RFR: 6506405: Math.abs(float) is slow [v2]

[Brian Burkhalter]

> Please consider this change to make the `float` and `double` versions of `java.lang.Math.abs()` branch-free.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  6506405: Add comments, use new consts for masking

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4711/files
  - new: https://git.openjdk.java.net/jdk/pull/4711/files/60d461fc..ba950f60

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4711&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4711&range=00-01

  Stats: 22 lines in 3 files changed: 17 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4711.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4711/head:pull/4711

PR: https://git.openjdk.java.net/jdk/pull/4711