Mercurial > hg > graal-jvmci-8
diff src/share/vm/runtime/atomic.hpp @ 11033:d9eed26d638a
8009575: Reduce Symbol::_refcount from 4 bytes to 2 bytes
Summary: Added Atomic::inc(short*) to support this change.
Reviewed-by: coleenp, dcubed, dholmes, minqi
author | iklam |
---|---|
date | Sun, 23 Jun 2013 22:08:28 -0700 |
parents | 0598674c0056 |
children | de6a9e811145 |
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--- a/src/share/vm/runtime/atomic.hpp Fri Jun 21 10:55:26 2013 -0700 +++ b/src/share/vm/runtime/atomic.hpp Sun Jun 23 22:08:28 2013 -0700 @@ -64,11 +64,13 @@ // 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); @@ -95,4 +97,24 @@ 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