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

[Ivan Llopard]

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
>>>
>>>
>
>
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