RFC: Change uint8 to uint16_t for _num_regs

[Leslie Zhai]

Hi Aleksey,

Thanks for your kind response!


在 2021年04月01日 18:25, Aleksey Shipilev 写道:
> On 4/1/21 7:20 AM, Leslie Zhai wrote:
>> Patch:
>>
>> diff --git a/hotspot/src/share/vm/opto/chaitin.hpp
>> b/hotspot/src/share/vm/opto/chaitin.hpp
>> index de6d443..94f66b8 100644
>> --- a/hotspot/src/share/vm/opto/chaitin.hpp
>> +++ b/hotspot/src/share/vm/opto/chaitin.hpp
>> @@ -136,7 +136,7 @@ public:
>>
>>      // Number of registers this live range uses when it colors
>>    private:
>> -  uint8 _num_regs;              // 2 for Longs and Doubles, 1 for 
>> all else
>> +  uint16_t _num_regs;           // 2 for Longs and Doubles, 1 for 
>> all else
>>                                    // except _num_regs is kill count for
>> fat_proj
>>    public:
>>      int num_regs() const { return _num_regs; }
>
> Looks to me it was changed to uint16_t in JDK 9 by "8076276: Add 
> support for AVX512"
>   https://bugs.openjdk.java.net/browse/JDK-8076276
>
> Note that patch also changed:
>  -  uint8_t _reg_pressure;
>  +  uint16_t _reg_pressure;

Thanks!

Leslie Zhai

>
> From reading the uses of these fields, I think these are more or less 
> safe to widen.
>