[riscv-port] RFR: 8281967: riscv: Intrinsify bigIntegerLeftShift [v4]

[Taiping Guo]

> BigInteger intrinsic: bigIntegerLeftShift intrinsic is missed in current vm. It should be implemented.
> Since that there is no hardware that supports rvv1.0 for now, I used `test/jdk/java/math/BigInteger/ModPow.java` testcase to compare the number of instructions executed with and without intrinsic. The number of instructions executed for the method `shiftLeftImplWorker` compiled by C2 without intrinsic is about 9.2x ( vlen=256 ) that of version with intrinsic.
> 
> Full jtreg tests on qemu are passed without new failures.

Taiping Guo has updated the pull request incrementally with one additional commit since the last revision:

  add UseRVVForBigIntegerShiftIntrinsics option

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

Changes:
  - all: https://git.openjdk.java.net/riscv-port/pull/61/files
  - new: https://git.openjdk.java.net/riscv-port/pull/61/files/43ed654c..8e2d43b8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=riscv-port&pr=61&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=riscv-port&pr=61&range=02-03

  Stats: 8 lines in 3 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/riscv-port/pull/61.diff
  Fetch: git fetch https://git.openjdk.java.net/riscv-port pull/61/head:pull/61

PR: https://git.openjdk.java.net/riscv-port/pull/61