Convert some ObjC alloc msgSends to runtime calls

[pete]

Summary

It is faster to directly call the ObjC runtime for methods such as alloc/allocWithZone instead of sending a message to those functions.

This patch adds support for converting messages to alloc/allocWithZone to their equivalent runtime calls.

Tests included for the positive case of applying this transformation, negative tests that we ensure we only convert "alloc" to objc_alloc, not "alloc2", and also a driver test to ensure we enable this only for supported runtime versions.

[rjmccall]

include/clang/Basic/ObjCRuntime.h

189

"corresponding"

190

The actual code also rewrites allocWithZone: (which is why it's reasonable to pluralize "functions" in the method name).

200

Did we really add this so long ago? Wow.

lib/CodeGen/CGObjC.cpp

383

Using the word "selector" instead of "name" is both more technically accurate and nicely side-steps the difference between "alloc" (which you want to include) and "alloc:" (which you don't). You have this correct in the code.

[pete]

Thanks for the review. Have fixed the comments as suggested.

[pete]

include/clang/Basic/ObjCRuntime.h

200

Yeah! I was thinking that too!

[rjmccall]

lib/CodeGen/CGObjC.cpp

385

Actually, I'd suggest just rewriting this comment to look like the next one, it conveys the same idea but much more succinctly.

390

You should check !Args.front().hasLValue() here before calling getKnownRValue(). The test case would be some silly example where -allocWithZone: is declared with a parameter that's some big struct and the argument expression just loads it immediately from an l-value. Or you could just check that the parameter type is a pointer type.

[pete]

Added test for integer argument and updated code to only accept pointer types to allocWithZone.

[rjmccall]

LGTM.

[pete]

In D55349#1323926, @rjmccall wrote:

LGTM.

Thanks for the review! Landed in r348687.

include/clang/Basic/ObjCRuntime.h

bool hasNativeARC() const {
 
     case GCC: return false;
     case GNUstep: return getVersion() >= VersionTuple(1, 6);
     case ObjFW: return true;
     }
     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 correspond entrypoint:
+  ///   alloc => objc_alloc
+  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()) {
       case MacOSX:
         return getVersion() >= VersionTuple(10, 8);
       case iOS:
         return (getVersion() >= VersionTuple(6));
       case WatchOS:

include/clang/Driver/Options.td

 def fno_unwind_tables : Flag<["-"], "fno-unwind-tables">, Group<f_Group>;
 def fno_verbose_asm : Flag<["-"], "fno-verbose-asm">, Group<f_Group>;
 def fno_working_directory : Flag<["-"], "fno-working-directory">, Group<f_Group>;
 def fno_wrapv : Flag<["-"], "fno-wrapv">, Group<f_Group>;
 def fno_zero_initialized_in_bss : Flag<["-"], "fno-zero-initialized-in-bss">, Group<f_Group>;
 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>;
 def fobjc_atdefs : Flag<["-"], "fobjc-atdefs">, Group<clang_ignored_f_Group>;
 def fobjc_call_cxx_cdtors : Flag<["-"], "fobjc-call-cxx-cdtors">, Group<clang_ignored_f_Group>;
 def fobjc_exceptions: Flag<["-"], "fobjc-exceptions">, Group<f_Group>,
   HelpText<"Enable Objective-C exceptions">, Flags<[CC1Option]>;
 def fapplication_extension : Flag<["-"], "fapplication-extension">,

include/clang/Frontend/CodeGenOptions.def

 /// overflowing conversion matches the overflowing behavior of a target's native
 /// float-to-int conversion instructions.
 CODEGENOPT(StrictFloatCastOverflow, 1, 1)
 
 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.
 
 VALUE_CODEGENOPT(OptimizationLevel, 2, 0) ///< The -O[0-3] option specified.
 VALUE_CODEGENOPT(OptimizeSize, 2, 0) ///< If -Os (==1) or -Oz (==2) is specified.
 
