Re: [PATCH v2 0/5] loongarch: add relaxation support

[WANG Xuerui]

On 6/12/23 11:09, Xiaotian Wu wrote:
> 在 2023-06-12星期一的 06:35 +0800，Xi Ruoyao via Grub-devel写道：
> > On Wed, 2023-06-07 at 15:34 +0800, Xiaotian Wu wrote:
> > > Because the binutils of the loongarch architecture adds relaxation
> > > support [1], the next version of binutils will not be able to build
> > > grub.
> > >
> > > So we added the R_LARCH_B16, R_LARCH_B21 and R_LARCH_RELAX
> > > relocations
> > > to enhance grub compatibility.
> > Wouldn't it be easier to just pass -mno-relax to the toolchain when
> > we
> > build GRUB?  I don't think it makes too much sense to perform
> > relaxation
> > on a boot loader.  The boot loader is generally the coldest code
> > paths
> > in a system, so relaxing it won't give any real benefit (well, if you
> > reboot a system 100 times you may finally save one second), but
> > increases the maintenance burden.
> Yes, it's easy to pass -mno-relax, but binutils-2.40 doesn't support
> this option.
Then maybe probe it in grub's configure and add it to CFLAGS when it's 
supported? IIUC every toolchain with support for relaxation should 
provide this toggle, and we already probe several LoongArch-specific 
flags right now so the infra is already there.
> > Consider a new relaxation pattern is added after we release GRUB
> > 2.12.
> > Then if we simply pass -mno-relax, GRUB 2.12 will continue to work.
> > But
> > if we try to "support" relaxation this way, every distro will have to
> > patch GRUB 2.12 when the toolchain is updated.
> GRUB 2.12 has not been released yet. If this patch can be merged before
> the release of grub 2.12, every distribution does not need to be
> patched. Moreover, both binutils-2.40 and future binutils 2.41+ will be
> able to compile normally.
Consider a possible scenario where more relaxation patterns are 
implemented by future toolchains; I don't think grub should care, or get 
changed every single time when that happens.