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Add option to support clang LTO(Link Time Optimization) and time-traces#4890

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solotzg:lto
May 17, 2022
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Add option to support clang LTO(Link Time Optimization) and time-traces#4890
ti-chi-bot merged 4 commits intopingcap:masterfrom
solotzg:lto

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@solotzg solotzg commented May 13, 2022 •
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What problem does this PR solve?

Issue Number: ref #4909

Problem Summary:

What is changed and how it works?

For example:

tiflash/dbms/src/Storages/Transaction/TMTContext.cpp

Lines 74 to 82 in e03dcc1

KVStorePtr & TMTContext::getKVStore()
{
return kvstore;
}
const KVStorePtr & TMTContext::getKVStore() const
{
return kvstore;
}

Use objdump -d ${original-tiflash-binary} | grep 'getKVStore', you can see at least 63 records like:

...
 7b18a17:       e8 34 27 e5 ff          callq  796b150 <_ZN2DB10TMTContext10getKVStoreEv>
 7b82ba7:       e8 b4 85 de ff          callq  796b160 <_ZNK2DB10TMTContext10getKVStoreEv>
...

Other modules only can invoke TMTContext::getKVStore by calling method through instruction callq.
Because other object files can not optimize invoking TMTContext::getKVStore unless implementations of TMTContext::getKVStore is declared in header file(TMTContext.h).

With LTO, objdump -d ${new-tiflash-binary} | grep 'getKVStore' will get nothing. Because linker can analyze the whole context and make it inline automatically. It's friendly for forward declaration.

Binary size can be reduced from 329M to 293M.

Check List

Tests

  • Unit test
  • Integration test
  • Manual test (add detailed scripts or steps below)
  • No code

Side effects

  • Performance regression: Consumes more CPU
  • Performance regression: Consumes more Memory
  • Breaking backward compatibility

Documentation

  • Affects user behaviors
  • Contains syntax changes
  • Contains variable changes
  • Contains experimental features
  • Changes MySQL compatibility

Release note

None

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ti-chi-bot commented May 13, 2022 •
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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • SchrodingerZhu
  • zanmato1984

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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@ti-chi-bot ti-chi-bot added do-not-merge/needs-linked-issue release-note-none Denotes a PR that doesn't merit a release note. size/S Denotes a PR that changes 10-29 lines, ignoring generated files. labels May 13, 2022
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SchrodingerZhu commented May 13, 2022

For LTO, consider adding -fvisibility=hidden, -fvisibility-inlines-hidden, and enabling devirtualization flags if possible

@ti-chi-bot ti-chi-bot added the status/LGT1 Indicates that a PR has LGTM 1. label May 14, 2022
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solotzg commented May 15, 2022

For LTO, consider adding -fvisibility=hidden, -fvisibility-inlines-hidden, and enabling devirtualization flags if possible

Add flags -fvisibility=hidden -fvisibility-inlines-hidden -fwhole-program-vtables -fsplit-lto-unit

@solotzg solotzg requested a review from fuzhe1989 May 17, 2022 02:36
@solotzg solotzg mentioned this pull request May 17, 2022
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@solotzg solotzg added the type/enhancement The issue or PR belongs to an enhancement. label May 17, 2022
zanmato1984
zanmato1984 reviewed May 17, 2022
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@solotzg solotzg requested a review from zanmato1984 May 17, 2022 08:18
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zanmato1984 approved these changes May 17, 2022
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LGTM

@ti-chi-bot ti-chi-bot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels May 17, 2022
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solotzg commented May 17, 2022

/merge

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ti-chi-bot commented May 17, 2022

@solotzg: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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ti-chi-bot commented May 17, 2022

This pull request has been accepted and is ready to merge.

DetailsCommit hash: cd04a34

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label May 17, 2022
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sre-bot commented May 17, 2022

Coverage for changed files

no c/c++ source change detected

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18154      9788             46.08%    202633  97921        51.68%

full coverage report (for internal network access only)

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sre-bot commented May 17, 2022

Coverage for changed files

no c/c++ source change detected

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18154      9788             46.08%    202633  97908        51.68%

full coverage report (for internal network access only)

@ti-chi-bot ti-chi-bot merged commit 0477f96 into pingcap:master May 17, 2022
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sre-bot commented May 30, 2022

Coverage for changed files

no c/c++ source change detected

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18154      9788             46.08%    202633  97917        51.68%

full coverage report (for internal network access only)

This was referenced Jun 6, 2022
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@zanmato1984 zanmato1984 zanmato1984 approved these changes

@fuzhe1989 fuzhe1989 Awaiting requested review from fuzhe1989

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@SchrodingerZhu SchrodingerZhu SchrodingerZhu approved these changes

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