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Merge libcxxrt master fd484be8d1e94a1fcf6bc5c67e5c07b65ada19b6

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Interesting fixes:
47661d0 Match libc++abi/libsupc++ when demangling array types
e44a05c Fix unitialized variable in __cxa_demangle_gnu3 after #6 (#8)
5088b05 Remove some code duplication.
fd484be Atomics cleanup (#11)

MFC after:	2 weeks
This commit is contained in:
Dimitry Andric 2022-03-09 20:45:01 +01:00
commit 56aaed388b
7 changed files with 485 additions and 164 deletions
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108
contrib/libcxxrt/atomic.h
View File

@ -5,26 +5,98 @@
#ifndef __has_feature
# define __has_feature(x) 0
#endif
/**
* Swap macro that enforces a happens-before relationship with a corresponding
* ATOMIC_LOAD.
*/
#ifndef __has_extension
# define __has_extension(x) 0
#endif
#if !__has_extension(c_atomic)
# define _Atomic(T) T
#endif
#if __has_builtin(__c11_atomic_exchange)
#define ATOMIC_SWAP(addr, val)\
__c11_atomic_exchange(reinterpret_cast<_Atomic(__typeof__(val))*>(addr), val, __ATOMIC_ACQ_REL)
#elif __has_builtin(__sync_swap)
#define ATOMIC_SWAP(addr, val)\
__sync_swap(addr, val)
# define ATOMIC_BUILTIN(name) __c11_atomic_##name
#else
#define ATOMIC_SWAP(addr, val)\
__sync_lock_test_and_set(addr, val)
# define ATOMIC_BUILTIN(name) __atomic_##name##_n
#endif
#if __has_builtin(__c11_atomic_load)
#define ATOMIC_LOAD(addr)\
__c11_atomic_load(reinterpret_cast<_Atomic(__typeof__(*addr))*>(addr), __ATOMIC_ACQUIRE)
#else
#define ATOMIC_LOAD(addr)\
(__sync_synchronize(), *addr)
#endif
namespace
{
/**
* C++11 memory orders. We only need a subset of them.
*/
enum memory_order
{
/**
* Acquire order.
*/
acquire = __ATOMIC_ACQUIRE,
/**
* Release order.
*/
release = __ATOMIC_RELEASE,
/**
* Sequentially consistent memory ordering.
*/
seqcst = __ATOMIC_SEQ_CST
};
/**
* Atomic, implements a subset of `std::atomic`.
*/
template<typename T>
class atomic
{
/**
* The underlying value. Use C11 atomic qualification if available.
*/
_Atomic(T) val;
public:
/**
* Constructor, takes a value.
*/
atomic(T init) : val(init) {}
/**
* Atomically load with the specified memory order.
*/
T load(memory_order order = memory_order::seqcst)
{
return ATOMIC_BUILTIN(load)(&val, order);
}
/**
* Atomically store with the specified memory order.
*/
void store(T v, memory_order order = memory_order::seqcst)
{
return ATOMIC_BUILTIN(store)(&val, v, order);
}
/**
* Atomically exchange with the specified memory order.
*/
T exchange(T v, memory_order order = memory_order::seqcst)
{
return ATOMIC_BUILTIN(exchange)(&val, v, order);
}
/**
* Atomically exchange with the specified memory order.
*/
bool compare_exchange(T & expected,
T desired,
memory_order order = memory_order::seqcst)
{
#if __has_builtin(__c11_atomic_compare_exchange_strong)
return __c11_atomic_compare_exchange_strong(
&val, &expected, desired, order, order);
#else
return __atomic_compare_exchange_n(
&val, &expected, desired, true, order, order);
#endif
}
};
} // namespace
#undef ATOMIC_BUILTIN

21
contrib/libcxxrt/auxhelper.cc
View File

@ -34,6 +34,21 @@
#include <stdlib.h>
#include "stdexcept.h"
namespace {
/**
* Throw an exception if we're compiling with exceptions, otherwise abort.
*/
template<typename T>
void throw_exception()
{
#if !defined(_CXXRT_NO_EXCEPTIONS)
throw T();
#else
abort();
#endif
}
}
/**
* Called to generate a bad cast exception. This function is intended to allow
* compilers to insert code generating this exception without needing to
@ -41,7 +56,7 @@
*/
extern "C" void __cxa_bad_cast()
{
throw std::bad_cast();
throw_exception<std::bad_cast>();
}
/**
@ -51,7 +66,7 @@ extern "C" void __cxa_bad_cast()
*/
extern "C" void __cxa_bad_typeid()
{
throw std::bad_typeid();
throw_exception<std::bad_typeid>();
}
/**
@ -78,5 +93,5 @@ extern "C" void __cxa_deleted_virtual()
extern "C" void __cxa_throw_bad_array_new_length()
{
throw std::bad_array_new_length();
throw_exception<std::bad_array_new_length>();
}

