[llvm] r202731 - Revert "[C++11] Replace LLVM atomics with std::atomic."

Reid Kleckner rnk at google.com
Tue Mar 4 10:16:58 PST 2014


This also lead me to discover http://llvm.org/PR19043.  Be aware that
re-adding <atomic> includes will break the clang-cl self-host until that's
fixed.  The self-host is still broken for other C++11-related reasons at
the moment.


On Mon, Mar 3, 2014 at 10:02 AM, Benjamin Kramer
<benny.kra at googlemail.com>wrote:

> Author: d0k
> Date: Mon Mar  3 12:02:34 2014
> New Revision: 202731
>
> URL: http://llvm.org/viewvc/llvm-project?rev=202731&view=rev
> Log:
> Revert "[C++11] Replace LLVM atomics with std::atomic."
>
> Breaks the MSVC build.
> DataStream.cpp(44): error C2552: 'llvm::Statistic::Value' : non-aggregates
> cannot be initialized with initializer list
>
> Modified:
>     llvm/trunk/include/llvm/ADT/Statistic.h
>     llvm/trunk/include/llvm/PassSupport.h
>     llvm/trunk/include/llvm/Support/ManagedStatic.h
>     llvm/trunk/lib/IR/Attributes.cpp
>     llvm/trunk/lib/IR/DiagnosticInfo.cpp
>     llvm/trunk/lib/Support/ManagedStatic.cpp
>     llvm/trunk/lib/Support/Statistic.cpp
>     llvm/trunk/lib/Support/Threading.cpp
>     llvm/trunk/lib/Support/Timer.cpp
>
> Modified: llvm/trunk/include/llvm/ADT/Statistic.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/Statistic.h?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/ADT/Statistic.h (original)
> +++ llvm/trunk/include/llvm/ADT/Statistic.h Mon Mar  3 12:02:34 2014
> @@ -26,8 +26,8 @@
>  #ifndef LLVM_ADT_STATISTIC_H
>  #define LLVM_ADT_STATISTIC_H
>
> +#include "llvm/Support/Atomic.h"
>  #include "llvm/Support/Valgrind.h"
> -#include <atomic>
>
>  namespace llvm {
>  class raw_ostream;
> @@ -36,10 +36,10 @@ class Statistic {
>  public:
>    const char *Name;
>    const char *Desc;
> -  std::atomic<unsigned> Value;
> +  volatile llvm::sys::cas_flag Value;
>    bool Initialized;
>
> -  unsigned getValue() const { return Value; }
> +  llvm::sys::cas_flag getValue() const { return Value; }
>    const char *getName() const { return Name; }
>    const char *getDesc() const { return Desc; }
>
> @@ -63,54 +63,48 @@ public:
>      // atomic operation to update the value safely in the presence of
>      // concurrent accesses, but not to read the return value, so the
>      // return value is not thread safe.
