Canonicalize __atomic/sync_fetch_or/xor/and for constant mask.

Canoicalize & and nop_convert order for
__atomic_fetch_or_*, __atomic_fetch_xor_*,
__atomic_xor_fetch_*,__sync_fetch_and_or_*,
__sync_fetch_and_xor_*,__sync_xor_and_fetch_*,
__atomic_fetch_and_*,__sync_fetch_and_and_* when mask is constant.

.i.e.

+/* Canonicalize
+  _1 = __atomic_fetch_or_4 (&v, 1, 0);
+  _2 = (int) _1;
+  _5 = _2 & 1;
+
+to
+
+  _1 = __atomic_fetch_or_4 (&v, 1, 0);
+  _2 = _1 & 1;
+  _5 = (int) _2;

+/* Convert
+ _1 = __atomic_fetch_and_4 (a_6(D), 4294959103, 0);
+ _2 = (int) _1;
+ _3 = _2 & 8192;
+to
+  _1 = __atomic_fetch_and_4 (a_4(D), 4294959103, 0);
+  _7 = _1 & 8192;
+  _6 = (int) _7;
+ So it can be handled by  optimize_atomic_bit_test_and.  */

I'm trying to rewrite match part in match.pd and find the
canonicalization is ok when mask is constant, but not for variable
since it will be simplified back by
 /* In GIMPLE, getting rid of 2 conversions for one new results
    in smaller IL.  */
 (simplify
  (convert (bitop:cs@2 (nop_convert:s @0) @1))
  (if (GIMPLE
       && TREE_CODE (@1) != INTEGER_CST
       && tree_nop_conversion_p (type, TREE_TYPE (@2))
       && types_match (type, @0))
   (bitop @0 (convert @1)))))

The canonicalization for variabled is like

convert
  _1 = ~mask_7;
  _2 = (unsigned int) _1;
  _3 = __atomic_fetch_and_4 (ptr_6, _2, 0);
 _4 = (int) _3;
 _5 = _4 & mask_7;

to
  _1 = ~mask_7;
  _2 = (unsigned int) _1;
  _3 = __atomic_fetch_and_4 (ptr_6, _2, 0);
  _4 = (unsigned int) mask_7
  _6 = _3 & _4
  _5 = (int) _6

and be simplified back.

I've also tried another way of simplication like

convert
  _1 = ~mask_7;
  _2 = (unsigned int) _1;
  _3 = __atomic_fetch_and_4 (ptr_6, _2, 0);
 _4 = (int) _3;
 _5 = _4 & mask_7;

to
  _1 = (unsigned int)mask_7;
  _2 = ~ _1;
  _3 = __atomic_fetch_and_4 (ptr_6, _2, 0);
   _6 = _3 & _1
  _5 = (int)

but it's prevent by below since __atomic_fetch_and_4 is not CONST, but
we need to regenerate it with updated parameter.

  /* We can't and should not emit calls to non-const functions.  */
  if (!(flags_from_decl_or_type (decl) & ECF_CONST))
    return NULL;