RFR: 8278471: Reorder optimizations in addnode Ideal [v3]

[Zhiqiang Zang]

> Reorder optimizations in addnode so special cases appear before general cases; otherwise the special cases would be never covered.
> 
> `(a - b) + (c - d)` subsumes both `(a - b) + (b - c)` and `(a - b) + (c - a)`. Therefore `(a - b) + (b - c)` and `(a - b) + (c - a)` have to be placed before `(a - b) + (c - d)` so that they can work.

Zhiqiang Zang has updated the pull request incrementally with one additional commit since the last revision:

  remove unnecessary optimizations.

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6752/files
  - new: https://git.openjdk.java.net/jdk/pull/6752/files/10a51fdb..d4d2b180

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6752&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6752&range=01-02

  Stats: 10 lines in 1 file changed: 0 ins; 10 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6752.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6752/head:pull/6752

PR: https://git.openjdk.java.net/jdk/pull/6752