dibstar <dibyam4@xxxxxxxxx> writes:
> I looked into the code and saw the part that assumes power of two for
> unrolling:
>
> niter = expand_simple_binop (desc->mode, AND,
> niter,
> GEN_INT (max_unroll),
> NULL_RTX, 0, OPTAB_LIB_WIDEN);
>
> You had earlier mentioned that i need to change this code. I tried to
> understand this code but could not make head or tail out of it. Can you
> please tell me how to change this code so that i can force gcc to unroll
> runtime loops by all factors. Also, is there any need to change the code for
> constant loops so that gcc unrolls it by all factors?
I'm sorry, I'm happy to answer specific questions but I don't have time
to take on your project.
The statement quoted above is building code that in C would look like
niter &= max_unroll
Ian
> Ian Lance Taylor-3 wrote:
>>
>> dibstar <dibyam4@xxxxxxxxx> writes:
>>
>>> I am using gcc 4.4.5. I have looked into unroll_loop_runtime_iterations.
>>> Can
>>> you please tell me how to change this code to enable unrolling by all
>>> factors?
>>
>> I think I already did. You have to tell me which part of the
>> explanation you didn't understand.
>>
>> Ian
>>
>>> Ian Lance Taylor-3 wrote:
>>>>
>>>> dibstar <dibyam4@xxxxxxxxx> writes:
>>>>
>>>>> I wish to force gcc to unroll both the constant time iterating
>>>>> loops
>>>>> and the runtime iterating loops as outlined in loop-unroll.c. I
>>>>> modified
>>>>> the
>>>>> loop-unroll.c to place all unrolling decisions in the function
>>>>> decide-unroll-and-peel. I also made gcc interact with the user by
>>>>> asking
>>>>> the
>>>>> user the function name that which contains the desired loop and the
>>>>> loop
>>>>> number and the desired unroll factor. This seems to be fine for
>>>>> unrolling
>>>>> constant time iterating loops, i.e. i am able to unroll these loops by
>>>>> all
>>>>> factors from 1 to 8. However, for runtime loops, i get a segmentation
>>>>> fault.
>>>>> I analysed the code and found that gcc assumes that the unroll factor
>>>>> is
>>>>> a
>>>>> power of 2 for runtime loops. I wish to change this and force gcc to
>>>>> unroll
>>>>> a particular loop by all factors from 1 to 8. How can I do this?
>>>>
>>>> What version of gcc?
>>>>
>>>> I assume you mean decide_unrolling_and_peeling rather than
>>>> decide-unroll-and-peel.
>>>>
>>>> I agree that the code assumes that the unroll factor is a power of 2.
>>>> If you want to use a different factor, you will have to change the code.
>>>> Are you asking how to do that? Look in unroll_loop_runtime_iterations.
>>>> It uses AND; as the comment explains, that only works because it is
>>>> unrolling by a power of 2. If you want something else to work, you will
>>>> need to change that.
>>>>
>>>> Ian
>>>>
>>>>
>>
>>
