RFR: 8293287 add ReplayReduce flag

[Dean Long]

On Fri, 2 Sep 2022 16:07:47 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Add an experimental flag to help developers "reduce" a replay file.
>> 
>> As a first step, I plan to simulate reduced inlining. This will output multiple "compile" lines as if the first level of inlining never happened:
>> A --> B --> C
>> A --> D --> E
>> becomes
>> B --> C
>> D --> E
>> Developers can repeat iteratively until the replay crash no longer reproduces.
>
> src/hotspot/share/ci/ciEnv.cpp line 1651:
> 
>> 1649:   if (task) {
>> 1650: #ifdef COMPILER2
>> 1651:     if (ReplayReduce && compiler_data() != NULL) {
> 
> Is this feature when you are replaying compilation? If yes, add `ReplayCompiles` check too.

It seems most useful with ReplayCompiles, but I don't want to require it.  A developer might want to turn on ReplayReduce without ReplayCompiles, to save a replay step, for example when running generated tests from creduce or javafuzzer without an existing replay file.

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PR: https://git.openjdk.org/jdk/pull/10134