Request for review (S): CR 6889740 - G1: OpenDS fails with "unhandled exception in compiled code"

[john cuthbertson - Sun Microsystems]

Hi Everyone,

I've tweaked the change based on feedback from Christian and Tom. The 
new webrev can be found here:

http://cr.openjdk.java.net/~johnc/6889740/webrev.1/

Regards,

JohnC

On 10/27/09 14:51, john cuthbertson - Sun Microsystems wrote:
> Hi Everyone,
>
> Can I have a couple of volunteers to review the proposed fix for this 
> bug? The webrev can be found at 
> http://cr.openjdk.java.net/~johnc/6889740/webrev.0/.
>
> The issue is that bad code was being generated for the store operation 
> in the null case of the aastore bytecode template. The bad code was 
> caused by there being only one version of the store_heap_oop routine 
> that took a Register as the second argument. When the calling code 
> passed in NULL_WORD (0) to this routine the value was used as a 
> Register encoding and converted to Register(0), which is rax. Thus the 
> generated store was "mov (dst), $rax" instead of "mov (dst), $0x0". 
> This is normally not a problem as the preceding code in the template 
> fetches the value to be stored into rax. When the G1 pre-barrier code 
> calls the runtime, however, the value in rax can be overwritten and 
> the heap can become corrupted.
>
> Testing: OpenDS, jprt, refworkload, and the GC test suite.
>
> Thanks,
>
> JohnC