RFR (M): guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds 8-bit offset

[Chuck Rasbold]

Thanks, Vladimir.

I've updated the webrev so that it reflects bug number 8010437.

http://cr.openjdk.java.net/~rasbold/8010437/webrev.00/


On Wed, Mar 20, 2013 at 6:27 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com
> wrote:

> Thank you, Chuck
>
> I created bug 8010437 and will work on the patch.
>
> Thanks,
> Vladimir
>
> On 3/20/13 10:02 AM, Chuck Rasbold wrote:
>
>> http://cr.openjdk.java.net/~**rasbold/XXXXXXX/webrev.00/<http://cr.openjdk.java.net/~rasbold/XXXXXXX/webrev.00/>
>> <http://cr.openjdk.java.net/%**7Erasbold/XXXXXXX/webrev.00/<http://cr.openjdk.java.net/%7Erasbold/XXXXXXX/webrev.00/>
>> >
>>
>>
>> We occasionally get this guarantee failure from an older JVM (HotSpot
>> 22):
>>
>> #  Internal Error (assembler_x86.inline.hpp:46)
>> #  guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds
>> #  8-bit offset
>>
>> I'm encountering a case in C2 where a branch is incorrectly
>> converted to a short branch under very specific conditions. The root
>> cause occurs when a call and safepoint are adjacent in
>> consecutive blocks.  In shorten_branches(), an off-by-one
>> error exists in calculating the size of the trailing (safepoint) block
>> when it
>> potentially requires loop padding.
>>
>> This bug still exists in the current HotSpot 25, although I don't have
>> a testcase that reproduces there.
>>
>> However, with the improved guarantee from my webrev, but without the
>> actual fix, a hs25 CTW run on rt.jar fails.
>>
>> Can a bug be opened? Can I get an Oracle engineer to sponsor and
>> review my change?
>>
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/attachments/20130322/2ecbd5ba/attachment.html