[llvm-commits] [LLVMdev] [PATCH] Refactoring the DFA generator

[adasgupt at codeaurora.org]

Hi Ivan,

Sorry, I should have been more explicit in my last email. The patch looks
good to me. Please check that it applies on trunk and go ahead and commit.

Thanks
-Anshu



> Hi Anshu,
>
> Just in case you have forgotten this thread ;-). Is this patch ok to
> commit or does it not apply to trunk properly ?
> I can fix it if that's the problem.
>
> Ivan
>
> On 20/06/2012 19:33, Anshuman Dasgupta wrote:
>>
>> > Thanks for reviewing this. I added a top comment for AddInsnClass
>> and I fixed the violation of column numbers.
>>
>> Great. Looks good to me.
>>
>> > IMO, it wil be nice to keep it alive for performance comparisons.
>> Given the overall performance
>> > is rather determined by transition searches on the current state,
>> for small DFA tables may not be a win
>> > and it may still be the case for greater ones.
>>
>> I agree; let's keep it around for now.
>>
>> -Anshu
>>
>> ---
>> Qualcomm Innovation Center, Inc is a member of the Code Aurora Forum
>>
>>
>>
>> On 6/18/2012 3:47 AM, Ivan Llopard wrote:
>>> Hi Anshu,
>>>
>>> Thanks for reviewing this. I added a top comment for AddInsnClass and
>>> I fixed the violation of column numbers.
>>>
>>> On 15/06/2012 21:31, Anshuman Dasgupta wrote:
>>>> Hi Ivan,
>>>>
>>>> The patch looks good to me. I have a couple of minor comments:
>>>>
>>>> +void State::AddInsnClass(unsigned InsnClass,
>>>> Add a top level comment describing the function
>>>>
>>>> +  std::map<State*, std::set<Transition*, ltTransition>, ltState>
>>>> stateTransitions;
>>>> You should be able to use SmallSet here. Also, this line exceeds 80
>>>> columns.
>>>
>>> I tried but SmallSet is not iterable. SmallSetPtr could be useful
>>> here but it doesn't allow custom sorting.
>>>
>>>>
>>>>
>>>> On a related note, is the CachedTable mechanism in DFAPacketizer.h
>>>> useful for your architecture? Currently the DFA generator generates
>>>> one table for a given architecture. I had originally added the
>>>> CachedTable mechanism since for a given compilation and subtarget,
>>>> the DFA only uses the subset of the states and transitions. Using a
>>>> "cache" made sense. At one point, I'd like to change the code so
>>>> that it can generate one DFA for every subtarget and remove the
>>>> CachedTable mechanism. Given the size of the DFA for your
>>>> architecture, however, it may make sense to keep it around even if
>>>> it generates separate tables for each subtarget.
>>>
>>> I liked the cachedtable idea but I can't tell you if it's really
>>> useful in our case, I didn't make any performance tests in that regard.
>>> IMO, it wil be nice to keep it alive for performance comparisons.
>>> Given the overall performance is rather determined by transition
>>> searches on the current state, for small DFA tables may not be a win
>>> and it may still be the case for greater ones. We have a huge number
>>> of states but the number of distinct itineraries, or maximum possible
>>> transitions, remains quite small (11, it wasn't 13, my mistake).
>>>
>>> Ivan
>>>
>>>>
>>>> Thanks
>>>> -Anshu
>>>>
>>>> ---
>>>> Qualcomm Innovation Center, Inc is a member of the Code Aurora Forum
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 6/14/2012 8:22 AM, Ivan Llopard wrote:
>>>>> Hi,
>>>>>
>>>>> I've refactored the DFA generator in TableGen because it takes too
>>>>> much time to build the table of our BE and I'd like to share it.
>>>>> We have 15 functional units and 13 different itineraries which, in
>>>>> the worst case, can produce 13! states. Fortunately, many of those
>>>>> states are reused :-) but it still takes up to 11min to build the
>>>>> entire table. This patch reduces the build time to 5min, giving a
>>>>> speed-up factor greater than 2.
>>>>>
>>>>> It contains small changes:
>>>>> - Transitions are stored in a set for quicker searches
>>>>> - canAddInsnClass() API is split in two API's:
>>>>>   - canAddInsnClass() which perform a quick verification about the
>>>>> possibility of having new states for a given InsnClass
>>>>>   - AddInsnClass() performs the actual computation of possible
>>>>> states.
>>>>>
>>>>> I've regenerated the DFA table of Hexagon and all seems to be ok.
>>>>>
>>>>> What do you think about these changes ?
>>>>>
>>>>>
>>>>> Ivan
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>
>>>>
>>
>>
>