Re: [PATCH V11] VECT: Add decrement IV support in Loop Vectorizer

[Richard Sandiford <richard.sandiford@arm.com>]

"juzhe.zhong@rivai.ai" <juzhe.zhong@rivai.ai> writes:
> Hi, Richard. Thanks for the comments.
>
> Would you mind telling me whether it is possible that we can make decrement IV support into GCC middle-end ?
>
> If yes, could you tell what I should do next for the patches since I am confused that it seems the implementation of this
> patch should totally be abandoned and need to rewrite the whole thing.

No, I haven't said that.  Like I say, I haven't had time to review the
decrementing IV part of the patch yet.  But the change I mentioned
earlier seemed like an unrelated fix that should go in first.

I was hoping to partially unblock your work by reviewing that part in
isolation rather than waiting until I had time to review the whole patch.
But I guess that's just created confusion rather than been helpful, sorry.

In other words: the decrementing IV patch should (I hope) be an
optimisation.  It shouldn't be needed for correctness.  The current
incrementing IVs should work for LOAD_LEN, but perhaps inefficiently.
Is that right?

In contrast, the change to vect_get_loop_len is a correctness fix
and I can't see how RVV would work without it.

Thanks,
Richard