 /// Choose profile instrumenation kind or no instrumentation.
 ENUM_CODEGENOPT(ProfileInstr, ProfileInstrKind, 2, ProfileNone)

lib/CodeGen/CGObjC.cpp

if (CE->getCastKind() == CK_LValueToRValue) {
       if (CE->getSubExpr()->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
         return CE->getSubExpr();
     }
   }
 
   return nullptr;
 }
 
+/// The ObjC runtime may provide entrypoints that are likely to be faster
+/// than an ordinary message send of the appropriate selector.
+///
+/// The entrypoints are 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"
+/// behavior; if that's dynamically a large proportion of all objects, using
+/// the entrypoint will also be faster than using a message send.
+///
+/// If the runtime does support a required entrypoint, then this method will
+/// generate a call and return the resulting value.  Otherwise it will return
+/// None and the caller can generate a msgSend instead.
+static Optional<llvm::Value *>
+tryGenerateSpecializedMessageSend(CodeGenFunction &CGF, QualType ResultType,
+                                  llvm::Value *Receiver,
+                                  const CallArgList& Args, Selector Sel,
+                                  const ObjCMethodDecl *method) {
+  auto &CGM = CGF.CGM;
+  if (!CGM.getCodeGenOpts().ObjCConvertMessagesToRuntimeCalls)
+    return None;
+
+  auto &Runtime = CGM.getLangOpts().ObjCRuntime;
+  switch (Sel.getMethodFamily()) {
+  case OMF_alloc:
+    // Make sure the name is exactly 'alloc'.  All methods with that
+    // prefix are identified as OMF_alloc but we only want to call the
+    // runtime for this version.
+    if (Runtime.shouldUseRuntimeFunctionsForAlloc() &&
+        ResultType->isObjCObjectPointerType()) {
+        if (Sel.isUnarySelector() && Sel.getNameForSlot(0) == "alloc")
+          return CGF.EmitObjCAlloc(Receiver, CGF.ConvertType(ResultType));
+        // [Foo allocWithZone:nil] -> objc_allocWithZone(Foo)
+        if (Sel.isKeywordSelector() && Sel.getNumArgs() == 1 &&
+            Args.size() == 1 && Args.front().getKnownRValue().isScalar() &&
+            Sel.getNameForSlot(0) == "allocWithZone") {
+          const llvm::Value* arg = Args.front().getKnownRValue().getScalarVal();
+          if (isa<llvm::ConstantPointerNull>(arg))
+            return CGF.EmitObjCAllocWithZone(Receiver,
+                                             CGF.ConvertType(ResultType));
+          return None;
+        }
+    }
+    break;
+
+  default:
+    break;
+  }
+  return None;
+}
+
 RValue CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E,
                                             ReturnValueSlot Return) {
   // Only the lookup mechanism and first two arguments of the method
   // implementation vary between runtimes.  We can get the receiver and
   // arguments in generic code.
 
   bool isDelegateInit = E->isDelegateInitCall();
 
result = Runtime.GenerateMessageSendSuper(*this, Return, ResultType,
                                               E->getSelector(),
                                               OMD->getClassInterface(),
                                               isCategoryImpl,
                                               Receiver,
                                               isClassMessage,
                                               Args,
                                               method);
   } else {
+    // Call runtime methods directly if we can.
+    if (Optional<llvm::Value *> SpecializedResult =
+            tryGenerateSpecializedMessageSend(*this, ResultType, Receiver, Args,
+                                              E->getSelector(), method)) {
+      result = RValue::get(SpecializedResult.getValue());
+    } else {
       result = Runtime.GenerateMessageSend(*this, Return, ResultType,
-                                         E->getSelector(),
-                                         Receiver, Args, OID,
-                                         method);
+                                           E->getSelector(), Receiver, Args,
+                                           OID, method);
+    }
   }
 
   // For delegate init calls in ARC, implicitly store the result of
   // the call back into self.  This takes ownership of the value.
   if (isDelegateInit) {
     Address selfAddr =
       GetAddrOfLocalVar(cast<ObjCMethodDecl>(CurCodeDecl)->getSelfDecl());
     llvm::Value *newSelf = result.getScalarVal();
static llvm::Constant *createARCRuntimeFunction(CodeGenModule &CGM,
   return RTF;
 }
 
