RFR: 8267303: Replace MinObjectAlignmentSize usages for non-Java heap objects

[Coleen Phillimore]

On Sun, 4 Jul 2021 22:37:45 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Replace '3' and LogMinObjAlignmentInBytes with LogBytesPerWord (3 for LP64 and 2 for 32 bits).
>> Hoping git actions will test 32 bits.
>> Tested with tier1 on all Oracle platforms, but since I didn't change the values for our platforms, no failures expected.
>
> src/hotspot/share/oops/symbol.hpp line 158:
> 
>> 156:   static int max_length() { return max_symbol_length; }
>> 157:   unsigned identity_hash() const {
>> 158:     unsigned addr_bits = (unsigned)((uintptr_t)this >> (LogBytesPerWord + 3));
> 
> [pre-existing] I'm puzzled by the `+3` in this line.  I'm guessing this is `log2(sizeof(Symbol))`?

Oh that might be a good guess.  I thought it was just some way to randomize the address some more.  @yminqi or @iklam  would know since it was added with JDK-8130115.

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PR: https://git.openjdk.java.net/jdk/pull/4675