Make lazy vals and object native image friendly

Currently, creating a graal native image from scala 3 code is really cubersome, custom configuration needs to be provided for each object and lazy val. It is caused by reflection in LazyVals object.

This PR inlines reflection within each class and in this form Graal is able to inline such calls without any additional config.

Author: romanowski

compiler/src/dotty/tools/dotc/transform/LazyVals.scala

@@ -382,6 +382,7 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
     val thizClass = Literal(Constant(claz.info))
     val helperModule = requiredModule("scala.runtime.LazyVals")
     val getOffset = Select(ref(helperModule), lazyNme.RLazyVals.getOffset)
+    val getOffsetStatic = Select(ref(helperModule), lazyNme.RLazyVals.getOffsetStatic)
     var offsetSymbol: TermSymbol | Null = null
     var flag: Tree = EmptyTree
     var ord = 0
@@ -406,7 +407,8 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
           val flagName = LazyBitMapName.fresh(id.toString.toTermName)
           val flagSymbol = newSymbol(claz, flagName, containerFlags, defn.LongType).enteredAfter(this)
           flag = ValDef(flagSymbol, Literal(Constant(0L)))
-          val offsetTree = ValDef(offsetSymbol.nn, getOffset.appliedTo(thizClass, Literal(Constant(flagName.toString))))
+          val fieldTree = thizClass.select(lazyNme.RLazyVals.getDeclaredField).appliedTo(Literal(Constant(flagName.toString)))
+          val offsetTree = ValDef(offsetSymbol.nn, getOffsetStatic.appliedTo(fieldTree))
           info.defs = offsetTree :: info.defs
         }
 
@@ -416,7 +418,8 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
         val flagName = LazyBitMapName.fresh("0".toTermName)
         val flagSymbol = newSymbol(claz, flagName, containerFlags, defn.LongType).enteredAfter(this)
         flag = ValDef(flagSymbol, Literal(Constant(0L)))
-        val offsetTree = ValDef(offsetSymbol.nn, getOffset.appliedTo(thizClass, Literal(Constant(flagName.toString))))
+        val fieldTree = thizClass.select(lazyNme.RLazyVals.getDeclaredField).appliedTo(Literal(Constant(flagName.toString)))
+        val offsetTree = ValDef(offsetSymbol.nn, getOffsetStatic.appliedTo(fieldTree))
         appendOffsetDefs += (claz -> new OffsetInfo(List(offsetTree), ord))
     }
 
@@ -453,6 +456,8 @@ object LazyVals {
       val state: TermName             = N.state.toTermName
       val cas: TermName               = N.cas.toTermName
       val getOffset: TermName         = N.getOffset.toTermName
+      val getOffsetStatic: TermName   = "getOffsetStatic".toTermName
+      val getDeclaredField: TermName  = "getDeclaredField".toTermName
     }
     val flag: TermName        = "flag".toTermName
     val state: TermName       = "state".toTermName

library/src/scala/runtime/LazyVals.scala

@@ -106,6 +106,13 @@ object LazyVals {
     r
   }
 
+  def getOffsetStatic(field: java.lang.reflect.Field) =
+    val r = unsafe.objectFieldOffset(field)
+    if (debug)
+      println(s"getOffset(${field.getDeclaringClass}, ${field.getName}) = $r")
+    r
+
+
   object Names {
     final val state = "STATE"
     final val cas = "CAS"