RFR: 8373591: C2: Fix the memory around some intrinsics nodes [v3]

[Roland Westrelin]

On Tue, 16 Dec 2025 06:23:12 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This is extracted from #28570 , there are 2 issues here:
>> 
>> - Some intrinsics nodes advertise incorrect `adr_type`. For example, `AryEqNode` reports `adr_type` being `TypeAryPtr::BYTES` (it inherits this from `StrIntrinsicNode`). This is incorrect, however, as it can accept `char[]` inputs, too. Another case is `VectorizedHashCodeNode`, which reports its `adr_type` being `TypePtr::BOTTOM`, but it actually extracts a memory slice and does not consume the whole memory.
>> - For nodes such as `StrInflatedCopyNode`, as they consume more than they produce, during scheduling, we need to compute anti-dependencies. This is not the case, so we should fix it by making the nodes kill all the memory they consume. This issue is often not present because these intrinsics are not exposed bare to general usage.
>> 
>> Please kindly review, thanks a lot.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use MemBar instead of widening the intrinsic memory

src/hotspot/share/opto/graphKit.cpp line 4210:

> 4208:     //  StoreC -> MemBar -> MergeMem -> compress_string -> MergeMem -> CharMem
> 4209:     //                               -------------------------------->
> 4210:     Node* all_mem = reset_memory();

This code sequence is used several times. Would it make sense to factor it out in its own method?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28789#discussion_r2624030618