Merge pull request scala#4552 from lrytz/opt/closureInlining

Closure elimination for new backend

Author: retronym

src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala

@@ -140,7 +140,7 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
       if (AsmUtils.traceClassEnabled && cnode.name.contains(AsmUtils.traceClassPattern))
         AsmUtils.traceClass(cnode)
 
-      if (settings.YoptInlinerEnabled) {
+      if (settings.YoptAddToBytecodeRepository) {
         // The inliner needs to find all classes in the code repo, also those being compiled
         byteCodeRepository.add(cnode, ByteCodeRepository.CompilationUnit)
       }

src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala

@@ -44,6 +44,8 @@ abstract class BTypes {
 
   val inliner: Inliner[this.type]
 
+  val closureOptimizer: ClosureOptimizer[this.type]
+
   val callGraph: CallGraph[this.type]
 
   val backendReporting: BackendReporting

src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala

@@ -7,7 +7,7 @@ package scala.tools.nsc
 package backend.jvm
 
 import scala.tools.asm
-import scala.tools.nsc.backend.jvm.opt.{LocalOpt, CallGraph, Inliner, ByteCodeRepository}
+import scala.tools.nsc.backend.jvm.opt._
 import scala.tools.nsc.backend.jvm.BTypes.{InlineInfo, MethodInlineInfo, InternalName}
 import BackendReporting._
 import scala.tools.nsc.settings.ScalaSettings
@@ -42,6 +42,8 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
 
   val inliner: Inliner[this.type] = new Inliner(this)
 
+  val closureOptimizer: ClosureOptimizer[this.type] = new ClosureOptimizer(this)
+
   val callGraph: CallGraph[this.type] = new CallGraph(this)
 
   val backendReporting: BackendReporting = new BackendReportingImpl(global)

src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala

@@ -246,6 +246,28 @@ object BackendReporting {
   case class ResultingMethodTooLarge(calleeDeclarationClass: InternalName, name: String, descriptor: String,
                                      callsiteClass: InternalName, callsiteName: String, callsiteDesc: String) extends CannotInlineWarning
 
+  /**
+   * Used in `rewriteClosureApplyInvocations` when a closure apply callsite cannot be rewritten
+   * to the closure body method.
+   */
+  trait RewriteClosureApplyToClosureBodyFailed extends OptimizerWarning {
+    def pos: Position
+
+    override def emitWarning(settings: ScalaSettings): Boolean = this match {
+      case RewriteClosureAccessCheckFailed(_, cause) => cause.emitWarning(settings)
+      case RewriteClosureIllegalAccess(_, _)         => settings.YoptWarningEmitAtInlineFailed
+    }
+
+    override def toString: String = this match {
+      case RewriteClosureAccessCheckFailed(_, cause) =>
+        s"Failed to rewrite the closure invocation to its implementation method:\n" + cause
+      case RewriteClosureIllegalAccess(_, callsiteClass) =>
+        s"The closure body invocation cannot be rewritten because the target method is not accessible in class $callsiteClass."
+    }
+  }
+  case class RewriteClosureAccessCheckFailed(pos: Position, cause: OptimizerWarning) extends RewriteClosureApplyToClosureBodyFailed
+  case class RewriteClosureIllegalAccess(pos: Position, callsiteClass: InternalName) extends RewriteClosureApplyToClosureBodyFailed
+
   /**
    * Used in the InlineInfo of a ClassBType, when some issue occurred obtaining the inline information.
    */

src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala

@@ -216,20 +216,25 @@ abstract class GenBCode extends BCodeSyncAndTry {
     class Worker2 {
       def runGlobalOptimizations(): Unit = {
         import scala.collection.convert.decorateAsScala._
-        q2.asScala foreach {
-          case Item2(_, _, plain, _, _) =>
-            // skip mirror / bean: wd don't inline into tem, and they are not used in the plain class
-            if (plain != null) callGraph.addClass(plain)
+        if (settings.YoptBuildCallGraph) {
+          q2.asScala foreach {
+            case Item2(_, _, plain, _, _) =>
+              // skip mirror / bean: wd don't inline into tem, and they are not used in the plain class
+              if (plain != null) callGraph.addClass(plain)
+          }
         }
-        bTypes.inliner.runInliner()
+        if (settings.YoptInlinerEnabled)
+          bTypes.inliner.runInliner()
+        if (settings.YoptClosureElimination)
+          closureOptimizer.rewriteClosureApplyInvocations()
       }
 
       def localOptimizations(classNode: ClassNode): Unit = {
         BackendStats.timed(BackendStats.methodOptTimer)(localOpt.methodOptimizations(classNode))
       }
 
       def run() {
-        if (settings.YoptInlinerEnabled) runGlobalOptimizations()
+        runGlobalOptimizations()
 
         while (true) {
           val item = q2.poll

src/compiler/scala/tools/nsc/backend/jvm/analysis/InstructionStackEffect.scala

@@ -94,7 +94,7 @@ object InstructionStackEffect {
         val isSize2 = peekStack(0).getSize == 2
         if (isSize2) t(1, 0) else t(2, 0)
 
-      case DUP => t(0, 1)
+      case DUP => t(1, 2)
 
       case DUP_X1 => t(2, 3)
 
@@ -104,7 +104,7 @@ object InstructionStackEffect {
 
       case DUP2 =>
         val isSize2 = peekStack(0).getSize == 2
-        if (isSize2) t(0, 1) else t(0, 2)
+        if (isSize2) t(1, 2) else t(2, 4)
 
       case DUP2_X1 =>
         val isSize2 = peekStack(0).getSize == 2