21
contrib/libcxxrt/exception.cc
View File

@ -1,5 +1,6 @@
/*
* Copyright 2010-2011 PathScale, Inc. All rights reserved.
* Copyright 2021 David Chisnall. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
@ -289,9 +290,9 @@ using namespace ABI_NAMESPACE;
/** The global termination handler. */
static terminate_handler terminateHandler = abort;
static atomic<terminate_handler> terminateHandler = abort;
/** The global unexpected exception handler. */
static unexpected_handler unexpectedHandler = std::terminate;
static atomic<unexpected_handler> unexpectedHandler = std::terminate;
/** Key used for thread-local data. */
static pthread_key_t eh_key;
@ -744,12 +745,12 @@ static void throw_exception(__cxa_exception *ex)
ex->unexpectedHandler = info->unexpectedHandler;
if (0 == ex->unexpectedHandler)
{
ex->unexpectedHandler = unexpectedHandler;
ex->unexpectedHandler = unexpectedHandler.load();
}
ex->terminateHandler = info->terminateHandler;
if (0 == ex->terminateHandler)
{
ex->terminateHandler = terminateHandler;
ex->terminateHandler = terminateHandler.load();
}
info->globals.uncaughtExceptions++;
@ -1449,7 +1450,7 @@ namespace std
{
if (thread_local_handlers) { return pathscale::set_unexpected(f); }
return ATOMIC_SWAP(&unexpectedHandler, f);
return unexpectedHandler.exchange(f);
}
/**
* Sets the function that is called to terminate the program.
@ -1458,7 +1459,7 @@ namespace std
{
if (thread_local_handlers) { return pathscale::set_terminate(f); }
return ATOMIC_SWAP(&terminateHandler, f);
return terminateHandler.exchange(f);
}
/**
* Terminates the program, calling a custom terminate implementation if
@ -1474,7 +1475,7 @@ namespace std
// return.
abort();
}
terminateHandler();
terminateHandler.load()();
}
/**
* Called when an unexpected exception is encountered (i.e. an exception
@ -1491,7 +1492,7 @@ namespace std
// return.
abort();
}
unexpectedHandler();
unexpectedHandler.load()();
}
/**
* Returns whether there are any exceptions currently being thrown that
@ -1521,7 +1522,7 @@ namespace std
{
return info->unexpectedHandler;
}
return ATOMIC_LOAD(&unexpectedHandler);
return unexpectedHandler.load();
}
/**
* Returns the current terminate handler.
@ -1533,7 +1534,7 @@ namespace std
{
return info->terminateHandler;
}
return ATOMIC_LOAD(&terminateHandler);
return terminateHandler.load();
}
}
#if defined(__arm__) && !defined(__ARM_DWARF_EH__)

