On Wed, Apr 26, 2017 at 2:27 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Tue, Apr 18, 2017 at 12:51 PM, Bin Cheng <bin.ch...@arm.com> wrote:
>> Hi,
>> This patch adds new loop constraint flags marking prologue, epilogue and
>> versioned loops generated
>> by vectorizer, unroller and versioning. These flags will be used in IVOPTs
>> in order to differentiate
>> possible hot innermost loop from others. I also plan to use them to avoid
>> unnecessary cunroll on
>> such loops.
>> Is it OK?
>
> Hmm, it doesn't really match "constraints".
>
> I'd rather somehow track the "original" loop it was versioned / copied
> from plus either a
> "kind" (epilogue, prologue, version) or determine this from dominance
> relationship between
> the copy and the original loop.
Or we generalize "constraints flags", saying to introduce general
bit-wise flags for loop structure. Among these flags, one kind is
constraint flags, the rest are general flags. We could also change
boolean fields into such flags?
I do have following patches relying on this to avoid complete unroll
for prologue/epilogue loops.
>
> Thus,
>
> struct loop {
> ...
> /* If not zero the loop number this loop was copied from. */
> unsigned clone_of;
In this case, we need to track between different loops, which looks
like a burden. For example, we need to make sure loop number won't be
reused. Even more complicated, considering in extreme case that the
original loop could be removed.
>
> would that help? With knowing loop relation we can also more
> aggressively version
> and eventually later collapse the two versions again if we can still
> identify them and
> they are still reasonably similar.
>
> Richard.
>
>>
>> Thanks,
>> bin
>> 2017-04-11 Bin Cheng <bin.ch...@arm.com>
>>
>> * cfgloop.h (LOOP_C_PROLOG, LOOP_C_EPILOG, LOOP_C_VERSION): New.
>> * tree-ssa-loop-manip.c (tree_transform_and_unroll_loop): Set
>> LOOP_C_EPILOG for unrolled epilogue loop.
>> (vect_do_peeling): Set LOOP_C_PROLOG and LOOP_C_EPILOG for peeled
>> loops.
>> (vect_loop_versioning): Set LOOP_C_VERSION for versioned loop.
