[Bug tree-optimization/18431] New: Code for arrays and pointers are not the same

[pinskia at gcc dot gnu dot org]

We should produce the same code in the two loops
unsigned short *q;
#define NOSB 10
int last;
void h1()
{
 int i;
 for (i=0;i<last+NOSB;i++)
   {
     q[i] = 0;
   }
}
-----
unsigned short q[100];
#define NOSB 10
int last;
void h1()
{
 int i;
 for (i=0;i<last+NOSB;i++)
   {
     q[i] = 0;
   }
}

For the array one we produce:
L4:
        sth r0,0(r2)
        addi r2,r2,2
        bdnz L4
which is optimial but for the pointer one we produce:
L4:
        slwi r2,r9,1
        addi r9,r9,1
        sthx r0,r2,r11
        bdnz L4
which sucks as we have tree instructions in the loop instead of two.

I think this is a place where IV-OPTS is failing.

-- 
           Summary: Code for arrays and pointers are not the same
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18431