RFR: 8292640: C2: Remove unused scratch register usages on x86 [v2]

[Vladimir Ivanov]

> (PR is dependent on #9932.)
> 
> Remove redundant scratch register usages in C2 generated code on x86. 
> 
> Stubs put constants in code cache, so they are RIP-relative addressable from generated code. It allows to save on scratch registers when accessing constants.  
> 
> Testing: hs-tier1 - hs-tier4

Vladimir Ivanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9933/files
  - new: https://git.openjdk.org/jdk/pull/9933/files/aedcb3e1..aedcb3e1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9933&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9933&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9933.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9933/head:pull/9933

PR: https://git.openjdk.org/jdk/pull/9933