> -    ++Value;
> +    sys::AtomicIncrement(&Value);
>      return init();
>    }
>
>    unsigned operator++(int) {
>      init();
> -    unsigned OldValue = Value++;
> +    unsigned OldValue = Value;
> +    sys::AtomicIncrement(&Value);
>      return OldValue;
>    }
>
>    const Statistic &operator--() {
> -    --Value;
> +    sys::AtomicDecrement(&Value);
>      return init();
>    }
>
>    unsigned operator--(int) {
>      init();
> -    unsigned OldValue = Value--;
> +    unsigned OldValue = Value;
> +    sys::AtomicDecrement(&Value);
>      return OldValue;
>    }
>
>    const Statistic &operator+=(const unsigned &V) {
>      if (!V) return *this;
> -    Value += V;
> +    sys::AtomicAdd(&Value, V);
>      return init();
>    }
>
>    const Statistic &operator-=(const unsigned &V) {
>      if (!V) return *this;
> -    Value -= V;
> +    sys::AtomicAdd(&Value, -V);
>      return init();
>    }
>
>    const Statistic &operator*=(const unsigned &V) {
> -    unsigned Original, Result;
> -    do {
> -      Original = Value;
> -      Result = Original * V;
> -    } while (!Value.compare_exchange_strong(Original, Result));
> +    sys::AtomicMul(&Value, V);
>      return init();
>    }
>
>    const Statistic &operator/=(const unsigned &V) {
> -    unsigned Original, Result;
> -    do {
> -      Original = Value;
> -      Result = Original / V;
> -    } while (!Value.compare_exchange_strong(Original, Result));
> +    sys::AtomicDiv(&Value, V);
>      return init();
>    }
>
> @@ -157,7 +151,7 @@ public:
>  protected:
>    Statistic &init() {
>      bool tmp = Initialized;
> -    std::atomic_thread_fence(std::memory_order_seq_cst);
> +    sys::MemoryFence();
>      if (!tmp) RegisterStatistic();
>      TsanHappensAfter(this);
>      return *this;
> @@ -168,7 +162,7 @@ protected:
>  // STATISTIC - A macro to make definition of statistics really simple.
>  This
>  // automatically passes the DEBUG_TYPE of the file into the statistic.
>  #define STATISTIC(VARNAME, DESC) \
> -  static llvm::Statistic VARNAME = { DEBUG_TYPE, DESC, {}, 0 }
> +  static llvm::Statistic VARNAME = { DEBUG_TYPE, DESC, 0, 0 }
>
>  /// \brief Enable the collection and printing of statistics.
>  void EnableStatistics();
>
> Modified: llvm/trunk/include/llvm/PassSupport.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/PassSupport.h?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/PassSupport.h (original)
> +++ llvm/trunk/include/llvm/PassSupport.h Mon Mar  3 12:02:34 2014
> @@ -24,8 +24,8 @@
>  #include "Pass.h"
>  #include "llvm/InitializePasses.h"
>  #include "llvm/PassRegistry.h"
> +#include "llvm/Support/Atomic.h"
>  #include "llvm/Support/Valgrind.h"
> -#include <atomic>
>  #include <vector>
>
>  namespace llvm {
> @@ -147,21 +147,21 @@ private:
>  };
>
>  #define CALL_ONCE_INITIALIZATION(function) \
> -  static std::atomic<int> initialized; \
> -  int old_val = 0; \
> -  if (initialized.compare_exchange_strong(old_val, 1)) { \
> +  static volatile sys::cas_flag initialized = 0; \
> +  sys::cas_flag old_val = sys::CompareAndSwap(&initialized, 1, 0); \
> +  if (old_val == 0) { \
>      function(Registry); \
> -    std::atomic_thread_fence(std::memory_order_seq_cst); \
> +    sys::MemoryFence(); \
>      TsanIgnoreWritesBegin(); \
>      TsanHappensBefore(&initialized); \
>      initialized = 2; \
>      TsanIgnoreWritesEnd(); \
>    } else { \
> -    int tmp = initialized.load(); \
> -    std::atomic_thread_fence(std::memory_order_seq_cst); \
> +    sys::cas_flag tmp = initialized; \
> +    sys::MemoryFence(); \
>      while (tmp != 2) { \
> -      tmp = initialized.load(); \
> -      std::atomic_thread_fence(std::memory_order_seq_cst); \
> +      tmp = initialized; \
> +      sys::MemoryFence(); \
>      } \
>    } \
>    TsanHappensAfter(&initialized);
>
> Modified: llvm/trunk/include/llvm/Support/ManagedStatic.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ManagedStatic.h?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/ManagedStatic.h (original)
> +++ llvm/trunk/include/llvm/Support/ManagedStatic.h Mon Mar  3 12:02:34
> 2014
> @@ -14,9 +14,9 @@
>  #ifndef LLVM_SUPPORT_MANAGED_STATIC_H
>  #define LLVM_SUPPORT_MANAGED_STATIC_H
>
> +#include "llvm/Support/Atomic.h"
>  #include "llvm/Support/Threading.h"
>  #include "llvm/Support/Valgrind.h"
> -#include <atomic>
>
>  namespace llvm {
>
> @@ -64,8 +64,7 @@ public:
>    // Accessors.
