RFR: 8252219: C2: Randomize IGVN worklist for stress testing [v8]

[Roberto Castaneda Lozano]

"Merge master" (c2c31c3) addresses a trivial conflict caused by the 
integration of JDK-8253586 (https://github.com/openjdk/jdk/pull/334).

On 2020-09-25 09:54, Roberto Castaneda Lozano wrote:
>> Add `StressIGVN` option to let C2 randomize IGVN worklist order. When enabled, the worklist is shuffled before each
>> main run of the IGVN loop. Also add `GenerateStressSeed` and `StressSeed=N` options to randomly generate or specify the
>> seed. In either case, the seed is logged if `LogCompilation` is enabled. The new options are declared as
>> production+diagnostic for consistency with the existing `StressLCM` and `StressGCM` options.
> 
> Roberto Castaneda Lozano has updated the pull request with a new target base due to a merge or a rebase. The pull
> request now contains 14 commits:
> 
>   - Merge master
>   - Add missing @requires annotation to test case
>   - Empty commit to trigger jcheck after updating GitHub user name
>   - Generate random seed if 'StressSeed' is unset
>   - Use generic swap() for shuffling
>   - Add basic sanity test for stress IGVN options
>   - Fix typo
>   - Move shuffle() to PhaseIterGVN
>   - Define 'StressSeed' option as 'uint' rather than 'uintx'
>   - Apply minor rearrangements to simplify the patch
>   - ... and 4 more: https://git.openjdk.java.net/jdk/compare/37b70282...c2c31c3e
> 
> -------------
> 
> Changes: https://git.openjdk.java.net/jdk/pull/242/files
>   Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=242&range=07
>    Stats: 229 lines in 10 files changed: 224 ins; 0 del; 5 mod
>    Patch: https://git.openjdk.java.net/jdk/pull/242.diff
>    Fetch: git fetch https://git.openjdk.java.net/jdk pull/242/head:pull/242
> 
> PR: https://git.openjdk.java.net/jdk/pull/242
>