Introduce stats and stats_client libraries.

[pcc]

Summary

This is part of a new statistics gathering feature for the sanitizers.
See clang/docs/SanitizerStats.rst for further info and docs.

[krasin1]

lib/sanitizer_common/sanitizer_flags.cc

51

Are we restricted to use C++ strings here? The function is super scary right now.

99

I don't think that the flag value is limited by kMaxPathLength. Can you please choose a better limit? Or somehow check that the value fits the buffer?

lib/stats/stats.cc

40

s/unsigned/size_t/ maybe?

47

Probably, it makes sense to check that start != NULL to fail cleanly if WriteModuleReport is called on an unregistered module.

[eugenis]

lib/stats/stats.cc

50

This lazy file opening just complicates things. Maybe move to a separate function and call it from WriteFullReport ?

lib/stats/stats_client.cc

13

Please mention that it is intended to be linked into each individual module, and that it can not use the sanitizer_common infrastructure.

95

Why dlsym and not just declare an external function and call it directly?

test/cfi/stats.cpp

2

Does this work with the cross-dso mode?

[pcc]

• Switch to an alternative in-memory representation that avoids the need for linker magic

[pcc]

• Address review comments

lib/stats/stats.cc

41

It doesn't matter, this will never be more than 8.

48

Added a CHECK.

lib/stats/stats_client.cc

81

This won't work on Windows where DSOs can't directly call into the main executable.

test/cfi/stats.cpp

3

Almost; this initially gave duplicate symbol errors. To avoid a combinatorial explosion in the number of static sanitizer libraries I decided to start improving how we link them. First step: link stats without -whole-archive, and use -u to pull in the stats runtime. Also added an integration test here.

[pcc]

• Add CHECK to SubstituteForFlagValue

lib/sanitizer_common/sanitizer_flags.cc

51

I don't think we can use std::string here.

99

kMaxPathLength is 4096, which is probably enough (we use it in a bunch of other places elsewhere). I don't think this code matters enough to worry about using a variable-size buffer.

I've added a CHECK to the above function.

[krasin1]

lib/sanitizer_common/sanitizer_flags.cc

51

why? not that I insist, I just probably don't understand the constraints and interested to learn about that.

[pcc]

lib/sanitizer_common/sanitizer_flags.cc

51

If the C++ standard library is compiled with sanitizer instrumentation, we would have a circular dependency between sanitizer_common and the stdlib.

[krasin]

lib/sanitizer_common/sanitizer_flags.cc

51

You're right. Thank you for the reminder.

[eugenis]

lib/stats/stats.cc

88

There could be a data race if this is called from concurrent dlopen-ed module constructors.

[pcc]

• Add mutex to fix data race

[eugenis]

LGTM

lib/CMakeLists.txt

 
 if(COMPILER_RT_BUILD_SANITIZERS)
   if(COMPILER_RT_HAS_INTERCEPTION)
     add_subdirectory(interception)
   endif()
 
   if(COMPILER_RT_HAS_SANITIZER_COMMON)
     add_subdirectory(sanitizer_common)
+    add_subdirectory(stats)
     add_subdirectory(lsan)
     add_subdirectory(ubsan)
   endif()
 
   if(COMPILER_RT_HAS_ASAN)
     add_subdirectory(asan)
   endif()
 

lib/sanitizer_common/sanitizer_common.h

public:
   }
   uptr capacity() const {
     return capacity_;
   }
 
   void clear() { size_ = 0; }
   bool empty() const { return size() == 0; }
 
+  const T *begin() const {
+    return data();
+  }
+  T *begin() {
+    return data();
+  }
+  const T *end() const {
+    return data() + size();
+  }
+  T *end() {
+    return data() + size();
+  }
+
  private:
   void Resize(uptr new_capacity) {
     CHECK_GT(new_capacity, 0);
     CHECK_LE(size_, new_capacity);
     T *new_data = (T *)MmapOrDie(new_capacity * sizeof(T),
                                  "InternalMmapVector");
     internal_memcpy(new_data, data_, size_ * sizeof(T));
     T *old_data = data_;

lib/sanitizer_common/sanitizer_flags.h

 // CommonFlags defaults. Generally, it should only be used right after
 // SetCommonFlagsDefaults(), but before ParseCommonFlagsFromString(), and
 // only during the flags initialization (i.e. before they are used for
 // the first time).
 inline void OverrideCommonFlags(const CommonFlags &cf) {
   common_flags_dont_use.CopyFrom(cf);
 }
 
