[Bug rtl-optimization/85941] Zero extend from QI->SI lost if QI is referred to via subreg:HI

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85941

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
But this pattern:

(define_insn "zero_extendqisi2"
  [(set (match_operand:SI 0 "nonimmediate_operand" "=r")
        (zero_extend:SI (subreg:HI (match_operand:QI 1 "nonimmediate_operand"
"rm") 0)))]

Is saying a zero_extend from HI to SI.  But not from QI to SI.  This is a
paradoxical subreg.