[Bug c++/66555] New: Fails to warn for if (j == 0 && i == i)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66555

            Bug ID: 66555
           Summary: Fails to warn for if (j == 0 && i == i)
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

Just fixed a bug in the vectorizer with

@@ -5359,7 +5373,7 @@ vectorizable_store (gimple stmt, gimple_
              vect_finish_stmt_generation (stmt, incr, gsi);

              running_off = newoff;
-             if (j == 0 && i == i)
+             if (j == 0 && i == 0)
                STMT_VINFO_VEC_STMT (stmt_info) = *vec_stmt = assign;
              else
                STMT_VINFO_RELATED_STMT (prev_stmt_info) = assign;

and I wonder why we don't warn about this (well, I know, we only warn
if the whole if expr folds to a constant).

Applies to the C frontend as well.