Merge pull request scala#5290 from lrytz/sd48

SD-48 limit the lenght of inlined local variable names

Author: szeiger

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

@@ -1164,4 +1164,7 @@ object BTypes {
   // no static way (without symbol table instance) to get to nme.ScalaATTR / ScalaSignatureATTR
   val ScalaAttributeName    = "Scala"
   val ScalaSigAttributeName = "ScalaSig"
+
+  // when inlining, local variable names of the callee are prefixed with the name of the callee method
+  val InlinedLocalVariablePrefixMaxLenght = 128
 }

src/compiler/scala/tools/nsc/backend/jvm/opt/BytecodeUtils.scala

@@ -324,15 +324,33 @@ object BytecodeUtils {
    * Clone the local variable descriptors of `methodNode` and map their `start` and `end` labels
    * according to the `labelMap`.
    */
-  def cloneLocalVariableNodes(methodNode: MethodNode, labelMap: Map[LabelNode, LabelNode], prefix: String, shift: Int): List[LocalVariableNode] = {
-    methodNode.localVariables.iterator().asScala.map(localVariable => new LocalVariableNode(
-      prefix + localVariable.name,
-      localVariable.desc,
-      localVariable.signature,
-      labelMap(localVariable.start),
-      labelMap(localVariable.end),
-      localVariable.index + shift
-    )).toList
+  def cloneLocalVariableNodes(methodNode: MethodNode, labelMap: Map[LabelNode, LabelNode], calleeMethodName: String, shift: Int): List[LocalVariableNode] = {
+    methodNode.localVariables.iterator().asScala.map(localVariable => {
+      val name =
+        if (calleeMethodName.length + localVariable.name.length < BTypes.InlinedLocalVariablePrefixMaxLenght) {
+          calleeMethodName + "_" + localVariable.name
+        } else {
+          val parts = localVariable.name.split("_").toVector
+          val (methNames, varName) = (calleeMethodName +: parts.init, parts.last)
+          // keep at least 5 characters per method name
+          val maxNumMethNames = BTypes.InlinedLocalVariablePrefixMaxLenght / 5
+          val usedMethNames =
+            if (methNames.length < maxNumMethNames) methNames
+            else {
+              val half = maxNumMethNames / 2
+              methNames.take(half) ++ methNames.takeRight(half)
+            }
+          val charsPerMethod = BTypes.InlinedLocalVariablePrefixMaxLenght / usedMethNames.length
+          usedMethNames.foldLeft("")((res, methName) => res + methName.take(charsPerMethod) + "_") + varName
+        }
+      new LocalVariableNode(
+        name,
+        localVariable.desc,
+        localVariable.signature,
+        labelMap(localVariable.start),
+        labelMap(localVariable.end),
+        localVariable.index + shift)
+    }).toList
   }
 
   /**

src/compiler/scala/tools/nsc/backend/jvm/opt/Inliner.scala

@@ -382,7 +382,7 @@ class Inliner[BT <: BTypes](val btypes: BT) {
     callsiteMethod.instructions.insert(callsiteInstruction, clonedInstructions)
     callsiteMethod.instructions.remove(callsiteInstruction)
 
-    callsiteMethod.localVariables.addAll(cloneLocalVariableNodes(callee, labelsMap, callee.name + "_", localVarShift).asJava)
+    callsiteMethod.localVariables.addAll(cloneLocalVariableNodes(callee, labelsMap, callee.name, localVarShift).asJava)
     // prepend the handlers of the callee. the order of handlers matters: when an exception is thrown
     // at some instruction, the first handler guarding that instruction and having a matching exception
     // type is executed. prepending the callee's handlers makes sure to test those handlers first if

test/junit/scala/tools/nsc/backend/jvm/opt/InlinerTest.scala

@@ -1587,4 +1587,41 @@ class InlinerTest extends BytecodeTesting {
     val List(c, t) = compile(code)
     assertNoIndy(getMethod(c, "t1"))
   }
+
+  @Test
+  def limitInlinedLocalVariableNames(): Unit = {
+    val code =
+      """class C {
+        |  def f(x: Int): Int = x
+        |  @inline final def methodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(param: Int) =
+        |    f(param)
+        |  @inline final def anotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(param: Int) =
+        |    methodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(param))
+        |  @inline final def oneMoreMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(param: Int) =
+        |    anotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(param))
+        |  @inline final def yetAnotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(param: Int) =
+        |    oneMoreMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(param))
+        |  @inline final def oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(param: Int) =
+        |    yetAnotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(param))
+        |  def t(p: Int) =
+        |    oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(p)) +
+        |    oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence(f(p))
+        |}
+      """.stripMargin
+
+    val List(c) = compile(code)
+    assertEquals(getAsmMethod(c, "t").localVariables.asScala.toList.map(l => (l.name, l.index)).sortBy(_._2),List(
+      ("this",0),
+      ("p",1),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence_param",2),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchS_yetAnotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFren_param",3),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLik_yetAnotherMethodWithVeryVeryLongNameAlmost_oneMoreMethodWithVeryVeryLongNameAlmostLik_param",4),
+      ("oneLastMethodWithVeryVeryLongNam_yetAnotherMethodWithVeryVeryLong_oneMoreMethodWithVeryVeryLongNam_anotherMethodWithVeryVeryLongNam_param",5),
+      ("oneLastMethodWithVeryVery_yetAnotherMethodWithVeryV_oneMoreMethodWithVeryVery_anotherMethodWithVeryVery_methodWithVeryVeryLongNam_param",6),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchSentence_param",7),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFrenchS_yetAnotherMethodWithVeryVeryLongNameAlmostLikeAGermanWordOrAFren_param",8),
+      ("oneLastMethodWithVeryVeryLongNameAlmostLik_yetAnotherMethodWithVeryVeryLongNameAlmost_oneMoreMethodWithVeryVeryLongNameAlmostLik_param",9),
+      ("oneLastMethodWithVeryVeryLongNam_yetAnotherMethodWithVeryVeryLong_oneMoreMethodWithVeryVeryLongNam_anotherMethodWithVeryVeryLongNam_param",10),
+      ("oneLastMethodWithVeryVery_yetAnotherMethodWithVeryV_oneMoreMethodWithVeryVery_anotherMethodWithVeryVery_methodWithVeryVeryLongNam_param",11)))
+  }
 }