RFR: 8352415: x86: Tighten up template interpreter method entry code

[Aleksey Shipilev]

Interpreter performance is the still important for faster startup, since it would carry application until compilers kick in. After looking at Leyden scenarios in Xint mode, I believe incremental improvements are possible in template interpreter to make it faster.

One of those improvements is tightening up method entry code. Profiling shows the hottest path in the whole ordeal for non-native methods is resolving the Java mirror to store the GC root for currently executing Method*. It involves 4-5 chained memory accesses, which incurs significant latency.

We can massage the code to reuse some memory accesses and also spread them out to allow more latency-hiding hardware mechanisms to kick in.

Additional testing:
 - [x] Ad-hoc `-Xint` benchmarks
 - [ ] Linux x86_64 server fastdebug, `all`

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/24114/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24114&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352415
  Stats: 27 lines in 1 file changed: 11 ins; 1 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/24114.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24114/head:pull/24114

PR: https://git.openjdk.org/jdk/pull/24114