Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -1652,6 +1652,13 @@
   let Documentation = [AnyX86InterruptDocs];
 }
 
+def AnyX86NoCallerSavedRegisters : InheritableAttr,
+                                   TargetSpecificAttr<TargetAnyX86> {
+  let Spellings = [GNU<"no_caller_saved_registers">];
+  let Subjects = SubjectList<[FunctionLike], WarnDiag, "ExpectedFunction">;
+  let Documentation = [AnyX86NoCallerSavedRegistersDocs];
+}
+
 def X86ForceAlignArgPointer : InheritableAttr, TargetSpecificAttr<TargetX86> {
   let Spellings = [GNU<"force_align_arg_pointer">];
   // Technically, this appertains to a FunctionDecl, but the target-specific
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td
+++ include/clang/Basic/AttrDocs.td
@@ -2170,6 +2170,20 @@
   }];
 }
 
+def AnyX86NoCallerSavedRegistersDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Use this attribute to indicate that the specified function has no
+caller-saved registers.  That is, all registers are callee-saved.
+The compiler generates proper function entry and exit sequences to
+save and restore any modified registers.
+
+The user can call functions specified with the 'no_caller_saved_registers'
+attribute from an interrupt handler without saving and restoring all
+call clobbered registers.
+  }];
+}
+
 def SwiftCallDocs : Documentation {
   let Category = DocCatVariable;
   let Content = [{
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1673,6 +1673,8 @@
       RetAttrs.addAttribute(llvm::Attribute::NoAlias);
     if (TargetDecl->hasAttr<ReturnsNonNullAttr>())
       RetAttrs.addAttribute(llvm::Attribute::NonNull);
+    if (TargetDecl->hasAttr<AnyX86NoCallerSavedRegistersAttr>())
+      FuncAttrs.addAttribute("no_caller_saved_registers");
 
     HasAnyX86InterruptAttr = TargetDecl->hasAttr<AnyX86InterruptAttr>();
     HasOptnone = TargetDecl->hasAttr<OptimizeNoneAttr>();
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -5910,6 +5910,10 @@
     handleTypeTagForDatatypeAttr(S, D, Attr);
     break;
 
+  case AttributeList::AT_AnyX86NoCallerSavedRegisters:
+    handleSimpleAttribute<AnyX86NoCallerSavedRegistersAttr>(S, D, Attr);
+    break;
+
   case AttributeList::AT_RenderScriptKernel:
     handleSimpleAttribute<RenderScriptKernelAttr>(S, D, Attr);
     break;
Index: test/CodeGenCXX/attr-x86-no_caller_saved_registers.cpp
===================================================================
--- test/CodeGenCXX/attr-x86-no_caller_saved_registers.cpp
+++ test/CodeGenCXX/attr-x86-no_caller_saved_registers.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-win32 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-pc-win32 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnux32 %s -emit-llvm -o - | FileCheck %s
+
+// CHECK: foo{{[^#]*}}#[[ATTRS:[0-9]+]]
+__attribute__((no_caller_saved_registers)) void foo() {}
+namespace S {
+// CHECK: bar{{[^#]*}}#[[ATTRS]]
+__attribute__((no_caller_saved_registers)) void bar(int *a) { foo(); }
+}
+
+struct St {
+  static void baz(int *a) __attribute__((no_caller_saved_registers)) { S::bar(a); }
+};
+
+__attribute((no_caller_saved_registers)) void (*foobar)(void);
+
+// CHECK-LABEL: @main
+int main(int argc, char **argv) {
+  St::baz(&argc);
+  // CHECK: [[FOOBAR:%.+]] = load void ()*, void ()** @{{.*}}foobar{{.*}},
+  // CHECK-NEXT: call void [[FOOBAR]]() #[[ATTRS1:.+]]
+  foobar();
+  return 0;
+}
+
+// CHECK: baz{{[^#]*}}#[[ATTRS]]
+
+// CHECK: attributes #[[ATTRS]] = {
+// CHECK-SAME: "no_caller_saved_registers"
+// CHECK-SAME: }
+// CHECK: attributes #[[ATTRS1]] = { "no_caller_saved_registers" }
Index: test/SemaCXX/attr-x86-no_caller_saved_registers.cpp
===================================================================
--- test/SemaCXX/attr-x86-no_caller_saved_registers.cpp
+++ test/SemaCXX/attr-x86-no_caller_saved_registers.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple x86_64-pc-win32 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple i386-pc-win32 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnux32 -fsyntax-only -verify %s
+
+struct a {
+  int b __attribute__((no_caller_saved_registers)); // expected-warning {{'no_caller_saved_registers' attribute only applies to functions}}
+  static void foo(int *a) __attribute__((no_caller_saved_registers)) {}
+};
+
+struct a test __attribute__((no_caller_saved_registers)); // expected-warning {{'no_caller_saved_registers' attribute only applies to functions}}
+
+__attribute__((no_caller_saved_registers(999))) void bar(int *) {} // expected-error {{'no_caller_saved_registers' attribute takes no arguments}}
+
+__attribute__((no_caller_saved_registers)) void foo(int *) {}
+
+int main(int argc, char **argv) {
+  a::foo(&argc);
+  foo(&argc);
+  return 0;
+}