RFR: 8325681: C2 inliner rejects to inline a deeper callee because the methoddata of caller is immature. [v2]

[Vladimir Kozlov]

On Mon, 26 Feb 2024 04:05:11 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> This patch uses the methoddata of a method no matter it is mature or not to initialize `ciCallProfile`. Previously, C2 drops premature methoddata and leaves _count field of ciCallProfile -1. This leads C2 refuses to inline the callsite because its frequency is too low(-1 < MinInlineFrequencyRatio).  
>> 
>> In the given example, we observes that baz was not inlined because of 'low call site frequency'.  This is wrong because its real frequency is 10% > MinInlineFrequencyRatio. 
>> 
>> 
>> 60 13 b 4 UnderProfiledSubprocedure::foo (9 bytes)
>>                               @ 5 UnderProfiledSubprocedure::bar (6 bytes) inline (hot)
>>                                 @ 1 UnderProfiledSubprocedure::baz (19 bytes) failed to inline: low call site frequency
>
> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update the comment.

@veresov please look on these changes.

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PR Comment: https://git.openjdk.org/jdk/pull/17957#issuecomment-1964744408