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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/59464] Unnecessary vector register spill
Date: Wed, 11 Dec 2013 09:21:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59464

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-12-11
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
struct8 (struct test_structure_8 ts)
{
  vector(4) float vect__2.10;
  vector(4) float vect_ts_f1_9.9;
  struct test_structure_8 D.1759;

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  vect_ts_f1_9.9_15 = MEM[(struct  *)&ts];
  vect__2.10_17 = vect_ts_f1_9.9_15 + { 1.0e+0, 1.0e+0, 1.0e+0, 1.0e+0 };
  MEM[(struct  *)&D.1759] = vect__2.10_17;
  return D.1759;
;;    succ:       EXIT

}

OTOH the code generated is much much worse if you disable vectorization.

Then we should make sure the stack slot we spill the arguments to is
properly aligned so we can avoid the UNSPEC_LOADU.  This eventually
can lead to cleanup opportunities.

Ideally we'd recognize that we can more optimally load from the argument
registers into a V4SF register of course (but due to the way we do argument
setup during expand this may not be easily possible).

It's of course the bad ABI choice that leads to this mess ...