fix for SI-5672

src/compiler/scala/tools/nsc/backend/icode/Members.scala

@@ -257,11 +257,23 @@ trait Members {
           var succ = bb
           do {
             succ = nextBlock(succ);
-            bb.removeLastInstruction
-            succ.toList foreach { i => bb.emit(i, i.pos) }
-            code.removeBlock(succ)
+            val lastInstr = bb.lastInstruction
+            /* Ticket SI-5672
+             * Besides removing the control-flow instruction at the end of `bb` (usually a JUMP), we have to pop any values it pushes.
+             * Examples:
+             *   `SWITCH` consisting of just the default case, or
+             *   `CJUMP(targetBlock, targetBlock, _, _)` ie where success and failure targets coincide (this one consumes two stack values).
+             */
+            val oldTKs = lastInstr.consumedTypes
+            assert(lastInstr.consumed == oldTKs.size, "Someone forgot to override consumedTypes() in " +  lastInstr)
+
+              bb.removeLastInstruction
+              for(tk <- oldTKs.reverse) { bb.emit(DROP(tk), lastInstr.pos) }
+              succ.toList foreach { i => bb.emit(i, i.pos) }
+              code.removeBlock(succ)
+              exh foreach { e => e.covered = e.covered - succ }
+
             nextBlock -= bb
-            exh foreach { e => e.covered = e.covered - succ }
           } while (nextBlock.isDefinedAt(succ))
           bb.close
         } else

src/compiler/scala/tools/nsc/backend/icode/Opcodes.scala

@@ -436,6 +436,8 @@ trait Opcodes { self: ICodes =>
       override def consumed = 1
       override def produced = 0
 
+      override val consumedTypes = List(INT)
+
       def flatTagsCount: Int = { var acc = 0; var rest = tags; while(rest.nonEmpty) { acc += rest.head.length; rest = rest.tail }; acc } // a one-liner
     }
 
@@ -470,6 +472,8 @@ trait Opcodes { self: ICodes =>
 
       override def consumed = 2
       override def produced = 0
+
+      override val consumedTypes = List(kind, kind)
     }
 
     /** This class represents a CZJUMP instruction
@@ -489,6 +493,8 @@ trait Opcodes { self: ICodes =>
 
       override def consumed = 1
       override def produced = 0
+
+      override val consumedTypes = List(kind)
     }
 
 
@@ -499,6 +505,8 @@ trait Opcodes { self: ICodes =>
     case class RETURN(kind: TypeKind) extends Instruction {
       override def consumed = if (kind == UNIT) 0 else 1
       override def produced = 0
+
+      // TODO override val consumedTypes = List(kind)
     }
 
     /** This class represents a THROW instruction

src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala

@@ -1646,7 +1646,7 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       // TODO: if patterns allow switch but the type of the scrutinee doesn't, cast (type-test) the scrutinee to the corresponding switchable type and switch on the result
       if (regularSwitchMaker.switchableTpe(scrutSym.tpe)) {
         val caseDefsWithDefault = regularSwitchMaker(cases map {c => (scrutSym, c)}, pt)
-        if (caseDefsWithDefault.length <= 2) None // not worth emitting a switch... also, the optimizer has trouble digesting tiny switches, apparently, so let's be nice and not generate them
+        if (caseDefsWithDefault isEmpty) None // not worth emitting a switch.
         else {
           // match on scrutSym -- converted to an int if necessary -- not on scrut directly (to avoid duplicating scrut)
           val scrutToInt: Tree =

