src/share/vm/runtime/atomic.hpp

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*** 62,76 **** --- 62,78 ---- // See comment above about using jlong atomics on 32-bit platforms static jlong add (jlong add_value, volatile jlong* dest); // Atomically increment location inline static void inc (volatile jint* dest); + static void inc (volatile jshort* dest); inline static void inc_ptr(volatile intptr_t* dest); inline static void inc_ptr(volatile void* dest); // Atomically decrement a location inline static void dec (volatile jint* dest); + static void dec (volatile jshort* dest); inline static void dec_ptr(volatile intptr_t* dest); inline static void dec_ptr(volatile void* dest); // Performs atomic exchange of *dest with exchange_value. Returns old prior value of *dest. inline static jint xchg(jint exchange_value, volatile jint* dest);
*** 93,98 **** --- 95,120 ---- inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value); inline static void* cmpxchg_ptr(void* exchange_value, volatile void* dest, void* compare_value); }; + // To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially + // aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to + // achieve is to place your short value next to another short value, which doesn't need atomic ops. + // + // Example + // ATOMIC_SHORT_PAIR( + // volatile short _refcount, // needs atomic operation + // unsigned short _length // number of UTF8 characters in the symbol (does not need atomic op) + // ); + + #ifdef VM_LITTLE_ENDIAN + #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ + non_atomic_decl; \ + atomic_decl + #else + #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ + atomic_decl ; \ + non_atomic_decl + #endif + #endif // SHARE_VM_RUNTIME_ATOMIC_HPP