Re: [PATCH] RISC-V: fix compile error from decuplicated __ALTERNATIVE_CFG_2

Andrew Jones
2023-01-04T15:13:30Z

On Wed, Jan 04, 2023 at 01:29:25PM +0000, Conor Dooley wrote:
> On Tue, Jan 03, 2023 at 10:42:28PM +0100, Heiko Stuebner wrote:
> > From: Heiko Stuebner <heiko.stuebner@vrull.eu>
>
> > RISC-V: fix compile error from decuplicated __ALTERNATIVE_CFG_2
>
> Hey Heiko/Palmer,
>
> Was a little hard to tell from Drew's mail if he was objecting to this
> variant of the patch, but FWIW s/decup/dedup/ if this gets applied
> as-is.

I wasn't completely objecting, but rather suggesting we still try to
factor out what we can. However, after reading a bit more about macros
I tried this

.macro ALTERNATIVE_CFG_2 old_c, new_c_1, vendor_id_1, errata_id_1, enable_1, \
new_c_2, vendor_id_2, errata_id_2, enable_2
- ALTERNATIVE_CFG \old_c, \new_c_1, \vendor_id_1, \errata_id_1, \enable_1
+ ALTERNATIVE_CFG "\old_c", "\new_c_1", \vendor_id_1, \errata_id_1, \enable_1
ALT_NEW_CONTENT \vendor_id_2, \errata_id_2, \enable_2, \new_c_2
.endm

which appears to work for my simple test. Does that work for you too,
Heiko? If so, then I think I'd prefer we do that. Also, we may want to add
quotes to all macro arguments which may contain spaces, even if things
seem to work now, e.g. the \new_c_2 argument passed to ALT_NEW_CONTENT.

Thanks,
drew

>
> Thanks,
> Conor.
>
> > On the non-assembler-side wrapping alternative-macros inside other macros
> > to prevent duplication of code works, as the end result will just be a
> > string that gets fed to the asm instruction.
> >
> > In real assembler code, wrapping .macro blocks inside other .macro blocks
> > brings more restrictions on usage and the optimization done by
> > commit 2ba8c7dc71c0 ("riscv: Don't duplicate __ALTERNATIVE_CFG in __ALTERNATIVE_CFG_2")
> > results in a compile error like:
> >
> > ../arch/riscv/lib/strcmp.S: Assembler messages:
> > ../arch/riscv/lib/strcmp.S:15: Error: too many positional arguments
> > ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> > ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "887:"
> > ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> > ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "887:"
> > ../arch/riscv/lib/strcmp.S:15: Error: backward ref to unknown label "886:"
> > ../arch/riscv/lib/strcmp.S:15: Error: attempt to move .org backwards
> >
> > Going back to the original code for the non-assembler-part makes that
> > code work again. So this reverts the #ifdef ASSEMBLY part of that commit
> > to the previous variant with duplicated base.
> >
> > Fixes: 2ba8c7dc71c0 ("riscv: Don't duplicate __ALTERNATIVE_CFG in __ALTERNATIVE_CFG_2")
> > Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> > ---
> > I was of two minds about either to revert the full patch, or doing just
> > this partial one for the ASSEMBLY part. I did go with this variant, as I
> > still like the idea of deduplicating as much as possible :-)
> >
> > arch/riscv/include/asm/alternative-macros.h | 13 ++++++++++++-
> > 1 file changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
> > index 7226e2462584..e7bdb2a510a4 100644
> > --- a/arch/riscv/include/asm/alternative-macros.h
> > +++ b/arch/riscv/include/asm/alternative-macros.h
> > @@ -44,9 +44,20 @@
> > ALT_NEW_CONTENT \vendor_id, \errata_id, \enable, \new_c
> > .endm
> >
> > +/*
> > + * Using ALTERNATIVE_CFG inside ALTERNATIVE_CFG_2 results in compile errors.
> > + * So the common code needs to stay duplicated.
> > + */
> > .macro ALTERNATIVE_CFG_2 old_c, new_c_1, vendor_id_1, errata_id_1, enable_1, \
> > new_c_2, vendor_id_2, errata_id_2, enable_2
> > - ALTERNATIVE_CFG \old_c, \new_c_1, \vendor_id_1, \errata_id_1, \enable_1
> > +886 :
> > + .option push
> > + .option norvc
> > + .option norelax
> > + \old_c
> > + .option pop
> > +887 :
> > + ALT_NEW_CONTENT \vendor_id_1, \errata_id_1, \enable_1, \new_c_1
> > ALT_NEW_CONTENT \vendor_id_2, \errata_id_2, \enable_2, \new_c_2
> > .endm
> >
> > --
> > 2.35.1
> >
> >
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