RFR: 8345067: C2: enable implicit null checks for ZGC reads [v2]

[Roberto Castañeda Lozano]

On Thu, 8 May 2025 15:22:33 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Roberto Castañeda Lozano has updated the pull request incrementally with nine additional commits since the last revision:
>> 
>>  - Generalize tests by removing requires annotation and adding local applyIf rules
>>  - Assert that we do not move control nodes
>>  - Extend comment about hoisting DecodeN inputs
>>  - Apply Emanuels suggestions to ensure_node_is_at_block_or_above
>>  - Rename auxiliary functions
>>  - Rename auxiliary functions
>>  - Clarify scope of move_into
>>  - Extend comment about MachTemp nodes
>>  - Extract and reuse legitimize_address test
>
> src/hotspot/share/opto/lcm.cpp line 95:
> 
>> 93: }
>> 94: 
>> 95: void PhaseCFG::maybe_hoist_into(Node* n, Block* b) {
> 
> Consider adding asserts into these 2 new methods to make sure that they operate only on **data** and not control nodes.

Thanks, done (commit b198fca8).

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PR Review Comment: https://git.openjdk.org/jdk/pull/25066#discussion_r2087192210