http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #14 from Ira Rosen 2011-12-13 16:27:19 UTC
---
(In reply to comment #13)
>
> However, I don't fully understand Richard Guenther's example. Yes his
> example requires -fassociative-math to be vectorized, however, my example
> would tr
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #13 from fb.programming at gmail dot com 2011-12-12 14:20:58 UTC ---
(In reply to comment #9)
> So, you are suggesting to remove the need in flag_associative_math for fp for
> cases when a reduction computation is already unrolled by t
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #12 from Dominique d'Humieres
2011-12-12 12:47:54 UTC ---
> > even when the above loops are unrolled. How can the loop L5 be unrolled if
> > it
> > is only there for a "scalar epilogue"?
>
> It can't be unrolled, since the alignment
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #11 from Ira Rosen 2011-12-12 11:27:26 UTC
---
Right. We need to check that there is no load permutation.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #10 from Richard Guenther 2011-12-12
11:24:22 UTC ---
Hmm. But we are vectorizing
sum += a[i]
sum += a[i+1]
the same as
sum += a[i+1]
sum += a[i]
no? Thus you have to check whether the summation occours in "memory order"
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #9 from Ira Rosen 2011-12-12 11:13:24 UTC
---
(In reply to comment #7)
>
> In some cases it might be necessary but not here:
>
> sum1+=a;
> sum2+=a;
>
> gives exactly the same result as
>
> (sum1, sum2) += (a, a);
>
So, you a
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #8 from Ira Rosen 2011-12-12 11:03:59 UTC
---
(In reply to comment #6)
> While investigating pr51597, I have found that vectorized loops in programs as
> simple as
>
> subroutine spmmult(x,b,ad)
> implicit none
> integer, parameter
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #7 from fb.programming at gmail dot com 2011-12-11 14:55:13 UTC ---
(In reply to comment #5)
> > (3) If I change all double's into float's in the code above it seems to
> I think you are looking at the scalar epilogue. The number of i
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #6 from Dominique d'Humieres 2011-12-11
14:14:01 UTC ---
> I think you are looking at the scalar epilogue. The number of iterations is
> unknown, so we need an epilogue loop for the case that number of iterations is
> not a multiple o
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #5 from Ira Rosen 2011-12-11 13:30:41 UTC
---
(In reply to comment #4)
> Looks like there has been some great progress in gcc 4.7!
>
> Still I think it behaves slightly buggy.
>
> (1) In this case it should work without -funsafe-mat
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #4 from fb.programming at gmail dot com 2011-12-11 11:52:30 UTC ---
Looks like there has been some great progress in gcc 4.7!
Still I think it behaves slightly buggy.
(1) In this case it should work without -funsafe-math-optimizations
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #3 from Ira Rosen 2011-12-11 08:48:24 UTC
---
It gets vectorized with 4.7.
I guess, due to this 4.7 patch
http://gcc.gnu.org/ml/gcc-patches/2011-09/msg00620.html.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
--- Comment #2 from fb.programming at gmail dot com 2011-12-11 08:33:40 UTC ---
(In reply to comment #1)
g++-4.6.2 -S -Wall -O3 -ftree-vectorize -ftree-vectorizer-verbose=2 \
-ffast-math -fno-vect-cost-model
gives me exactly the same a
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499
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--- Comment #1 from Ir
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