Index: lib/Target/X86/X86AsmPrinter.h
===================================================================
--- lib/Target/X86/X86AsmPrinter.h
+++ lib/Target/X86/X86AsmPrinter.h
@@ -107,6 +107,8 @@
     SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());
   }
 
+  void EmitFunctionEntryLabel() override;
+
   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                        unsigned AsmVariant, const char *ExtraCode,
                        raw_ostream &OS) override;
Index: lib/Target/X86/X86AsmPrinter.cpp
===================================================================
--- lib/Target/X86/X86AsmPrinter.cpp
+++ lib/Target/X86/X86AsmPrinter.cpp
@@ -73,6 +73,23 @@
   return false;
 }
 
+void X86AsmPrinter::EmitFunctionEntryLabel() {
+  // If a hotpatch function, we need to ensure 64 (32-bit) or 128 (64-bit)
+  // bytes of padding precede the label.  This is the scratch space used
+  // by the hotpatching mechanism to insert a jump to the patch code.  The
+  // movl %edi, %edi instruction emitted as the very first instruction of
+  // a hotpatch function is usually overwritten with a short jump
+  // instruction when the patch is installed, so it will jump directly into
+  // this space.
+  if (MF->getFunction()->hasFnAttribute("ms-hotpatch")) {
+    // FIXME: Figure out some way to use the X86AsmBackend::writeNopData()
+    // method for this.
+    OutStreamer->EmitFill(Subtarget->is64Bit() ? 128 : 64, 0xcc);
+  }
+
+  AsmPrinter::EmitFunctionEntryLabel();
+}
+
 /// printSymbolOperand - Print a raw symbol reference operand.  This handles
 /// jump tables, constant pools, global address and external symbols, all of
 /// which print to a label with various suffixes for relocation types etc.
Index: lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- lib/Target/X86/X86FrameLowering.cpp
+++ lib/Target/X86/X86FrameLowering.cpp
@@ -927,6 +927,7 @@
   bool NeedsWinCFI = IsWin64Prologue && Fn->needsUnwindTableEntry();
   bool NeedsDwarfCFI =
       !IsWin64Prologue && (MMI.hasDebugInfo() || Fn->needsUnwindTableEntry());
+  bool IsMSHotpatch = Fn->hasFnAttribute("ms-hotpatch");
   unsigned FramePtr = TRI->getFrameRegister(MF);
   const unsigned MachineFramePtr =
       STI.isTarget64BitILP32()
@@ -975,6 +976,16 @@
     MFI->setStackSize(StackSize);
   }
 
+  if (IsMSHotpatch && !Is64Bit)
+    // Add a no-op movl %edi, %edi instruction.  A short jump instruction
+    // will be written over it if a patch is installed.  This particular
+    // instruction is often used as a sort of magic number indicating that
+    // this function can be patched.
+    // N.B. This MI *must* be the first instruction, or the hook won't work.
+    BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32rr_REV), X86::EDI)
+      .addReg(X86::EDI)
+      .setMIFlag(MachineInstr::FrameSetup);
+
   // Insert stack pointer adjustment for later moving of return addr.  Only
   // applies to tail call optimized functions where the callee argument stack
   // size is bigger than the callers.
@@ -1068,7 +1079,9 @@
     if (!IsWin64Prologue && !IsFunclet) {
       // Update EBP with the new base value.
       BuildMI(MBB, MBBI, DL,
-              TII.get(Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr),
+              TII.get(IsMSHotpatch ?
+                      (Uses64BitFramePtr ? X86::MOV64rr_REV : X86::MOV32rr_REV):
+                      (Uses64BitFramePtr ? X86::MOV64rr : X86::MOV32rr)),
               FramePtr)
           .addReg(StackPtr)
           .setMIFlag(MachineInstr::FrameSetup);
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -2495,9 +2495,10 @@
   const TargetFrameLowering &TFI = *Subtarget.getFrameLowering();
 
   const Function* Fn = MF.getFunction();
-  if (Fn->hasExternalLinkage() &&
-      Subtarget.isTargetCygMing() &&
-      Fn->getName() == "main")
+  if ((Fn->hasExternalLinkage() &&
+       Subtarget.isTargetCygMing() &&
+       Fn->getName() == "main") ||
+      Fn->hasFnAttribute("ms-hotpatch"))
     FuncInfo->setForceFramePointer(true);
 
   MachineFrameInfo *MFI = MF.getFrameInfo();
Index: test/CodeGen/X86/ms-hotpatch-attr.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/ms-hotpatch-attr.ll
@@ -0,0 +1,16 @@
+; RUN: llc < %s -march=x86 -filetype=asm | FileCheck -check-prefix=CHECK-32 %s
+; RUN: llc < %s -march=x86-64 -filetype=asm | FileCheck -check-prefix=CHECK-64 %s
+
+; CHECK-32: .space 64,204
+; CHECK-32-LABEL: foo:
+; CHECK-32: movl %edi, %edi
+; CHECK-32-NEXT: pushl %ebp
+; CHECK-32-NEXT: movl %esp, %ebp
+; CHECK-64: .space 128,204
+; CHECK-64-LABEL: foo:
+; CHECK-64: pushq %rbp
+; CHECK-64-NEXT: movq %rsp, %rbp
+define void @foo() nounwind "ms-hotpatch" {
+entry:
+  ret void
+}