[riscv-port] RFR: 8281632: riscv: Improve interpreter stack banging

[Yadong Wang]

With reference to https://bugs.openjdk.java.net/browse/JDK-8072070, there is the same issue on the riscv platform.
 

Every time we enter a method in interpreter, we bang a lot of stack ahead for shadow zone checks. I believe this could be made significantly better, e.g. by checking how far away we are from the stack_overflow_limit.


Hotspot/jdk tier1 passed on unmatched, and all jtreg cases were tested on Qemu without new failures.

Performed the performance regression test in SPECjvm2008 sunflow, and achieved 17% improvement in the interpreter-only mode.

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Commit messages:
 - 8281632: riscv: Improve interpreter stack banging

Changes: https://git.openjdk.java.net/riscv-port/pull/58/files
 Webrev: https://webrevs.openjdk.java.net/?repo=riscv-port&pr=58&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281632
  Stats: 32 lines in 2 files changed: 22 ins; 2 del; 8 mod
  Patch: https://git.openjdk.java.net/riscv-port/pull/58.diff
  Fetch: git fetch https://git.openjdk.java.net/riscv-port pull/58/head:pull/58

PR: https://git.openjdk.java.net/riscv-port/pull/58