356
contrib/libcxxrt/guard.cc
View File

@ -1,5 +1,6 @@
/*
* Copyright 2010-2012 PathScale, Inc. All rights reserved.
* Copyright 2021 David Chisnall. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
@ -40,12 +41,11 @@
* is heavily optimised towards the case where the static has already been
* initialised.
*/
#include "atomic.h"
#include <assert.h>
#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <assert.h>
#include "atomic.h"
// Older GCC doesn't define __LITTLE_ENDIAN__
#ifndef __LITTLE_ENDIAN__
@ -62,102 +62,282 @@
# endif
#endif
/*
* The least significant bit of the guard variable indicates that the object
* has been initialised, the most significant bit is used for a spinlock.
* The Itanium C++ ABI defines guard words that are 64-bit (32-bit on AArch32)
* values with one bit defined to indicate that the guarded variable is and
* another bit to indicate that it's currently locked (initialisation in
* progress). The bit to use depends on the byte order of the target.
*
* On many 32-bit platforms, 64-bit atomics are unavailable (or slow) and so we
* treat the two halves of the 64-bit word as independent values and
*/
namespace
{
/**
* The state of the guard variable when an attempt is made to lock it.
*/
enum class GuardState
{
/**
* The lock is not held but is not needed because initialisation is
* one.
*/
InitDone,
/**
* Initialisation is not done but the lock is held by the caller.
*/
InitLockSucceeded,
/**
* Attempting to acquire the lock failed.
*/
InitLockFailed
};
/**
* Class encapsulating a single atomic word being used to represent the
* guard. The word size is defined by the type of `GuardWord`. The bit
* used to indicate the locked state is `1<<LockedBit`, the bit used to
* indicate the initialised state is `1<<InitBit`.
*/
template<typename GuardWord, int LockedBit, int InitBit>
struct SingleWordGuard
{
/**
* The value indicating that the lock bit is set (and no other bits).
*/
static constexpr GuardWord locked = static_cast<GuardWord>(1)
<< LockedBit;
/**
* The value indicating that the initialised bit is set (and all other
* bits are zero).
*/
static constexpr GuardWord initialised = static_cast<GuardWord>(1)
<< InitBit;
/**
* The guard variable.
*/
atomic<GuardWord> val;
public:
/**
* Release the lock and set the initialised state. In the single-word
* implementation here, these are both done by a single store.
*/
void unlock(bool isInitialised)
{
val.store(isInitialised ? initialised : 0, memory_order::release);
#ifndef NDEBUG
GuardWord init_state = initialised;
assert(*reinterpret_cast<uint8_t*>(&init_state) != 0);
#endif
}
/**
* Try to acquire the lock. This has a tri-state return, indicating
* either that the lock was acquired, it wasn't acquired because it was
* contended, or it wasn't acquired because the guarded variable is
* already initialised.
*/
GuardState try_lock()
{
GuardWord old = 0;
// Try to acquire the lock, assuming that we are in the state where
// the lock is not held and the variable is not initialised (so the
// expected value is 0).
if (val.compare_exchange(old, locked))
{
return GuardState::InitLockSucceeded;
}
// If the CAS failed and the old value indicates that this is
// initialised, return that initialisation is done and skip further
// retries.
if (old == initialised)
{
return GuardState::InitDone;
}
// Otherwise, report failure.
return GuardState::InitLockFailed;
}
/**
* Check whether the guard indicates that the variable is initialised.
*/
bool is_initialised()
{
return (val.load(memory_order::acquire) & initialised) ==
initialised;
}
};
/**
* Class encapsulating using two 32-bit atomic values to represent a 64-bit
* guard variable.
*/
template<int LockedBit, int InitBit>
class DoubleWordGuard
{
/**
* The value of `lock_word` when the lock is held.
*/
static constexpr uint32_t locked = static_cast<uint32_t>(1)
<< LockedBit;
/**
* The value of `init_word` when the guarded variable is initialised.
*/
static constexpr uint32_t initialised = static_cast<uint32_t>(1)
<< InitBit;
/**
* The word used for the initialised flag. This is always the first
* word irrespective of endian because the generated code compares the
* first byte in memory against 0.
*/
atomic<uint32_t> init_word;
/**
* The word used for the lock.
*/
atomic<uint32_t> lock_word;
public:
/**
* Try to acquire the lock. This has a tri-state return, indicating
* either that the lock was acquired, it wasn't acquired because it was
* contended, or it wasn't acquired because the guarded variable is
* already initialised.
*/
GuardState try_lock()
{
uint32_t old = 0;
// Try to acquire the lock
if (lock_word.compare_exchange(old, locked))
{
// If we succeeded, check if initialisation has happened. In
// this version, we don't have atomic manipulation of both the
// lock and initialised bits together. Instead, we have an
// ordering rule that the initialised bit is only ever updated
// with the lock held.
if (is_initialised())
{
// If another thread did manage to initialise this, release
// the lock and notify the caller that initialisation is
// done.
lock_word.store(initialised, memory_order::release);
return GuardState::InitDone;
}
return GuardState::InitLockSucceeded;
}
return GuardState::InitLockFailed;
}
/**
* Set the initialised state and release the lock. In this
* implementation, this is ordered, not atomic: the initialise bit is
* set while the lock is held.
*/
void unlock(bool isInitialised)
{
init_word.store(isInitialised ? initialised : 0,
memory_order::release);
lock_word.store(0, memory_order::release);
assert((*reinterpret_cast<uint8_t*>(this) != 0) == isInitialised);
}
/**
* Return whether the guarded variable is initialised.
*/
bool is_initialised()
{
return (init_word.load(memory_order::acquire) & initialised) ==
initialised;
}
};
// Check that the two implementations are the correct size.
static_assert(sizeof(SingleWordGuard<uint32_t, 31, 0>) == sizeof(uint32_t),
"Single-word 32-bit guard must be 32 bits");
