Support benchmarking of resident compilation

compilation/src/main/dotc/scala/tools/benchmark/BenchmarkDriver.scala

@@ -12,7 +12,7 @@ trait BenchmarkDriver extends BaseBenchmarkDriver {
       ctx.setSetting(ctx.settings.classpath,
                      depsClasspath.mkString(File.pathSeparator))
     }
-    ctx.setSetting(ctx.settings.migration, true)
+    ctx.setSetting(ctx.settings.migration, false)
     ctx.setSetting(ctx.settings.d, tempDir.getAbsolutePath)
     ctx.setSetting(ctx.settings.language, List("Scala2"))
     val compiler = new dotty.tools.dotc.Compiler

compilation/src/main/scala/scala/tools/nsc/ScalacBenchmark.scala

@@ -25,6 +25,7 @@ trait BaseBenchmarkDriver {
   def corpusSourcePath: Path
   def compilerArgs: List[String]
   def sourceFiles: List[String]
+  def isResident: Boolean = false
 }
 
 @State(Scope.Benchmark)
@@ -40,6 +41,11 @@ class ScalacBenchmark extends BenchmarkDriver {
   @Param(value = Array("latest"))
   var corpusVersion: String = _
 
+  @Param(value = Array("false"))
+  var resident: Boolean = false
+
+  override def isResident = resident
+
   var depsClasspath: String = _
 
   def compilerArgs: List[String] = if (source.startsWith("@")) source :: Nil else Nil

compilation/src/main/scalac/scala/tools/benchmark/BenchmarkDriver.scala

@@ -4,31 +4,47 @@ import java.nio.file._
 import scala.tools.nsc._
 
 trait BenchmarkDriver extends BaseBenchmarkDriver {
+  private var driver: MainClass = _
+  private var files: List[String] = _
+
+  // MainClass is copy-pasted from compiler for source compatibility with 2.10.x - 2.13.x
+  private class MainClass extends Driver with EvalLoop {
+    var compiler: Global = _
+    override def newCompiler(): Global = {
+      compiler = Global(settings, reporter)
+      compiler
+    }
+
+    override protected def processSettingsHook(): Boolean = {
+      if (source == "scala")
+        settings.sourcepath.value = Paths.get(s"../corpus/$source/$corpusVersion/library").toAbsolutePath.normalize.toString
+      else
+        settings.usejavacp.value = true
+      settings.outdir.value = tempDir.getAbsolutePath
+      settings.nowarn.value = true
+      if (depsClasspath != null)
+        settings.processArgumentString(s"-cp $depsClasspath")
+      true
+    }
+  }
+
   def compileImpl(): Unit = {
-    // MainClass is copy-pasted from compiler for source compatibility with 2.10.x - 2.13.x
-    class MainClass extends Driver with EvalLoop {
-      def resident(compiler: Global): Unit = loop { line =>
-        val command = new CompilerCommand(line split "\\s+" toList, new Settings(scalacError))
+    if (isResident) {
+      if (driver == null) {
+        driver = new MainClass
+        driver.process(allArgs.toArray)
+        val command  = new CompilerCommand(allArgs, driver.compiler.settings)
+        files = command.files
+      } else {
+        val compiler = driver.compiler
         compiler.reporter.reset()
-        new compiler.Run() compile command.files
+        new compiler.Run() compile files
       }
 
-      override def newCompiler(): Global = Global(settings, reporter)
-
-      override protected def processSettingsHook(): Boolean = {
-        if (source == "scala")
-          settings.sourcepath.value = Paths.get(s"../corpus/$source/$corpusVersion/library").toAbsolutePath.normalize.toString
-        else
-          settings.usejavacp.value = true
-        settings.outdir.value = tempDir.getAbsolutePath
-        settings.nowarn.value = true
-        if (depsClasspath != null)
-          settings.processArgumentString(s"-cp $depsClasspath")
-        true
-      }
+    } else {
+      driver = new MainClass
+      driver.process(allArgs.toArray)
     }
-    val driver = new MainClass
-    driver.process(allArgs.toArray)
     assert(!driver.reporter.hasErrors)
   }