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

["hutchinsonandy at gcc dot gnu dot org" <gcc-bugzilla 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