RemoteAST: Tweak swift-remoteast-test to reuse the context

I need this to reproduce a test failure.

Author: slavapestov

tools/swift-remoteast-test/swift-remoteast-test.cpp

@@ -40,15 +40,24 @@ using namespace swift::remoteAST;
 /// The context for the code we're running.  Set by the observer.
 static ASTContext *Context = nullptr;
 
+/// The RemoteAST for the code we're running.
+std::shared_ptr<MemoryReader> reader;
+std::unique_ptr<RemoteASTContext> remoteContext;
+
+static RemoteASTContext &getRemoteASTContext() {
+  if (remoteContext)
+    return *remoteContext;
+
+  std::shared_ptr<MemoryReader> reader(new InProcessMemoryReader());
+  remoteContext.reset(new RemoteASTContext(*Context, std::move(reader)));
+  return *remoteContext;
+}
+
 // FIXME: swiftcall
 /// func printType(forMetadata: Any.Type)
 LLVM_ATTRIBUTE_USED extern "C" void SWIFT_REMOTEAST_TEST_ABI
 printMetadataType(const Metadata *typeMetadata) {
-  assert(Context && "context was not set");
-
-  std::shared_ptr<MemoryReader> reader(new InProcessMemoryReader());
-  RemoteASTContext remoteAST(*Context, std::move(reader));
-
+  auto &remoteAST = getRemoteASTContext();
   auto &out = llvm::outs();
 
   auto result =
@@ -66,11 +75,7 @@ printMetadataType(const Metadata *typeMetadata) {
 /// func printDynamicType(_: AnyObject)
 LLVM_ATTRIBUTE_USED extern "C" void SWIFT_REMOTEAST_TEST_ABI
 printHeapMetadataType(void *object) {
-  assert(Context && "context was not set");
-
-  std::shared_ptr<MemoryReader> reader(new InProcessMemoryReader());
-  RemoteASTContext remoteAST(*Context, std::move(reader));
-
+  auto &remoteAST = getRemoteASTContext();
   auto &out = llvm::outs();
 
   auto metadataResult =
@@ -94,11 +99,7 @@ printHeapMetadataType(void *object) {
 
 static void printMemberOffset(const Metadata *typeMetadata,
                               StringRef memberName, bool passMetadata) {
-  assert(Context && "context was not set");
-
-  std::shared_ptr<MemoryReader> reader(new InProcessMemoryReader());
-  RemoteASTContext remoteAST(*Context, std::move(reader));
-
+  auto &remoteAST = getRemoteASTContext();
   auto &out = llvm::outs();
 
   // The first thing we have to do is get the type.
@@ -147,10 +148,7 @@ printTypeMetadataMemberOffset(const Metadata *typeMetadata,
 LLVM_ATTRIBUTE_USED extern "C" void SWIFT_REMOTEAST_TEST_ABI
 printDynamicTypeAndAddressForExistential(void *object,
                                          const Metadata *typeMetadata) {
-  assert(Context && "context was not set");
-  std::shared_ptr<MemoryReader> reader(new InProcessMemoryReader());
-  RemoteASTContext remoteAST(*Context, std::move(reader));
-
+  auto &remoteAST = getRemoteASTContext();
   auto &out = llvm::outs();
 
   // First, retrieve the static type of the existential, so we can understand