[Bug c/61473] New: register sized memmove not inlined

[Bug c/61473] New: register sized memmove not inlined

[jtaylor.debian at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473

            Bug ID: 61473
           Summary: register sized memmove not inlined
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jtaylor.debian at googlemail dot com

in this example file compiled with gcc-4.10 -O3 inlines the memcpy, but not the
memmove:

#include <string.h>
void a(int *a, int *b)
{
    memcpy(a, b, sizeof(*a));
}

void b(int *a, int *b)
{
    memmove(a, b, sizeof(*a));
}


at least on x86 the integer can be stored in fully in a register and saved back
to arbitrary aligned memory, so it should not matter if the two address overlap
and gcc should be able to replace it with a much faster inline memcpy.
Currently gcc only inlines the memmove for 1 byte types.

I am using a recent svn copy of gcc:
$ gcc-4.10 --version
gcc (GCC) 4.10.0 20140605 (experimental)

[Bug c/61473] register sized memmove not inlined

[jtaylor.debian at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473

--- Comment #1 from Julian Taylor <jtaylor.debian at googlemail dot com> ---
I am using glibc 2.19-0ubuntu6 from the ubuntu 14.04 trusty repository

[Bug middle-end/61473] register sized memmove not inlined

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2014-06-12
          Component|c                           |middle-end
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The transform is simply not implemented for memmove but simplification always
goes through memmove -> memcpy and then applies this optimization to memcpy.
But of course here the memmove -> memcpy transform is not valid.

[Bug middle-end/61473] register sized memmove not inlined

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Fri Jul 11 13:42:55 2014
New Revision: 212452

URL: https://gcc.gnu.org/viewcvs?rev=212452&root=gcc&view=rev
Log:
2014-07-11  Richard Biener  <rguenther@suse.de>

    PR middle-end/61473
    * builtins.c (fold_builtin_memory_op): Inline memory moves
    that can be implemented with a single load followed by a
    single store.
    (c_strlen): Only warn when only_value is not 2.

    * gcc.dg/memmove-4.c: New testcase.
    * gcc.dg/strlenopt-8.c: XFAIL.
    * gfortran.dg/coarray_lib_realloc_1.f90: Adjust.

Added:
    trunk/gcc/testsuite/gcc.dg/memmove-4.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/strlenopt-8.c
    trunk/gcc/testsuite/gfortran.dg/coarray_lib_realloc_1.f90

[Bug middle-end/61473] register sized memmove not inlined

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.