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

[solotzg]

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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• SchrodingerZhu
• zanmato1984

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[SchrodingerZhu]

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

[solotzg]

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

[zanmato1984]

LGTM

[solotzg]

/merge

[ti-chi-bot]

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[ti-chi-bot]

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

Commit hash: cd04a34

[sre-bot]

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)

[sre-bot]

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)

[sre-bot]

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)