Re: [PATCH 12/19] riscv: Create xtheadvector file

[Charlie Jenkins <charlie@rivosinc.com>]

On Fri, Apr 12, 2024 at 12:30:32PM +0100, Conor Dooley wrote:
> On Thu, Apr 11, 2024 at 09:11:18PM -0700, Charlie Jenkins wrote:
> > These definitions didn't fit anywhere nicely, so create a new file to
> > house various xtheadvector instruction encodings.
> > 
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> >  arch/riscv/include/asm/xtheadvector.h | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/arch/riscv/include/asm/xtheadvector.h b/arch/riscv/include/asm/xtheadvector.h
> > new file mode 100644
> > index 000000000000..348263ea164c
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/xtheadvector.h
> > @@ -0,0 +1,25 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +/*
> > + * Vector 0.7.1 as used for example on T-Head Xuantie cores, uses an older
> > + * encoding for vsetvli (ta, ma vs. d1), so provide an instruction for
> > + * vsetvli	t4, x0, e8, m8, d1
> > + */
> > +#define THEAD_VSETVLI_T4X0E8M8D1	".long	0x00307ed7\n\t"
> > +#define THEAD_VSETVLI_X0X0E8M8D1	".long	0x00307057\n\t"
> > +
> > +/*
> > + * While in theory, the vector-0.7.1 vsb.v and vlb.v result in the same
> > + * encoding as the standard vse8.v and vle8.v, compilers seem to optimize
> > + * the call resulting in a different encoding and then using a value for
> > + * the "mop" field that is not part of vector-0.7.1
> > + * So encode specific variants for vstate_save and _restore.
> 
> This wording seems oddly familiar to me, did Heiko not write this?

Yeah, I wasn't sure how to attribute him. He wrote almost all of the
lines in this file, but I put it together into this file. What is the
standard way of doing that?

- Charlie

> 
> > + */
> > +#define THEAD_VSB_V_V0T0		".long	0x02028027\n\t"
> > +#define THEAD_VSB_V_V8T0		".long	0x02028427\n\t"
> > +#define THEAD_VSB_V_V16T0		".long	0x02028827\n\t"
> > +#define THEAD_VSB_V_V24T0		".long	0x02028c27\n\t"
> > +#define THEAD_VLB_V_V0T0		".long	0x012028007\n\t"
> > +#define THEAD_VLB_V_V8T0		".long	0x012028407\n\t"
> > +#define THEAD_VLB_V_V16T0		".long	0x012028807\n\t"
> > +#define THEAD_VLB_V_V24T0		".long	0x012028c07\n\t"
> > 
> > -- 
> > 2.44.0
> >