static_assert(sizeof(SingleWordGuard<uint64_t, 63, 0>) == sizeof(uint64_t),
"Single-word 64-bit guard must be 64 bits");
static_assert(sizeof(DoubleWordGuard<31, 0>) == sizeof(uint64_t),
"Double-word guard must be 64 bits");
#ifdef __arm__
// ARM ABI - 32-bit guards.
typedef uint32_t guard_t;
typedef uint32_t guard_lock_t;
static const uint32_t LOCKED = static_cast<guard_t>(1) << 31;
static const uint32_t INITIALISED = 1;
#define LOCK_PART(guard) (guard)
#define INIT_PART(guard) (guard)
/**
* The Arm PCS defines a variant of the Itanium ABI with 32-bit lock words.
*/
using Guard = SingleWordGuard<uint32_t, 31, 0>;
#elif defined(_LP64)
typedef uint64_t guard_t;
typedef uint64_t guard_lock_t;
# if defined(__LITTLE_ENDIAN__)
static const guard_t LOCKED = static_cast<guard_t>(1) << 63;
static const guard_t INITIALISED = 1;
/**
* On little-endian 64-bit platforms the guard word is a single 64-bit
* atomic with the lock in the high bit and the initialised flag in the low
* bit.
*/
using Guard = SingleWordGuard<uint64_t, 63, 0>;
# else
static const guard_t LOCKED = 1;
static const guard_t INITIALISED = static_cast<guard_t>(1) << 56;
/**
* On bit-endian 64-bit platforms, the guard word is a single 64-bit atomic
* with the lock in the low bit and the initialised bit in the highest
* byte.
*/
using Guard = SingleWordGuard<uint64_t, 0, 56>;
# endif
#define LOCK_PART(guard) (guard)
#define INIT_PART(guard) (guard)
#else
typedef uint32_t guard_lock_t;
# if defined(__LITTLE_ENDIAN__)
typedef struct {
uint32_t init_half;
uint32_t lock_half;
} guard_t;
static const uint32_t LOCKED = static_cast<guard_lock_t>(1) << 31;
static const uint32_t INITIALISED = 1;
/**
* 32-bit platforms use the same layout as 64-bit.
*/
using Guard = DoubleWordGuard<31, 0>;
# else
typedef struct {
uint32_t init_half;
uint32_t lock_half;
} guard_t;
static_assert(sizeof(guard_t) == sizeof(uint64_t), "");
static const uint32_t LOCKED = 1;
static const uint32_t INITIALISED = static_cast<guard_lock_t>(1) << 24;
/**
* 32-bit platforms use the same layout as 64-bit.
*/
using Guard = DoubleWordGuard<0, 24>;
# endif
#define LOCK_PART(guard) (&(guard)->lock_half)
#define INIT_PART(guard) (&(guard)->init_half)
#endif
static const guard_lock_t INITIAL = 0;
} // namespace
/**
* Acquires a lock on a guard, returning 0 if the object has already been
* initialised, and 1 if it has not. If the object is already constructed then
* this function just needs to read a byte from memory and return.
*/
extern "C" int __cxa_guard_acquire(volatile guard_t *guard_object)
extern "C" int __cxa_guard_acquire(Guard *guard_object)
{
guard_lock_t old;
// Not an atomic read, doesn't establish a happens-before relationship, but
// if one is already established and we end up seeing an initialised state
// then it's a fast path, otherwise we'll do something more expensive than
// this test anyway...
if (INITIALISED == *INIT_PART(guard_object))
return 0;
// Spin trying to do the initialisation
for (;;)
// Check if this is already initialised. If so, we don't have to do
// anything.
if (guard_object->is_initialised())
{
// Loop trying to move the value of the guard from 0 (not
// locked, not initialised) to the locked-uninitialised
// position.
old = __sync_val_compare_and_swap(LOCK_PART(guard_object),
INITIAL, LOCKED);
if (old == INITIAL) {
// Lock obtained. If lock and init bit are
// in separate words, check for init race.
if (INIT_PART(guard_object) == LOCK_PART(guard_object))
return 1;
if (INITIALISED != *INIT_PART(guard_object))
return 1;
// No need for a memory barrier here,
// see first comment.
*LOCK_PART(guard_object) = INITIAL;
return 0;
}
// If lock and init bit are in the same word, check again
// if we are done.
if (INIT_PART(guard_object) == LOCK_PART(guard_object) &&
old == INITIALISED)
return 0;
assert(old == LOCKED);
// Another thread holds the lock.
// If lock and init bit are in different words, check
// if we are done before yielding and looping.
if (INIT_PART(guard_object) != LOCK_PART(guard_object) &&
INITIALISED == *INIT_PART(guard_object))
// Spin trying to acquire the lock. If we fail to acquire the lock the
// first time then another thread will *probably* initialise it, but if the
// constructor throws an exception then we may have to try again in this
// thread.
for (;;)
{
// Try to acquire the lock.
switch (guard_object->try_lock())
{
// If we failed to acquire the lock but another thread has
// initialised the lock while we were waiting, return immediately
// indicating that initialisation is not required.
case GuardState::InitDone:
return 0;
// If we acquired the lock, return immediately to start
// initialisation.
case GuardState::InitLockSucceeded:
return 1;
// If we didn't acquire the lock, pause and retry.
case GuardState::InitLockFailed:
break;
}
sched_yield();
}
}
@ -166,28 +346,16 @@ extern "C" int __cxa_guard_acquire(volatile guard_t *guard_object)
* Releases the lock without marking the object as initialised. This function
* is called if initialising a static causes an exception to be thrown.
*/
extern "C" void __cxa_guard_abort(volatile guard_t *guard_object)
extern "C" void __cxa_guard_abort(Guard *guard_object)
{
__attribute__((unused))
bool reset = __sync_bool_compare_and_swap(LOCK_PART(guard_object),
LOCKED, INITIAL);
assert(reset);
guard_object->unlock(false);
}
/**
* Releases the guard and marks the object as initialised. This function is
* called after successful initialisation of a static.
*/
extern "C" void __cxa_guard_release(volatile guard_t *guard_object)
extern "C" void __cxa_guard_release(Guard *guard_object)
{
guard_lock_t old;
if (INIT_PART(guard_object) == LOCK_PART(guard_object))
old = LOCKED;
else
old = INITIAL;
__attribute__((unused))
bool reset = __sync_bool_compare_and_swap(INIT_PART(guard_object),
old, INITIALISED);
assert(reset);
if (INIT_PART(guard_object) != LOCK_PART(guard_object))
*LOCK_PART(guard_object) = INITIAL;
guard_object->unlock(true);
}

