Debug flag to print a summary of the inliner's work

Example output below. Note that inlining List.map fails because the
trait forwarder uses `INVOKESPECIAL` for now, will change with pr 5177.

$ cat Test.scala
class C {
  def foo = Map(1 -> 'a', 2 -> 'b')
  def bar(l: List[Int]) = l.map(_ + 1)
}

$ qsc -Yopt-log-inline _ -Yopt:l:classpath Test.scala
Inlining into C.foo (initially 36 instructions, ultimately 72):
  - Inlined scala/Predef$ArrowAssoc$.$minus$greater$extension (8 instructions) 2 times: the callee is annotated `@inline`

Inlining into C.bar (initially 12 instructions, ultimately 12):
  - Failed to inline scala/collection/immutable/List.map (the callee is a higher-order method, the argument for parameter (bf: Function1) is a function literal): The callee scala/collection/immutable/List::map(Lscala/Function1;Lscala/collection/generic/CanBuildFrom;)Ljava/lang/Object; contains the instruction INVOKESPECIAL scala/collection/TraversableLike.map (Lscala/Function1;Lscala/collection/generic/CanBuildFrom;)Ljava/lang/Object;
that would cause an IllegalAccessError when inlined into class C.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 9a0d86a94d..aa43772dd7 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -302,7 +302,9 @@ trait ScalaSettings extends AbsScalaSettings
   def YoptWarningNoInlineMissingBytecode            = YoptWarnings.contains(YoptWarningsChoices.noInlineMissingBytecode)
   def YoptWarningNoInlineMissingScalaInlineInfoAttr = YoptWarnings.contains(YoptWarningsChoices.noInlineMissingScalaInlineInfoAttr)
 
-  val YoptTrace = StringSetting("-Yopt-trace", "package/Class.method", "Trace the optimizer progress for a specific method.", "")
+  val YoptTrace = StringSetting("-Yopt-trace", "package/Class.method", "Trace the optimizer progress for methods; `_` to print all, prefix match to select.", "")
+
+  val YoptLogInline = StringSetting("-Yopt-log-inline", "package/Class.method", "Print a summary of inliner activity; `_` to print all, prefix match to select.", "")
 
   private def removalIn212 = "This flag is scheduled for removal in 2.12. If you have a case where you need this flag then please report a bug."