Re: [Qemu-devel] [PATCH v10 14/14] target/arm: Send interrupts on PMU counter overflow

[Richard Henderson]

On 1/19/19 8:40 AM, Aaron Lindsay wrote:
> In practice, I think only the 32nd bit would ever need to be cleared,
> but I agree it is more correct to clear them all.
> 
>> Given that it is architecturally defined to 32-bits, I think you could really
>> just drop the define and use
>>
>>     uint32_t new_pmevcntr = ...;
>>     if (env->cp15.c14_pmevcntr[counter] & ~new_pmevcntr & INT32_MIN)
>>
>> with equal clarity.
> 
> I don't know whether it is important for the resolution of this patch,
> but what did you mean by the following?:
> 
>> The type of new_pmevcntr means you don't have to clear any
>> high bits either.

If you use uint32_t, then no *explicit* clearing of the high bits is necessary,
and is implied by the assignment back to env->cp15.c14_pmevcntr[counter].


r~