update BackendUtils.classfileVersionMap

[xuwei-k]

delete old versions

https://www.scala-lang.org/news/next-scala-lts-jdk.html

• fix use StringConcatFactory by default #24781

[He-Pin]

Add a comment here:

//java 8~16 support has been dropped`

[WojciechMazur]

LGTM, thank you for these changes.

Potentially we can also remove the now deadcode logic for String Concat used in JDK8

scala3/compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala

Lines 1306 to 1326 in 6bdf209

	// `StringConcatFactory` only got added in JDK 9, so use `StringBuilder` for lower
	if (backendUtils.classfileVersion < asm.Opcodes.V9) {
	// Estimate capacity needed for the string builder
	val approxBuilderSize = concatArguments.view.map {
	case Literal(Constant(s: String)) => s.length
	case Literal(c @ Constant(_)) if c.isNonUnitAnyVal => String.valueOf(c).length
	case _ => 0
	}.sum
	bc.genNewStringBuilder(approxBuilderSize)
	stack.push(jlStringBuilderRef) // during the genLoad below, there is a reference to the StringBuilder on the stack
	for (elem <- concatArguments) {
	val elemType = tpeTK(elem)
	genLoad(elem, elemType)
	bc.genStringBuilderAppend(elemType)
	}
	stack.pop()
	bc.genStringBuilderEnd
	} else {

However it can also be done in the follow up. I leave the decision up to you, we'd most likely merge it tomorrow and backport to 3.8.0-RC5

[tanishiking]

One nitpick, but otherwise LGTM from myside. (but we can merge it without fixing if we're in rush)

[tanishiking]

because Java9+ uses https://openjdk.org/jeps/280 👍

[tanishiking]

I believe this is converting arrays to lists for structural equality of InvokeDynamic, but bsmArgs shouldn't have Array...
It turned out this is the consequence of a long-time bug in AsmConverters 😄 The following diff should fix without convertInvokeDynamicArray.

diff --git a/compiler/test/dotty/tools/backend/jvm/AsmConverters.scala b/compiler/test/dotty/tools/backend/jvm/AsmConverters.scala
index c751937bd9..dfa7ed25ab 100644
--- a/compiler/test/dotty/tools/backend/jvm/AsmConverters.scala
+++ b/compiler/test/dotty/tools/backend/jvm/AsmConverters.scala
@@ -148,7 +148,7 @@ object ASMConverters {
 
     private def convertBsmArgs(a: Array[Object]): List[Object] = a.iterator.map({
       case h: asm.Handle => convertMethodHandle(h)
-      case _ => a // can be: Class, method Type, primitive constant
+      case x => x // can be: Class, method Type, primitive constant
     }).toList
 
     private def convertMethodHandle(h: asm.Handle): MethodHandle = MethodHandle(h.getTag, h.getOwner, h.getName, h.getDesc, h.isInterface)