Request for review: 7117052 instanceKlass::_init_state can be u1 type
jiangli.zhou at oracle.com
Fri Dec 2 11:12:50 PST 2011
On 12/02/2011 11:01 AM, Tom Rodriguez wrote:
> Looks good.
> On Dec 2, 2011, at 10:53 AM, Jiangli Zhou wrote:
>> Hi Tom,
>> Thanks for the suggestion. I changed TypeInt::BOOL to TypeInt::UBYTE in c2 code. The updated webrev is: http://cr.openjdk.java.net/~jiangli/7117052/webrev.01/.
>> On 12/01/2011 12:42 PM, Tom Rodriguez wrote:
>>> On Dec 1, 2011, at 10:51 AM, Jiangli Zhou wrote:
>>>> The instanceKlass::_init_state is defined as instanceKlass::ClassState type, which is an enum. Currently there are 7 class states defined. The instanceKlass::_init_state can be changed to u1 type, which could hold up 256 states. There are unused bytes after instanceKlass::_idnum_allocated_count field. Changing _init_state to u1 and move it to after the _idnum_allocate_count field would save 4-byte for each loaded class.
>>> The code in C2 to load it as T_BOOLEAN is somewhat questionable. In particular typing the result as a TypeInt::BOOL says that it only returns 0 or 1, which is definitely not true. It should be TypeInt::UBYTE which is the default type of a LoadUBNode. Using T_BOOLEAN still seems a little wonky but we don't have a BasicType for unsigned byte.
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