Re: [PATCH 0/7] tcg: Document *swap/deposit helpers

["Alex Bennée" <alex.bennee@linaro.org>]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> While reviewing a recent patch from Richard optimizing
> deposit() [*] I ended looking at the *swap friends, taking
> some notes, which then evolved to proper documentation.
>
> [*]
> https://lore.kernel.org/qemu-devel/20230816145547.477974-3-richard.henderson@linaro.org/

We already have some documentation in tcg.rst:

   * - bswap16_i32/i64 *t0*, *t1*, *flags*

     - | 16 bit byte swap on the low bits of a 32/64 bit input.
       |
       | If *flags* & ``TCG_BSWAP_IZ``, then *t1* is known to be zero-extended from bit 15.
       | If *flags* & ``TCG_BSWAP_OZ``, then *t0* will be zero-extended from bit 15.
       | If *flags* & ``TCG_BSWAP_OS``, then *t0* will be sign-extended from bit 15.
       |
       | If neither ``TCG_BSWAP_OZ`` nor ``TCG_BSWAP_OS`` are set, then the bits of *t0* above bit 15 may contain any value.

   * - bswap32_i64 *t0*, *t1*, *flags*

     - | 32 bit byte swap on a 64-bit value.  The flags are the same as for bswap16,
         except they apply from bit 31 instead of bit 15.

   * - bswap32_i32 *t0*, *t1*, *flags*

       bswap64_i64 *t0*, *t1*, *flags*

     - | 32/64 bit byte swap. The flags are ignored, but still present
         for consistency with the other bswap opcodes.

In an ideal world we could generate kdoc from the source file and
include it in the rest of the tcg docs. I'm not sure if it worth the
churn though? Richard?

https://qemu.readthedocs.io/en/master/devel/tcg-ops.html

>
> Philippe Mathieu-Daudé (7):
>   tcg/tcg-op: Document bswap16() byte pattern
>   tcg/tcg-op: Document bswap32() byte pattern
>   tcg/tcg-op: Document bswap64() byte pattern
>   tcg/tcg-op: Document hswap() byte pattern
>   tcg/tcg-op: Document wswap() byte pattern
>   tcg/tcg-op: Document deposit_z()
>   target/cris: Fix a typo in gen_swapr()
>
>  docs/devel/tcg-ops.rst  | 12 ++++++
>  target/cris/translate.c | 20 +++++----
>  tcg/tcg-op.c            | 96 +++++++++++++++++++++++++++++++----------
>  3 files changed, 96 insertions(+), 32 deletions(-)


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro