RFR: 8319850: PrintInlining should print which methods are late inlines [v29]
Theo Weidmann
tweidmann at openjdk.org
Wed Jan 29 08:54:21 UTC 2025
> This PR overhauls the print inlining system. It now allows to record multiple inlining messages per potential inline/call site. Since inlines can trigger further inlines, the entire print inlining information is now stored as a tree. This structure enables more detailed logging and prevents the accidental overwriting of useful logs, an issue encountered in the past.
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> Also, prints will contain detailed information about which methods are late inlines.
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> This rewrite became necessary due to the hard-to-understand way in which the old print inlining worked, which made it almost impossible to implement printing which methods are late inlines without losing previous print statements (see discussion below).
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> Here is a new example print output, showing different messages logged for the same location. In this case, a nice progression, from not being able to inline to late inline can be witnessed.
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> @ 18 java.lang.invoke.MethodHandle::invokeBasic()V (0 bytes) failed to inline: receiver not constant callee changed to java.lang.invoke.LambdaForm$DMH/0x000000012a403470::invokeStatic (17 bytes) force inline by annotation late inline succeeded (method handle)
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> Naturally, the output of print inlining changes with this PR, but I tried to keep the changes small.
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> ----
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> Original PR description before rewrite:
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> In https://github.com/openjdk/jdk/pull/16595 @caojoshua previously suggested changes to indicate which calls were inlined late, when printing inlines. This PR re-introduces the changes from the previously closed PR and fixes a minor issue where asserts were triggered.
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> Concerns were raised by @rwestrel in the previous PR:
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>> When InlineTree::ok_to_inline() is called, some diagnostic message is recorded for the call site. Do I understand right that with this patch, if the call is inlined late, then that message is dropped and replaced by a new "late inline.." message? If that's the case, isn't it the case that sometimes the InlineTree::ok_to_inline() has some useful information that's lost when late inlining happens?
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> As already pointed out in the PR by @caojoshua, this does not matter for string/methodhandle/vector/boxing late inlines, as they are [only performed if ok_to_inline() returns true](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/doCall.cpp#L189). This is also the only call to ok_to_inline().
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> The only other location, where late inline call generators are created, are calls to CallGenerator::for_late_inline_virtual(), which ...
Theo Weidmann has updated the pull request incrementally with one additional commit since the last revision:
Update bytecodeInfo.cpp
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Changes:
- all: https://git.openjdk.org/jdk/pull/21899/files
- new: https://git.openjdk.org/jdk/pull/21899/files/2db77384..c005f6b6
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=21899&range=28
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=21899&range=27-28
Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
Patch: https://git.openjdk.org/jdk/pull/21899.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/21899/head:pull/21899
PR: https://git.openjdk.org/jdk/pull/21899
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