Re: [PATCH 4/5] ARC: add support for DSP-enabled userspace applications

[Vineet Gupta]

On 3/4/20 3:51 AM, Eugeniy Paltsev wrote:
>>> +                "r" (_saveto),                                       \
>>> +                "r" (_readfrom),                                     \
>>> +                "I" (_aux),                                          \
>>> +                "I" (_offt)                                          \
>>> +             :                                                       \
>>
>> AEX with "I" constraint will likely be an 8 byte instructions always. Best to give
>> compiler wiggle room with "Ir"
>
> Could you please explain how "Ir" will work in this case?
> Does this mean that compiler can pass the value either as constant ('I') or
> via register ('r')?

Right. If the same compile-time const is used multiple times, say SR of same value
to a reg, if can decide to hoist the value in a register, if you provide it "r" or
"Ir", leading to shorter overall code.

-Vineet