Shark OSR support

[Gary Benson]

Hi all,

This patch adds support for on-stack replacement (OSR) to Shark.  OSR
allows long running methods to be JIT compiled while they are running.
After a certain number of backedges, the interpreter packs the
method's stack frame into a buffer and compiles a special version of
the method that will unpack the buffer and start at the backedge in
question.  This allows methods to be compiled that wouldn't normally,
and probably makes the JIT warm up faster.

If you're running with -J-XX:+PrintCompilation you'll see OSR
compilations in the log, marked with '%' signs:

  1       java.lang.String::hashCode (60 bytes)
  2       java.lang.String::indexOf (152 bytes)
  3       java.lang.String::charAt (33 bytes)
  4       sun.nio.cs.UTF_8$Encoder::encodeArrayLoop (490 bytes)
  1%      java.lang.String::indexOf @ 65 (163 bytes)
  2%      java.io.UnixFileSystem::normalize @ 13 (75 bytes)
  3%      sun.nio.cs.UTF_8$Decoder::decodeArrayLoop @ 76 (553 bytes)
  5       java.lang.String::equals (91 bytes)
  6  !    java.io.BufferedReader::readLine (300 bytes)
  7       java.lang.String::lastIndexOf (157 bytes)
  8       java.io.UnixFileSystem::normalize (75 bytes)
  9       java.lang.Object::<init> (1 bytes)
 10       sun.nio.cs.UTF_8$Decoder::decodeArrayLoop (553 bytes)
 11       java.lang.String::compareTo (147 bytes)
  4%s     java.util.Hashtable::contains @ 31 (66 bytes)
 12       java.lang.Math::min (11 bytes)
 ...

Cheers,
Gary

-- 
http://gbenson.net/
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