[Bug other/17105] New: Opportunity to improve aliasing analysis

["gcc-bugzilla at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Description:
A non-optimal code sequence is illustraded.    Duplicate using gcc 3.5 and
command line:

gcc -O3 -m64 -c test.c


Testcase:
static int s1, s2;
int *p;

void foo ()
{

  s1 = 1;
  *p = 2;
  /* Shouldn't have to reload s1 here. It has not had its
     address taken so it shouldn't be aliased to *p. */
  s2 = s1;

}

Assembly:
.foo:
      ld 9,.LC1@toc(2)
      li 0,1
      ld 10,.LC0@toc(2)
      ld 11,0(9)
      li 9,2
      stw 0,0(10)
      stw 9,0(11)
      ld 8,.LC2@toc(2)
      lwz 0,0(10)  <--- reload is unnecessary.
      stw 0,0(8)
      blr



-- 
           Summary: Opportunity to improve aliasing analysis
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P1
         Component: other
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steinmtz at us dot ibm dot com
                CC: gcc-bugs at gcc dot gnu dot org,steinmtz at us dot ibm
                    dot com
 GCC build triplet: powerpc64-linux
  GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17105