3 files changed, 43 insertions, 0 deletions
diff --git a/clang/include/clang/Basic/ObjCRuntime.h b/clang/include/clang/Basic/ObjCRuntime.h
index c307c964339..f8b4826d3dd 100644
--- a/clang/include/clang/Basic/ObjCRuntime.h
+++ b/clang/include/clang/Basic/ObjCRuntime.h
@@ -173,6 +173,43 @@ public:
     llvm_unreachable("bad kind");
   }
 
+  /// Does this runtime provide entrypoints that are likely to be faster
+  /// than an ordinary message send of the "alloc" selector?
+  ///
+  /// The "alloc" entrypoint is guaranteed to be equivalent to just sending the
+  /// corresponding message.  If the entrypoint is implemented naively as just a
+  /// message send, using it is a trade-off: it sacrifices a few cycles of
+  /// overhead to save a small amount of code.  However, it's possible for
+  /// runtimes to detect and special-case classes that use "standard"
+  /// alloc behavior; if that's dynamically a large proportion of all
+  /// objects, using the entrypoint will also be faster than using a message
+  /// send.
+  ///
+  /// When this method returns true, Clang will turn non-super message sends of
+  /// certain selectors into calls to the corresponding entrypoint:
+  ///   alloc => objc_alloc
+  ///   allocWithZone:nil => objc_allocWithZone
+  bool shouldUseRuntimeFunctionsForAlloc() const {
+    switch (getKind()) {
+    case FragileMacOSX:
+      return false;
+    case MacOSX:
+      return getVersion() >= VersionTuple(10, 10);
+    case iOS:
+      return getVersion() >= VersionTuple(8);
+    case WatchOS:
+      return true;
+
+    case GCC:
+      return false;
+    case GNUstep:
+      return false;
+    case ObjFW:
+      return false;
+    }
+    llvm_unreachable("bad kind");
+  }
+
   /// Does this runtime supports optimized setter entrypoints?
   bool hasOptimizedSetter() const {
     switch (getKind()) {
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index cde7d805077..0a96820734d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1473,6 +1473,10 @@ def fno_zero_initialized_in_bss : Flag<["-"], "fno-zero-initialized-in-bss">, Gr
 def fobjc_arc : Flag<["-"], "fobjc-arc">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Synthesize retain and release calls for Objective-C pointers">;
 def fno_objc_arc : Flag<["-"], "fno-objc-arc">, Group<f_Group>;
+def fobjc_convert_messages_to_runtime_calls :
+  Flag<["-"], "fobjc-convert-messages-to-runtime-calls">, Group<f_Group>;
+def fno_objc_convert_messages_to_runtime_calls :
+  Flag<["-"], "fno-objc-convert-messages-to-runtime-calls">, Group<f_Group>, Flags<[CC1Option]>;
 def fobjc_arc_exceptions : Flag<["-"], "fobjc-arc-exceptions">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Use EH-safe code when synthesizing retains and releases in -fobjc-arc">;
 def fno_objc_arc_exceptions : Flag<["-"], "fno-objc-arc-exceptions">, Group<f_Group>;
diff --git a/clang/include/clang/Frontend/CodeGenOptions.def b/clang/include/clang/Frontend/CodeGenOptions.def
index e531bb80ff5..952aa588b60 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.def
+++ b/clang/include/clang/Frontend/CodeGenOptions.def
@@ -149,6 +149,8 @@ CODEGENOPT(UniformWGSize     , 1, 0) ///< -cl-uniform-work-group-size
 CODEGENOPT(NoZeroInitializedInBSS , 1, 0) ///< -fno-zero-initialized-in-bss.
 /// Method of Objective-C dispatch to use.
 ENUM_CODEGENOPT(ObjCDispatchMethod, ObjCDispatchMethodKind, 2, Legacy)
+/// Replace certain message sends with calls to ObjC runtime entrypoints
+CODEGENOPT(ObjCConvertMessagesToRuntimeCalls , 1, 1)
 CODEGENOPT(OmitLeafFramePointer , 1, 0) ///< Set when -momit-leaf-frame-pointer is
                                         ///< enabled.