diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -110,6 +110,8 @@
 ///< XRay instrumentation.
 VALUE_CODEGENOPT(XRayInstructionThreshold , 32, 200)
 
+VALUE_CODEGENOPT(PatchableFunctionEntrySize , 32, 0) ///< Number of NOPs at function entry
+
 CODEGENOPT(InstrumentForProfiling , 1, 0) ///< Set when -pg is enabled.
 CODEGENOPT(CallFEntry , 1, 0) ///< Set when -mfentry is enabled.
 CODEGENOPT(MNopMCount , 1, 0) ///< Set when -mnop-mcount is enabled.
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -74,6 +74,7 @@
   "unsupported runtime library '%0' for platform '%1'">;
 def err_drv_invalid_unwindlib_name : Error<
   "invalid unwind library name in argument '%0'">;
+def err_drv_incompatible_options : Error<"'%0' and '%1' cannot be used together">;
 def err_drv_incompatible_unwindlib : Error<
   "--rtlib=libgcc requires --unwindlib=libgcc">;
 def err_drv_invalid_stdlib_name : Error<
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1700,6 +1700,8 @@
 def fno_max_type_align : Flag<["-"], "fno-max-type-align">, Group<f_Group>;
 def fpascal_strings : Flag<["-"], "fpascal-strings">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Recognize and construct Pascal-style string literals">;
+def fpatchable_function_entry : Joined<["-"], "fpatchable-function-entry=">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Generate N NOPs at function entry">;
 def fpcc_struct_return : Flag<["-"], "fpcc-struct-return">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Override the default ABI to return all structs on the stack">;
 def fpch_preprocess : Flag<["-"], "fpch-preprocess">, Group<f_Group>;
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -824,6 +824,8 @@
       Fn->addFnAttr(
           "patchable-function-entry",
           (Twine(Attr->getSize()) + "," + Twine(Attr->getStart())).str());
+    else if (unsigned Size = CGM.getCodeGenOpts().PatchableFunctionEntrySize)
+      Fn->addFnAttr("patchable-function-entry", (Twine(Size) + ",0").str());
   }
 
   // Add no-jump-tables value.
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4998,6 +4998,24 @@
   const XRayArgs &XRay = TC.getXRayArgs();
   XRay.addArgs(TC, Args, CmdArgs, InputType);
 
+  if (Arg *A = Args.getLastArg(options::OPT_fpatchable_function_entry)) {
+    StringRef S0 = A->getValue(), S = S0;
+    unsigned Size, Start = 0;
+    if (!Triple.isAArch64() && Triple.getArch() != llvm::Triple::x86 &&
+        Triple.getArch() != llvm::Triple::x86_64)
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << A->getAsString(Args) << TripleStr;
+    else if (S.consumeInteger(10, Size) ||
+             (!S.empty() && (!S.consume_front(",") ||
+                             S.consumeInteger(10, Start) || !S.empty())))
+      D.Diag(diag::err_drv_invalid_argument_to_option)
+          << S0 << A->getOption().getName();
+    else if (Start)
+      D.Diag(diag::err_drv_clang_unsupported) << Start;
+    else
+      CmdArgs.push_back(Args.MakeArgString(A->getSpelling() + Twine(Size)));
+  }
+
   if (TC.SupportsProfiling()) {
     Args.AddLastArg(CmdArgs, options::OPT_pg);
 
diff --git a/clang/lib/Driver/XRayArgs.cpp b/clang/lib/Driver/XRayArgs.cpp
--- a/clang/lib/Driver/XRayArgs.cpp
+++ b/clang/lib/Driver/XRayArgs.cpp
@@ -70,6 +70,13 @@
       D.Diag(diag::err_drv_clang_unsupported)
           << (std::string(XRayInstrumentOption) + " on " + Triple.str());
     }
+
+    // Both XRay and -fpatchable-function-entry use
+    // TargetOpcode::PATCHABLE_FUNCTION_ENTER.
+    if (Arg *A = Args.getLastArg(options::OPT_fpatchable_function_entry))
+      D.Diag(diag::err_drv_incompatible_options)
+          << "-fxray-instrument" << A->getSpelling();
+
     XRayInstrument = true;
     if (const Arg *A =
             Args.getLastArg(options::OPT_fxray_instruction_threshold_,
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1101,6 +1101,8 @@
       parseXRayInstrumentationBundle("-fxray-instrumentation-bundle=", A, Args,
                                      Diags, Opts.XRayInstrumentationBundle);
 
+  Opts.PatchableFunctionEntrySize =
+      getLastArgIntValue(Args, OPT_fpatchable_function_entry, 0, Diags);
   Opts.InstrumentForProfiling = Args.hasArg(OPT_pg);
   Opts.CallFEntry = Args.hasArg(OPT_mfentry);
   Opts.MNopMCount = Args.hasArg(OPT_mnop_mcount);
diff --git a/clang/test/CodeGen/patchable-function-entry.c b/clang/test/CodeGen/patchable-function-entry.c
--- a/clang/test/CodeGen/patchable-function-entry.c
+++ b/clang/test/CodeGen/patchable-function-entry.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple aarch64 -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -fpatchable-function-entry=1 -o - | FileCheck --check-prefixes=CHECK,OPT %s
 
 // CHECK: define void @f0() #0
 __attribute__((patchable_function_entry(0))) void f0() {}
@@ -16,5 +17,9 @@
 __attribute__((patchable_function_entry(2,0))) void f20decl();
 __attribute__((noinline)) void f20decl() {}
 
+// OPT: define void @f() #2
+void f() {}
+
 // CHECK: attributes #0 = { {{.*}} "patchable-function-entry"="0,0"
 // CHECK: attributes #1 = { {{.*}} "patchable-function-entry"="2,0"
+// OPT:   attributes #2 = { {{.*}} "patchable-function-entry"="1,0"
diff --git a/clang/test/Sema/patchable-function-entry-attr.cpp b/clang/test/Sema/patchable-function-entry-attr.cpp
--- a/clang/test/Sema/patchable-function-entry-attr.cpp
+++ b/clang/test/Sema/patchable-function-entry-attr.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple aarch64 -fsyntax-only -verify=silence %s
+// RUN: %clang_cc1 -triple i386 -fsyntax-only -verify=silence %s
 // RUN: %clang_cc1 -triple x86_64 -fsyntax-only -verify=silence %s
 // RUN: %clang_cc1 -triple ppc64le -fsyntax-only -verify %s