RFR: Load coops base shift from AOTRuntimeConstants in AOT code [v2]

[Vladimir Kozlov]

On Wed, 11 Sep 2024 14:45:58 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

>> This PR modifies AOT compiled method code to load compressed oops base and shift constants via the AOTRuntimeConstants area rather than encode them as immediates. It also unlatches the currently forced setting of UseCompatibleCompressedOops, allowing the heap to be allocated wherever it will fit.
>
> Andrew Dinn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   only check UseCompatibleCompressedOops on 64 bit builds

src/hotspot/cpu/aarch64/aarch64.ad line 5175:

> 5173: operand indirectN(iRegN reg)
> 5174: %{
> 5175:   predicate(CompressedOops::shift() == 0 && !SCCache::is_on_for_write());

Does it imply that with SCC is on_write we will not have the shift == 0?

src/hotspot/share/code/SCCache.cpp line 682:

> 680:   if (UseCompatibleCompressedOops && (_compressedOopShift != (uint)CompressedOops::shift())) {
> 681:     log_warning(scc, init)("Disable Startup Code Cache: '%s' was created with CompressedOops::shift() = %d vs current %d and UseCompatibleCompressedOops=%s", cache_path, _compressedOopShift, CompressedOops::shift(),
> 682:                            UseCompatibleCompressedOops ? "true" : "false");

Why print flags value when you check it in the condition - it will be `true`

src/hotspot/share/code/SCCache.hpp line 621:

> 619:   uint _grain_shift;
> 620:   uint _card_shift;
> 621:   address _coops_base;

Move `address` first for better fields alignment

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PR Review Comment: https://git.openjdk.org/leyden/pull/20#discussion_r1757268153
PR Review Comment: https://git.openjdk.org/leyden/pull/20#discussion_r1757265220
PR Review Comment: https://git.openjdk.org/leyden/pull/20#discussion_r1757257861