Re: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility functions

[Philippe Mathieu-Daudé]

On 1/22/21 10:59 PM, Taylor Simpson wrote:
>> -----Original Message-----
>> From: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com> On
>> Behalf Of Philippe Mathieu-Daudé
>> Sent: Friday, January 22, 2021 12:09 PM
>> To: Taylor Simpson <tsimpson@quicinc.com>; qemu-devel@nongnu.org
>> Cc: richard.henderson@linaro.org; alex.bennee@linaro.org;
>> laurent@vivier.eu; ale@rev.ng; Brian Cain <bcain@quicinc.com>
>> Subject: Re: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility
>> functions
>>
>> Hi Taylor,
>>
>> On 1/20/21 4:28 AM, Taylor Simpson wrote:
>>> Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
>>> ---
>>>  target/hexagon/arch.h |  35 ++++++
>>>  target/hexagon/arch.c | 294
>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 329 insertions(+)
>>>  create mode 100644 target/hexagon/arch.h
>>>  create mode 100644 target/hexagon/arch.c
>>>
>>> diff --git a/target/hexagon/arch.h b/target/hexagon/arch.h
>>> new file mode 100644
>>> index 0000000..a8374a3
>>> --- /dev/null
>>> +++ b/target/hexagon/arch.h
>>
>> Maybe rename "arch_utils.[ch]"?
> 
> Any particular reason?

I was thinking about not being confused by an architecture specific
file when doing refactors involving multiple architectures. But this
isn't a great improvement neither... No problem.

> 
>>
>>> +extern int arch_sf_invsqrt_common(float32 *Rs, float32 *Rd, int *adjust,
>>> +                                  float_status *fp_status);
>>
>> (Again, no need for 'extern').
> 
> OK, I will change these.
> 
>>> diff --git a/target/hexagon/arch.c b/target/hexagon/arch.c
>>> new file mode 100644
>>> index 0000000..c59cad5
>>> --- /dev/null
>>> +++ b/target/hexagon/arch.c
>> ...
>>
>>> +#define RAISE_FP_EXCEPTION \
>>> +    do {} while (0)            /* Not modelled in qemu user mode */
>>
>> I don't understand why... Can you explain please?
> 
> Our Linux kernel only sets the relevant bits in USR (user status register).  
> The exception isn't raised to user mode.

Hmm while you introduce the linux-user implementation of your port,
this file is not restricted to user mode. Thinking about avoiding
head aches to someone wanting to add system mode emulation (or a
BSD port??), maybe your helpers should consider that.
Maybe some cheap #ifdef'ry CONFIG_USER_ONLY with a comment explaining
why there is nothing to do in user mode, and g_assert_not_reached()
else. Not sure, just wondering...

Regards,

Phil.