RFR: 8368811: [Leyden] Use AOTRuntimeConstants table for card_table::_byte_map_base

Vladimir Kozlov kvn at openjdk.org
Sun Sep 28 00:02:02 UTC 2025


Currently we use `Relocation` info to patch `card_table::_byte_map_base` referenced in compiled code. This is not completely correct since this is not address. We currently have special check in `AOTCodeCache::init2()` to skip AOT code generation and usage if `byte_map_base` is not relocatable [aotCodeCache.cpp#L341](https://github.com/openjdk/leyden/blob/premain/src/hotspot/share/code/aotCodeCache.cpp#L341)

To avoid this we should use existing `AOTRuntimeConstants` table to load `byte_map_base` from it.

I also added few missing loads `card_shift` from `AOTRuntimeConstants` table. Actually I am not sure why we have it in `AOTRuntimeConstants` table.  From what I see, it is based on `GCCardSizeInBytes` flag [cardTable.cpp#L46](https://github.com/openjdk/leyden/blob/premain/src/hotspot/share/gc/shared/cardTable.cpp#L46) and never modified. The flags is not adjusted ergonomically.  So we can simple record the flag in AOT code configuration and verify it when loading AOT code. 

@adinn  what do you think about `card_shift` in `AOTRuntimeConstants` table? You added it there.

Changes were testing tier1-5.

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Commit messages:
 - 8368811: [Leyden] Use AOTRuntimeConstants table for card_table::_byte_map_base

Changes: https://git.openjdk.org/leyden/pull/102/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=102&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368811
  Stats: 355 lines in 18 files changed: 203 ins; 113 del; 39 mod
  Patch: https://git.openjdk.org/leyden/pull/102.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/102/head:pull/102

PR: https://git.openjdk.org/leyden/pull/102


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