Re: final i386.floating.record.patch

paawan oza
2009-08-05T13:48:50Z

Hi Hui and Michael,

Sure, I will preserve it. I modify the code and preserve it.
I will send you the updated patch soon.

this modification does not affect the core functionality, but as you suggested, we are debugger, and should revert all register back.

thank you for your inputs.
Regards,
Oza.

--- On Wed, 8/5/09, Michael Snyder <msnyder@vmware.com> wrote:

> From: Michael Snyder <msnyder@vmware.com>
> Subject: Re: final i386.floating.record.patch
> To: "paawan oza" <paawan1982@yahoo.com>
> Cc: "Hui Zhu" <teawater@gmail.com>, "gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
> Date: Wednesday, August 5, 2009, 7:03 AM
> paawan oza wrote:
> > Hi Hui,
> >
> > please find my analysis as follows.
> >
> > following are the registers which you may find it
> different.
> >
> > fstat
> > ftag
> > fiseg
> > fioff
> > foseg
> > fooff
> > fop
> >
> > In my opinion, we do not need to record all these
> registers. because these registers are purly depends on
> instruction's execution status in FPU unit.
> >
> >
> > for e.g.
> > fop register stores te last opcode executed by x87 FPU
> unit.
> > fstat register may contain c0, c1, c2, c3 flag
> status...
> >
> > why we dont need to record, because even if we reply
> the recod...
> > Anyway these register are going to be change by FPU HW
> unit based on any fp insn's nature and its execution. (next
> insn which FPU is going to execute)
> >
> > so it doesnt make much sense to store it, because even
> if we restore it, FPU unit doesnt use them directly, but FPU
> HW sets them after executing current fp insn. so anyway they
> are going to reset as soon as FPU executes next insn.
> >
> > but still if you feel that we must record those
> registers because user might want to observe those
> registers, then I can do that.
> >
> > please let me know you opinion about it.
>
> It may be that saving the registers is not purely
> necessary, but
> we are not just a simulator -- we are a debugger.  The
> user might
> be confused if he steps backward and sees that the register
> did not
> change.
>
> So I think we should preserve it and revert it.
>
>