+void SubstituteForFlagValue(const char *s, char *out, uptr out_size);
+
 class FlagParser;
 void RegisterCommonFlags(FlagParser *parser,
                          CommonFlags *cf = &common_flags_dont_use);
 void RegisterIncludeFlags(FlagParser *parser, CommonFlags *cf);
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_FLAGS_H

lib/sanitizer_common/sanitizer_flags.cc

 #include "sanitizer_flags.inc"
 #undef COMMON_FLAG
 }
 
 void CommonFlags::CopyFrom(const CommonFlags &other) {
   internal_memcpy(this, &other, sizeof(*this));
 }
 
-// Copy the string from "s" to "out", replacing "%b" with the binary basename.
-static void SubstituteBinaryName(const char *s, char *out, uptr out_size) {
+// Copy the string from "s" to "out", making the following substitutions:
+// %b = binary basename
+// %p = pid
+void SubstituteForFlagValue(const char *s, char *out, uptr out_size) {
   char *out_end = out + out_size;
   while (*s && out < out_end - 1) {
-    if (s[0] != '%' || s[1] != 'b') { *out++ = *s++; continue; }
+    if (s[0] != '%') {
+      *out++ = *s++;
+      continue;
+    }
+    switch (s[1]) {
+      case 'b': {
         const char *base = GetProcessName();
         CHECK(base);
         while (*base && out < out_end - 1)
           *out++ = *base++;
         s += 2; // skip "%b"
+        break;
+      }
+      case 'p': {
+        int pid = internal_getpid();
+        char buf[32];
+        char *buf_pos = buf + 32;
+        do {
+          *--buf_pos = (pid % 10) + '0';
+          pid /= 10;
+        } while (pid);
+        while (buf_pos < buf + 32 && out < out_end - 1)
+          *out++ = *buf_pos++;
+        s += 2; // skip "%p"
+        break;
+      }
+      default:
+        *out++ = *s++;
+        break;
+    }
   }
+  CHECK(out < out_end - 1);
   *out = '\0';
 }
 
 class FlagHandlerInclude : public FlagHandlerBase {
   FlagParser *parser_;
   bool ignore_missing_;
 
  public:
   explicit FlagHandlerInclude(FlagParser *parser, bool ignore_missing)
       : parser_(parser), ignore_missing_(ignore_missing) {}
   bool Parse(const char *value) final {
     if (internal_strchr(value, '%')) {
       char *buf = (char *)MmapOrDie(kMaxPathLength, "FlagHandlerInclude");
-      SubstituteBinaryName(value, buf, kMaxPathLength);
+      SubstituteForFlagValue(value, buf, kMaxPathLength);
       bool res = parser_->ParseFile(buf, ignore_missing_);
       UnmapOrDie(buf, kMaxPathLength);
       return res;
     }
     return parser_->ParseFile(value, ignore_missing_);
   }
 };
 

lib/sanitizer_common/sanitizer_internal_defs.h

 #endif
 typedef u64  OFF64_T;
 
 #if (SANITIZER_WORDSIZE == 64) || SANITIZER_MAC
 typedef uptr operator_new_size_type;
 #else
 typedef u32 operator_new_size_type;
 #endif
-}  // namespace __sanitizer
 
 
-using namespace __sanitizer;  // NOLINT
 // ----------- ATTENTION -------------
 // This header should NOT include any other headers to avoid portability issues.
 
