Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td	(revision 195153)
+++ include/clang/Basic/Attr.td	(working copy)
@@ -613,6 +613,11 @@
   let Subjects = [ObjCInterface];
 }
 
+def OptimizeNone : InheritableAttr {
+  let Spellings = [GNU<"optnone">, CXX11<"clang", "optnone">];
+  let Subjects = [Function, ObjCMethod];
+}
+
 def Overloadable : Attr {
   let Spellings = [GNU<"overloadable">];
 }
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp	(revision 195153)
+++ lib/CodeGen/CodeGenModule.cpp	(working copy)
@@ -678,6 +678,10 @@
     // Naked implies noinline: we should not be inlining such functions.
     B.addAttribute(llvm::Attribute::Naked);
     B.addAttribute(llvm::Attribute::NoInline);
+  } else if (D->hasAttr<OptimizeNoneAttr>()) {
+    // OptimizeNone implies noinline; we should not be inlining such functions.
+    B.addAttribute(llvm::Attribute::OptimizeNone);
+    B.addAttribute(llvm::Attribute::NoInline);
   } else if (D->hasAttr<NoInlineAttr>()) {
     B.addAttribute(llvm::Attribute::NoInline);
   } else if ((D->hasAttr<AlwaysInlineAttr>() ||
@@ -696,6 +700,12 @@
   if (D->hasAttr<MinSizeAttr>())
     B.addAttribute(llvm::Attribute::MinSize);
 
+  if (D->hasAttr<OptimizeNoneAttr>()) {
+    // OptimizeNone wins over OptimizeForSize and MinSize.
+    B.removeAttribute(llvm::Attribute::OptimizeForSize);
+    B.removeAttribute(llvm::Attribute::MinSize);
+  }
+
   if (LangOpts.getStackProtector() == LangOptions::SSPOn)
     B.addAttribute(llvm::Attribute::StackProtect);
   else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp	(revision 195153)
+++ lib/Sema/SemaDeclAttr.cpp	(working copy)
@@ -1764,6 +1764,12 @@
     return;
   }
 
+  if (D->hasAttr<OptimizeNoneAttr>()) {
+    S.Diag(Attr.getLoc(), diag::err_attributes_are_not_compatible)
+      << Attr.getName() << "'optnone'";
+    return;
+  }
+
   D->addAttr(::new (S.Context)
              AlwaysInlineAttr(Attr.getRange(), S.Context,
                               Attr.getAttributeSpellingListIndex()));
@@ -3637,6 +3643,25 @@
              Attr.getAttributeSpellingListIndex()));
 }
 
