Change the driver's logic about Objective-C runtimes:  abstract out a
structure to hold inferred information, then propagate each invididual
bit down to -cc1.  Separate the bits of "supports weak" and "has a native
ARC runtime";  make the latter a CodeGenOption.

The tool chain is still driving this decision, because it's the place that
has the required deployment target information on Darwin, but at least it's
better-factored now.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134453 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index b4501ac..68ebc1b 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -19,6 +19,7 @@
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/HostInfo.h"
+#include "clang/Driver/ObjCRuntime.h"
 #include "clang/Driver/OptTable.h"
 #include "clang/Driver/Option.h"
 #include "clang/Driver/Options.h"
@@ -74,8 +75,7 @@
   return true;
 }
 
-/// Darwin provides an ARC runtime starting in MacOS X 10.7 and iOS 5.0.
-bool Darwin::HasARCRuntime() const {
+bool Darwin::hasARCRuntime() const {
   // FIXME: Remove this once there is a proper way to detect an ARC runtime
   // for the simulator.
   switch (ARCRuntimeForSimulator) {
@@ -93,6 +93,14 @@
     return !isMacosxVersionLT(10, 7);
 }
 
+/// Darwin provides an ARC runtime starting in MacOS X 10.7 and iOS 5.0.
+void Darwin::configureObjCRuntime(ObjCRuntime &runtime) const {
+  if (runtime.getKind() != ObjCRuntime::NeXT)
+    return ToolChain::configureObjCRuntime(runtime);
+
+  runtime.HasARC = runtime.HasWeak = hasARCRuntime();
+}
+
 // FIXME: Can we tablegen this?
 static const char *GetArmArchForMArch(llvm::StringRef Value) {
   if (Value == "armv6k")