public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug fortran/30398] New: memmove for string operations
@ 2007-01-06 22:05 tkoenig at gcc dot gnu dot org
2007-01-06 22:07 ` [Bug fortran/30398] " tkoenig at gcc dot gnu dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: tkoenig at gcc dot gnu dot org @ 2007-01-06 22:05 UTC (permalink / raw)
To: gcc-bugs
The compiler should be able to detect that s and c
are not aliased, so a call to memcpy instead of memmove
could be issued.
$ cat memmove.f90
program main
character(len=1) :: s
character(len=2) :: c
s = 'a'
c = repeat(s,2)
end program main
$ gfortran -fdump-tree-original memmove.f90
$ cat memmove.f90.003t.original
MAIN__ ()
{
char c[1:2];
char s[1:1];
_gfortran_set_std (70, 127, 0);
s[1]{lb: 1 sz: 1} = "a"[1]{lb: 1 sz: 1};
{
char str.0[2];
_gfortran_string_repeat ((char[1:] *) &str.0, 1, &s, 2);
__builtin_memmove (&c, (char[1:] *) &str.0, 2);
}
}
--
Summary: memmove for string operations
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tkoenig at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30398
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug fortran/30398] memmove for string operations
2007-01-06 22:05 [Bug fortran/30398] New: memmove for string operations tkoenig at gcc dot gnu dot org
@ 2007-01-06 22:07 ` tkoenig at gcc dot gnu dot org
2007-01-22 10:03 ` fxcoudert at gcc dot gnu dot org
2007-04-13 15:27 ` [Bug tree-optimization/30398] " tobi at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: tkoenig at gcc dot gnu dot org @ 2007-01-06 22:07 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from tkoenig at gcc dot gnu dot org 2007-01-06 22:07 -------
(In reply to comment #0)
> The compiler should be able to detect that s and c
> are not aliased, so a call to memcpy instead of memmove
> could be issued.
Or, even better, the memmove/memcpy could be ommitted completely,
by using the variable directly as the target.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30398
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug fortran/30398] memmove for string operations
2007-01-06 22:05 [Bug fortran/30398] New: memmove for string operations tkoenig at gcc dot gnu dot org
2007-01-06 22:07 ` [Bug fortran/30398] " tkoenig at gcc dot gnu dot org
@ 2007-01-22 10:03 ` fxcoudert at gcc dot gnu dot org
2007-04-13 15:27 ` [Bug tree-optimization/30398] " tobi at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: fxcoudert at gcc dot gnu dot org @ 2007-01-22 10:03 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from fxcoudert at gcc dot gnu dot org 2007-01-22 10:02 -------
(In reply to comment #1)
> Or, even better, the memmove/memcpy could be ommitted completely,
> by using the variable directly as the target.
The string_repeat() function could be generated directly by the front-end,
because it's really simple code:
void
string_repeat (char * dest, GFC_INTEGER_4 slen,
const char * src, GFC_INTEGER_4 ncopies)
{
int i;
/* See if ncopies is valid. */
if (ncopies < 0)
{
/* The error is already reported. */
runtime_error ("Augument NCOPIES is negative.");
}
/* Copy characters. */
for (i = 0; i < ncopies; i++)
{
memmove (dest + (i * slen), src, slen);
}
}
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2007-01-22 10:02:53
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30398
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/30398] memmove for string operations
2007-01-06 22:05 [Bug fortran/30398] New: memmove for string operations tkoenig at gcc dot gnu dot org
2007-01-06 22:07 ` [Bug fortran/30398] " tkoenig at gcc dot gnu dot org
2007-01-22 10:03 ` fxcoudert at gcc dot gnu dot org
@ 2007-04-13 15:27 ` tobi at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: tobi at gcc dot gnu dot org @ 2007-04-13 15:27 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from tobi at gcc dot gnu dot org 2007-04-13 16:27 -------
With FX' patch to inline REPEAT (see PR31304), we are left with this as final
dump after a -O compilation:
;; Function MAIN__ (MAIN__)
MAIN__ ()
{
char[1:] * pstr.1;
char s[1:1];
char c[1:2];
void * D.1004;
<bb 2>:
_gfortran_set_std (68, 127, 0, 0, 0);
s[1]{lb: 1 sz: 1} = 97;
D.1004 = _gfortran_internal_malloc (2);
pstr.1 = (char[1:] *) D.1004;
__builtin_memcpy ((char *) pstr.1, &s, 1);
__builtin_memcpy (pstr.1 + 1B, &s, 1);
__builtin_memmove (&c, pstr.1, 2);
_gfortran_internal_free (pstr.1);
return;
}
The call to memmove makes it way into the assembly, even though pstr and c
can't alias. This is now an optimizer issue, moving to component
tree-optimization, as the tree-ssa optimizers should be able to eliminate the
memmove in favor of a memcpy. Or even better, get rid of the whole copying
business and predict the correct results. If that's possible it would be great
to have a way to get rid of the then unnecessary temporary allocation.
--
tobi at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |tobi at gcc dot gnu dot org,
| |fxcoudert at gcc dot gnu dot
| |org
Component|fortran |tree-optimization
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30398
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2007-04-13 15:27 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-01-06 22:05 [Bug fortran/30398] New: memmove for string operations tkoenig at gcc dot gnu dot org
2007-01-06 22:07 ` [Bug fortran/30398] " tkoenig at gcc dot gnu dot org
2007-01-22 10:03 ` fxcoudert at gcc dot gnu dot org
2007-04-13 15:27 ` [Bug tree-optimization/30398] " tobi at gcc dot gnu dot org
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).