RFR: 8375536: PPC64: Implement special MachNodes for floating point CMove [v6]

[David Briemann]

> Adds the following mach nodes:
> match(Set dst (CMoveF (Binary cop (CmpF op1 op2)) (Binary src1 src2)));
> match(Set dst (CMoveD (Binary cop (CmpD op1 op2)) (Binary src1 src2)));
> match(Set dst (CMoveF (Binary cop (CmpD op1 op2)) (Binary src1 src2)));
> match(Set dst (CMoveD (Binary cop (CmpF op1 op2)) (Binary src1 src2)));

David Briemann has updated the pull request incrementally with one additional commit since the last revision:

  add helpful comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29281/files
  - new: https://git.openjdk.org/jdk/pull/29281/files/3d1aa822..8fad3756

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29281&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29281&range=04-05

  Stats: 9 lines in 1 file changed: 6 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29281.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29281/head:pull/29281

PR: https://git.openjdk.org/jdk/pull/29281