Change 6420645 causes SIGBUS during deoptimisation at a safepoint on 64bit-SPARC

[Coleen Phillimore - Sun Microsystems]

I filed one this morning too, but didn't put hotspot-compiler-dev on the 
interest list 'cause I thought it'd bounce.
CR 6879831 Created, P2 hotspot/runtime_syst Change for compressed oops 
causes SIGBUS during deoptimisation at a safepoint on 64bit-SPARC
but I just closed it as a duplicate of yours since you've added more 
information to yours, and it should be in the c2 category.
Thanks,
Coleen

On 09/08/09 16:57, Vladimir Kozlov wrote:
> Thank you, Volker
>
> I filed C2 bug since the fix is for .ad file and is not related to COOP:
>
> 6880034: SIGBUS during deoptimisation at a safepoint on 64bit-SPARC
>
> Vladimir
>
> Volker Simonis wrote:
>> Hi Coleen,
>>
>> did you filed/found a bug report for this issue. I can volunteer to
>> open a bug for this and once there's a bug ID I could also submit a
>> patch to fix it if that would help. I just would like to keep this
>> issue tracked.
>>
>> Regards,
>> Volker
>>
>> On 9/1/09, Tom Rodriguez <Thomas.Rodriguez at sun.com> wrote:
>>>> The problem can be easily solved by switching back to the old
>>>> implementation of frame::oopmapreg_to_location(), but I
>>> assume there
>>>> was a rational behind the change and that the new implementation is
>>>> probably necessary for compressed oops (at least that's what the whole
>>>> change was all about). So I dug a little further and found that in my
>>>> opinion the root cause of the whole problem is the strange numbering
>>>> of the 16 upper double registers in sparc.ad. They are defined as
>>>> follows:
>>>>
>>>> reg_def R_D32x(SOC, SOC, Op_RegD,255, F32->as_VMReg());
>>>> reg_def R_D32 (SOC, SOC, Op_RegD,  1, F32->as_VMReg()->next());
>>>> reg_def R_D34x(SOC, SOC, Op_RegD,255, F34->as_VMReg());
>>>> reg_def R_D34 (SOC, SOC, Op_RegD,  3, F34->as_VMReg()->next());
>>>> ...
>>>> reg_def R_D62x(SOC, SOC, Op_RegD,255, F62->as_VMReg());
>>>> reg_def R_D62 (SOC, SOC, Op_RegD, 31, F62->as_VMReg()->next());
>>>>
>>>  I don't really know why it's done this way.  It's certainly not 
>>> consistent
>>> with the others.  If it all works better I'd be ok with correcting.
>>>
>>>
>>>> PS: while I was hunting the error, I also stumbled across the
>>>> following code in RegisterSaver::save_live_registers():
>>>>
>>>>  // Save all the FP registers
>>>>  int offset = d00_offset;
>>>>  for( int i=0; i<64; i+=2 ) {
>>>>   FloatRegister f = as_FloatRegister(i);
>>>>   __ stf(FloatRegisterImpl::D,  f, SP, offset+STACK_BIAS);
>>>>
>>> map->set_callee_saved(VMRegImpl::stack2reg(offset>>2),
>>> f->as_VMReg());
>>>>   if (true) {
>>>>     map->set_callee_saved(VMRegImpl::stack2reg((offset +
>>>> sizeof(float))>>2), f->as_VMReg()->next());
>>>>   }
>>>>   offset += sizeof(double);
>>>>  }
>>>>
>>>  That would probably be ok too.
>>>
>>>  tom
>>>
>>>
>>>> In my opinion, this could be changed to:
>>>>
>>>>  // Save all the FP registers
>>>>  int offset = d00_offset;
>>>>  for( int i=0; i<64; i+=2 ) {
>>>>   FloatRegister f = as_FloatRegister(i);
>>>>   __ stf(FloatRegisterImpl::D,  f, SP, offset+STACK_BIAS);
>>>>
>>> map->set_callee_saved(VMRegImpl::stack2reg(offset>>2),
>>> f->as_VMReg());
>>>>   if (i < 32) { // VS 2009-08-31: the 16 upper double registers
>>>> can't be used as floats anyway
>>>>     map->set_callee_saved(VMRegImpl::stack2reg((offset +
>>>> sizeof(float))>>2), f->as_VMReg()->next());
>>>>   }
>>>>   offset += sizeof(double);
>>>>  }
>>>>
>>>> because the 16 upper double registers can't be used as floats anyway.
>>>> Again, I didn't found any regression in my few tests. What do you
>>>> think?
>>>> <DeoptTest.java>
>>>>
>>>