[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

Richard Biener  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
  Known to work||8.0
 Resolution|--- |FIXED

--- Comment #5 from Richard Biener  ---
Fixed on trunk.

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

--- Comment #6 from Richard Biener  ---
Author: rguenth
Date: Thu Jul 20 11:17:21 2017
New Revision: 250382

URL: https://gcc.gnu.org/viewcvs?rev=250382=gcc=rev
Log:
2017-07-20  Richard Biener  

PR tree-optimization/61171
* tree-vectorizer.h (slp_instance): Add reduc_phis member.
(vect_analyze_stmt): Add slp instance parameter.
(vectorizable_reduction): Likewise.
* tree-vect-loop.c (vect_analyze_loop_operations): Adjust.
(vect_is_simple_reduction): Deal with chains not detected
as SLP reduction chain, specifically not properly associated
chains containing a mix of plus/minus.
(get_reduction_op): Remove.
(get_initial_defs_for_reduction): Simplify, pass in whether
this is a reduction chain, pass in the SLP node for the PHIs.
(vect_create_epilog_for_reduction): Get the SLP instance as
arg and adjust.
(vectorizable_reduction): Get the SLP instance as arg.
During analysis remember the SLP node with the PHIs in the
instance.  Simplify getting at the vectorized reduction PHIs.
* tree-vect-slp.c (vect_slp_analyze_node_operations): Pass
through SLP instance.
(vect_slp_analyze_operations): Likewise.
* tree-vect-stms.c (vect_analyze_stmt): Likewise.
(vect_transform_stmt): Likewise.

* g++.dg/vect/pr61171.cc: New testcase.
* gfortran.dg/vect/pr61171.f: Likewise.
* gcc.dg/vect/vect-reduc-11.c: Likewise.

Added:
trunk/gcc/testsuite/g++.dg/vect/pr61171.cc
trunk/gcc/testsuite/gcc.dg/vect/vect-reduc-11.c
trunk/gcc/testsuite/gfortran.dg/vect/pr61171.f
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-vect-loop.c
trunk/gcc/tree-vect-slp.c
trunk/gcc/tree-vect-stmts.c
trunk/gcc/tree-vectorizer.h

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

Richard Biener  changed:

   What|Removed |Added

 Status|NEW |ASSIGNED
   Last reconfirmed|2015-04-29 00:00:00 |2017-6-8
   Assignee|unassigned at gcc dot gnu.org  |rguenth at gcc dot 
gnu.org

--- Comment #4 from Richard Biener  ---
Reconfirmed, mine.

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

Andrew Pinski  changed:

   What|Removed |Added

   Severity|normal  |enhancement

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

--- Comment #3 from Richard Biener  ---
it's a matter of association being "unfortunate" or vector reduction detection
being too simplistic.

  # prephitmp_21 = PHI 
...
  _2 = pretmp_18 + prephitmp_21;
  _9 = _2 - _6;

needs to be associated as

  _2 = pretmp_18 - _6;
  _9 = prephitmp_21 + _2;

usually reassoc is responsible for ensuring this but given its last iteration
is before LIM pulls out the global it has no chance to fix things up.

One fix would be to split out enough from reassoc into a worker that can
be called from vectorization or to run LIM before reassoc.

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[alalaw01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

alalaw01 at gcc dot gnu.org changed:

   What|Removed |Added

 CC||alalaw01 at gcc dot gnu.org

--- Comment #2 from alalaw01 at gcc dot gnu.org ---
This vectorizes fine, if vv is made a local variable:

float isOk() {
  float vv = 0;
  for (int j=0U; jN; ++j) {
float ax = xx-px[j];
vv+=ax;
  }
  return vv;
}

[Bug tree-optimization/61171] vectorization fails for a reduction in presence of subtraction

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61171

Richard Biener rguenth at gcc dot gnu.org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2015-04-29
 Ever confirmed|0   |1

--- Comment #1 from Richard Biener rguenth at gcc dot gnu.org ---
Confirmed.