Index: include/clang/Basic/BuiltinsX86.def
===================================================================
--- include/clang/Basic/BuiltinsX86.def
+++ include/clang/Basic/BuiltinsX86.def
@@ -1880,6 +1880,11 @@
 TARGET_BUILTIN(__builtin_ia32_monitorx, "vv*UiUi", "", "mwaitx")
 TARGET_BUILTIN(__builtin_ia32_mwaitx, "vUiUiUi", "", "mwaitx")
 
+// WAITPKG
+TARGET_BUILTIN(__builtin_ia32_umonitor, "vv*", "", "waitpkg")
+TARGET_BUILTIN(__builtin_ia32_umwait, "UcUiUiUi", "", "waitpkg")
+TARGET_BUILTIN(__builtin_ia32_tpause, "UcUiUiUi", "", "waitpkg")
+
 // CLZERO
 TARGET_BUILTIN(__builtin_ia32_clzero, "vv*", "", "clzero")
 
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -2678,6 +2678,8 @@
 def mno_vaes : Flag<["-"], "mno-vaes">, Group<m_x86_Features_Group>;
 def mvpclmulqdq : Flag<["-"], "mvpclmulqdq">, Group<m_x86_Features_Group>;
 def mno_vpclmulqdq : Flag<["-"], "mno-vpclmulqdq">, Group<m_x86_Features_Group>;
+def mwaitpkg : Flag<["-"], "mwaitpkg">, Group<m_x86_Features_Group>;
+def mno_waitpkg : Flag<["-"], "mno-waitpkg">, Group<m_x86_Features_Group>;
 def mxop : Flag<["-"], "mxop">, Group<m_x86_Features_Group>;
 def mno_xop : Flag<["-"], "mno-xop">, Group<m_x86_Features_Group>;
 def mxsave : Flag<["-"], "mxsave">, Group<m_x86_Features_Group>;
Index: lib/Basic/Targets/X86.h
===================================================================
--- lib/Basic/Targets/X86.h
+++ lib/Basic/Targets/X86.h
@@ -102,6 +102,7 @@
   bool HasRetpolineExternalThunk = false;
   bool HasLAHFSAHF = false;
   bool HasWBNOINVD = false;
+  bool HasWAITPKG = false;
 
 protected:
   /// \brief Enumeration of all of the X86 CPUs supported by Clang.
Index: lib/Basic/Targets/X86.cpp
===================================================================
--- lib/Basic/Targets/X86.cpp
+++ lib/Basic/Targets/X86.cpp
@@ -247,6 +247,7 @@
   case CK_Tremont:
     setFeatureEnabledImpl(Features, "cldemote", true);
     setFeatureEnabledImpl(Features, "gfni", true);
+    setFeatureEnabledImpl(Features, "waitpkg", true);
     LLVM_FALLTHROUGH;
   case CK_GoldmontPlus:
     setFeatureEnabledImpl(Features, "rdpid", true);
@@ -818,6 +819,8 @@
       HasRetpolineExternalThunk = true;
     } else if (Feature == "+sahf") {
       HasLAHFSAHF = true;
+    } else if (Feature == "+waitpkg") {
+      HasWAITPKG = true;
     }
 
     X86SSEEnum Level = llvm::StringSwitch<X86SSEEnum>(Feature)
@@ -1172,6 +1175,8 @@
     Builder.defineMacro("__RDPID__");
   if (HasCLDEMOTE)
     Builder.defineMacro("__CLDEMOTE__");
+  if (HasWAITPKG)
+    Builder.defineMacro("__WAITPKG__");
 
   // Each case falls through to the previous one here.
   switch (SSELevel) {
@@ -1323,6 +1328,7 @@
       .Case("vaes", true)
       .Case("vpclmulqdq", true)
       .Case("wbnoinvd", true)
+      .Case("waitpkg", true)
       .Case("x87", true)
       .Case("xop", true)
       .Case("xsave", true)
@@ -1399,6 +1405,7 @@
       .Case("vaes", HasVAES)
       .Case("vpclmulqdq", HasVPCLMULQDQ)
       .Case("wbnoinvd", HasWBNOINVD)
+      .Case("waitpkg", HasWAITPKG)
       .Case("x86", true)
       .Case("x86_32", getTriple().getArch() == llvm::Triple::x86)
       .Case("x86_64", getTriple().getArch() == llvm::Triple::x86_64)
Index: lib/Headers/CMakeLists.txt
===================================================================
--- lib/Headers/CMakeLists.txt
+++ lib/Headers/CMakeLists.txt
@@ -96,6 +96,7 @@
   varargs.h
   vecintrin.h
   vpclmulqdqintrin.h
+  waitpkgintrin.h
   wbnoinvdintrin.h
   wmmintrin.h
   __wmmintrin_aes.h
Index: lib/Headers/cpuid.h
===================================================================
--- lib/Headers/cpuid.h
+++ lib/Headers/cpuid.h
@@ -177,6 +177,7 @@
 #define bit_AVX512VBMI       0x00000002
 #define bit_PKU              0x00000004
 #define bit_OSPKE            0x00000010
+#define bit_WAITPKG          0x00000020
 #define bit_AVX512VBMI2      0x00000040
 #define bit_SHSTK            0x00000080
 #define bit_GFNI             0x00000100
Index: lib/Headers/waitpkgintrin.h
===================================================================
--- /dev/null
+++ lib/Headers/waitpkgintrin.h
@@ -0,0 +1,56 @@
+/*===----------------------- waitpkgintrin.h - WAITPKG --------------------===
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ *===-----------------------------------------------------------------------===
+ */
+#ifndef __X86INTRIN_H
+#error "Never use <waitpkgintrin.h> directly; include <x86intrin.h> instead."
+#endif
+
+#ifndef _WAITPKGINTRIN_H
+#define _WAITPKGINTRIN_H
+
+/* Define the default attributes for the functions in this file. */
+#define __DEFAULT_FN_ATTRS \
+  __attribute__((__always_inline__, __nodebug__,  __target__("waitpkg")))
+
+static __inline__ void __DEFAULT_FN_ATTRS
+_umonitor (void * __address)
+{
+  __builtin_ia32_umonitor (__address);
+}
+
+static __inline__ unsigned char __DEFAULT_FN_ATTRS
+_umwait (unsigned int __control, unsigned long long __counter)
+{
+  return __builtin_ia32_umwait (__control,
+    (unsigned int)(__counter >> 32), (unsigned int)__counter);
+}
+
+static __inline__ unsigned char __DEFAULT_FN_ATTRS
+_tpause (unsigned int __control, unsigned long long __counter)
+{
+  return __builtin_ia32_tpause (__control,
+    (unsigned int)(__counter >> 32), (unsigned int)__counter);
+}
+
+#undef __DEFAULT_FN_ATTRS
+
+#endif /* _WAITPKGINTRIN_H */
Index: lib/Headers/x86intrin.h
===================================================================
--- lib/Headers/x86intrin.h
+++ lib/Headers/x86intrin.h
@@ -96,4 +96,8 @@
 #include <cldemoteintrin.h>
 #endif
 
