[PATCH 1/6] powerpc: Add ZERO_GPRS macros for register clears

[Christophe Leroy]

Le 01/06/2022 à 07:48, Rohan McLure a écrit :
> [You don't often get email from rmclure at linux.ibm.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> Macros for restoring saving registers to and from the stack exist.
> Provide a macro for simply zeroing a range of gprs, or an individual
> gpr.
> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
>   arch/powerpc/include/asm/ppc_asm.h | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
> index 4dea2d963738..3fb37a9767f7 100644
> --- a/arch/powerpc/include/asm/ppc_asm.h
> +++ b/arch/powerpc/include/asm/ppc_asm.h
> @@ -33,6 +33,19 @@
>          .endr
>   .endm
> 
> +/*
> + * Simplification of OP_REGS, for an arbitrary right hand operand.
> + *
> + *   op  reg, rhs

You call it "BINOP" but it is rare to have a binary operation with only 
two operands. Another name could be more appropriate ?
Or keep it as BINOP if you see another future use ? In that case have 
the 3 operands, then 'li r, 0' is same as 'addi r, 0, 0'

> + */
> +.macro BINOP_REGS op, rhs, start, end
> +       .Lreg=\start
> +       .rept (\end - \start + 1)
> +       \op .Lreg, \rhs
> +       .Lreg=.Lreg+1
> +       .endr
> +.endm
> +
>   /*
>    * Macros for storing registers into and loading registers from
>    * exception frames.
> @@ -49,6 +62,10 @@
>   #define REST_NVGPRS(base)              REST_GPRS(13, 31, base)
>   #endif
> 
> +#define ZERO_GPRS(start, end)          BINOP_REGS li, 0, start, end
> +#define ZERO_NVGPRS()                  ZERO_GPRS(14, 31)
> +#define ZERO_GPR(n)                    ZERO_GPRS(n, n)

Maybe it would be more explicit to use ZEROIZE_

> +
>   #define SAVE_GPR(n, base)              SAVE_GPRS(n, n, base)
>   #define REST_GPR(n, base)              REST_GPRS(n, n, base)
> 
> --
> 2.34.1
>