RFR: Load coops base shift from AOTRuntimeConstants in AOT code

[Andrew Dinn]

On Wed, 11 Sep 2024 14:01:59 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.

This has been shown to cater for different encodings by successfully running a javac compile of HelloWorld in two relevant scenarios:

1) Pass -XX:+UseCompatibleCompressedOops to the assembly run; omit it from the production run 
2) default heap size on assembly run; pass -Xmx12M to production run

In case 1
  for the assembly run the heap starts at 0x80800000, coops base is 0x80000000 and coops shift is 3
  for the production run the heap is at 0x414000000 coops base is 0x0 and coops shift is 3
In case 2
  for the assembly run the heap is at 0x414000000 coops base is 0x0 and coops shift is 3
  for the production run the heap is at 0xff000000, coops base is 0x0 and shift is 0

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PR Comment: https://git.openjdk.org/leyden/pull/20#issuecomment-2343808594