pete updated this revision to Diff 40705.
pete added a comment.

After chatting with John offline, he mentioned that this code could be shared 
with all ObjC CG's if I put it in EmitObjCMessageExpr.

This moves it here and also checks that we don't do the retain/release 
call->msgSend optimization when GC is enabled.  There's also a test for that 
case.


http://reviews.llvm.org/D14737

Files:
  include/clang/Basic/ObjCRuntime.h
  include/clang/Driver/Options.td
  include/clang/Frontend/CodeGenOptions.def
  lib/CodeGen/CGObjC.cpp
  lib/CodeGen/CodeGenFunction.h
  lib/CodeGen/CodeGenModule.h
  lib/Driver/Tools.cpp
  lib/Frontend/CompilerInvocation.cpp
  test/CodeGenObjC/convert-messages-to-runtime-calls.m
  test/Driver/objc-convert-messages-to-runtime-calls.m

Index: test/Driver/objc-convert-messages-to-runtime-calls.m
===================================================================
--- /dev/null
+++ test/Driver/objc-convert-messages-to-runtime-calls.m
@@ -0,0 +1,9 @@
+// RUN: %clang %s -### -o %t.o 2>&1 -fsyntax-only -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 -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"
+
+
Index: test/CodeGenObjC/convert-messages-to-runtime-calls.m
===================================================================
--- /dev/null
+++ test/CodeGenObjC/convert-messages-to-runtime-calls.m
@@ -0,0 +1,76 @@
+// 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
+// Make sure we don't do calls to retain/release when using GC.
+// RUN: %clang_cc1 -fobjc-runtime=macosx-10.10.0 -emit-llvm -o - %s -fobjc-gc | FileCheck %s --check-prefix=GC
+// 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
+
+@interface NSObject
++ (id)alloc;
++ (id)alloc2;
+- (id)init;
+- (id)retain;
+- (void)release;
+- (id)autorelease;
+@end
+
+@interface NSString : NSObject
+- (void)retain_self;
+- (void)retain_super;
+@end
+
+// CHECK-LABEL: define {{.*}}void @test1
+void test1(id x) {
+  // MSGS: {{call.*@objc_msgSend}}
+  // MSGS: {{call.*@objc_msgSend}}
+  // MSGS: {{call.*@objc_msgSend}}
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_alloc}}
+  // CALLS: {{call.*@objc_retain}}
+  // CALLS: {{call.*@objc_release}}
+  // CALLS: {{call.*@objc_autorelease}}
+  // GC: {{call.*@objc_alloc}}
+  // GC: {{call.*@objc_msgSend}}
+  // GC: {{call.*@objc_msgSend}}
+  // GC: {{call.*@objc_msgSend}}
+  [NSObject alloc];
+  [x retain];
+  [x release];
+  [x autorelease];
+}
+
+// CHECK-LABEL: define {{.*}}void @test2
+void test2() {
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_msgSend}}
+  // GC: {{call.*@objc_msgSend}}
+  // Make sure alloc has the correct name and number of types.
+  [NSObject alloc2];
+}
+
+@implementation NSString
+
+// Make sure we can convert a message to a dynamic receiver to a call
+// CHECK-LABEL: define {{.*}}void @retain_self
+- (void)retain_self {
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_retain}}
+  // GC: {{call.*@objc_msgSend}}
+  [self retain];
+}
+
+// Make sure we never convert a message to super to a call
+// CHECK-LABEL: define {{.*}}void @retain_super
+- (void)retain_super {
+  // MSGS: {{call.*@objc_msgSend}}
+  // CALLS: {{call.*@objc_msgSend}}
+  // GC: {{call.*@objc_msgSend}}
+  [super retain];
+}
+
+@end
\ No newline at end of file
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -609,6 +609,9 @@
     }
   }
 
+  if (Args.hasArg(OPT_fno_objc_convert_messages_to_runtime_calls))
+    Opts.ObjCConvertMessagesToRuntimeCalls = 0;
+
   Opts.EmulatedTLS =
       Args.hasFlag(OPT_femulated_tls, OPT_fno_emulated_tls, false);
 
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -4901,6 +4901,12 @@
 
   }
 
+  // Allow the user to control whether messages can be converted to runtime
+  // functions.
+  if (types::isObjC(InputType) &&
+      Args.getLastArg(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 (rewriteKind != RK_None)
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -111,6 +111,9 @@
 struct ObjCEntrypoints {
   ObjCEntrypoints() { memset(this, 0, sizeof(*this)); }
 
+  /// void objc_alloc(id);
+  llvm::Constant *objc_alloc;
+
     /// void objc_autoreleasePoolPop(void*);
   llvm::Constant *objc_autoreleasePoolPop;
 
