Fixed a bug in the optimizer which was preventi...

Fixed a bug in the optimizer which was preventing private methods from
being inlined. Also relaxes a condition related to the "liftedTry"
problem: the inliner has to exclude certain methods from consideration
if there is a value on the stack and the method being inlined has
exception handlers. The new condition is as before, except that it does
not exclude methods of the "try/finally" variety (i.e. finalizers, but
no other exception handlers.) This is necessary to optimize this common
pattern:

  @inline private def foo(body: => Unit) {
    val saved = something
    try body
    finally something = saved
  }

The closure for "body" can be fully eliminated, but only if the contents
of foo can be inlined into the caller.

Closes #4764, review by rompf.

5 files changed, 112 insertions, 0 deletions

diff --git a/test/files/pos/inliner2.flags b/test/files/pos/inliner2.flags
new file mode 100644
index 0000000000..ea03113c66
--- /dev/null
+++ b/test/files/pos/inliner2.flags
@@ -0,0 +1 @@
+-optimise -Xfatal-warnings
\ No newline at end of file
diff --git a/test/files/pos/inliner2.scala b/test/files/pos/inliner2.scala
new file mode 100644
index 0000000000..bc83e04312
--- /dev/null
+++ b/test/files/pos/inliner2.scala
@@ -0,0 +1,57 @@
+// This isn't actually testing much, because no warning is emitted in versions
+// before the fix which comes with this because the method isn't even considered
+// for inlining due to the bug.
+class A {
+  private var debug = false
+  @inline private def ifelse[T](cond: => Boolean, ifPart: => T, elsePart: => T): T =
+    if (cond) ifPart else elsePart
+
+  final def bob1() = ifelse(debug, 1, 2)
+  final def bob2() = if (debug) 1 else 2
+}
+// Cool:
+//
+// % ls -1 /tmp/2901/
+// A$$anonfun$bob1$1.class
+// A$$anonfun$bob1$2.class
+// A$$anonfun$bob1$3.class
+// A.class
+// % ls -1 /tmp/trunk
+// A.class
+//
+// Observations:
+//
+// (1) The inlined version accesses the field: the explicit one calls the accessor.
+// (2) The inlined version fails to eliminate boxing.  With reference types it emits
+//     an unneeded checkcast.
+// (3) The private var debug is mangled to A$$debug, but after inlining it is never accessed
+//     from outside of the class and doesn't need mangling.
+// (4) We could forego emitting bytecode for ifelse entirely if it has been
+//     inlined at all sites.
+//
+// Generated bytecode for the above:
+//
+// public final int bob1();
+//   Code:
+//    Stack=1, Locals=1, Args_size=1
+//    0:  aload_0
+//    1:  getfield  #11; //Field A$$debug:Z
+//    4:  ifeq  14
+//    7:  iconst_1
+//    8:  invokestatic  #41; //Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
+//    11: goto  18
+//    14: iconst_2
+//    15: invokestatic  #41; //Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
+//    18: invokestatic  #45; //Method scala/runtime/BoxesRunTime.unboxToInt:(Ljava/lang/Object;)I
+//    21: ireturn
+//
+// public final int bob2();
+//   Code:
+//    Stack=1, Locals=1, Args_size=1
+//    0:  aload_0
+//    1:  invokevirtual #48; //Method A$$debug:()Z
+//    4:  ifeq  11
+//    7:  iconst_1
+//    8:  goto  12
+//    11: iconst_2
+//    12: ireturn
diff --git a/test/files/run/private-inline.check b/test/files/run/private-inline.check
new file mode 100644
index 0000000000..209e3ef4b6
--- /dev/null
+++ b/test/files/run/private-inline.check
@@ -0,0 +1 @@
+20
diff --git a/test/files/run/private-inline.flags b/test/files/run/private-inline.flags
new file mode 100644
index 0000000000..eb4d19bcb9
--- /dev/null
+++ b/test/files/run/private-inline.flags
@@ -0,0 +1 @@
+-optimise
\ No newline at end of file
diff --git a/test/files/run/private-inline.scala b/test/files/run/private-inline.scala
new file mode 100644
index 0000000000..5181ac8ba3
--- /dev/null
+++ b/test/files/run/private-inline.scala
@@ -0,0 +1,52 @@
+
+final class A {
+  private var x1 = false
+  var x2 = false
+
+  // manipulates private var
+  @inline private def wrapper1[T](body: => T): T = {
+    val saved = x1
+    x1 = true
+    try body
+    finally x1 = saved
+  }
+  // manipulates public var
+  @inline private def wrapper2[T](body: => T): T = {
+    val saved = x2
+    x2 = true
+    try body
+    finally x2 = saved
+  }
+
+  // not inlined
+  def f1a() = wrapper1(5)
+  // inlined!
+  def f1b() = identity(wrapper1(5))
+
+  // not inlined
+  def f2a() = wrapper2(5)
+  // inlined!
+  def f2b() = identity(wrapper2(5))
+}
+
+object Test {
+  def methodClasses = List("f1a", "f1b", "f2a", "f2b") map ("A$$anonfun$" + _ + "$1")
+
+  def main(args: Array[String]): Unit = {
+    val a = new A
+    import a._
+    println(f1a() + f1b() + f2a() + f2b())
+
+    // Don't know how else to test this: all these should have been
+    // inlined, so all should fail.
+    methodClasses foreach { clazz =>
+
+      val foundClass = (
+        try   Class.forName(clazz)
+        catch { case _ => null }
+      )
+
+      assert(foundClass == null, foundClass)
+    }
+  }
+}