 /// Perform an operation having the signature
 ///   i8* (i8*)
 /// where a null input causes a no-op and returns null.
 static llvm::Value *emitARCValueOperation(CodeGenFunction &CGF,
                                           llvm::Value *value,
+                                          llvm::Type *returnType,
                                           llvm::Constant *&fn,
                                           StringRef fnName,
                                           bool isTailCall = false) {
   if (isa<llvm::ConstantPointerNull>(value))
     return value;
 
   if (!fn) {
     llvm::FunctionType *fnType =
       llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, false);
     fn = createARCRuntimeFunction(CGF.CGM, fnType, fnName);
   }
 
   // Cast the argument to 'id'.
-  llvm::Type *origType = value->getType();
+  llvm::Type *origType = returnType ? returnType : value->getType();
   value = CGF.Builder.CreateBitCast(value, CGF.Int8PtrTy);
 
   // Call the function.
   llvm::CallInst *call = CGF.EmitNounwindRuntimeCall(fn, value);
   if (isTailCall)
     call->setTailCall();
 
   // Cast the result back to the original type.
if (type->isBlockPointerType())
     return EmitARCRetainBlock(value, /*mandatory*/ false);
   else
     return EmitARCRetainNonBlock(value);
 }
 
 /// Retain the given object, with normal retain semantics.
 ///   call i8* \@objc_retain(i8* %value)
 llvm::Value *CodeGenFunction::EmitARCRetainNonBlock(llvm::Value *value) {
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
                                CGM.getObjCEntrypoints().objc_retain,
                                "objc_retain");
 }
 
 /// Retain the given block, with _Block_copy semantics.
 ///   call i8* \@objc_retainBlock(i8* %value)
 ///
 /// \param mandatory - If false, emit the call with metadata
 /// indicating that it's okay for the optimizer to eliminate this call
 /// if it can prove that the block never escapes except down the stack.
 llvm::Value *CodeGenFunction::EmitARCRetainBlock(llvm::Value *value,
                                                  bool mandatory) {
   llvm::Value *result
-    = emitARCValueOperation(*this, value,
+    = emitARCValueOperation(*this, value, nullptr,
                             CGM.getObjCEntrypoints().objc_retainBlock,
                             "objc_retainBlock");
 
   // If the copy isn't mandatory, add !clang.arc.copy_on_escape to
   // tell the optimizer that it doesn't need to do this copy if the
   // block doesn't escape, where being passed as an argument doesn't
   // count as escaping.
   if (!mandatory && isa<llvm::Instruction>(result)) {

 /// Retain the given object which is the result of a function call.
 ///   call i8* \@objc_retainAutoreleasedReturnValue(i8* %value)
 ///
 /// Yes, this function name is one character away from a different
 /// call with completely different semantics.
 llvm::Value *
 CodeGenFunction::EmitARCRetainAutoreleasedReturnValue(llvm::Value *value) {
   emitAutoreleasedReturnValueMarker(*this);
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
               CGM.getObjCEntrypoints().objc_retainAutoreleasedReturnValue,
                                "objc_retainAutoreleasedReturnValue");
 }
 
 /// Claim a possibly-autoreleased return value at +0.  This is only
 /// valid to do in contexts which do not rely on the retain to keep
 /// the object valid for all of its uses; for example, when
 /// the value is ignored, or when it is being assigned to an
 /// __unsafe_unretained variable.
 ///
 ///   call i8* \@objc_unsafeClaimAutoreleasedReturnValue(i8* %value)
 llvm::Value *
 CodeGenFunction::EmitARCUnsafeClaimAutoreleasedReturnValue(llvm::Value *value) {
   emitAutoreleasedReturnValueMarker(*this);
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
               CGM.getObjCEntrypoints().objc_unsafeClaimAutoreleasedReturnValue,
                                "objc_unsafeClaimAutoreleasedReturnValue");
 }
 