54
contrib/libcxxrt/memory.cc
View File

@ -51,7 +51,7 @@ typedef void (*new_handler)();
* The function to call when allocation fails. By default, there is no
* handler and a bad allocation exception is thrown if an allocation fails.
*/
static new_handler new_handl;
static atomic<new_handler> new_handl{nullptr};
namespace std
{
@ -61,12 +61,13 @@ namespace std
__attribute__((weak))
new_handler set_new_handler(new_handler handler)
{
return ATOMIC_SWAP(&new_handl, handler);
return new_handl.exchange(handler);
}
__attribute__((weak))
new_handler get_new_handler(void)
{
return ATOMIC_LOAD(&new_handl);
return new_handl.load();
}
}
@ -79,6 +80,32 @@ namespace std
#define BADALLOC
#endif
namespace
{
/**
* Helper for forwarding from no-throw operators to versions that can
* return nullptr. Catches any exception and converts it into a nullptr
* return.
*/
template<void*(New)(size_t)>
void *noexcept_new(size_t size)
{
#if !defined(_CXXRT_NO_EXCEPTIONS)
try
{
return New(size);
} catch (...)
{
// nothrow operator new should return NULL in case of
// std::bad_alloc exception in new handler
return nullptr;
}
#else
return New(size);
#endif
}
}
__attribute__((weak))
void* operator new(size_t size) BADALLOC
@ -97,7 +124,11 @@ void* operator new(size_t size) BADALLOC
}
else
{
#if !defined(_CXXRT_NO_EXCEPTIONS)
throw std::bad_alloc();
#else
break;
#endif
}
mem = malloc(size);
}
@ -105,16 +136,11 @@ void* operator new(size_t size) BADALLOC
return mem;
}
__attribute__((weak))
void* operator new(size_t size, const std::nothrow_t &) NOEXCEPT
{
try {
return :: operator new(size);
} catch (...) {
// nothrow operator new should return NULL in case of
// std::bad_alloc exception in new handler
return NULL;
}
return noexcept_new<(::operator new)>(size);
}
@ -135,13 +161,7 @@ void * operator new[](size_t size) BADALLOC
__attribute__((weak))
void * operator new[](size_t size, const std::nothrow_t &) NOEXCEPT
{
try {
return ::operator new[](size);
} catch (...) {
// nothrow operator new should return NULL in case of
// std::bad_alloc exception in new handler
return NULL;
}
return noexcept_new<(::operator new[])>(size);
}

45
contrib/libcxxrt/noexception.cc Normal file
View File

@ -0,0 +1,45 @@
/*
* Copyright 2021 Microsoft. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
namespace std
{
/**
* Returns whether there are any exceptions currently being thrown that
* have not been caught. Without exception support this is always false.
*/
bool uncaught_exception() throw()
{
return false;
}
/**
* Returns the number of exceptions currently being thrown that have not
* been caught. Without exception support this is always 0.
*/
int uncaught_exceptions() throw()
{
return 0;
}
}