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SubjectRe: [PATCH] riscv: lib: Support csum on GCC <11
On Thu, Jan 18, 2024 at 01:53:59PM -0800, Charlie Jenkins wrote:
> The OutputOperands field for asm goto statements is only supported
> starting from GCC 11. Split the asm goto to remove the use of this
> feature.
>
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> Fixes: a04c192eabfb ("riscv: Add checksum library")
> ---
> The OutputOperands field for asm goto statements is only supported
> starting from GCC 11. Split the asm goto to remove the use of this
> feature.

Maybe this is a super naive question, but is it possible to just not
use the custom csum code for gcc older than 11?

> ---
> arch/riscv/lib/csum.c | 42 ++++++++++++++++++++++++++++++------------
> 1 file changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c
> index 06ce8e7250d9..23be289f52b6 100644
> --- a/arch/riscv/lib/csum.c
> +++ b/arch/riscv/lib/csum.c
> @@ -177,22 +177,35 @@ do_csum_with_alignment(const unsigned char *buff, int len)
> : no_zbb);
>
> #ifdef CONFIG_32BIT
> - asm_volatile_goto(".option push \n\
> + /*
> + * OutputOperands in asm goto is not supported until GCC 11, so
> + * this asm has to be split to be compatible.
> + */
> + asm (".option push \n\
> .option arch,+zbb \n\
> rori %[fold_temp], %[csum], 16 \n\
> andi %[offset], %[offset], 1 \n\
> add %[csum], %[fold_temp], %[csum] \n\
> - beq %[offset], zero, %l[end] \n\
> - rev8 %[csum], %[csum] \n\
> .option pop"
> : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
> - : [offset] "r" (offset)
> - :
> - : end);
> + : [offset] "r" (offset));
> +
> + if (offset == 0)
> + goto end;
> +
> + asm (".option push \n\
> + .option arch, +zbb \n\
> + rev8 %[csum], %[csum] \n\
> + .option pop"
> + : [csum] "+r" (csum));
>
> return (unsigned short)csum;
> #else /* !CONFIG_32BIT */
> - asm_volatile_goto(".option push \n\
> + /*
> + * OutputOperands in asm goto is not supported until GCC 11, so
> + * this asm has to be split to be compatible.
> + */
> + asm (".option push \n\
> .option arch,+zbb \n\
> rori %[fold_temp], %[csum], 32 \n\
> add %[csum], %[fold_temp], %[csum] \n\
> @@ -200,13 +213,18 @@ do_csum_with_alignment(const unsigned char *buff, int len)
> roriw %[fold_temp], %[csum], 16 \n\
> addw %[csum], %[fold_temp], %[csum] \n\
> andi %[offset], %[offset], 1 \n\
> - beq %[offset], zero, %l[end] \n\
> - rev8 %[csum], %[csum] \n\
> .option pop"
> : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
> - : [offset] "r" (offset)
> - :
> - : end);
> + : [offset] "r" (offset));
> +
> + if (offset == 0)
> + goto end;
> +
> + asm (".option push \n\
> + .option arch, +zbb \n\
> + rev8 %[csum], %[csum] \n\
> + .option pop"
> + : [csum] "+r" (csum));
>
> return (csum << 16) >> 48;
> #endif /* !CONFIG_32BIT */
>
> ---
> base-commit: 080c4324fa5e81ff3780206a138223abfb57a68e
> change-id: 20240118-csum_remove_output_operands_asm_goto-49922c141ce7
> --
> - Charlie
>
>
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