RFR: 8205592: BigDecimal.doubleValue() is depressingly slow [v2]

[Raffaello Giulietti]

> A reimplementation of `BigDecimal.[double|float]Value()` to enhance performance, avoiding an intermediate string and its subsequent parsing on the slow path.

Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:

  Renamed local variable b to w in full[Float|Double]Value().

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9410/files
  - new: https://git.openjdk.org/jdk/pull/9410/files/75fde901..f679fb2b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9410&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9410&range=00-01

  Stats: 25 lines in 1 file changed: 0 ins; 0 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/9410.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/9410/head:pull/9410

PR: https://git.openjdk.org/jdk/pull/9410