Enable nullness analysis in the inliner

When inlining an instance call, the inliner has to ensure that a NPE
is still thrown if the receiver object is null. By using the nullness
analysis, we can avoid emitting this code in case the receiver object
is known to be not-null.

3 files changed, 19 insertions, 3 deletions

diff --git a/test/files/neg/inlineMaxSize.check b/test/files/neg/inlineMaxSize.check
index d218a8b6e2..9d790e154c 100644
--- a/test/files/neg/inlineMaxSize.check
+++ b/test/files/neg/inlineMaxSize.check
@@ -2,8 +2,8 @@ inlineMaxSize.scala:7: warning: C::i()I is annotated @inline but could not be in
 The size of the callsite method C::j()I
 would exceed the JVM method size limit after inlining C::i()I.
 
-  @inline final def j = i + i
-                            ^
+  @inline final def j = i + i + i
+                                ^
 error: No warnings can be incurred under -Xfatal-warnings.
 one warning found
 one error found
diff --git a/test/files/neg/inlineMaxSize.scala b/test/files/neg/inlineMaxSize.scala
index 16dc0d9538..9d2db1a357 100644
--- a/test/files/neg/inlineMaxSize.scala
+++ b/test/files/neg/inlineMaxSize.scala
@@ -4,5 +4,5 @@ class C {
   @inline final def g = f + f + f + f + f + f + f + f + f + f
   @inline final def h = g + g + g + g + g + g + g + g + g + g
   @inline final def i = h + h + h + h + h + h + h + h + h + h
-  @inline final def j = i + i
+  @inline final def j = i + i + i
 }
diff --git a/test/junit/scala/tools/nsc/backend/jvm/opt/InlinerTest.scala b/test/junit/scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
index 0fc3601603..b8c5f85c49 100644
--- a/test/junit/scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
+++ b/test/junit/scala/tools/nsc/backend/jvm/opt/InlinerTest.scala
@@ -975,4 +975,20 @@ class InlinerTest extends ClearAfterClass {
     val List(c) = compile(code)
     assertInvoke(getSingleMethod(c, "t"), "java/lang/Error", "<init>")
   }
+
+  @Test
+  def noRedunantNullChecks(): Unit = {
+    val code =
+      """class C {
+        |  @inline final def f: String = "hai!"
+        |  def t(c: C) = {c.f; c.f} // null check on the first, but not the second
+        |}
+      """.stripMargin
+
+    val List(c) = compile(code)
+    val t = getSingleMethod(c, "t").instructions
+    assertNoInvoke(t)
+    assert(2 == t.collect({case Ldc(_, "hai!") => }).size)     // twice the body of f
+    assert(1 == t.collect({case Jump(IFNONNULL, _) => }).size) // one single null check
+  }
 }