test/files/run/inline-ex-handlers.check

@@ -1,27 +1,23 @@
 172c172
-<   locals: value x$1, value x1, value x2, value x
+<   locals: value x$1, value x1
 ---
->   locals: value x$1, value x1, value x2, value x, variable boxed1
+>   locals: value x$1, value x1, variable boxed1
 174c174
-<   blocks: [1,2,3,5,6,7]
+<   blocks: [1,2,3,4]
 ---
->   blocks: [1,3,5,6]
-180,182d179
+>   blocks: [1,3,4]
+186a187,188
+>     92	STORE_LOCAL(variable boxed1)
+>     92	LOAD_LOCAL(variable boxed1)
+195,197d196
 <     92	JUMP 2
 <     
 <   2: 
-194,196d190
-<     92	JUMP 7
-<     
-<   7: 
-204a199,200
->     92	STORE_LOCAL(variable boxed1)
->     92	LOAD_LOCAL(variable boxed1)
-395c391
+385c384
 <   blocks: [1,2,3,4,5,8,11,13,14,16]
 ---
 >   blocks: [1,2,3,5,8,11,13,14,16,17]
-419c415,424
+409c408,417
 <     103	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -34,15 +30,15 @@
 >     106	LOAD_LOCAL(value x3)
 >     106	IS_INSTANCE REF(class MyException)
 >     106	CZJUMP (BOOL)NE ? 5 : 11
-432,434d436
+422,424d429
 <     101	JUMP 4
 <     
 <   4: 
-522c524
+512c517
 <   blocks: [1,2,3,4,6,7,8,9,10]
 ---
 >   blocks: [1,2,3,4,6,7,8,9,10,11,12,13]
-551c553,558
+541c546,551
 <     306	THROW(MyException)
 ---
 >     ?	JUMP 11
@@ -51,7 +47,7 @@
 >     ?	LOAD_LOCAL(variable monitor4)
 >     305	MONITOR_EXIT
 >     ?	JUMP 12
-557c564,570
+547c557,563
 <     ?	THROW(Throwable)
 ---
 >     ?	JUMP 12
@@ -61,7 +57,7 @@
 >     304	MONITOR_EXIT
 >     ?	STORE_LOCAL(value t)
 >     ?	JUMP 13
-563c576,589
+553c569,582
 <     ?	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(value t)
@@ -78,30 +74,29 @@
 >     310	CALL_PRIMITIVE(EndConcat)
 >     310	CALL_METHOD scala.Predef.println (dynamic)
 >     310	JUMP 2
-587c613
+577c606
 <     catch (Throwable) in ArrayBuffer(7, 8, 9, 10) starting at: 6
 ---
 >     catch (Throwable) in ArrayBuffer(7, 8, 9, 10, 11) starting at: 6
-590c616
+580c609
 <     catch (Throwable) in ArrayBuffer(4, 6, 7, 8, 9, 10) starting at: 3
 ---
 >     catch (Throwable) in ArrayBuffer(4, 6, 7, 8, 9, 10, 11, 12) starting at: 3
-622c648
+612c641
 <   blocks: [1,2,3,4,5,6,7,9,10]
 ---
 >   blocks: [1,2,3,4,5,6,7,9,10,11,12]
-646c672,673
+636c665,671
 <     78	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
 >     ?	JUMP 11
-647a675,679
+>     
 >   11: 
 >     81	LOAD_LOCAL(value e)
 >     ?	STORE_LOCAL(variable exc1)
 >     ?	JUMP 12
->     
-675c707,721
+665c700,714
 <     81	THROW(Exception)
 ---
 >     ?	STORE_LOCAL(variable exc1)
@@ -119,15 +114,15 @@
 >     84	STORE_LOCAL(variable result)
 >     84	LOAD_LOCAL(variable exc1)
 >     84	THROW(Throwable)
-697c743
+687c736
 <     catch (<none>) in ArrayBuffer(4, 6, 7, 9) starting at: 3
 ---
 >     catch (<none>) in ArrayBuffer(4, 6, 7, 9, 11) starting at: 3
-723c769
+713c762
 <   blocks: [1,2,3,4,5,6,9,12,14,17,18,19,22,25,27,28,30,31]
 ---
 >   blocks: [1,2,3,4,5,6,9,12,14,17,18,19,22,25,27,28,30,31,32,33,34]
-747c793,800
+737c786,793
 <     172	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -138,12 +133,12 @@
 >     170	STORE_LOCAL(value x3)
 >     170	SCOPE_ENTER value x3
 >     170	JUMP 18
-803c856,857
+793c849,850
 <     177	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
 >     ?	JUMP 33
-807c861,868
+797c854,861
 <     170	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -154,17 +149,17 @@
 >     169	STORE_LOCAL(value x3)
 >     169	SCOPE_ENTER value x3
 >     169	JUMP 5
-840c901,902
+830c894,895
 <     182	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(variable exc2)
 >     ?	JUMP 34
-844c906,907
+834c899,900
 <     169	THROW(Throwable)
 ---
 >     ?	STORE_LOCAL(variable exc2)
 >     ?	JUMP 34
-845a909,921
+835a902,914