 /// Release the given object.
 ///   call void \@objc_release(i8* %value)
 void CodeGenFunction::EmitARCRelease(llvm::Value *value,
                                      ARCPreciseLifetime_t precise) {
llvm::Value *CodeGenFunction::EmitARCStoreStrong(LValue dst,
   EmitARCRelease(oldValue, dst.isARCPreciseLifetime());
 
   return newValue;
 }
 
 /// Autorelease the given object.
 ///   call i8* \@objc_autorelease(i8* %value)
 llvm::Value *CodeGenFunction::EmitARCAutorelease(llvm::Value *value) {
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
                                CGM.getObjCEntrypoints().objc_autorelease,
                                "objc_autorelease");
 }
 
 /// Autorelease the given object.
 ///   call i8* \@objc_autoreleaseReturnValue(i8* %value)
 llvm::Value *
 CodeGenFunction::EmitARCAutoreleaseReturnValue(llvm::Value *value) {
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
                             CGM.getObjCEntrypoints().objc_autoreleaseReturnValue,
                                "objc_autoreleaseReturnValue",
                                /*isTailCall*/ true);
 }
 
 /// Do a fused retain/autorelease of the given object.
 ///   call i8* \@objc_retainAutoreleaseReturnValue(i8* %value)
 llvm::Value *
 CodeGenFunction::EmitARCRetainAutoreleaseReturnValue(llvm::Value *value) {
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
                      CGM.getObjCEntrypoints().objc_retainAutoreleaseReturnValue,
                                "objc_retainAutoreleaseReturnValue",
                                /*isTailCall*/ true);
 }
 
 /// Do a fused retain/autorelease of the given object.
 ///   call i8* \@objc_retainAutorelease(i8* %value)
 /// or
llvm::Value *CodeGenFunction::EmitARCRetainAutorelease(QualType type,
   value = EmitARCAutorelease(value);
   return Builder.CreateBitCast(value, origType);
 }
 
 /// Do a fused retain/autorelease of the given object.
 ///   call i8* \@objc_retainAutorelease(i8* %value)
 llvm::Value *
 CodeGenFunction::EmitARCRetainAutoreleaseNonBlock(llvm::Value *value) {
-  return emitARCValueOperation(*this, value,
+  return emitARCValueOperation(*this, value, nullptr,
                                CGM.getObjCEntrypoints().objc_retainAutorelease,
                                "objc_retainAutorelease");
 }
 
 /// i8* \@objc_loadWeak(i8** %addr)
 /// Essentially objc_autorelease(objc_loadWeakRetained(addr)).
 llvm::Value *CodeGenFunction::EmitARCLoadWeak(Address addr) {
   return emitARCLoadOperation(*this, addr,
llvm::Value *CodeGenFunction::EmitObjCMRRAutoreleasePoolPush() {
   Selector InitSel = getContext().Selectors.getSelector(0, &II);
   RValue InitRV =
     Runtime.GenerateMessageSend(*this, ReturnValueSlot(),
                                 getContext().getObjCIdType(),
                                 InitSel, Receiver, Args);
   return InitRV.getScalarVal();
 }
 
+/// Allocate the given objc object.
+///   call i8* \@objc_alloc(i8* %value)
+llvm::Value *CodeGenFunction::EmitObjCAlloc(llvm::Value *value,
+                                            llvm::Type *resultType) {
+  return emitARCValueOperation(*this, value, resultType,
+                               CGM.getObjCEntrypoints().objc_alloc,
+                               "objc_alloc");
+}
+
+/// Allocate the given objc object.
+///   call i8* \@objc_allocWithZone(i8* %value)
+llvm::Value *CodeGenFunction::EmitObjCAllocWithZone(llvm::Value *value,
+                                                    llvm::Type *resultType) {
+  return emitARCValueOperation(*this, value, resultType,
+                               CGM.getObjCEntrypoints().objc_allocWithZone,
+                               "objc_allocWithZone");
+}
+
 /// Produce the code to do a primitive release.
 /// [tmp drain];
 void CodeGenFunction::EmitObjCMRRAutoreleasePoolPop(llvm::Value *Arg) {
   IdentifierInfo *II = &CGM.getContext().Idents.get("drain");
   Selector DrainSel = getContext().Selectors.getSelector(0, &II);
   CallArgList Args;
   CGM.getObjCRuntime().GenerateMessageSend(*this, ReturnValueSlot(),
                               getContext().VoidTy, DrainSel, Arg, Args);

