[Bug c/36598] New: Failed optimisation of return of struct argment in memcpy-1.c

[Bug c/36598] New: Failed optimisation of return of struct argment in memcpy-1.c

[hutchinsonandy at gcc dot gnu dot org]

Testcase gcc.dg/memcpy-1.c fails on AVR target.

Failure occurs because the return value is not simplified to avoid memcpy. This
test works on i686 and I can't see why same optimization should not apply to
AVR

Test is:

/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times "nasty_local" 0 "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */
struct a {int a,b,c;} a;
int test(struct a a)
{
struct a nasty_local;
__builtin_memcpy (&nasty_local,&a, sizeof(a));
return nasty_local.a;
}

On i686 we get:

;; Function test (test)

Analyzing Edge Insertions.
test (struct a a)
{
<bb 2>:
  return a.a;

}


BUT on AVR we get:


;; Function test (test)

Analyzing Edge Insertions.
test (struct a a)
{
  struct a nasty_local;

<bb 2>:
  nasty_local = a;
  return nasty_local.a;

}

I have confirmed the final AVR code is suboptimal.


-- 
           Summary: Failed optimisation of return of struct argment in
                    memcpy-1.c
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hutchinsonandy at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: avr-unknown-none


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug c/36598] Failed optimisation of return of struct argment in memcpy-1.c

[joseph at codesourcery dot com]

------- Comment #1 from joseph at codesourcery dot com  2008-06-22 13:32 -------
Subject: Re:   New: Failed optimisation of return of struct
 argment in memcpy-1.c

On Sun, 22 Jun 2008, hutchinsonandy at gcc dot gnu dot org wrote:

> Testcase gcc.dg/memcpy-1.c fails on AVR target.

Have you looked at bug 31677 which suggests using the option "--param 
sra-max-structure-size=32"?  If that works for AVR, you could submit a 
patch to add it to the testcase for all targets.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug c/36598] Failed optimisation of return of struct argment in memcpy-1.c

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #2 from hutchinsonandy at gcc dot gnu dot org  2008-06-22 14:33 -------
Thanks for information

--param sra-max-structure-size=32 does indeed remove test failure and produces
optimal code.

But changing the testcase does not remove the optimization problem - unless
sra-max-structure-size was always used. So there is problem somewhere else to
fix.

See also:

http://gcc.gnu.org/ml/gcc-patches/2007-12/msg01144.html

Andy


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug c/36598] Failed optimisation of return of struct argment in memcpy-1.c

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-06-22 14:50 -------
This is really not a task for SRA but for struct copy propagation (which we
do not do).  See PR14295.

As this testcase was for SRA you can either XFAIL it for avr or see if the
cost metrics need adjustment.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |14295


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug c/36598] Failed optimisation of return of struct argment in memcpy-1.c

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #4 from hutchinsonandy at gcc dot gnu dot org  2008-06-22 16:11 -------
Quite possibly due to cost metrics. They are far from ideal.

Will mark test XFAIL until we can investigate and fix.


-- 

hutchinsonandy at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eric dot weddington at atmel
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug middle-end/36598] Failed optimisation of return of struct argment in memcpy-1.c

[hutchinsonandy at gcc dot gnu dot org]

------- Comment #5 from hutchinsonandy at gcc dot gnu dot org  2008-06-30 22:39 -------
Subject: Bug 36598

Author: hutchinsonandy
Date: Mon Jun 30 22:38:34 2008
New Revision: 137298

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=137298
Log:
PR target/36598
* gcc.dg/memcpy-1.c: Mark test XFAIL for avr target.

Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/memcpy-1.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug middle-end/36598] Failed optimisation of return of struct argment in memcpy-1.c

[danglin at gcc dot gnu dot org]

------- Comment #6 from danglin at gcc dot gnu dot org  2009-02-20 18:05 -------
*** Bug 39245 has been marked as a duplicate of this bug. ***


-- 

danglin at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |danglin at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug middle-end/36598] Failed optimisation of return of struct argment in memcpy-1.c

[danglin at gcc dot gnu dot org]

------- Comment #7 from danglin at gcc dot gnu dot org  2009-02-20 18:08 -------
Test also fails on powerpc64 with -m32, arm.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug middle-end/36598] Failed optimisation of return of struct argment in memcpy-1.c

[ubizjak at gmail dot com]

------- Comment #8 from ubizjak at gmail dot com  2009-02-20 19:49 -------
(In reply to comment #7)
> Test also fails on powerpc64 with -m32, arm.

And sh4.

http://gcc.gnu.org/ml/gcc-testresults/2009-02/msg01952.html


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kkojima at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
 GCC target triplet|avr-unknown-none            |
   Last reconfirmed|0000-00-00 00:00:00         |2009-02-20 19:49:15
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

[Bug middle-end/36598] Failed optimisation of return of struct argment in memcpy-1.c

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36598

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

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

--- Comment #9 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-06 10:15:42 UTC ---
Fixed for avr and ppc at least.