Improve tagged pointer emulation#6545
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headius merged 2 commits intojruby:masterfrom Feb 1, 2021
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* Floats are considered equal? if they have the same value within flonum range. * Float#object_id and ObjectSpace.id2ref produce and recognize the flonum bits for round-tripping IDs. * RubyFloat.eql added to short-circuit RubyBasicObject.eql dynamic call. Ref ruby/spec#829
In CRuby, only integer values within the valid range for fixnum tagged pointers are considered identical. JRuby considered all Fixnum objects identical. This commit narows the JRuby identity logic to only values within the fixnum tagged pointer range.
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This commit improves the emulation of CRuby's fixnum and flonum tagged pointers.
Float emulation of flonum:
object_idthat is reversible by ObjectSpace._id2ref.equal?.Fixnum emulation of fixnum:
equal?. Previously all equivalent Fixnum objects were consideredequal?.Impact to existing behavior:
_id2ref, non-fixnum non-flonum values are now modulo 4. This means we have halved the number of incremental object ID values available (Long.MAX_VALUE / 4 versus Long.MAX_VALUE / 2 for fixnum emulation alone).See ruby/spec#829 for some discussion of this.