lib/CodeGen/CodeGenFunction.h

public:
 
   std::pair<LValue,llvm::Value*>
   EmitARCStoreAutoreleasing(const BinaryOperator *e);
   std::pair<LValue,llvm::Value*>
   EmitARCStoreStrong(const BinaryOperator *e, bool ignored);
   std::pair<LValue,llvm::Value*>
   EmitARCStoreUnsafeUnretained(const BinaryOperator *e, bool ignored);
 
+  llvm::Value *EmitObjCAlloc(llvm::Value *value,
+                             llvm::Type *returnType);
+  llvm::Value *EmitObjCAllocWithZone(llvm::Value *value,
+                                     llvm::Type *returnType);
   llvm::Value *EmitObjCThrowOperand(const Expr *expr);
   llvm::Value *EmitObjCConsumeObject(QualType T, llvm::Value *Ptr);
   llvm::Value *EmitObjCExtendObjectLifetime(QualType T, llvm::Value *Ptr);
 
   llvm::Value *EmitARCExtendBlockObject(const Expr *expr);
   llvm::Value *EmitARCReclaimReturnedObject(const Expr *e,
                                             bool allowUnsafeClaim);
   llvm::Value *EmitARCRetainScalarExpr(const Expr *expr);

lib/CodeGen/CodeGenModule.h

bool operator<(const OrderGlobalInits &RHS) const {
     return std::tie(priority, lex_order) <
            std::tie(RHS.priority, RHS.lex_order);
   }
 };
 
 struct ObjCEntrypoints {
   ObjCEntrypoints() { memset(this, 0, sizeof(*this)); }
 
-    /// void objc_autoreleasePoolPop(void*);
+  /// void objc_alloc(id);
+  llvm::Constant *objc_alloc;
+
+  /// void objc_allocWithZone(id);
+  llvm::Constant *objc_allocWithZone;
+
   llvm::Constant *objc_autoreleasePoolPop;
 
   /// void *objc_autoreleasePoolPush(void);
   llvm::Constant *objc_autoreleasePoolPush;
 
   /// id objc_autorelease(id);
   llvm::Constant *objc_autorelease;
 

lib/Driver/ToolChains/Clang.cpp

static void RenderObjCOptions(const ToolChain &TC, const Driver &D,
 
   // Silence warning for full exception code emission options when explicitly
   // set to use no ARC.
   if (Args.hasArg(options::OPT_fno_objc_arc)) {
     Args.ClaimAllArgs(options::OPT_fobjc_arc_exceptions);
     Args.ClaimAllArgs(options::OPT_fno_objc_arc_exceptions);
   }
 
+  // Allow the user to control whether messages can be converted to runtime
+  // functions.
+  if (types::isObjC(Input.getType())) {
+    auto *Arg = Args.getLastArg(
+        options::OPT_fobjc_convert_messages_to_runtime_calls,
+        options::OPT_fno_objc_convert_messages_to_runtime_calls);
+    if (Arg &&
+        Arg->getOption().matches(
+            options::OPT_fno_objc_convert_messages_to_runtime_calls))
+      CmdArgs.push_back("-fno-objc-convert-messages-to-runtime-calls");
+  }
+
   // -fobjc-infer-related-result-type is the default, except in the Objective-C
   // rewriter.
   if (InferCovariantReturns)
     CmdArgs.push_back("-fno-objc-infer-related-result-type");
 
   // Pass down -fobjc-weak or -fno-objc-weak if present.
   if (types::isObjC(Input.getType())) {
     auto WeakArg =

lib/Frontend/CompilerInvocation.cpp

if (Method == ~0U) {
       Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Name;
       Success = false;
     } else {
       Opts.setObjCDispatchMethod(
         static_cast<CodeGenOptions::ObjCDispatchMethodKind>(Method));
     }
   }
 
