Re: [PATCH v3 13/29] tcg/s390: Support bswap flags

[Peter Maydell]

On Sat, 26 Jun 2021 at 07:44, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> For INDEX_op_bswap16_i64, use 64-bit instructions so that we can
> easily provide the extension to 64-bits.  Drop the special case,
> previously used, where the input is already zero-extended -- the
> minor code size savings is not worth the complication.
>
> Cc: qemu-s390x@nongnu.org
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

> +    case INDEX_op_bswap32_i32:
>          tcg_out_insn(s, RRE, LRVR, args[0], args[1]);
>          break;

When we're working with i32s, is the top half of the host register
zero or garbage ? I guess either way LRVR does the right thing.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM