https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107208
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[aarch64] llvm generate |[aarch64] _complex integer
|better code than gcc base |return types could be
|on _Complex type mul |improved
Component|rtl-optimization |middle-end
Last reconfirmed| |2022-10-11
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yes it is due to return value and how it is done:
(insn 32 28 33 2 (clobber (reg/i:CDI 0 x0)) "/app/example.cpp":6:1 -1
(nil))
(insn 33 32 34 2 (set (reg:DI 0 x0)
(reg:DI 102 [ <retval> ])) "/app/example.cpp":6:1 -1
(nil))
(insn 34 33 35 2 (set (reg:DI 1 x1 [+8 ])
(reg:DI 103 [ <retval>+8 ])) "/app/example.cpp":6:1 -1
(nil))
(insn 35 34 0 2 (use (reg/i:CDI 0 x0)) "/app/example.cpp":6:1 -1
(nil))
So this is not _Complex integer multiplies at all but rather just the return
values and the register allocator.
I wonder why Complex float is expanded slightly differently (and better here):
(insn 34 33 35 2 (set (reg:SF 32 v0)
(reg:SF 115)) "/app/example.cpp":6:1 -1
(nil))
(insn 35 34 36 2 (set (reg:SF 33 v1)
(reg:SF 118)) "/app/example.cpp":6:1 -1
(nil))
(insn 36 35 37 2 (use (reg:SF 32 v0)) "/app/example.cpp":6:1 -1
(nil))
(insn 37 36 0 2 (use (reg:SF 33 v1)) "/app/example.cpp":6:1 -1
(nil))
Who chose CDI for the integer case but a pair of SF for the float case ...
