src/hotspot/os_cpu/linux_zero/atomic_linux_zero.hpp

rev 48027 : 8192123: Zero should use compiler built-ins for atomics on linux-arm

*** 28,98 ****
  
  #include "runtime/os.hpp"
  
  // Implementation of class atomic
  
- #ifdef ARM
- 
- /*
-  * __kernel_cmpxchg
-  *
-  * Atomically store newval in *ptr if *ptr is equal to oldval for user space.
-  * Return zero if *ptr was changed or non-zero if no exchange happened.
-  * The C flag is also set if *ptr was changed to allow for assembly
-  * optimization in the calling code.
-  *
-  */
- 
- typedef int (__kernel_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
- #define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) 0xffff0fc0)
- 
- 
- 
- /* Perform an atomic compare and swap: if the current value of `*PTR'
-    is OLDVAL, then write NEWVAL into `*PTR'.  Return the contents of
-    `*PTR' before the operation.*/
- static inline int arm_compare_and_swap(int newval,
-                                        volatile int *ptr,
-                                        int oldval) {
-   for (;;) {
-       int prev = *ptr;
-       if (prev != oldval)
-         return prev;
- 
-       if (__kernel_cmpxchg (prev, newval, ptr) == 0)
-         // Success.
-         return prev;
- 
-       // We failed even though prev == oldval.  Try again.
-     }
- }
- 
- /* Atomically add an int to memory.  */
- static inline int arm_add_and_fetch(int add_value, volatile int *ptr) {
-   for (;;) {
-       // Loop until a __kernel_cmpxchg succeeds.
- 
-       int prev = *ptr;
- 
-       if (__kernel_cmpxchg (prev, prev + add_value, ptr) == 0)
-         return prev + add_value;
-     }
- }
- 
- /* Atomically write VALUE into `*PTR' and returns the previous
-    contents of `*PTR'.  */
- static inline int arm_lock_test_and_set(int newval, volatile int *ptr) {
-   for (;;) {
-       // Loop until a __kernel_cmpxchg succeeds.
-       int prev = *ptr;
- 
-       if (__kernel_cmpxchg (prev, newval, ptr) == 0)
-         return prev;
-     }
- }
- #endif // ARM
- 
  template<size_t byte_size>
  struct Atomic::PlatformAdd
    : Atomic::AddAndFetch<Atomic::PlatformAdd<byte_size> >
  {
    template<typename I, typename D>
--- 28,37 ----
*** 103,136 ****
  template<typename I, typename D>
  inline D Atomic::PlatformAdd<4>::add_and_fetch(I add_value, D volatile* dest) const {
    STATIC_ASSERT(4 == sizeof(I));
    STATIC_ASSERT(4 == sizeof(D));
  
- #ifdef ARM
-   return add_using_helper<int>(arm_add_and_fetch, add_value, dest);
- #else
    return __sync_add_and_fetch(dest, add_value);
- #endif // ARM
  }
  
  template<>
  template<typename I, typename D>
  inline D Atomic::PlatformAdd<8>::add_and_fetch(I add_value, D volatile* dest) const {
    STATIC_ASSERT(8 == sizeof(I));
    STATIC_ASSERT(8 == sizeof(D));
- 
    return __sync_add_and_fetch(dest, add_value);
  }
  
  template<>
  template<typename T>
  inline T Atomic::PlatformXchg<4>::operator()(T exchange_value,
                                               T volatile* dest) const {
    STATIC_ASSERT(4 == sizeof(T));
- #ifdef ARM
-   return xchg_using_helper<int>(arm_lock_test_and_set, exchange_value, dest);
- #else
    // __sync_lock_test_and_set is a bizarrely named atomic exchange
    // operation.  Note that some platforms only support this with the
    // limitation that the only valid value to store is the immediate
    // constant 1.  There is a test for this in JNI_CreateJavaVM().
    T result = __sync_lock_test_and_set (dest, exchange_value);
--- 42,67 ----
*** 138,148 ****
    // (see atomic.hpp). However, __sync_lock_test_and_set is not
    // a full memory barrier, but an acquire barrier. Hence, this added
    // barrier.
    __sync_synchronize();
    return result;
- #endif // ARM
  }
  
  template<>
  template<typename T>
  inline T Atomic::PlatformXchg<8>::operator()(T exchange_value,
--- 69,78 ----
*** 162,176 ****
  inline T Atomic::PlatformCmpxchg<4>::operator()(T exchange_value,
                                                  T volatile* dest,
                                                  T compare_value,
                                                  cmpxchg_memory_order order) const {
    STATIC_ASSERT(4 == sizeof(T));
- #ifdef ARM
-   return cmpxchg_using_helper<int>(arm_compare_and_swap, exchange_value, dest, compare_value);
- #else
    return __sync_val_compare_and_swap(dest, compare_value, exchange_value);
- #endif // ARM
  }
  
  template<>
  template<typename T>
  inline T Atomic::PlatformCmpxchg<8>::operator()(T exchange_value,
--- 92,102 ----