RFR: 8367341: C2: apply KnownBits and unsigned bounds to And / Or operations

[Quan Anh Mai]

On Mon, 13 Oct 2025 12:29:01 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Hi,
>> 
>> This PR improves the implementation of `AndNode/OrNode/XorNode::Value` by taking advantages of the additional information in `TypeInt`. The implementation is pretty straightforward. A clever trick is that by analyzing the negative and positive ranges of a `TypeInt` separately, we have better info for the leading bits. I also implement gtest unit tests to verify the correctness and monotonicity of the inference functions.
>> 
>> Please take a look and leave your reviews, thanks a lot.
>
> src/hotspot/share/opto/rangeinference.hpp line 199:
> 
>> 197:   S _hi;
>> 198:   U _ulo;
>> 199:   U _uhi;
> 
> Why not use `RangeInt`?

These are the mirrors of `TypeInt` and `TypeLong` so they need to be structurally similar to `TypeInt` and `TypeLong`.

> src/hotspot/share/opto/rangeinference.hpp line 218:
> 
>> 216:   bool contains(U u) const;
>> 217:   bool contains(const TypeIntMirror& o) const;
>> 218:   bool operator==(const TypeIntMirror& o) const;
> 
> Could we limit this to `DEBUG_ONLY`?

Maybe, it disables these gtest in product builds, however. What do you think?

> src/hotspot/share/opto/rangeinference.hpp line 221:
> 
>> 219: 
>> 220:   template <class T>
>> 221:   TypeIntMirror cast() const;
> 
> Can you explain what this casting method is for?

This is to mimic the behaviour when we do `t1->meet(t2)->cast<TypeInt>()`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27618#discussion_r2431572634
PR Review Comment: https://git.openjdk.org/jdk/pull/27618#discussion_r2431574484
PR Review Comment: https://git.openjdk.org/jdk/pull/27618#discussion_r2431578081