 // Common defs.
 #define INLINE inline
 #define INTERFACE_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
 #define SANITIZER_WEAK_DEFAULT_IMPL \
   extern "C" SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE NOINLINE

 # define THREAD_CALLING_CONV __stdcall
 #else  // _WIN32
 typedef void* thread_return_t;
 # define THREAD_CALLING_CONV
 #endif  // _WIN32
 typedef thread_return_t (THREAD_CALLING_CONV *thread_callback_t)(void* arg);
 
 // NOTE: Functions below must be defined in each run-time.
-namespace __sanitizer {
 void NORETURN Die();
 
 // FIXME: No, this shouldn't be in the sanitizer interface.
 SANITIZER_INTERFACE_ATTRIBUTE
 void NORETURN CheckFailed(const char *file, int line, const char *cond,
                           u64 v1, u64 v2);
-}  // namespace __sanitizer
 
 // Check macro
 #define RAW_CHECK_MSG(expr, msg) do { \
   if (UNLIKELY(!(expr))) { \
     RawWrite(msg); \
     Die(); \
   } \
 } while (0)

 #undef UINT64_MAX
 #define UINT64_MAX             (__UINT64_C(18446744073709551615))
 
 enum LinkerInitialized { LINKER_INITIALIZED = 0 };
 
 #if !defined(_MSC_VER) || defined(__clang__)
 # define GET_CALLER_PC() (uptr)__builtin_return_address(0)
 # define GET_CURRENT_FRAME() (uptr)__builtin_frame_address(0)
+inline void Trap() {
+  __builtin_trap();
+}
 #else
 extern "C" void* _ReturnAddress(void);
 # pragma intrinsic(_ReturnAddress)
 # define GET_CALLER_PC() (uptr)_ReturnAddress()
 // CaptureStackBackTrace doesn't need to know BP on Windows.
 // FIXME: This macro is still used when printing error reports though it's not
 // clear if the BP value is needed in the ASan reports on Windows.
 # define GET_CURRENT_FRAME() (uptr)0xDEADBEEF
+
+extern "C" void __ud2(void);
+# pragma intrinsic(__ud2)
+inline void Trap() {
+  __ud2();
+}
 #endif
 
 #define HANDLE_EINTR(res, f)                                       \
   {                                                                \
     int rverrno;                                                   \
     do {                                                           \
       res = (f);                                                   \
     } while (internal_iserror(res, &rverrno) && rverrno == EINTR); \
   }
 
 // Forces the compiler to generate a frame pointer in the function.
 #define ENABLE_FRAME_POINTER                                       \
   do {                                                             \
     volatile uptr enable_fp;                                       \
     enable_fp = GET_CURRENT_FRAME();                               \
     (void)enable_fp;                                               \
   } while (0)
 
+}  // namespace __sanitizer
+
+using namespace __sanitizer;  // NOLINT
+
 #endif  // SANITIZER_DEFS_H

lib/sanitizer_common/sanitizer_symbolizer.h

public:
   // to distinguish system library calls made in user code from calls made
   // during in-process symbolization.
   typedef void (*StartSymbolizationHook)();
   typedef void (*EndSymbolizationHook)();
   // May be called at most once.
   void AddHooks(StartSymbolizationHook start_hook,
                 EndSymbolizationHook end_hook);
 
+  LoadedModule *FindModuleForAddress(uptr address);
+
  private:
   // GetModuleNameAndOffsetForPC has to return a string to the caller.
   // Since the corresponding module might get unloaded later, we should create
   // our owned copies of the strings that we can safely return.
   // ModuleNameOwner does not provide any synchronization, thus calls to
   // its method should be protected by |mu_|.
   class ModuleNameOwner {
    public:
private:
     BlockingMutex *mu_;
   } module_names_;
 
   /// Platform-specific function for creating a Symbolizer object.
   static Symbolizer *PlatformInit();
 
   bool FindModuleNameAndOffsetForAddress(uptr address, const char **module_name,
                                          uptr *module_offset);
-  LoadedModule *FindModuleForAddress(uptr address);
   LoadedModule modules_[kMaxNumberOfModules];
   uptr n_modules_;
   // If stale, need to reload the modules before looking up addresses.
   bool modules_fresh_;
 
