RFR: 8275167: x86 intrinsic for unsignedMultiplyHigh [v2]

[Vamsi Parasa]

> Optimize the new Math.unsignedMultiplyHigh using the x86 mul instruction. This change show 1.87X improvement on a micro benchmark.

Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:

  refactoring to remove code duplication by using a common routine for UMulHiLNode and MulHiLNode

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5933/files
  - new: https://git.openjdk.java.net/jdk/pull/5933/files/cb30b268..a10a9fbe

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5933&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5933&range=00-01

  Stats: 25 lines in 2 files changed: 12 ins; 12 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5933.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5933/head:pull/5933

PR: https://git.openjdk.java.net/jdk/pull/5933