public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/30442] New: Array initialization can use memset builtin function
@ 2007-01-11 19:53 ubizjak at gmail dot com
2007-01-11 22:16 ` [Bug middle-end/30442] " pinskia at gcc dot gnu dot org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: ubizjak at gmail dot com @ 2007-01-11 19:53 UTC (permalink / raw)
To: gcc-bugs
Array initialization could use memset builtin function. In following two
testcases, array is initialized without use of memset:
--cut here--
long long foo(long long *);
long long test1(void)
{
long long a[32];
a[0] = 0;
a[1] = 0;
a[2] = 0;
a[3] = 0;
a[4] = 0;
a[5] = 0;
a[6] = 0;
a[7] = 0;
a[8] = 0;
a[9] = 0;
a[10] = 0;
a[11] = 0;
a[12] = 0;
a[13] = 0;
a[14] = 0;
a[15] = 0;
a[16] = 0;
a[17] = 0;
a[18] = 0;
a[19] = 0;
a[20] = 0;
a[21] = 0;
a[22] = 0;
a[23] = 0;
a[24] = 0;
a[25] = 0;
a[26] = 0;
a[27] = 0;
a[28] = 0;
a[29] = 0;
a[30] = 0;
a[31] = 0;
return foo(a);
}
long long test2(void)
{
long long a[32];
int i;
for (i = 0; i < 32; i++)
a[i] = 0;
return foo(a);
}
--cut here--
gcc -O3 -m32 -S -fomit-frame-pointer
test1:
subl $268, %esp
leal 8(%esp), %eax
movl $0, 8(%esp)
movl $0, 12(%esp)
movl $0, 16(%esp)
movl $0, 20(%esp)
movl $0, 24(%esp)
movl $0, 28(%esp)
movl $0, 32(%esp)
movl $0, 36(%esp)
movl $0, 40(%esp)
movl $0, 44(%esp)
movl $0, 48(%esp)
movl $0, 52(%esp)
movl $0, 56(%esp)
movl $0, 60(%esp)
movl $0, 64(%esp)
movl $0, 68(%esp)
movl $0, 72(%esp)
movl $0, 76(%esp)
movl $0, 80(%esp)
movl $0, 84(%esp)
movl $0, 88(%esp)
movl $0, 92(%esp)
movl $0, 96(%esp)
movl $0, 100(%esp)
movl $0, 104(%esp)
movl $0, 108(%esp)
movl $0, 112(%esp)
movl $0, 116(%esp)
movl $0, 120(%esp)
movl $0, 124(%esp)
movl $0, 128(%esp)
movl $0, 132(%esp)
movl $0, 136(%esp)
movl $0, 140(%esp)
movl $0, 144(%esp)
movl $0, 148(%esp)
movl $0, 152(%esp)
movl $0, 156(%esp)
movl $0, 160(%esp)
movl $0, 164(%esp)
movl $0, 168(%esp)
movl $0, 172(%esp)
movl $0, 176(%esp)
movl $0, 180(%esp)
movl $0, 184(%esp)
movl $0, 188(%esp)
movl $0, 192(%esp)
movl $0, 196(%esp)
movl $0, 200(%esp)
movl $0, 204(%esp)
movl $0, 208(%esp)
movl $0, 212(%esp)
movl $0, 216(%esp)
movl $0, 220(%esp)
movl $0, 224(%esp)
movl $0, 228(%esp)
movl $0, 232(%esp)
movl $0, 236(%esp)
movl $0, 240(%esp)
movl $0, 244(%esp)
movl $0, 248(%esp)
movl $0, 252(%esp)
movl $0, 256(%esp)
movl $0, 260(%esp)
movl %eax, (%esp)
call foo
addl $268, %esp
ret
test2:
subl $268, %esp
movl $2, %eax
movl $0, 8(%esp)
leal 8(%esp), %edx
movl $0, 12(%esp)
.p2align 4,,7
.L2:
movl $0, -8(%edx,%eax,8)
movl $0, -4(%edx,%eax,8)
addl $1, %eax
cmpl $33, %eax
jne .L2
movl %edx, (%esp)
call foo
addl $268, %esp
ret
IIRC, this optimization was recently implemented in gfrortran...
--
Summary: Array initialization can use memset builtin function
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ubizjak at gmail dot com
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/30442] Array initialization can use memset builtin function
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
@ 2007-01-11 22:16 ` pinskia at gcc dot gnu dot org
2007-01-14 5:01 ` [Bug middle-end/30442] Expanded array " pinskia at gcc dot gnu dot org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-01-11 22:16 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2007-01-11 22:16 -------
> IIRC, this optimization was recently implemented in gfrortran...
That is because in Fortran, you have "a = 0" and instead of lowering it into a
loop, it lowers it to a memset instead.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30442
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/30442] Expanded array initialization can use memset builtin function
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
2007-01-11 22:16 ` [Bug middle-end/30442] " pinskia at gcc dot gnu dot org
@ 2007-01-14 5:01 ` pinskia at gcc dot gnu dot org
2007-11-09 13:09 ` johan dot walles at gmail dot com
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-01-14 5:01 UTC (permalink / raw)
To: gcc-bugs
------- 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
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/30442] Expanded array initialization can use memset builtin function
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
2007-01-11 22:16 ` [Bug middle-end/30442] " pinskia at gcc dot gnu dot org
2007-01-14 5:01 ` [Bug middle-end/30442] Expanded array " pinskia at gcc dot gnu dot org
@ 2007-11-09 13:09 ` johan dot walles at gmail dot com
2008-03-12 11:06 ` ubizjak at gmail dot com
2008-03-13 6:51 ` irar at il dot ibm dot com
4 siblings, 0 replies; 6+ messages in thread
From: johan dot walles at gmail dot com @ 2007-11-09 13:09 UTC (permalink / raw)
To: gcc-bugs
------- 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
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/30442] Expanded array initialization can use memset builtin function
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
` (2 preceding siblings ...)
2007-11-09 13:09 ` johan dot walles at gmail dot com
@ 2008-03-12 11:06 ` ubizjak at gmail dot com
2008-03-13 6:51 ` irar at il dot ibm dot com
4 siblings, 0 replies; 6+ messages in thread
From: ubizjak at gmail dot com @ 2008-03-12 11:06 UTC (permalink / raw)
To: gcc-bugs
------- 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
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug middle-end/30442] Expanded array initialization can use memset builtin function
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
` (3 preceding siblings ...)
2008-03-12 11:06 ` ubizjak at gmail dot com
@ 2008-03-13 6:51 ` irar at il dot ibm dot com
4 siblings, 0 replies; 6+ messages in thread
From: irar at il dot ibm dot com @ 2008-03-13 6:51 UTC (permalink / raw)
To: gcc-bugs
------- 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
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2008-03-13 6:51 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-01-11 19:53 [Bug c/30442] New: Array initialization can use memset builtin function ubizjak at gmail dot com
2007-01-11 22:16 ` [Bug middle-end/30442] " pinskia at gcc dot gnu dot org
2007-01-14 5:01 ` [Bug middle-end/30442] Expanded array " pinskia at gcc dot gnu dot org
2007-11-09 13:09 ` johan dot walles at gmail dot com
2008-03-12 11:06 ` ubizjak at gmail dot com
2008-03-13 6:51 ` irar at il dot ibm dot com
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).