RFR: 8371178: Preserve fast version of getfield and putfield in AOTCache

[Ioi Lam]

On Tue, 4 Nov 2025 02:10:13 GMT, Ashutosh Mehra <asmehra at openjdk.org> wrote:

> Preserve the "fast" version of `getfield` and `putfield` bytecodes in the AOTCache during the assembly phase if the constant pool entry referred by the bytecodes is stored in resolved state in the AOTCache.
> 
> Testing:
> Testing with JTREG="AOT_JDK=true" TEST=hotspot_runtime_no_cds passed on x86-64

src/hotspot/share/cds/aotMetaspace.cpp line 556:

> 554:         case ztos:
> 555:           new_code = Bytecodes::_fast_bgetfield;
> 556:           break;

Why is this `switch` block necessary? Is it possible for `new_code` to be different than `*bcs.bcp()`? If not, it might be easier to initialize `new_code` to `Bytecodes::_illegal` and then do the rewriting only if `new_code` has been updated.

src/hotspot/share/cds/aotMetaspace.cpp line 635:

> 633:     }
> 634:     case Bytecodes::_aload_0:
> 635:       new_code = Bytecodes::_nofast_aload_0;

Maybe add a comment here that `_fast_Xaccess_0` bytecodes will be reverted?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28121#discussion_r2491222034
PR Review Comment: https://git.openjdk.org/jdk/pull/28121#discussion_r2491238312