Remove stale local variables and exception handlers after DCE

This is required for correctness of the generated bytecode. Exception
handlers and local variable descriptors specify code offset ranges.
These offsets have to exist, not be eliminated.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
index a788cea532..ba94a9c44c 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
@@ -14,6 +14,7 @@ import scala.annotation.switch
 import scala.reflect.internal.util.Statistics
 
 import scala.tools.asm
+import scala.tools.asm.tree.ClassNode
 
 /*
  *  Prepare in-memory representations of classfiles using the ASM Tree API, and serialize them to disk.
@@ -214,6 +215,14 @@ abstract class GenBCode extends BCodeSyncAndTry {
      *          - converting the plain ClassNode to byte array and placing it on queue-3
      */
     class Worker2 {
+      def localOptimizations(classNode: ClassNode): Unit = {
+        def dce(): Boolean = BackendStats.timed(BackendStats.bcodeDceTimer) {
+          if (settings.YoptUnreachableCode) opt.LocalOpt.removeUnreachableCode(classNode)
+          else false
+        }
+
+        dce()
+      }
 
       def run() {
         while (true) {
@@ -224,9 +233,7 @@ abstract class GenBCode extends BCodeSyncAndTry {
           }
           else {
             try {
-              val dceStart = Statistics.startTimer(BackendStats.bcodeDceTimer)
-              if (settings.YoptUnreachableCode) opt.LocalOpt.removeUnreachableCode(item.plain)
-              Statistics.stopTimer(BackendStats.bcodeDceTimer, dceStart)
+              localOptimizations(item.plain)
               addToQ3(item)
           } catch {
               case ex: Throwable =>