Make scala.runtime.Comparator faster

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Aladdin: [http://scala-webapps.epfl.ch/bugtracking/contribs/load.do?id=479 contrib 479]

With new numbers implementation some calls to == are replaced with call to scala.runtime.Comparator.equals.

That comparator works slow if operands are not equal and not instanceof Number.

I've optimized Comparator a bit. Result is: [http://mx1.ru/~yozh/scala-comparator/Comparator.java] (diff: [http://mx1.ru/~yozh/scala-comparator/Comparator.java.diff]).

I've tested with [http://mx1.ru/~yozh/scala-comparator/Test.java] and got results:

with new comparator: about 1.7 s
with orig comparator: about 2.3 s
with o.equals(o2): about 1.0 s

So overhead of old comparator in test is about 1.3 s vs. overhead of new comparator about 0.7 seconds.

Test executed on PPC notebook (1.5 HHz, 1.5Gb) on JDK 1.5.

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Imported From: https://issues.scala-lang.org/browse/SI-38?orig=1
Reporter: @michelou

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@dubochet said:
Modified comparator as requested by submitter.

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@odersky said:
Milestone 2.6.1 deleted