RFR: 8315066: Add unsigned bounds and known bits to TypeInt/Long [v18]

[Quan Anh Mai]

On Wed, 11 Sep 2024 05:24:38 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remove leftover code
>
> src/hotspot/share/opto/rangeinference.hpp line 69:
> 
>> 67:     return (v & _zeros) == 0 && (v & _ones) == _ones;
>> 68:   }
>> 69: };
> 
> It will be good if we add basic operations to KnowBits like.
> KnownBits.getMaxValue() returning ~ZEROS
> KnownBits.getMinValue() returning  ONE
> KnownBits.and(KnownBits arg)
> KnownBits.or(KnownBits arg)
> KnownBits.xor(KnownBits args)
> KnownBits.not()
> 
> 
> These can be quite handy during data flow analysis using KnownBits

Yes I think they would be helpful in later patches when implementing `Value` methods of several nodes to take advantage of additional `TypeInt` information.

> src/hotspot/share/opto/type.hpp line 661:
> 
>> 659:   // the below constraints, see contains(jint)
>> 660:   const jint _lo, _hi;       // Lower bound, upper bound in the signed domain
>> 661:   const juint _ulo, _uhi;    // Lower bound, upper bound in the unsigned domain
> 
> Can't we do without explicit fields to record unsigned hi / lo ?
> We just need to present a unsigned view of signed _lo and _hi which can be done using safe macros.

No we can't, consider `TypeInt::NON_ZERO`. It would have `_lo = min_jint`, `_hi = max_jint`, `_zeros = 0`, `_ones = 0`. Which make it impossible to distinguish from `TypeInt::INT` without unsigned bounds.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1757237569
PR Review Comment: https://git.openjdk.org/jdk/pull/17508#discussion_r1757240241