[Bug rtl-optimization/115877] [15 Regression] wrong code at -Os (missing zero extension)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115877

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
                 CC|                            |law at gcc dot gnu.org
   Last reconfirmed|                            |2024-07-11

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Looks like ext_dce is doing something wrong:

Processing insn:
    8: r107:SI=zero_extend(r105:HI)
      REG_DEAD r105:HI
Trying to simplify pattern:
(zero_extend:SI (reg:HI 105 [ _2 ]))
rescanning insn with uid = 8.
Successfully transformed to:
(subreg:SI (reg:HI 105 [ _2 ]) 0)


I am not sure if that is valid.

Note 105 is defined as:
(insn 7 6 8 2 (set (reg:HI 105 [ _2 ])
        (not:HI (reg:HI 106 [ uD.2773 ]))) "/app/example.cpp":7:8 933
{*one_cmplhi2_1}
     (expr_list:REG_DEAD (reg:HI 106 [ uD.2773 ])
        (expr_list:REG_EQUAL (not:HI (mem/c:HI (symbol_ref:DI ("u") [flags 0x2]
 <var_decl 0x78f8cd010cf0 u>) [1 uD.2773+0 S2 A16]))
            (nil))))