RFR: 8230401: ClassLoaderData::_keep_alive is read with wrong type in c2i entry barrier

[Zhengyu Gu]

Hi Erik,

Looks good.

Thanks for fixing it.

-Zhengyu

On 8/30/19 11:43 AM, Erik Österlund wrote:
> Hi,
> 
> Zhengyu noticed that the ClassLoaderData::_keep_alive field is a short, 
> but the c2i entry barrier reads it with cmpl, treating it like an int.
> 
> First of all, thanks Zhengyu for spotting that. Nice catch.
> 
> Encoding cmpw is not currently supported for x86_64 extended registers, 
> used in the barriers. So my proposed fix is to simply change the type of 
> _keep_alive to int. Because the 2 extra bytes will become padding 
> anyway, so we are not really saving any bytes by making it s2.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8230401
> 
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8230401/webrev.00/
> 
> Thanks,
> /Erik