 >   34: 
 >     184	LOAD_MODULE object Predef
 >     184	CONSTANT("finally")
@@ -178,19 +173,19 @@
 >     185	LOAD_LOCAL(variable exc2)
 >     185	THROW(Throwable)
 >     
-866c942
+856c935
 <     catch (Throwable) in ArrayBuffer(17, 18, 19, 22, 25, 27, 28, 30) starting at: 4
 ---
 >     catch (Throwable) in ArrayBuffer(17, 18, 19, 22, 25, 27, 28, 30, 32) starting at: 4
-869c945
+859c938
 <     catch (<none>) in ArrayBuffer(4, 5, 6, 9, 12, 17, 18, 19, 22, 25, 27, 28, 30) starting at: 3
 ---
 >     catch (<none>) in ArrayBuffer(4, 5, 6, 9, 12, 17, 18, 19, 22, 25, 27, 28, 30, 32, 33) starting at: 3
-895c971
+885c964
 <   blocks: [1,2,3,6,7,8,11,14,16,17,19]
 ---
 >   blocks: [1,2,3,6,7,8,11,14,16,17,19,20]
-919c995,1002
+909c988,995
 <     124	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -201,15 +196,15 @@
 >     122	STORE_LOCAL(value x3)
 >     122	SCOPE_ENTER value x3
 >     122	JUMP 7
-979c1062
+969c1055
 <     catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 14, 16, 17, 19) starting at: 3
 ---
 >     catch (IllegalArgumentException) in ArrayBuffer(6, 7, 8, 11, 14, 16, 17, 19, 20) starting at: 3
-1005c1088
+995c1081
 <   blocks: [1,2,3,4,5,8,11,15,16,17,19]
 ---
 >   blocks: [1,2,3,5,8,11,15,16,17,19,20]
-1029c1112,1121
+1019c1105,1114
 <     148	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -222,15 +217,15 @@
 >     154	LOAD_LOCAL(value x3)
 >     154	IS_INSTANCE REF(class MyException)
 >     154	CZJUMP (BOOL)NE ? 5 : 11
-1050,1052d1141
+1040,1042d1134
 <     145	JUMP 4
 <     
 <   4: 
-1285c1374
+1275c1367
 <   blocks: [1,2,3,4,5,7]
 ---
 >   blocks: [1,2,3,4,5,7,8]
-1309c1398,1405
+1299c1391,1398
 <     38	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
@@ -241,16 +236,16 @@
 >     42	CONSTANT("IllegalArgumentException")
 >     42	CALL_METHOD scala.Predef.println (dynamic)
 >     42	JUMP 2
-1358c1454
+1348c1447
 <   blocks: [1,2,3,4,5,8,11,13,14,16,17,19]
 ---
 >   blocks: [1,2,3,5,8,11,13,14,16,17,19,20]
-1382c1478,1479
+1372c1471,1472
 <     203	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
 >     ?	JUMP 20
-1402c1499,1508
+1392c1492,1501
 <     209	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value ex5)
@@ -263,15 +258,15 @@
 >     212	LOAD_LOCAL(value x3)
 >     212	IS_INSTANCE REF(class MyException)
 >     212	CZJUMP (BOOL)NE ? 5 : 11
-1415,1417d1520
+1405,1407d1513
 <     200	JUMP 4
 <     
 <   4: 
-1477c1580
+1467c1573
 <   blocks: [1,2,3,4,5,7]
 ---
 >   blocks: [1,2,3,4,5,7,8]
-1501c1604,1611
+1491c1597,1604
 <     58	THROW(IllegalArgumentException)
 ---
 >     ?	STORE_LOCAL(value e)
@@ -282,11 +277,11 @@
 >     62	CONSTANT("RuntimeException")
 >     62	CALL_METHOD scala.Predef.println (dynamic)
 >     62	JUMP 2
-1550c1660
+1540c1653
 <   blocks: [1,2,3,4]
 ---
 >   blocks: [1,2,3,4,5]
-1570c1680,1685
+1560c1673,1678
 <     229	THROW(MyException)
 ---
 >     ?	JUMP 5
@@ -295,19 +290,19 @@
 >     ?	LOAD_LOCAL(variable monitor1)
 >     228	MONITOR_EXIT
 >     228	THROW(Throwable)
-1576c1691
+1566c1684
 <     ?	THROW(Throwable)
 ---
 >     228	THROW(Throwable)
-1604c1719
+1594c1712
 <   locals: value args, variable result, variable monitor2, variable monitorResult1
 ---
 >   locals: value exception$1, value args, variable result, variable monitor2, variable monitorResult1
-1606c1721
+1596c1714
 <   blocks: [1,2,3,4]
 ---
 >   blocks: [1,2,3,4,5]
-1629c1744,1752
+1619c1737,1745
 <     245	THROW(MyException)
 ---
 >     ?	STORE_LOCAL(value exception$1)
@@ -319,7 +314,7 @@
 >     ?	LOAD_LOCAL(variable monitor2)
 >     244	MONITOR_EXIT
 >     244	THROW(Throwable)
-1635c1758
+1625c1751
 <     ?	THROW(Throwable)
 ---
 >     244	THROW(Throwable)