[NFC] [AutoDiff] Minor cleanup.

include/swift/Basic/LangOptions.h

@@ -329,7 +329,9 @@ namespace swift {
 
     /// Whether to enable experimental differentiable programming features:
     /// `@differentiable` declaration attribute, etc.
-    bool EnableExperimentalDifferentiableProgramming = false;
+    // SWIFT_ENABLE_TENSORFLOW
+    // The default on tensorflow branch is true. On master, it is false.
+    bool EnableExperimentalDifferentiableProgramming = true;
 
     /// Whether to enable #quote, #unquote and @quoted.
     bool EnableExperimentalQuasiquotes = false;

unittests/AST/SILAutoDiffIndices.cpp → unittests/AST/AutoDiffIndexSubset.cpp

@@ -1,4 +1,4 @@
-//===--- SILAutoDiffIndices.cpp - Tests SILAutoDiffIndices ----------------===//
+//===--- AutoDiffIndexSubset.cpp - Tests AutoDiffIndexSubset --------------===//
 //
 // This source file is part of the Swift.org open source project
 //

unittests/AST/CMakeLists.txt

@@ -1,8 +1,8 @@
 add_swift_unittest(SwiftASTTests
   ArithmeticEvaluator.cpp
-  DiagnosticConsumerTests.cpp
   # SWIFT_ENABLE_TENSORFLOW
-  SILAutoDiffIndices.cpp
+  AutoDiffIndexSubset.cpp
+  DiagnosticConsumerTests.cpp
   SourceLocTests.cpp
   TestContext.cpp
   TypeMatchTests.cpp