[Bug tree-optimization/101187] enhancement for vector logic right shift with constant bigger than element precision

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101187

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-06-24

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Sth as simple as

(simplify
 (rshift @0 INTEGER_CST@1)
 (if (TYPE_UNSIGNED (type)
      && compare_tree_int (@1, element_precision (type)) >= 0)
  { build_zero_cst (type); }))

does the trick.  Of course it's quite limited and we could handle
undefined left-shifts as well (even arithmetic ones).