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

[Volker Simonis]

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>
> >
>
>