RFR: 8255397: x86: coalesce reference and int entry points into vtos bytecodes [v2]

[Claes Redestad]

> On x86 - both 32- and 64-bit - the code laid out for transitionining into a vtos bytecode when having a reference and int top-of-stack state is semantically identical, and can be coalesced.
> 
> This patch removes a short jump on some cases which is marginally beneficial when interpreting, while measurably reducing overhead of generating the interpreter itself.

Claes Redestad 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. The pull request contains four additional commits since the last revision:

 - Drop verification from comment
 - Introduce push_i_or_ptr
 - Merge branch 'master' into atos_itos_opt
 - x86: coalesce some ptr and int entry points

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/865/files
  - new: https://git.openjdk.java.net/jdk/pull/865/files/c44b673f..6595372e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=865&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=865&range=00-01

  Stats: 2959 lines in 131 files changed: 2034 ins; 559 del; 366 mod
  Patch: https://git.openjdk.java.net/jdk/pull/865.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/865/head:pull/865

PR: https://git.openjdk.java.net/jdk/pull/865