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h
+++ lib/CodeGen/CodeGenFunction.h
@@ -2799,6 +2799,7 @@
   std::pair<LValue,llvm::Value*>
   EmitARCStoreStrong(const BinaryOperator *e, bool ignored);
 
+  llvm::Value *EmitObjCAlloc(llvm::Value *value);
   llvm::Value *EmitObjCThrowOperand(const Expr *expr);
   llvm::Value *EmitObjCConsumeObject(QualType T, llvm::Value *Ptr);
   llvm::Value *EmitObjCExtendObjectLifetime(QualType T, llvm::Value *Ptr);
Index: lib/CodeGen/CGObjC.cpp
===================================================================
--- lib/CodeGen/CGObjC.cpp
+++ lib/CodeGen/CGObjC.cpp
@@ -460,10 +460,53 @@
                                               Args,
                                               method);
   } else {
-    result = Runtime.GenerateMessageSend(*this, Return, ResultType,
-                                         E->getSelector(),
-                                         Receiver, Args, OID,
-                                         method);
+    // Call runtime methods directly if we can.
+    Optional<RValue> CallResult = None;
+    if (method && CGM.getCodeGenOpts().ObjCConvertMessagesToRuntimeCalls) {
+      auto &Runtime = CGM.getLangOpts().ObjCRuntime;
+      if (method->getMethodFamily() == OMF_alloc &&
+          Runtime.shouldUseRuntimeFunctionsForAlloc()) {
+        // 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.
+        Selector S = method->getSelector();
+        if (S.isUnarySelector() && S.getNameForSlot(0) == "alloc" &&
+            ResultType->isObjCIdType())
+          CallResult = RValue::get(EmitObjCAlloc(Receiver));
+      } else if (CGM.getLangOpts().getGC() == LangOptions::NonGC &&
+                 Runtime.shouldUseARCFunctionsForRetainRelease()) {
+        switch (method->getMethodFamily()) {
+          case OMF_autorelease:
+            if (ResultType->isObjCIdType())
+              CallResult = RValue::get(EmitARCAutorelease(Receiver));
+            break;
+
+          case OMF_retain:
+            if (ResultType->isObjCIdType())
+              CallResult = RValue::get(EmitARCRetainNonBlock(Receiver));
+            break;
+
+          case OMF_release:
+            if (ResultType->isVoidType()) {
+              EmitARCRelease(Receiver, ARCImpreciseLifetime);
+              CallResult = RValue::get(nullptr);
+            }
+            break;
+          default:
+            break;
+        }
+      }
+    }
+
+    // If we didn't convert a message send in to a call, then we should emit
+    // the message instead.
+    if (CallResult)
+      result = CallResult.getValue();
+    else
+      result = Runtime.GenerateMessageSend(*this, Return, ResultType,
+                                           E->getSelector(),
+                                           Receiver, Args, OID,
+                                           method);
   }
 
   // For delegate init calls in ARC, implicitly store the result of
@@ -2333,6 +2376,14 @@
   return InitRV.getScalarVal();
 }
 
+/// Allocate the given objc object.
+///   call i8* \@objc_alloc(i8* %value)
+llvm::Value *CodeGenFunction::EmitObjCAlloc(llvm::Value *value) {
+  return emitARCValueOperation(*this, value,
+                               CGM.getObjCEntrypoints().objc_alloc,
+                               "objc_alloc");
+}
+
 /// Produce the code to do a primitive release.
 /// [tmp drain];
 void CodeGenFunction::EmitObjCMRRAutoreleasePoolPop(llvm::Value *Arg) {
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -95,6 +95,8 @@
 CODEGENOPT(NoZeroInitializedInBSS , 1, 0) ///< -fno-zero-initialized-in-bss.
 /// \brief 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.
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -892,6 +892,8 @@
 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 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>;
Index: include/clang/Basic/ObjCRuntime.h
===================================================================
--- include/clang/Basic/ObjCRuntime.h
+++ include/clang/Basic/ObjCRuntime.h
@@ -171,6 +171,68 @@
     llvm_unreachable("bad kind");
   }
 
+  /// Does this runtime provide ARC entrypoints that are likely to be faster
+  /// than an ordinary message send of the appropriate selector?
+
+  /// The ARC 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"
+  /// retain/release behavior; if that's dynamically a large proportion of all
+  /// retained 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:
+  ///   retain => objc_retain
+  ///   release => objc_release
+  bool shouldUseARCFunctionsForRetainRelease() 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 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"
+  /// 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");
+  }
+
   /// \brief Does this runtime supports optimized setter entrypoints?
   bool hasOptimizedSetter() const {
     switch (getKind()) {
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