RFR: 8330157: C2: Add a stress flag for bailouts [v7]

[Emanuel Peter]

On Mon, 1 Jul 2024 07:01:44 GMT, Daniel Skantz <duke at openjdk.org> wrote:

>> Daniel Skantz has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remaining review comments
>
> test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CtwRunner.java line 307:
> 
>> 305:                 "-XX:+StressIncrementalInlining",
>> 306:                 "-XX:+StressBailout",
>> 307:                 "-XX:StressBailoutProbability=100_000_000",
> 
> This value allows us to compile any given method with high probability.
> The largest number of `failing()` checks that I have seen so far is 10**6.
> 
> I am not sure if this could hide an infinite compilation due to an unrelated bug.
> If we want to guard against edge cases, we could do an additional check against
> the stress seed, for example disabling this stress mode if `!(_stress_seed % 10)`.

Or you somehow randomly enable/disable the `StressBailout` flag? Stuffing too much special-logic into the internals could be quite confusing for the flag-user.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19646#discussion_r1660567846