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

teawater
2008-10-22T16:43:16Z

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
>