libsanitizer/sanitizer_common/sanitizer_atomic_clang_mips.h

   1 //===-- sanitizer_atomic_clang_mips.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_MIPS_H
  15 #define SANITIZER_ATOMIC_CLANG_MIPS_H
  16
  17 namespace __sanitizer {
  18
  19 // MIPS32 does not support atomics > 4 bytes. To address this lack of
  20 // functionality, the sanitizer library provides helper methods which use an
  21 // internal spin lock mechanism to emulate atomic operations when the size is
  22 // 8 bytes.
  23 static void __spin_lock(volatile int *lock) {
  24   while (__sync_lock_test_and_set(lock, 1))
  25     while (*lock) {
  26     }
  27 }
  28
  29 static void __spin_unlock(volatile int *lock) { __sync_lock_release(lock); }
  30
  31 // Make sure the lock is on its own cache line to prevent false sharing.
  32 // Put it inside a struct that is aligned and padded to the typical MIPS
  33 // cacheline which is 32 bytes.
  34 static struct {
  35   int lock;
  36   char pad[32 - sizeof(int)];
  37 } __attribute__((aligned(32))) lock = {0, {0}};
  38
  39 template <>
  40 inline atomic_uint64_t::Type atomic_fetch_add(volatile atomic_uint64_t *ptr,
  41                                               atomic_uint64_t::Type val,
  42                                               memory_order mo) {
  43   DCHECK(mo &
  44          (memory_order_relaxed | memory_order_release | memory_order_seq_cst));
  45   DCHECK(!((uptr)ptr % sizeof(*ptr)));
  46
  47   atomic_uint64_t::Type ret;
  48
  49   __spin_lock(&lock.lock);
  50   ret = *(const_cast<atomic_uint64_t::Type volatile *>(&ptr->val_dont_use));
  51   ptr->val_dont_use = ret + val;
  52   __spin_unlock(&lock.lock);
  53
  54   return ret;
  55 }
  56
  57 template <>
  58 inline atomic_uint64_t::Type atomic_fetch_sub(volatile atomic_uint64_t *ptr,
  59                                               atomic_uint64_t::Type val,
  60                                               memory_order mo) {
  61   return atomic_fetch_add(ptr, -val, mo);
  62 }
  63
  64 template <>
  65 inline bool atomic_compare_exchange_strong(volatile atomic_uint64_t *ptr,
  66                                            atomic_uint64_t::Type *cmp,
  67                                            atomic_uint64_t::Type xchg,
  68                                            memory_order mo) {
  69   DCHECK(mo &
  70          (memory_order_relaxed | memory_order_release | memory_order_seq_cst));
  71   DCHECK(!((uptr)ptr % sizeof(*ptr)));
  72
  73   typedef atomic_uint64_t::Type Type;
  74   Type cmpv = *cmp;
  75   Type prev;
  76   bool ret = false;
  77
  78   __spin_lock(&lock.lock);
  79   prev = *(const_cast<Type volatile *>(&ptr->val_dont_use));
  80   if (prev == cmpv) {
  81     ret = true;
  82     ptr->val_dont_use = xchg;
  83   }
  84   __spin_unlock(&lock.lock);
  85
  86   return ret;
  87 }
  88
  89 template <>
  90 inline atomic_uint64_t::Type atomic_load(const volatile atomic_uint64_t *ptr,
  91                                          memory_order mo) {
  92   DCHECK(mo &
  93          (memory_order_relaxed | memory_order_release | memory_order_seq_cst));
  94   DCHECK(!((uptr)ptr % sizeof(*ptr)));
  95
  96   atomic_uint64_t::Type zero = 0;
  97   volatile atomic_uint64_t *Newptr =
  98       const_cast<volatile atomic_uint64_t *>(ptr);
  99   return atomic_fetch_add(Newptr, zero, mo);
 100 }
 101
 102 template <>
 103 inline void atomic_store(volatile atomic_uint64_t *ptr, atomic_uint64_t::Type v,
 104                          memory_order mo) {
 105   DCHECK(mo &
 106          (memory_order_relaxed | memory_order_release | memory_order_seq_cst));
 107   DCHECK(!((uptr)ptr % sizeof(*ptr)));
 108
 109   __spin_lock(&lock.lock);
 110   ptr->val_dont_use = v;
 111   __spin_unlock(&lock.lock);
 112 }
 113
 114 }  // namespace __sanitizer
 115
 116 #endif  // SANITIZER_ATOMIC_CLANG_MIPS_H
 117