Merge pull request #3765 from retronym/ticket/8601

Reining on over eager optimizations (take 2)

2 files changed, 10 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/opt/ClosureElimination.scala b/src/compiler/scala/tools/nsc/backend/opt/ClosureElimination.scala
index c49f23852f..a866173a88 100644
--- a/src/compiler/scala/tools/nsc/backend/opt/ClosureElimination.scala
+++ b/src/compiler/scala/tools/nsc/backend/opt/ClosureElimination.scala
@@ -56,11 +56,8 @@ abstract class ClosureElimination extends SubComponent {
       case (BOX(t1), UNBOX(t2)) if (t1 == t2) =>
         Some(Nil)
 
-      case (LOAD_FIELD(sym, isStatic), DROP(_)) if !sym.hasAnnotation(definitions.VolatileAttr) =>
-        if (isStatic)
-          Some(Nil)
-        else
-          Some(DROP(REFERENCE(definitions.ObjectClass)) :: Nil)
+      case (LOAD_FIELD(sym, /* isStatic */false), DROP(_)) if !sym.hasAnnotation(definitions.VolatileAttr) && inliner.isClosureClass(sym.owner) =>
+        Some(DROP(REFERENCE(definitions.ObjectClass)) :: Nil)
 
       case _ => None
     }
diff --git a/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala b/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
index 90c37ba0b3..4b419b210c 100644
--- a/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
+++ b/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
@@ -169,9 +169,14 @@ abstract class DeadCodeElimination extends SubComponent {
 
             case RETURN(_) | JUMP(_) | CJUMP(_, _, _, _) | CZJUMP(_, _, _, _) | STORE_FIELD(_, _) |
                  THROW(_)   | LOAD_ARRAY_ITEM(_) | STORE_ARRAY_ITEM(_) | SCOPE_ENTER(_) | SCOPE_EXIT(_) | STORE_THIS(_) |
-                 LOAD_EXCEPTION(_) | SWITCH(_, _) | MONITOR_ENTER() | MONITOR_EXIT() | CHECK_CAST(_) =>
+                 LOAD_EXCEPTION(_) | SWITCH(_, _) | MONITOR_ENTER() | MONITOR_EXIT() | CHECK_CAST(_) | CREATE_ARRAY(_, _) =>
               moveToWorkList()
 
+            case LOAD_FIELD(sym, isStatic) if isStatic || !inliner.isClosureClass(sym.owner) =>
+              // static load may trigger static initization.
+              // non-static load can throw NPE (but we know closure fields can't be accessed via a
+              // null reference.
+              moveToWorkList()
             case CALL_METHOD(m1, _) if isSideEffecting(m1) =>
               moveToWorkList()
 
@@ -193,6 +198,8 @@ abstract class DeadCodeElimination extends SubComponent {
               moveToWorkListIf(necessary)
             case LOAD_MODULE(sym) if isLoadNeeded(sym) =>
               moveToWorkList() // SI-4859 Module initialization might side-effect.
+            case CALL_PRIMITIVE(Arithmetic(DIV | REM, INT | LONG) | ArrayLength(_)) =>
+              moveToWorkList() // SI-8601 Might divide by zero
             case _ => ()
               moveToWorkListIf(cond = false)
           }