[Bug target/112919] LoongArch: Alignments in tune parameters are not precise and they regress performance

["xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112919

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://github.com/loongson
                   |                            |-community/discussions/issu
                   |                            |es/23
                 CC|                            |chenglulu at loongson dot cn,
                   |                            |xen0n at gentoo dot org
             Target|                            |loongarch64-*-*

--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Jia Jie reported a huge performance regression running Coremarks from GCC 13 to
14, and I can confirm it on LA664.

It seems a part of the regression is caused by over-aligning the labels.  On a
LA664 with different configurations I get Coremarks Iterations/Sec values (the
larger the better):

21120 with GCC 13.2.0
18320 with GCC 14.0.0 (with the default: -falign-labels=16
-falign-functions=32)
19972 with GCC 14.0.0 + -falign-loops=32 -falign-labels=4 -falign-jumps=4
-falign-functions=32 (the best I've got)
19938 with GCC 14.0.0 + -falign-loops=32 -falign-labels=4 -falign-jumps=4
-falign-functions=16
19964 with GCC 14.0.0 + -falign-loops=32 -falign-labels=4 -falign-jumps=4
-falign-functions=64
19276 with GCC 14.0.0 + -falign-loops=32 -falign-labels=8 -falign-jumps=4
-falign-functions=32
19674 with GCC 14.0.0 + -falign-loops=32 -falign-labels=4 -falign-jumps=8
-falign-functions=32
19752 with GCC 14.0.0 + -falign-loops=16 -falign-labels=4 -falign-jumps=4
-falign-functions=32
19922 with GCC 14.0.0 + -falign-loops=64 -falign-labels=4 -falign-jumps=4
-falign-functions=32

Lulu: can you help to run some other benchmarks like SPEC (I don't have an
access to it) and update these values for LA464 and LA664?