RFR (M): guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds 8-bit offset
vladimir.kozlov at oracle.com
Wed Mar 20 18:27:10 PDT 2013
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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