>    C &operator*() {
>      void* tmp = Ptr;
> -    if (llvm_is_multithreaded())
> -      std::atomic_thread_fence(std::memory_order_seq_cst);
> +    if (llvm_is_multithreaded()) sys::MemoryFence();
>      if (!tmp) RegisterManagedStatic(object_creator<C>,
> object_deleter<C>::call);
>      TsanHappensAfter(this);
>
> @@ -73,8 +72,7 @@ public:
>    }
>    C *operator->() {
>      void* tmp = Ptr;
> -    if (llvm_is_multithreaded())
> -      std::atomic_thread_fence(std::memory_order_seq_cst);
> +    if (llvm_is_multithreaded()) sys::MemoryFence();
>      if (!tmp) RegisterManagedStatic(object_creator<C>,
> object_deleter<C>::call);
>      TsanHappensAfter(this);
>
> @@ -82,8 +80,7 @@ public:
>    }
>    const C &operator*() const {
>      void* tmp = Ptr;
> -    if (llvm_is_multithreaded())
> -      std::atomic_thread_fence(std::memory_order_seq_cst);
> +    if (llvm_is_multithreaded()) sys::MemoryFence();
>      if (!tmp) RegisterManagedStatic(object_creator<C>,
> object_deleter<C>::call);
>      TsanHappensAfter(this);
>
> @@ -91,8 +88,7 @@ public:
>    }
>    const C *operator->() const {
>      void* tmp = Ptr;
> -    if (llvm_is_multithreaded())
> -      std::atomic_thread_fence(std::memory_order_seq_cst);
> +    if (llvm_is_multithreaded()) sys::MemoryFence();
>      if (!tmp) RegisterManagedStatic(object_creator<C>,
> object_deleter<C>::call);
>      TsanHappensAfter(this);
>
>
> Modified: llvm/trunk/lib/IR/Attributes.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Attributes.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/IR/Attributes.cpp (original)
> +++ llvm/trunk/lib/IR/Attributes.cpp Mon Mar  3 12:02:34 2014
> @@ -18,6 +18,7 @@
>  #include "LLVMContextImpl.h"
>  #include "llvm/ADT/StringExtras.h"
>  #include "llvm/IR/Type.h"
> +#include "llvm/Support/Atomic.h"
>  #include "llvm/Support/Debug.h"
>  #include "llvm/Support/ManagedStatic.h"
>  #include "llvm/Support/Mutex.h"
>
> Modified: llvm/trunk/lib/IR/DiagnosticInfo.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DiagnosticInfo.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/IR/DiagnosticInfo.cpp (original)
> +++ llvm/trunk/lib/IR/DiagnosticInfo.cpp Mon Mar  3 12:02:34 2014
> @@ -19,14 +19,14 @@
>  #include "llvm/IR/Function.h"
>  #include "llvm/IR/Instruction.h"
>  #include "llvm/IR/Metadata.h"
> -#include <atomic>
> +#include "llvm/Support/Atomic.h"
>  #include <string>
>
>  using namespace llvm;
>
>  int llvm::getNextAvailablePluginDiagnosticKind() {
> -  static std::atomic<int> PluginKindID(DK_FirstPluginKind);
> -  return ++PluginKindID;
> +  static sys::cas_flag PluginKindID = DK_FirstPluginKind;
> +  return (int)sys::AtomicIncrement(&PluginKindID);
>  }
>
>  DiagnosticInfoInlineAsm::DiagnosticInfoInlineAsm(const Instruction &I,
>
> Modified: llvm/trunk/lib/Support/ManagedStatic.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/ManagedStatic.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/ManagedStatic.cpp (original)
> +++ llvm/trunk/lib/Support/ManagedStatic.cpp Mon Mar  3 12:02:34 2014
> @@ -13,6 +13,7 @@
>
>  #include "llvm/Support/ManagedStatic.h"
