[lworld] RFR: 8377414: [lworld] Improve acmp expansion

[Chen Liang]

On Sat, 7 Feb 2026 16:30:43 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

> Hi,
> 
> This PR improves the acmp expansion:
> 
> - Do an incremental inlining for easier graph modification.
> - Take advantage of field values in addition to field types to shortcut the substitutability check.
> 
> Please take a look and leave your review, thanks a lot.

src/hotspot/share/opto/callnode.cpp line 1387:

> 1385: // Try to replace a runtime call to the substitutability test by either a simple pointer comparison
> 1386: // if either operand is not a value object, or comparing their fields if either operand is an
> 1387: // object of a known value type

I think now the contract is substitutability is only called with two non-null value objects of the same class. You can probably be less strict here?

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PR Review Comment: https://git.openjdk.org/valhalla/pull/2066#discussion_r2777799266