Constant time reference counting

effekt/jvm/src/main/scala/effekt/Runner.scala

@@ -287,17 +287,24 @@ object LLVMRunner extends Runner[String] {
 
   def libuvArgs(using C: Context): Seq[String] =
     val OS = System.getProperty("os.name").toLowerCase
+
+    // only relevant for macOS
+    val arch: String = System.getProperty("os.arch")
+    assert(!OS.contains("mac") || List("aarch64", "x86_64").contains(arch), "If you have a macbook -> It should have either an aarch64 or x86_64 architecture.")
+
     val libraries = C.config.clangLibraries.toOption.map(file).orElse {
       OS match {
-        case os if os.contains("mac")  => Some(file("/opt/homebrew/lib"))
+        case os if os.contains("mac") && arch.equals("aarch64")  => Some(file("/opt/homebrew/lib"))
+        case os if os.contains("mac")  => Some(file("/usr/local/lib"))
         case os if os.contains("win") => None
         case os if os.contains("linux") => Some(file("/usr/local/lib"))
         case os => None
       }
     }
     val includes = C.config.clangIncludes.toOption.map(file).orElse {
       OS match {
-        case os if os.contains("mac")  => Some(file("/opt/homebrew/include"))
+        case os if os.contains("mac") && arch.equals("aarch64") => Some(file("/opt/homebrew/include"))
+        case os if os.contains("mac") => Some(file("/usr/local/include"))
         case os if os.contains("win") => None
         case os if os.contains("linux") => Some(file("/usr/local/include"))
         case os => None

effekt/jvm/src/test/scala/effekt/FlatTests.scala

@@ -0,0 +1,24 @@
+package effekt
+
+import sbt.io.*
+import sbt.io.syntax.*
+
+import java.io.File
+import scala.language.implicitConversions
+import scala.sys.process.Process
+
+// df: My own test class to run my requested tests automatically
+class FlatTests extends EffektTests {
+
+  def backendName = "llvm"
+
+  override def valgrind = false // works on linux only
+
+  override lazy val positives: Set[File] = Set(
+    examplesDir / "flat" / "optimized"
+  )
+
+  override lazy val withoutOptimizations: Set[File] = Set(
+    examplesDir / "flat" / "nooptimized",
+  )
+}

effekt/jvm/src/test/scala/effekt/LLVMTests.scala

@@ -12,7 +12,7 @@ class LLVMTests extends EffektTests {
 
   override def valgrind = sys.env.get("EFFEKT_VALGRIND").nonEmpty
   override def debug = sys.env.get("EFFEKT_DEBUG").nonEmpty
-
+  
   override lazy val positives: Set[File] = Set(
     examplesDir / "llvm",
     examplesDir / "pos",