Re: [PATCH 02/11] tcg: Add tcg_gen_revbit{32,64}

["Philippe Mathieu-Daudé" <philmd@oss.qualcomm.com>]

Hi Richard,

On 31/7/26 02:04, Richard Henderson wrote:
> Add generic expanders for reversing bits within a word.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/tcg/tcg-op-common.h |  3 ++
>   include/tcg/tcg-op.h        |  5 ++++
>   tcg/tcg-op.c                | 59 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 67 insertions(+)
> 
> diff --git a/include/tcg/tcg-op-common.h b/include/tcg/tcg-op-common.h
> index 1fe342db0d..91f59dc11e 100644
> --- a/include/tcg/tcg-op-common.h
> +++ b/include/tcg/tcg-op-common.h

> @@ -275,6 +276,8 @@ void tcg_gen_smax_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>   void tcg_gen_umin_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>   void tcg_gen_umax_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>   void tcg_gen_abs_i64(TCGv_i64, TCGv_i64);
> +void tcg_gen_revbit32_i64(TCGv_i64 ret, TCGv_i64 arg, int flags);
> +void tcg_gen_revbit64_i64(TCGv_i64 ret, TCGv_i64 arg);

Could the bswap flag be defined once per target?

- output sign-extended (TCG_BSWAP_OS):

   alpha, hppa, loongarch, m68k, mips, riscv, rx, sh4, tricore

- output zero-extended (TCG_BSWAP_OZ):

   arm, avr, hexagon, microblaze, openrisc, ppc, sparc, x86, xtensa

- input/output zero-extended (TCG_BSWAP_IZ | TCG_BSWAP_OZ):

   s390x

Having to manually encode it on each frontend doesn't sound optimal.

Note, we have some target-specific TCG information in TCGCPUOps
(useful at runtime for heterogeneous emulation).