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

[Vladimir Kozlov]

On Mon, 23 Feb 2026 16:59:53 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

> Generated stubs and nmethods embed some runtime-derived constants, such as the card table base, directly into code as instruction operands. AOT code generation cannot rely on these constants being valid between the assembly run and a production run and adjusting the constants at load time is not currently supported. So, instead AOT generation must employ code which loads the constants from a table whose address can be relocated at load time.

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?

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PR Review Comment: https://git.openjdk.org/jdk/pull/29884#discussion_r2844615937