[Bug debug/106746] [13 Regression] '-fcompare-debug' failure (length) with -O2 -fsched2-use-superblocks since r13-2041-g6624ad73064de241

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106746

--- Comment #7 from H.J. Lu <hjl.tools at gmail dot com> ---
Specifically,

     /* We can canonicalize SIGN_EXTEND (op) as ZERO_EXTEND (op) when
         we know the sign bit of OP must be clear.  */
      if (val_signbit_known_clear_p (GET_MODE (op),
                                     nonzero_bits (op, GET_MODE (op))))
        return simplify_gen_unary (ZERO_EXTEND, mode, op, GET_MODE (op));

triggers the failure.