RFR: 8253002: Remove the unused SafePointNode::_oop_map field [v2]

[Jorn Vernee]

> Hi,
> 
> I've been looking a lot at the code for generating oop maps for call nodes lately, and noticed that SafePointNode had
> an oopMap field that was unused (which led to some confusion as to where the oop map was actually set).
> The oop map is instead generated and set in buildOopMap OopFlow::compute_reach after matching:
> https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/buildOopMap.cpp#L122 So the field on the ideal node
> is unused.  This patch removes the field and cleans up related code. I've left a comment in SafePointNode to point
> people looking for the oop map at buildOopMap.cpp
> Thanks,
> Jorn
> 
> Testing: local build + tier1,tier2,tier3

Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:

  Review comments:
  - Remove comment in SafePointNode
  - Remove forward declaration of class OopMap

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/109/files
  - new: https://git.openjdk.java.net/jdk/pull/109/files/05bdc4dc..d636dcd3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=109&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=109&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/109.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/109/head:pull/109

PR: https://git.openjdk.java.net/jdk/pull/109