   // Platform-specific default demangler, must not return nullptr.
   const char *PlatformDemangle(const char *name);
   void PlatformPrepareForSandboxing();

lib/stats/CMakeLists.txt

+include_directories(..)
+
+add_custom_target(stats)
+
+if(APPLE)
+  set(STATS_LIB_FLAVOR SHARED)
+else()
+  set(STATS_LIB_FLAVOR STATIC)
+endif()
+
+add_compiler_rt_runtime(clang_rt.stats
+  ${STATS_LIB_FLAVOR}
+  ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
+  OS ${SANITIZER_COMMON_SUPPORTED_OS}
+  SOURCES stats.cc
+  OBJECT_LIBS RTSanitizerCommon
+              RTSanitizerCommonLibc
+  CFLAGS ${SANITIZER_COMMON_CFLAGS}
+  PARENT_TARGET stats)
+
+add_compiler_rt_runtime(clang_rt.stats_client
+  STATIC
+  ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
+  OS ${SANITIZER_COMMON_SUPPORTED_OS}
+  SOURCES stats_client.cc
+  CFLAGS ${SANITIZER_COMMON_CFLAGS}
+  PARENT_TARGET stats)

lib/stats/stats.h

+//===-- stats.h -------------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Data definitions for sanitizer statistics gathering.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SANITIZER_STATS_STATS_H
+#define SANITIZER_STATS_STATS_H
+
+#include "sanitizer_common/sanitizer_internal_defs.h"
+
+namespace __sanitizer {
+
+// Number of bits in data that are used for the sanitizer kind. Needs to match
+// llvm::kSanitizerStatKindBits in
+// llvm/include/llvm/Transforms/Utils/SanitizerStats.h
+enum { kKindBits = 3 };
+
+struct StatInfo {
+  uptr addr;
+  uptr data;
+};
+
+struct StatModule {
+  StatModule *next;
+  u32 size;
+  StatInfo infos[1];
+};
+
+inline uptr CountFromData(uptr data) {
+  return data & ((1ull << (sizeof(uptr) * 8 - kKindBits)) - 1);
+}
+
+}
+
+#endif

lib/stats/stats.cc

+//===-- stats.cc ----------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Sanitizer statistics gathering. Manages statistics for a process and is
+// responsible for writing the report file.
+//
+//===----------------------------------------------------------------------===//
+
+#include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_internal_defs.h"
+#if SANITIZER_POSIX
+#include "sanitizer_common/sanitizer_posix.h"
+#endif
+#include "sanitizer_common/sanitizer_symbolizer.h"
+#include "stats/stats.h"
+#if SANITIZER_POSIX
+#include <signal.h>
+#endif
+
+using namespace __sanitizer;
+
+namespace {
+
+InternalMmapVectorNoCtor<StatModule **> modules;
+StaticSpinMutex modules_mutex;
+
+fd_t stats_fd;
+
+void WriteLE(fd_t fd, uptr val) {
+  char chars[sizeof(uptr)];
+  for (unsigned i = 0; i != sizeof(uptr); ++i) {
+    chars[i] = val >> (i * 8);
+  }
+  WriteToFile(fd, chars, sizeof(uptr));
+}
+
+void OpenStatsFile(const char *path_env) {
+  InternalScopedBuffer<char> path(kMaxPathLength);
+  SubstituteForFlagValue(path_env, path.data(), kMaxPathLength);
+
+  error_t err;
+  stats_fd = OpenFile(path.data(), WrOnly, &err);
+  if (stats_fd == kInvalidFd) {
+    Report("stats: failed to open %s for writing (reason: %d)\n", path.data(),
+           err);
+    return;
+  }
+  char sizeof_uptr = sizeof(uptr);
+  WriteToFile(stats_fd, &sizeof_uptr, 1);
+}
+
+void WriteModuleReport(StatModule **smodp) {
+  CHECK(smodp);
+  const char *path_env = GetEnv("SANITIZER_STATS_PATH");
+  if (!path_env || stats_fd == kInvalidFd)
+    return;
+  if (!stats_fd)
+    OpenStatsFile(path_env);
+  LoadedModule *mod = Symbolizer::GetOrInit()->FindModuleForAddress(
+      reinterpret_cast<uptr>(smodp));
+  WriteToFile(stats_fd, mod->full_name(),
+              internal_strlen(mod->full_name()) + 1);
+  for (StatModule *smod = *smodp; smod; smod = smod->next) {
+    for (u32 i = 0; i != smod->size; ++i) {
+      StatInfo *s = &smod->infos[i];
+      if (!s->addr)
+        continue;
+      WriteLE(stats_fd, s->addr - mod->base_address());
+      WriteLE(stats_fd, s->data);
+    }
+  }
+  WriteLE(stats_fd, 0);
+  WriteLE(stats_fd, 0);
+}
+
+} // namespace
+
+extern "C"
+SANITIZER_INTERFACE_ATTRIBUTE
+unsigned __sanitizer_stats_register(StatModule **mod) {
+  SpinMutexLock l(&modules_mutex);
+  modules.push_back(mod);
+  return modules.size() - 1;
+}
+
+extern "C"
+SANITIZER_INTERFACE_ATTRIBUTE
+void __sanitizer_stats_unregister(unsigned index) {
+  SpinMutexLock l(&modules_mutex);
+  WriteModuleReport(modules[index]);
+  modules[index] = 0;
+}
+
+namespace {
+
+void WriteFullReport() {
+  SpinMutexLock l(&modules_mutex);
+  for (StatModule **mod : modules) {
+    if (!mod)
+      continue;
+    WriteModuleReport(mod);
+  }
+  if (stats_fd != 0 && stats_fd != kInvalidFd) {
+    CloseFile(stats_fd);
+    stats_fd = kInvalidFd;
+  }
+}
+
+#if SANITIZER_POSIX
+void USR2Handler(int sig) {
+  WriteFullReport();
+}
+#endif
+
+struct WriteReportOnExitOrSignal {
+  WriteReportOnExitOrSignal() {
+#if SANITIZER_POSIX
+    struct sigaction sigact;
+    internal_memset(&sigact, 0, sizeof(sigact));
+    sigact.sa_handler = USR2Handler;
+    internal_sigaction(SIGUSR2, &sigact, nullptr);
+#endif
+  }
+
+  ~WriteReportOnExitOrSignal() {
+    WriteFullReport();
+  }
+} wr;
+
+} // namespace

