------- Comment #5 from rguenther at suse dot de 2009-09-27 09:43 -------
Subject: Re: vector loads are unnecessarily
split into high and low loads
On Sun, 27 Sep 2009, irar at il dot ibm dot com wrote:
> ------- Comment #4 from irar at il dot ibm dot com 2009-09-27 08:06 -------
> (In reply to comment #1)
> > The interesting thing is that data-ref analysis sees 128bit alignment but
> > the vectorizer still produces
> > vect_var_.24_59 = M*vect_p.20_57{misalignment: 0};
> > D.2564_12 = *D.2563_11;
> > vect_var_.25_61 = vect_var_.24_59 * vect_cst_.26_60;
> > D.2565_13 = D.2564_12 * 2.2999999523162841796875e+0;
> > M*vect_p.27_64{misalignment: 0} = vect_var_.25_61;
> > thus, unknown misalignment.
> > (instantiate_scev
> > (instantiate_below = 3)
> > (evolution_loop = 1)
> > (chrec = {i_10(D), +, 4}_1)
> > (res = {i_10(D), +, 4}_1))
> > base_address: i_10(D)
> > offset from base address: 0
> > constant offset from base address: 0
> > step: 4
> > aligned to: 128
> > base_object: *i_10(D)
> > Creating dr for *D.2562_7
> > (res = {f_6(D), +, 4}_1))
> > base_address: f_6(D)
> > offset from base address: 0
> > constant offset from base address: 0
> > step: 4
> > aligned to: 128
> > base_object: *f_6(D)
> > t2.i:5: note: === vect_enhance_data_refs_alignment ===
> > t2.i:5: note: Vectorizing an unaligned access.
> > t2.i:5: note: Vectorizing an unaligned access.
>
> "aligned to" refers to the offset misalignment and not to the misalignment of
> base.
Hmm, I believe it refers to base + offset + constant offset.
> attribute aligned works only for arrays, i.e., declarations, and not for
> pointer arguments.
I have to check that - I believe that in principle it should work.
> For pointers the vectorizer only checks TYPE_ALIGN_UNIT of
> the base type.
That should be ok. I guess I have to see what's going on here.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41464
