1 //===--- Stack.h - Utilities for dealing with stack space -------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// Defines utilities for dealing with stack allocation and stack space.
11 ///
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_BASIC_STACK_H
15 #define LLVM_CLANG_BASIC_STACK_H
16 
17 #include <cstddef>
18 
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/Support/Compiler.h"
21 
22 namespace clang {
23   /// The amount of stack space that Clang would like to be provided with.
24   /// If less than this much is available, we may be unable to reach our
25   /// template instantiation depth limit and other similar limits.
26   constexpr size_t DesiredStackSize = 8 << 20;
27 
28   /// Call this once on each thread, as soon after starting the thread as
29   /// feasible, to note the approximate address of the bottom of the stack.
30   void noteBottomOfStack();
31 
32   /// Determine whether the stack is nearly exhausted.
33   bool isStackNearlyExhausted();
34 
35   void runWithSufficientStackSpaceSlow(llvm::function_ref<void()> Diag,
36                                        llvm::function_ref<void()> Fn);
37 
38   /// Run a given function on a stack with "sufficient" space. If stack space
39   /// is insufficient, calls Diag to emit a diagnostic before calling Fn.
40   inline void runWithSufficientStackSpace(llvm::function_ref<void()> Diag,
41                                           llvm::function_ref<void()> Fn) {
42 #ifdef LLVM_ENABLE_THREADS
43     if (LLVM_UNLIKELY(isStackNearlyExhausted()))
44       runWithSufficientStackSpaceSlow(Diag, Fn);
45     else
46       Fn();
47 #else
48     if (LLVM_UNLIKELY(isStackNearlyExhausted()))
49       Diag();
50     Fn();
51 #endif
52   }
53 } // end namespace clang
54 
55 #endif // LLVM_CLANG_BASIC_STACK_H
56