RFR: 8347555: [REDO] C2: implement optimization for series of Add of unique value [v8]

[Kangcheng Xu]

> [JDK-8347555](https://bugs.openjdk.org/browse/JDK-8347555) is a redo of [JDK-8325495](https://bugs.openjdk.org/browse/JDK-8325495) was [first merged](https://git.openjdk.org/jdk/pull/20754) then backed out due to a regression. This patch redos the feature and fixes the bit shift overflow problem. For more information please refer to the previous PR.
> 
> When constanlizing multiplications (possibly in forms on `lshifts`), the multiplier is upgraded to long and then later narrowed to int if needed. However, when a `lshift` operand is exactly `32`, overflowing an int, using long has an unexpected result. (i.e., `(1 << 32) = 1` and `(int) (1L << 32) = 0`)
> 
> The following was implemented to address this issue.
> 
> if (UseNewCode2) {
>     *multiplier = bt == T_INT
>         ? (jlong) (1 << con->get_int()) // loss of precision is expected for int as it overflows
>         : ((jlong) 1) << con->get_int();
> } else {
>     *multiplier = ((jlong) 1 << con->get_int());
> }
> 
> 
> Two new bitshift overflow tests were added.

Kangcheng Xu has updated the pull request incrementally with one additional commit since the last revision:

  implement @eme64's suggestions

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23506/files
  - new: https://git.openjdk.org/jdk/pull/23506/files/851bfb2f..f71a1dc0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23506&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23506&range=06-07

  Stats: 107 lines in 3 files changed: 11 ins; 43 del; 53 mod
  Patch: https://git.openjdk.org/jdk/pull/23506.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23506/head:pull/23506

PR: https://git.openjdk.org/jdk/pull/23506