lib/stats/stats_client.cc

+//===-- stats_client.cc ---------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Sanitizer statistics gathering. Manages statistics for a module (executable
+// or DSO) and registers statistics with the process.
+//
+// This is linked into each individual modle and cannot directly use functions
+// declared in sanitizer_common.
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <dlfcn.h>
+#endif
+#include <stdint.h>
+#include <stdio.h>
+
+#include "sanitizer_common/sanitizer_internal_defs.h"
+#include "stats/stats.h"
+
+using namespace __sanitizer;
+
+namespace {
+
+void *LookupSymbolFromMain(const char *name) {
+#ifdef _WIN32
+  return reinterpret_cast<void *>(GetProcAddress(GetModuleHandle(0), name));
+#else
+  return dlsym(RTLD_DEFAULT, name);
+#endif
+}
+
+StatModule *list;
+
+struct RegisterSanStats {
+  unsigned module_id;
+
+  RegisterSanStats() {
+    typedef unsigned (*reg_func_t)(StatModule **);
+    reg_func_t reg_func = reinterpret_cast<reg_func_t>(
+        LookupSymbolFromMain("__sanitizer_stats_register"));
+    if (reg_func)
+      module_id = reg_func(&list);
+  }
+
+  ~RegisterSanStats() {
+    typedef void (*unreg_func_t)(unsigned);
+    unreg_func_t unreg_func = reinterpret_cast<unreg_func_t>(
+        LookupSymbolFromMain("__sanitizer_stats_unregister"));
+    if (unreg_func)
+      unreg_func(module_id);
+  }
+} reg;
+
+}
+
+extern "C" void __sanitizer_stat_init(StatModule *mod) {
+  mod->next = list;
+  list = mod;
+}
+
+extern "C" void __sanitizer_stat_report(StatInfo *s) {
+  s->addr = GET_CALLER_PC();
+#if defined(_WIN64) && !defined(__clang__)
+  uptr old_data = InterlockedIncrement64(reinterpret_cast<LONG64 *>(&s->data));
+#elif defined(_WIN32) && !defined(__clang__)
+  uptr old_data = InterlockedIncrement(&s->data);
+#else
+  uptr old_data = __sync_fetch_and_add(&s->data, 1);
+#endif
+
+  // Overflow check.
+  if (CountFromData(old_data + 1) == 0)
+    Trap();
+}

