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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108516] Useless movzx instruction emitted when loading 8
 bits from 24 bit struct
Date: Tue, 24 Jan 2023 13:15:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108516

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-01-24
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed:

Trying 16 -> 6:
   16: r86:QI#0=3Dzero_extract(r87:HI,0x8,0x8)
      REG_DEAD r87:HI
    6: r84:SI=3Dzero_extend(r86:QI)
      REG_DEAD r86:QI
Failed to match this instruction:
(set (reg:SI 84 [ s.e2 ])
    (zero_extract:SI (reg:HI 87)
        (const_int 8 [0x8])
        (const_int 8 [0x8])))=