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

[Xi Ruoyao]

On Mon, 2023-06-12 at 14:54 +0800, WANG Xuerui wrote:
> 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.

--no-relax is accepted even with ld-2.38, the man page says:

           On platforms where the feature is not supported, both --relax and
           --no-relax are accepted, but ignored.

And it *should* disable relax for ld-2.41.  If not I'd consider it a bug
and we should fix it for Binutils.

If --no-relax behaves as expected I guess we just need

    LDFLAGS_PLATFORM += -Wl,--no-relax

in "if test "x$target_cpu" = xloongarch64" block.

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University