diff --git a/clang/lib/Basic/Stack.cpp b/clang/lib/Basic/Stack.cpp
new file mode 100644
index 0000000..667db5c
--- /dev/null
+++ b/clang/lib/Basic/Stack.cpp
@@ -0,0 +1,71 @@
+//===--- Stack.h - Utilities for dealing with stack space -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Defines utilities for dealing with stack allocation and stack space.
+///
+//===----------------------------------------------------------------------===//
+
+#include "clang/Basic/Stack.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/CrashRecoveryContext.h"
+
+static LLVM_THREAD_LOCAL void *BottomOfStack = nullptr;
+
+static void *getStackPointer() {
+#if __GNUC__ || __has_builtin(__builtin_frame_address)
+  return __builtin_frame_address(0);
+#elif defined(_MSC_VER)
+  return _AddressOfReturnAddress();
+#else
+  char CharOnStack = 0;
+  // The volatile store here is intended to escape the local variable, to
+  // prevent the compiler from optimizing CharOnStack into anything other
+  // than a char on the stack.
+  //
+  // Tested on: MSVC 2015 - 2019, GCC 4.9 - 9, Clang 3.2 - 9, ICC 13 - 19.
+  char *volatile Ptr = &CharOnStack;
+  return Ptr;
+#endif
+}
+
+void clang::noteBottomOfStack() {
+  if (!BottomOfStack)
+    BottomOfStack = getStackPointer();
+}
+
+bool clang::isStackNearlyExhausted() {
+  // We consider 256 KiB to be sufficient for any code that runs between checks
+  // for stack size.
+  constexpr size_t SufficientStack = 256 << 10;
+
+  // If we don't know where the bottom of the stack is, hope for the best.
+  if (!BottomOfStack)
+    return false;
+
+  intptr_t StackDiff = (intptr_t)getStackPointer() - (intptr_t)BottomOfStack;
+  size_t StackUsage = (size_t)std::abs(StackDiff);
+
+  // If the stack pointer has a surprising value, we do not understand this
+  // stack usage scheme. (Perhaps the target allocates new stack regions on
+  // demand for us.) Don't try to guess what's going on.
+  if (StackUsage > DesiredStackSize)
+    return false;
+
+  return StackUsage >= DesiredStackSize - SufficientStack;
+}
+
+void clang::runWithSufficientStackSpaceSlow(llvm::function_ref<void()> Diag,
+                                            llvm::function_ref<void()> Fn) {
+  llvm::CrashRecoveryContext CRC;
+  CRC.RunSafelyOnThread([&] {
+    noteBottomOfStack();
+    Diag();
+    Fn();
+  }, DesiredStackSize);
+}