+static void handleOptimizeNoneAttr(Sema &S, Decl *D,
+                                   const AttributeList &Attr) {
+  if (!isa<FunctionDecl>(D) && !isa<ObjCMethodDecl>(D)) {
+    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)
+      << Attr.getName() << ExpectedFunctionOrMethod;
+    return;
+  }
+
+  if (D->hasAttr<AlwaysInlineAttr>()) {
+    S.Diag(Attr.getLoc(), diag::err_attributes_are_not_compatible)
+      << Attr.getName() << "'always_inline'";
+    return;
+  }
+
+  D->addAttr(::new (S.Context)
+             OptimizeNoneAttr(Attr.getRange(), S.Context,
+                              Attr.getAttributeSpellingListIndex()));
+}
+
 static void handleNoInstrumentFunctionAttr(Sema &S, Decl *D,
                                            const AttributeList &Attr) {
   if (!isa<FunctionDecl>(D)) {
@@ -4662,6 +4687,9 @@
   case AttributeList::AT_MinSize:
     handleMinSizeAttr(S, D, Attr);
     break;
+  case AttributeList::AT_OptimizeNone:
+    handleOptimizeNoneAttr(S, D, Attr);
+    break;
   case AttributeList::AT_Format:      handleFormatAttr      (S, D, Attr); break;
   case AttributeList::AT_FormatArg:   handleFormatArgAttr   (S, D, Attr); break;
   case AttributeList::AT_CUDAGlobal:  handleGlobalAttr      (S, D, Attr); break;
Index: test/CodeGen/attr-optnone.c
===================================================================
--- test/CodeGen/attr-optnone.c	(revision 0)
+++ test/CodeGen/attr-optnone.c	(revision 0)
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fms-compatibility -emit-llvm < %s > %t
+// RUN: FileCheck %s --check-prefix=PRESENT < %t
+// RUN: FileCheck %s --check-prefix=ABSENT  < %t
+
+__attribute__((optnone)) __forceinline
+int test2() { return 0; }
+// PRESENT-DAG: @test2{{.*}}[[ATTR2:#[0-9]+]]
+
+__attribute__((optnone)) __attribute__((minsize))
+int test3() { return 0; }
+// PRESENT-DAG: @test3{{.*}}[[ATTR3:#[0-9]+]]
+
+__attribute__((optnone)) __attribute__((cold))
+int test4() { return test2(); }
+// PRESENT-DAG: @test4{{.*}}[[ATTR4:#[0-9]+]]
+// Also check that test2 isn't inlined into test4 (optnone trumps forceinline).
+// PRESENT-DAG: call i32 @test2
+
+// Check that we set both attributes noinline and optnone on each function.
+// PRESENT-DAG: attributes [[ATTR2]] = { {{.*}}noinline{{.*}}optnone{{.*}} }
+// PRESENT-DAG: attributes [[ATTR3]] = { {{.*}}noinline{{.*}}optnone{{.*}} }
+// PRESENT-DAG: attributes [[ATTR4]] = { {{.*}}noinline{{.*}}optnone{{.*}} }
+
+// Check that no 'optsize' or 'minsize' attributes appear.
+// ABSENT-NOT: optsize
+// ABSENT-NOT: minsize
Index: test/SemaCXX/attr-optnone.cpp
===================================================================
--- test/SemaCXX/attr-optnone.cpp	(revision 0)
+++ test/SemaCXX/attr-optnone.cpp	(revision 0)
@@ -0,0 +1,44 @@
+// RUN: %clang_cc1 -std=c++11 -fms-compatibility -fsyntax-only -verify %s
+
+int foo() __attribute__((optnone));
+int bar() __attribute__((optnone)) __attribute__((noinline));
+
+int baz() __attribute__((always_inline)) __attribute__((optnone)); // expected-error{{'always_inline' and 'optnone' attributes are not compatible}}
+int qux() __attribute__((optnone)) __attribute__((always_inline)); // expected-error{{'optnone' and 'always_inline' attributes are not compatible}}
+
+int globalVar __attribute__((optnone)); // expected-warning{{'optnone' attribute only applies to functions}}
+
+int fubar(int __attribute__((optnone)), int); // expected-warning{{'optnone' attribute only applies to functions}}
+
+struct A {
+  int aField __attribute__((optnone));  // expected-warning{{'optnone' attribute only applies to functions}}
+};
+
+struct B {
+  void foo() __attribute__((optnone));
+  static void bar() __attribute__((optnone));
+};
+
+// Verify that we can specify the [[clang::optnone]] syntax as well.
+
+[[clang::optnone]]
+int foo2();
+[[clang::optnone]]
+int bar2() __attribute__((noinline));
+
+[[clang::optnone]]
+int baz2() __attribute__((always_inline)); // expected-error{{'always_inline' and 'optnone' attributes are not compatible}}
+
+[[clang::optnone]] int globalVar2; //expected-warning{{'optnone' attribute only applies to functions}}
+
+struct A2 {
+  [[clang::optnone]] int aField; // expected-warning{{'optnone' attribute only applies to functions}}
+};
+
+struct B2 {
+  [[clang::optnone]]
+  void foo();
+  [[clang::optnone]]
+  static void bar();
+};
+
Index: test/SemaObjC/method-attributes.m
===================================================================
--- test/SemaObjC/method-attributes.m	(revision 195153)
+++ test/SemaObjC/method-attributes.m	(working copy)
@@ -8,6 +8,7 @@
 -(void) m0 __attribute__((noreturn));
 -(void) m1 __attribute__((unused));
 -(void) m2 __attribute__((stdcall));
+-(void) m3 __attribute__((optnone));
 @end