1  //===-- sanitizer_atomic_clang.h --------------------------------*- 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  // This file is a part of ThreadSanitizer/AddressSanitizer runtime.
      10  // Not intended for direct inclusion. Include sanitizer_atomic.h.
      11  //
      12  //===----------------------------------------------------------------------===//
      13  
      14  #ifndef SANITIZER_ATOMIC_CLANG_H
      15  #define SANITIZER_ATOMIC_CLANG_H
      16  
      17  #if defined(__i386__) || defined(__x86_64__)
      18  # include "sanitizer_atomic_clang_x86.h"
      19  #else
      20  # include "sanitizer_atomic_clang_other.h"
      21  #endif
      22  
      23  namespace __sanitizer {
      24  
      25  // We would like to just use compiler builtin atomic operations
      26  // for loads and stores, but they are mostly broken in clang:
      27  // - they lead to vastly inefficient code generation
      28  // (http://llvm.org/bugs/show_bug.cgi?id=17281)
      29  // - 64-bit atomic operations are not implemented on x86_32
      30  // (http://llvm.org/bugs/show_bug.cgi?id=15034)
      31  // - they are not implemented on ARM
      32  // error: undefined reference to '__atomic_load_4'
      33  
      34  // See http://www.cl.cam.ac.uk/~pes20/cpp/cpp0xmappings.html
      35  // for mappings of the memory model to different processors.
      36  
      37  inline void atomic_signal_fence(memory_order) {
      38    __asm__ __volatile__("" ::: "memory");
      39  }
      40  
      41  inline void atomic_thread_fence(memory_order) {
      42    __sync_synchronize();
      43  }
      44  
      45  template<typename T>
      46  inline typename T::Type atomic_fetch_add(volatile T *a,
      47      typename T::Type v, memory_order mo) {
      48    (void)mo;
      49    DCHECK(!((uptr)a % sizeof(*a)));
      50    return __sync_fetch_and_add(&a->val_dont_use, v);
      51  }
      52  
      53  template<typename T>
      54  inline typename T::Type atomic_fetch_sub(volatile T *a,
      55      typename T::Type v, memory_order mo) {
      56    (void)mo;
      57    DCHECK(!((uptr)a % sizeof(*a)));
      58    return __sync_fetch_and_add(&a->val_dont_use, -v);
      59  }
      60  
      61  template<typename T>
      62  inline typename T::Type atomic_exchange(volatile T *a,
      63      typename T::Type v, memory_order mo) {
      64    DCHECK(!((uptr)a % sizeof(*a)));
      65    if (mo & (memory_order_release | memory_order_acq_rel | memory_order_seq_cst))
      66      __sync_synchronize();
      67    v = __sync_lock_test_and_set(&a->val_dont_use, v);
      68    if (mo == memory_order_seq_cst)
      69      __sync_synchronize();
      70    return v;
      71  }
      72  
      73  template <typename T>
      74  inline bool atomic_compare_exchange_strong(volatile T *a, typename T::Type *cmp,
      75                                             typename T::Type xchg,
      76                                             memory_order mo) {
      77    // Transitioned from __sync_val_compare_and_swap to support targets like
      78    // SPARC V8 that cannot inline atomic cmpxchg.  __atomic_compare_exchange
      79    // can then be resolved from libatomic.  __ATOMIC_SEQ_CST is used to best
      80    // match the __sync builtin memory order.
      81    return __atomic_compare_exchange(&a->val_dont_use, cmp, &xchg, false,
      82                                     __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
      83  }
      84  
      85  template<typename T>
      86  inline bool atomic_compare_exchange_weak(volatile T *a,
      87                                           typename T::Type *cmp,
      88                                           typename T::Type xchg,
      89                                           memory_order mo) {
      90    return atomic_compare_exchange_strong(a, cmp, xchg, mo);
      91  }
      92  
      93  }  // namespace __sanitizer
      94  
      95  // This include provides explicit template instantiations for atomic_uint64_t
      96  // on MIPS32, which does not directly support 8 byte atomics. It has to
      97  // proceed the template definitions above.
      98  #if defined(_MIPS_SIM) && defined(_ABIO32) && _MIPS_SIM == _ABIO32
      99  #  include "sanitizer_atomic_clang_mips.h"
     100  #endif
     101  
     102  #undef ATOMIC_ORDER
     103  
     104  #endif  // SANITIZER_ATOMIC_CLANG_H