>  #include "llvm/Config/config.h"
> +#include "llvm/Support/Atomic.h"
>  #include <cassert>
>  using namespace llvm;
>
> @@ -27,7 +28,7 @@ void ManagedStaticBase::RegisterManagedS
>        void* tmp = Creator ? Creator() : 0;
>
>        TsanHappensBefore(this);
> -      std::atomic_thread_fence(std::memory_order_seq_cst);
> +      sys::MemoryFence();
>
>        // This write is racy against the first read in the ManagedStatic
>        // accessors. The race is benign because it does a second read
> after a
>
> Modified: llvm/trunk/lib/Support/Statistic.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Statistic.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/Statistic.cpp (original)
> +++ llvm/trunk/lib/Support/Statistic.cpp Mon Mar  3 12:02:34 2014
> @@ -76,7 +76,7 @@ void Statistic::RegisterStatistic() {
>        StatInfo->addStatistic(this);
>
>      TsanHappensBefore(this);
> -    std::atomic_thread_fence(std::memory_order_seq_cst);
> +    sys::MemoryFence();
>      // Remember we have been registered.
>      TsanIgnoreWritesBegin();
>      Initialized = true;
>
> Modified: llvm/trunk/lib/Support/Threading.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/Threading.cpp (original)
> +++ llvm/trunk/lib/Support/Threading.cpp Mon Mar  3 12:02:34 2014
> @@ -13,8 +13,8 @@
>
>  #include "llvm/Support/Threading.h"
>  #include "llvm/Config/config.h"
> +#include "llvm/Support/Atomic.h"
>  #include "llvm/Support/Mutex.h"
> -#include <atomic>
>  #include <cassert>
>
>  using namespace llvm;
> @@ -31,7 +31,7 @@ bool llvm::llvm_start_multithreaded() {
>
>    // We fence here to ensure that all initialization is complete BEFORE we
>    // return from llvm_start_multithreaded().
> -  std::atomic_thread_fence(std::memory_order_seq_cst);
> +  sys::MemoryFence();
>    return true;
>  #else
>    return false;
> @@ -44,7 +44,7 @@ void llvm::llvm_stop_multithreaded() {
>
>    // We fence here to insure that all threaded operations are complete
> BEFORE we
>    // return from llvm_stop_multithreaded().
> -  std::atomic_thread_fence(std::memory_order_seq_cst);
> +  sys::MemoryFence();
>
>    multithreaded_mode = false;
>    delete global_lock;
>
> Modified: llvm/trunk/lib/Support/Timer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Timer.cpp?rev=202731&r1=202730&r2=202731&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Support/Timer.cpp (original)
> +++ llvm/trunk/lib/Support/Timer.cpp Mon Mar  3 12:02:34 2014
> @@ -81,14 +81,14 @@ raw_ostream *llvm::CreateInfoOutputFile(
>  static TimerGroup *DefaultTimerGroup = 0;
>  static TimerGroup *getDefaultTimerGroup() {
>    TimerGroup *tmp = DefaultTimerGroup;
> -  std::atomic_thread_fence(std::memory_order_seq_cst);
> +  sys::MemoryFence();
>    if (tmp) return tmp;
>
>    llvm_acquire_global_lock();
>    tmp = DefaultTimerGroup;
>    if (!tmp) {
>      tmp = new TimerGroup("Miscellaneous Ungrouped Timers");
> -    std::atomic_thread_fence(std::memory_order_seq_cst);
> +    sys::MemoryFence();
>      DefaultTimerGroup = tmp;
>    }
>    llvm_release_global_lock();
>
>
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