On Mon, Jan 13, 2014 at 5:37 AM, Richard Biener <rguent...@suse.de> wrote:
> On Wed, 27 Nov 2013, Jakub Jelinek wrote:
>
>> On Wed, Nov 27, 2013 at 10:53:56AM +0100, Richard Biener wrote:
>> > Hmm. I'm still thinking that we should handle this during the regular
>> > transform step.
>>
>> I wonder if it can't be done instead just in vectorizable_load,
>> if LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo) and the load is
>> invariant, just emit the (broadcasted) load not inside of the loop, but on
>> the loop preheader edge.
>
> So this implements this suggestion, XFAILing the no longer handled cases.
> For example we get
>
> _94 = *b_8(D);
> vect_cst_.18_95 = {_94, _94, _94, _94};
> _99 = prolog_loop_adjusted_niters.9_132 * 4;
> vectp_a.22_98 = a_6(D) + _99;
> ivtmp.43_77 = (unsigned long) vectp_a.22_98;
>
> <bb 13>:
> # ivtmp.41_67 = PHI <ivtmp.41_70(3), 0(12)>
> # ivtmp.43_71 = PHI <ivtmp.43_69(3), ivtmp.43_77(12)>
> vect__10.19_97 = vect_cst_.18_95 + { 1, 1, 1, 1 };
> _76 = (void *) ivtmp.43_71;
> MEM[base: _76, offset: 0B] = vect__10.19_97;
>
> ...
>
> instead of having hoisted *b_8 + 1 as scalar computation. Not sure
> why LIM doesn't hoist the vector variant later.
>
> vect__10.19_97 = vect_cst_.18_95 + vect_cst_.20_96;
> invariant up to level 1, cost 1.
>
> ah, the cost thing. Should be "improved" to see that hoisting
> reduces the number of live SSA names in the loop.
>
> Eventually lower_vector_ssa could optimize vector to scalar
> code again ... (ick).
>
> Bootstrap / regtest running on x86_64.
>
> Comments?
>
> Thanks,
> Richard.
>
> 2014-01-13 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/58921
> PR tree-optimization/59006
> * tree-vect-loop-manip.c (vect_loop_versioning): Remove code
> hoisting invariant stmts.
> * tree-vect-stmts.c (vectorizable_load): Insert the splat of
> invariant loads on the preheader edge if possible.
>
This caused:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59841
H.J.