+#if !defined(_MSC_VER) || __has_feature(modules) || defined(__WAITPKG__)
+#include <waitpkgintrin.h>
+#endif
+
 #endif /* __X86INTRIN_H */
Index: test/CodeGen/waitpkg.c
===================================================================
--- /dev/null
+++ test/CodeGen/waitpkg.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 %s -ffreestanding -triple x86_64-unknown-unknown -emit-llvm -target-feature +waitpkg -Wall -pedantic -o - | FileCheck %s
+// RUN: %clang_cc1 %s -ffreestanding -triple i386-unknown-unknown -emit-llvm -target-feature +waitpkg -Wall -pedantic -o - | FileCheck %s
+
+#include <x86intrin.h>
+
+#include <stddef.h>
+#include <stdint.h>
+
+void test_umonitor(void *address) {
+  //CHECK-LABEL: @test_umonitor
+  //CHECK: call void @llvm.x86.umonitor(i8* %{{.*}})
+  return _umonitor(address);
+}
+
+uint8_t test_umwait(uint32_t control, uint64_t counter) {
+  //CHECK-LABEL: @test_umwait
+  //CHECK: call i8 @llvm.x86.umwait(i32 %{{.*}}, i32 %{{.*}}, i32 %{{.*}})
+  return _umwait(control, counter);
+}
+
+uint8_t test_tpause(uint32_t control, uint64_t counter) {
+  //CHECK-LABEL: @test_tpause
+  //CHECK: call i8 @llvm.x86.tpause(i32 %{{.*}}, i32 %{{.*}}, i32 %{{.*}})
+  return _tpause(control, counter);
+}
Index: test/Driver/x86-target-features.c
===================================================================
--- test/Driver/x86-target-features.c
+++ test/Driver/x86-target-features.c
@@ -144,3 +144,8 @@
 // RUN: %clang -target i386-linux-gnu -mretpoline -mno-retpoline-external-thunk %s -### -o %t.o 2>&1 | FileCheck -check-prefix=NO-RETPOLINE-EXTERNAL-THUNK %s
 // RETPOLINE-EXTERNAL-THUNK: "-target-feature" "+retpoline-external-thunk"
 // NO-RETPOLINE-EXTERNAL-THUNK: "-target-feature" "-retpoline-external-thunk"
+
+// RUN: %clang -target i386-linux-gnu -mwaitpkg %s -### -o %t.o 2>&1 | FileCheck -check-prefix=WAITPKG %s
+// RUN: %clang -target i386-linux-gnu -mno-waitpkg %s -### -o %t.o 2>&1 | FileCheck -check-prefix=NO-WAITPKG %s
+// WAITPKG: "-target-feature" "+waitpkg"
+// NO-WAITPKG: "-target-feature" "-waitpkg"
Index: test/Preprocessor/predefined-arch-macros.c
===================================================================
--- test/Preprocessor/predefined-arch-macros.c
+++ test/Preprocessor/predefined-arch-macros.c
@@ -1482,6 +1482,7 @@
 // CHECK_TRM_M32: #define __SSE_MATH__ 1
 // CHECK_TRM_M32: #define __SSE__ 1
 // CHECK_TRM_M32: #define __SSSE3__ 1
+// CHECK_TRM_M32: #define __WAITPKG__ 1
 // CHECK_TRM_M32: #define __XSAVEC__ 1
 // CHECK_TRM_M32: #define __XSAVEOPT__ 1
 // CHECK_TRM_M32: #define __XSAVES__ 1
@@ -1518,6 +1519,7 @@
 // CHECK_TRM_M64: #define __SSE4_2__ 1
 // CHECK_TRM_M64: #define __SSE__ 1
 // CHECK_TRM_M64: #define __SSSE3__ 1
+// CHECK_TRM_M64: #define __WAITPKG__ 1
 // CHECK_TRM_M64: #define __XSAVEC__ 1
 // CHECK_TRM_M64: #define __XSAVEOPT__ 1
 // CHECK_TRM_M64: #define __XSAVES__ 1