test/cfi/CMakeLists.txt

 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
   )
 
 set(CFI_TEST_DEPS ${SANITIZER_COMMON_LIT_TEST_DEPS})
 if(NOT COMPILER_RT_STANDALONE_BUILD)
   list(APPEND CFI_TEST_DEPS
     opt
     ubsan
+    stats
+    sanstats
   )
   if(COMPILER_RT_HAS_CFI)
     list(APPEND CFI_TEST_DEPS cfi)
   endif()
   if(LLVM_ENABLE_PIC AND LLVM_BINUTILS_INCDIR)
     list(APPEND CFI_TEST_DEPS
       LLVMgold
     )

test/cfi/cross-dso/stats.cpp

+// RUN: %clangxx_cfi_dso -DSHARED_LIB -fPIC -g -fsanitize-stats -shared -o %t.so %s
+// RUN: %clangxx_cfi_dso -g -fsanitize-stats -o %t %s %t.so
+// RUN: env SANITIZER_STATS_PATH=%t.stats %t
+// RUN: sanstats %t.stats | FileCheck %s
+
+struct ABase {};
+
+struct A : ABase {
+  virtual void vf() {}
+  void nvf() {}
+};
+
+extern "C" void vcall(A *a);
+extern "C" void nvcall(A *a);
+
+#ifdef SHARED_LIB
+
+extern "C" __attribute__((noinline)) void vcall(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] vcall cfi-vcall 37
+  a->vf();
+}
+
+extern "C" __attribute__((noinline)) void nvcall(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] nvcall cfi-nvcall 51
+  a->nvf();
+}
+
+#else
+
+extern "C" __attribute__((noinline)) A *dcast(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] dcast cfi-derived-cast 24
+  return (A *)(ABase *)a;
+}
+
+extern "C" __attribute__((noinline)) A *ucast(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] ucast cfi-unrelated-cast 81
+  return (A *)(char *)a;
+}
+
+extern "C" __attribute__((noinline)) void unreachable(A *a) {
+  // CHECK-NOT: unreachable
+  a->vf();
+}
+
+int main() {
+  A a;
+  for (unsigned i = 0; i != 37; ++i)
+    vcall(&a);
+  for (unsigned i = 0; i != 51; ++i)
+    nvcall(&a);
+  for (unsigned i = 0; i != 24; ++i)
+    dcast(&a);
+  for (unsigned i = 0; i != 81; ++i)
+    ucast(&a);
+  for (unsigned i = 0; i != 0; ++i)
+    unreachable(&a);
+}
+
+#endif

test/cfi/stats.cpp

+// RUN: %clangxx_cfi -g -fsanitize-stats -o %t %s
+// RUN: env SANITIZER_STATS_PATH=%t.stats %t
+// RUN: sanstats %t.stats | FileCheck %s
+
+struct ABase {};
+
+struct A : ABase {
+  virtual void vf() {}
+  void nvf() {}
+};
+
+extern "C" __attribute__((noinline)) void vcall(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] vcall cfi-vcall 37
+  a->vf();
+}
+
+extern "C" __attribute__((noinline)) void nvcall(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] nvcall cfi-nvcall 51
+  a->nvf();
+}
+
+extern "C" __attribute__((noinline)) A *dcast(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] dcast cfi-derived-cast 24
+  return (A *)(ABase *)a;
+}
+
+extern "C" __attribute__((noinline)) A *ucast(A *a) {
+  // CHECK: stats.cpp:[[@LINE+1]] ucast cfi-unrelated-cast 81
+  return (A *)(char *)a;
+}
+
+extern "C" __attribute__((noinline)) void unreachable(A *a) {
+  // CHECK-NOT: unreachable
+  a->vf();
+}
+
+int main() {
+  A a;
+  for (unsigned i = 0; i != 37; ++i)
+    vcall(&a);
+  for (unsigned i = 0; i != 51; ++i)
+    nvcall(&a);
+  for (unsigned i = 0; i != 24; ++i)
+    dcast(&a);
+  for (unsigned i = 0; i != 81; ++i)
+    ucast(&a);
+  for (unsigned i = 0; i != 0; ++i)
+    unreachable(&a);
+}