[Bug tree-optimization/93080] insert of an extraction on the same location is not optimized

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93080

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note the patch also does not handle the following (or something a little more
complex):

/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
#define vector __attribute__((__vector_size__(4*sizeof(int)) ))

vector int g(vector int a, int c)
{
  int b = a[2];
  a[1] = c;
  a[2] = b;
  return a;
}

/* { dg-final { scan-tree-dump-times "BIT_INSERT_EXPR" 1 "optimized" } } */
/* { dg-final { scan-tree-dump-times "BIT_FIELD_REF" 0 "optimized" } } */