https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116398
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> (insn 6 3 12 2 (set (reg:DI 105 [ dataD.4432 ])
> (sign_extend:DI (reg/v:SI 102 [ dataD.4432 ])))
> "/app/example.cpp":3:12 105 {*extendsidi2_aarch64}
> (expr_list:REG_DEAD (reg/v:SI 102 [ dataD.4432 ])
> (nil)))
> (insn 12 6 13 2 (set (reg:DI 110 [ _3+8 ])
> (ashiftrt:DI (reg:DI 105 [ dataD.4432 ])
> (const_int 11 [0xb]))) "/app/example.cpp":3:29 755
> {*aarch64_ashr_sisd_or_int_di3}
> (nil))
> (insn 13 12 23 2 (set (reg:DI 109 [ _3 ])
> (ashift:DI (reg:DI 105 [ dataD.4432 ])
> (const_int 53 [0x35]))) "/app/example.cpp":3:29 751
> {*aarch64_ashl_sisd_or_int_di3}
> (expr_list:REG_DEAD (reg:DI 105 [ dataD.4432 ])
> (nil)))
> ...
>
> Could be just simplified to (ignore the ordering difference):
>
> (insn 23 13 24 2 (set (reg:DI 109 [ _3+8 ])
> (ashift:DI (subreg:DI (reg:SI 105) 0)
> (const_int 53 [0x35]))) "/app/example.cpp":4:1 751
> {*aarch64_ashl_sisd_or_int_di3}
> (nil))
> (insn 24 23 19 2 (set (reg:DI 110 [ _3 ])
> (sign_extract:DI (subreg:DI (reg:SI 105) 0)
> (const_int 21 [0x15])
> (const_int 11 [0xb]))) "/app/example.cpp":4:1 801 {*extvdi}
> (expr_list:REG_DEAD (reg:SI 113)
> (nil)))
>
> Which is what combine did in GCC 14.
>
> Is this because only combine knows creats sign_extract?
But then again why didn't fwprop prop r105=sign_extend(r102) into insn 13? that
would have fixed it too. Even if insn 6 and insn 13 could not combine, they
could be executed in parrallel.
