[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2007-01-14 05:01:04         |2012-02-06

--- Comment #6 from Uros Bizjak <ubizjak at gmail dot com> 2012-02-06 21:40:50 UTC ---
Reconfirmed with 4.7.

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-05 10:50:22 UTC ---
The

long long test2(void)
{
  long long a[32];
  int i;

  for (i = 0; i < 32; i++)
    a[i] = 0;

  return foo(a);
}

loop is transformed to memset at -O3.  The unrolled version is not "re-rolled"
still, and basic-block vectorization does not catch it because of the
call in the basic-block.  I'm trying to fix that.

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

--- Comment #8 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-05 12:38:30 UTC ---
Author: rguenth
Date: Tue Jun  5 12:38:26 2012
New Revision: 188235

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=188235
Log:
2012-06-05  Richard Guenther  <rguenther@suse.de>

    PR tree-optimization/30442
    * tree-vect-data-refs.c (vect_analyze_data_refs): For basic-block
    vectorization stop analysis at the first stmt we cannot compute
    a data-reference for instead of giving up completely.

    * gcc.dg/vect/bb-slp-30.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/vect/bb-slp-30.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-data-refs.c

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

--- Comment #9 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-05 12:39:29 UTC ---
So, $summary is still true but we now at least vectorize the initialization.

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[irar at il dot ibm dot com]

------- Comment #5 from irar at il dot ibm dot com  2008-03-13 06:51 -------
(In reply to comment #4)
> This still happens on mainline.
> 
> I wonder if vectorizer infrastructure can be re-used here to detect unrolled
> and looped version of memset. In addition to loop that can be "vectorized", we
> have something resembling "vectorization" of straight code.

This code can be vectorized with basic block SLP, which is not implemented yet
(currently only SLP in loops is implemented).

> And looking at comment #3, the rewards from real-world code look really
> promising.
> 
However, in comment #3 there is a loop:

               :  MALLOC(visited, int, d->tindex);
 48796 16.2440 :  for (i = 0; i < d->tindex; ++i)
 94442 31.4394 :    visited[i] = 0;

There was an effort to replace such loops with calls to builtins -
http://gcc.gnu.org/ml/gcc-patches/2007-07/msg00054.html.

Ira


-- 

irar at il dot ibm dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |irar at il dot ibm dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[ubizjak at gmail dot com]

------- Comment #4 from ubizjak at gmail dot com  2008-03-12 11:05 -------
This still happens on mainline.

I wonder if vectorizer infrastructure can be re-used here to detect unrolled
and looped version of memset. In addition to loop that can be "vectorized", we
have something resembling "vectorization" of straight code.

And looking at comment #3, the rewards from real-world code look really
promising.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[johan dot walles at gmail dot com]

------- Comment #3 from johan dot walles at gmail dot com  2007-11-09 13:09 -------
This optimization would have made grep 2.5.3 30% faster in a real-world test
case:

http://bugs.debian.org/450649


-- 

johan dot walles at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |johan dot walles at gmail
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442

[Bug middle-end/30442] Expanded array initialization can use memset builtin function

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2007-01-14 05:01 -------
This is a bit complex, we could use a loop reroller to roll this into a loop
and then transform that loop into memset for test1.
For test2 it is simple and a patch was presented at last year's gcc summit (and
I posted an older version of that patch a year or two ago).


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
  GCC build triplet|i686-pc-linux-gnu           |
   GCC host triplet|i686-pc-linux-gnu           |
 GCC target triplet|i686-pc-linux-gnu           |
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2007-01-14 05:01:04
               date|                            |
            Summary|Array initialization can use|Expanded array
                   |memset builtin function     |initialization can use
                   |                            |memset builtin function


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442