+
+  if (Args.hasArg(OPT_fno_objc_convert_messages_to_runtime_calls))
+    Opts.ObjCConvertMessagesToRuntimeCalls = 0;
+
   if (Args.getLastArg(OPT_femulated_tls) ||
       Args.getLastArg(OPT_fno_emulated_tls)) {
     Opts.ExplicitEmulatedTLS = true;
     Opts.EmulatedTLS =
         Args.hasFlag(OPT_femulated_tls, OPT_fno_emulated_tls, false);
   }
 
   if (Arg *A = Args.getLastArg(OPT_ftlsmodel_EQ)) {

test/CodeGenObjC/convert-messages-to-runtime-calls.m

+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s -fno-objc-convert-messages-to-runtime-calls | FileCheck %s --check-prefix=MSGS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.9.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// RUN: %clang_cc1 -fobjc-runtime=macosx-fragile-10.10.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// RUN: %clang_cc1 -fobjc-runtime=ios-8.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=ios-7.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=MSGS
+// Note: This line below is for tvos for which the driver passes through to use the ios9.0 runtime.
+// RUN: %clang_cc1 -fobjc-runtime=ios-9.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+// RUN: %clang_cc1 -fobjc-runtime=watchos-2.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CALLS
+
+#define nil (id)0
+
+@interface NSObject
++ (id)alloc;
++ (id)allocWithZone:(void*)zone;
++ (id)alloc2;
+@end
+
+// CHECK-LABEL: define {{.*}}void @test1
+void test1(id x) {
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_alloc}}
+  [NSObject alloc];
+  [NSObject allocWithZone:nil];
+}
+
+// CHECK-LABEL: define {{.*}}void @test2
+void test2(void* x) {
+  // MSGS: {{call.*@objc_msgSend}}
+  // MSGS: {{call.*@objc_msgSend}}
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_msgSend}}
+  [NSObject alloc2];
+  [NSObject allocWithZone:(void*)-1];
+  [NSObject allocWithZone:x];
+}
+
+@class A;
+@interface B
++ (A*) alloc;
++ (A*)allocWithZone:(void*)zone;
+@end
+
+// Make sure we get a bitcast on the return type as the
+// call will return i8* which we have to cast to A*
+// CHECK-LABEL: define {{.*}}void @test_alloc_class_ptr
+A* test_alloc_class_ptr() {
+  // CALLS: {{call.*@objc_alloc}}
+  // CALLS-NEXT: bitcast i8*
+  // CALLS-NEXT: ret
+  return [B alloc];
+}
+
+// Make sure we get a bitcast on the return type as the
+// call will return i8* which we have to cast to A*
+// CHECK-LABEL: define {{.*}}void @test_alloc_class_ptr
+A* test_allocWithZone_class_ptr() {
+  // CALLS: {{call.*@objc_alloc}}
+  // CALLS-NEXT: bitcast i8*
+  // CALLS-NEXT: ret
+  return [B allocWithZone:nil];
+}
+
+

test/Driver/objc-convert-messages-to-runtime-calls.m

+// RUN: %clang %s -### -o %t.o 2>&1 -fsyntax-only -fobjc-convert-messages-to-runtime-calls -fno-objc-convert-messages-to-runtime-calls -target x86_64-apple-macosx10.10.0 | FileCheck  %s --check-prefix=DISABLE
+// RUN: %clang %s -### -o %t.o 2>&1 -fsyntax-only -fno-objc-convert-messages-to-runtime-calls -fobjc-convert-messages-to-runtime-calls -target x86_64-apple-macosx10.10.0 | FileCheck  %s --check-prefix=ENABLE
+
+// Check that we pass fobjc-convert-messages-to-runtime-calls only when supported, and not explicitly disabled.
+
+// DISABLE: "-fno-objc-convert-messages-to-runtime-calls"
+// ENABLE-NOT: "-fno-objc-convert-messages-to-runtime-calls"