Re: [discuss] semantics, "replay debugging" vs. "reverse debugging"

teawater
2008-10-22T16:48:15Z

And I think reverse without record in X86 is impossible beause the
size of its insn is not same.

On Thu, Oct 23, 2008 at 00:42, teawater <teawater@gmail.com> wrote:
> Sorry I am wrong.
> In ARM, Just adds set cpsr reg. So:
> add r0,r0,#10
> Can reverse without record too.
>
>
> On Thu, Oct 23, 2008 at 00:18, teawater <teawater@gmail.com> wrote:
>> I think your mean that add is a X86 instruction or ARM insn. But some
>> arch's add not set flag such as MIPS.
>>
>> addiu $1, $1, 10
>>
>> It not set anything except $1.
>>
>> And I said add insn just a example, I am not say for each arch and
>> each insn? just some of them.
>>
>>
>>
>> On Wed, Oct 22, 2008 at 21:37, Daniel Jacobowitz <drow@false.org> wrote:
>>>
>>> On Wed, Oct 22, 2008 at 11:25:17AM +0800, teawater wrote:
>>> > I think your not clear my idea.
>>> >
>>> > > I think maybe some instruction can do it.
>>> > > Such as add instruction. When it forward execute, it add some number
>>> > > to a value of register. When it reverse, it can sub this number from
>>> > > the value of register. It can reverse without record.
>>> >
>>> > Maybe you can read this part again.
>>> >
>>> > And what is the status of program? Most of time, it's just the values
>>> > of registers and memory. Do not think anything that complex.
>>>
>>> Jakob is right. For instance, if the add instruction sets an overflow
>>> flag in the status register, you can not figure out what the previous
>>> version of the overflow flag was after the instruction.
>>>
>>> --
>>> Daniel Jacobowitz
>>> CodeSourcery
>>
>