RFR: 8377554: Load card table base and other values via AOTRuntimeConstants in AOT code

[Andrew Dinn]

On Tue, 24 Feb 2026 09:57:20 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

>> src/hotspot/cpu/x86/gc/shared/cardTableBarrierSetAssembler_x86.cpp line 151:
>> 
>>> 149:   if (AOTCodeCache::is_on_for_dump()) {
>>> 150:     __ movptr(rscratch, ExternalAddress(AOTRuntimeConstants::card_table_address()));
>>> 151:     __ movq(rscratch, rscratch);
>> 
>> So why do you need this `movq`? I saw you pushed it to fix some issue. What was wrong?
>
> AOTRuntimeConstants::card_table_address() returns the address of the field in the static AOTRuntimeConstants object where the card table address (byte_map_base) is stored. So,
> 
>     __ movptr(rscratch, ExternalAddress(AOTRuntimeConstants::card_table_address()));
> 
> simply loads the  address of that field into `rscratch`. We need to load via that address to obtain the actual card table address.

This also needs fixing in premain.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29884#discussion_r2845745056