Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -3086,3 +3086,10 @@
   let Subjects = SubjectList<[Var]>;
   let Documentation = [AlwaysDestroyDocs];
 }
+
+def SpeculativeLoadHardening : InheritableAttr {
+  let Spellings = [GNU<"speculative_load_hardening">,
+                   CXX11<"", "speculative_load_hardening", 201811>];
+  let Subjects = SubjectList<[Function], ErrorDiag>;
+  let Documentation = [SpeculativeLoadHardeningDocs];
+}
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -3604,3 +3604,30 @@
 ``-std=c89``, ``-std=c94``, or ``-fgnu89-inline``.
   }];
 }
+
+def SpeculativeLoadHardeningDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+This attribute indicates that
+`Speculative Load Hardening <https://llvm.org/docs/SpeculativeLoadHardening.html>`_
+should be enabled for the function body. This is a best-effort attempt to
+mitigate all known speculative execution information leak vulnerabilities
+that are based on the fundamental principles of modern processors'
+speculative execution. These vulnerabilities are classified as "Spectre
+variant #1" vulnerabilities typically. Notably, this does not attempt to
+mitigate any vulnerabilities where the speculative execution and/or
+prediction devices of specific processors can be *completely* undermined
+(such as "Branch Target Injection", a.k.a, "Spectre variant #2"). Instead,
+this is a target-independent request to harden against the completely
+generic risk posed by speculative execution to incorrectly load secret data,
+making it available to some micro-architectural side-channel for information
+leak. For a processor without any speculative execution or predictors, this
+is expected to be a no-op.
+
+When inlining, the attribute is sticky. Inlining a function that carries
+this attribute will cause the caller to gain the attribute. This is intended
+to provide a maximally conservative model where the code in a function
+annotated with this attribute will always (even after inlining) end up
+hardened.
+  }];
+}
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -1850,6 +1850,8 @@
       FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
     if (TargetDecl->hasAttr<ConvergentAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::Convergent);
+    if (TargetDecl->hasAttr<SpeculativeLoadHardeningAttr>())
+      FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening);
 
     if (const FunctionDecl *Fn = dyn_cast<FunctionDecl>(TargetDecl)) {
       AddAttributesFromFunctionProtoType(
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -6365,6 +6365,9 @@
   case ParsedAttr::AT_Section:
     handleSectionAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_SpeculativeLoadHardening:
+    handleSimpleAttribute<SpeculativeLoadHardeningAttr>(S, D, AL);
+    break;
   case ParsedAttr::AT_CodeSeg:
     handleCodeSegAttr(S, D, AL);
     break;
Index: clang/test/CodeGen/attr-speculative-load-hardening.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-speculative-load-hardening.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -std=c++11 -disable-llvm-passes -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK1
+// RUN: %clang_cc1 -std=c++11 -disable-llvm-passes -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK2
+//
+// Check that we set the attribute on each function.
+
+[[speculative_load_hardening]]
+int test1() {
+  return 42;
+}
+
+int __attribute__((speculative_load_hardening)) test2() {
+  return 42;
+}
+// CHECK1: @{{.*}}test1{{.*}}[[SLH1:#[0-9]+]]
+// CHECK1: attributes [[SLH1]] = { {{.*}}speculative_load_hardening{{.*}} }
+
+// CHECK2: @{{.*}}test2{{.*}}[[SLH2:#[0-9]+]]
+// CHECK2: attributes [[SLH2]] = { {{.*}}speculative_load_hardening{{.*}} }
Index: clang/test/SemaCXX/attr-speculative-load-hardening.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/attr-speculative-load-hardening.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+int i __attribute__((speculative_load_hardening)); // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+
+void f1() __attribute__((speculative_load_hardening));
+void f2() __attribute__((speculative_load_hardening(1))); // expected-error {{'speculative_load_hardening' attribute takes no arguments}}
+
+template <typename T>
+void tf1() __attribute__((speculative_load_hardening));
+
+int f3(int __attribute__((speculative_load_hardening)), int); // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+
+struct A {
+  int f __attribute__((speculative_load_hardening));  // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+  void mf1() __attribute__((speculative_load_hardening));
+  static void mf2() __attribute__((speculative_load_hardening));
+};
+
+int ci [[speculative_load_hardening]]; // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+
+[[speculative_load_hardening]] void cf1();
+[[speculative_load_hardening(1)]] void cf2(); // expected-error {{'speculative_load_hardening' attribute takes no arguments}}
+
+template <typename T>
+[[speculative_load_hardening]]
+void ctf1();
+
+int cf3(int c[[speculative_load_hardening]], int); // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+
+struct CA {
+  int f [[speculative_load_hardening]];  // expected-error {{'speculative_load_hardening' attribute only applies to functions}}
+  [[speculative_load_hardening]] void mf1();
+  [[speculative_load_hardening]] static void mf2();
+};