RFR (M): guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds 8-bit offset
rasbold at google.com
Fri Mar 22 09:52:43 PDT 2013
I've updated the webrev so that it reflects bug number 8010437.
On Wed, Mar 20, 2013 at 6:27 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com
> Thank you, Chuck
> I created bug 8010437 and will work on the patch.
> On 3/20/13 10:02 AM, Chuck Rasbold wrote:
>> We occasionally get this guarantee failure from an older JVM (HotSpot
>> # 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?
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