Thanks :) indeed I think is the only way possible.
Can I ask one more question regarding L2 and memory latency ?
For a L2 cache access the latency is computed by (L1.latency + L2.latency)
or is the L2.latency ?
Similarly for memory ?
On Tue, Oct 23, 2012 at 10:54 AM, Mitch Hayenga <
mitch.hayenga+g...@gmail.com> wrote:
> No, that would not be enough. Doing that change would just make the front
> end assume no branch was ever taken (and the sim would actually crash
> because the commit logic would later would try to inform the front end
> about branches it never predicted).
>
> To do this (with the saving branch outcomes to a file & later just
> replaying them as if you had predicted them right the first time), you'd
> have to hook the proper spaces in the squash/update functions in
> bpred_unit_impl.hh to figure out what the correct predictions should have
> been. Then save these correct decisions off to a gzipped file (I haven't
> thought how big this is going to be, but this file will be pretty massive).
> Then re-run the simulation with the "predict" from bpred_unit_impl.hh just
> feeding the correct path information from this file.
>
>
> On Mon, Oct 22, 2012 at 9:14 PM, mihai pricopi <mihai.pric...@gmail.com>wrote:
>
>> Thanks.
>> Would be enough to change a bit the lookupAndUpdateNextPC() function such
>> that the return is always false ?
>> I mean changing the:
>>
>> if (!inst->isControl()) {
>> TheISA::advancePC(nextPC, inst->staticInst);
>> inst->setPredTarg(nextPC);
>> inst->setPredTaken(false);
>> return false;
>> }
>>
>>
>> to
>>
>> // if (!inst->isControl()) {
>> TheISA::advancePC(nextPC, inst->staticInst);
>> inst->setPredTarg(nextPC);
>> inst->setPredTaken(false);
>> return false;
>> // }
>>
>> ?
>>
>>
>> On Tue, Oct 23, 2012 at 10:02 AM, Mitch Hayenga <
>> mitch.hayenga+g...@gmail.com> wrote:
>>
>>> Since gem5 the O3 cpu model actually executes instructions @ execute
>>> (not fetch/decode) a perfect branch predictor is a bit tricky. Assuming
>>> you are running a single-threaded app in SE mode (so you don't have
>>> OS/multi-threaded time variance issues), you could simply run the
>>> application twice. Save the branch outcomes from the first run. Then
>>> re-run the app, with a "predictor" that just uses the branch results from
>>> the first time you ran the application.
>>>
>>> On Mon, Oct 22, 2012 at 8:43 PM, mihai pricopi
>>> <mihai.pric...@gmail.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I am using arm_detailed SE mode.
>>>> Is there a simple way to force the branch predictor to do perfect
>>>> prediction ?
>>>>
>>>> Thanks
>>>>
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>>>>
>>>
>>>
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>>
>>
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>
>
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