubclassFun) || {
-      (lhs, rhs) match {
-        case (LongType, ClassType(LongImpl.RuntimeLongClass, _)) =>
-          true
-        case (ClassType(BoxedLongClass, lhsNullable),
-            ClassType(LongImpl.RuntimeLongClass, rhsNullable)) =>
-          rhsNullable || !lhsNullable
-
-        case (ClassType(LongImpl.RuntimeLongClass, lhsNullable),
-            ClassType(BoxedLongClass, rhsNullable)) =>
-          rhsNullable || !lhsNullable
-
-        case _ =>
-          false
-      }
-    }
-  }
+  private def isSubtype(lhs: Type, rhs: Type): Boolean =
+    Types.isSubtype(lhs, rhs)(isSubclassFun)
 
   /** Transforms a statement.
    *
@@ -564,8 +545,16 @@ private[optimizer] abstract class OptimizerCore(
       case IsInstanceOf(expr, testType) =>
         trampoline {
           pretransformExpr(expr) { texpr =>
+            val texprType = texpr.tpe.base.toNonNullable
+
+            val staticSubtype = isSubtype(texprType, testType) || {
+              useRuntimeLong &&
+              texprType == ClassType(LongImpl.RuntimeLongClass, false) &&
+              testType == ClassType(BoxedLongClass, false)
+            }
+
             val result = {
-              if (isSubtype(texpr.tpe.base.toNonNullable, testType)) {
+              if (staticSubtype) {
                 if (texpr.tpe.isNullable)
                   BinaryOp(BinaryOp.!==, finishTransformExpr(texpr), Null())
                 else
