Re: [PATCH v2 8/8] linux-user: Simplify host <-> target errno conversion using macros

[Philippe Mathieu-Daudé]

On 7/8/21 5:30 PM, Laurent Vivier wrote:
> Le 08/07/2021 à 16:11, Philippe Mathieu-Daudé a écrit :
>> Convert the host_to_target_errno_table[] array to a switch case
>> to allow compiler optimizations. Extract the errnos list as to
>> a new includible unit, using a generic macro. Remove the code
>> related to target_to_host_errno_table[] initialization.
>>
> 
> Is there some performance penalties by using a switch() rather than an 
> array[] ?

Per Richard suggestion
https://www.mail-archive.com/qemu-devel@nongnu.org/msg821488.html
rather the opposite, it might be now easier for the compiler to
optimize. And we free unused entries in the array (.rodata).

>> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>  linux-user/syscall.c    | 169 +++++-----------------------------------
>>  linux-user/errnos.c.inc | 140 +++++++++++++++++++++++++++++++++
>>  2 files changed, 161 insertions(+), 148 deletions(-)
>>  create mode 100644 linux-user/errnos.c.inc
>>
> ...
>> diff --git a/linux-user/errnos.c.inc b/linux-user/errnos.c.inc
>> new file mode 100644
>> index 00000000000..807c97ca25e
>> --- /dev/null
>> +++ b/linux-user/errnos.c.inc
>> @@ -0,0 +1,140 @@
> ...
>> +#ifdef ERKFILL
> 
> You fix it in patch 1 but forgot to report it in your patch :)

Grrr :(