jdk 8292226: Prepare make for better Link Time Optimization support

The support for Link Time Optimization in the JDK's make system could do with some cleaning up, at the moment it simply assumes the compiler is gcc and sets the flags as such. Instead of introducing changes in bulk, as a first step, it would be good to simply supply the appropriate flags depending on the compiler and refine the flags for the one existing compiler with support for it. In practice the latter just means adding the proper -fuse-linker-plugin to gcc compile step when link-time-opt is specified, as without it the compiler generates both native code and information rich representation for Link Time Optimization. With this flag, native code generation is disabled and object files will contain only code required for Link Time Optimization, thus speeding up compile times as well.

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Issue

JDK-8292226: Prepare make for better Link Time Optimization support

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Aug 11 '22 04:08 TheShermanTanker

:wave: Welcome back jwaters! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

Aug 11 '22 04:08 bridgekeeper[bot]

@TheShermanTanker The following label will be automatically applied to this pull request:

build

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Aug 11 '22 05:08 openjdk[bot]

Webrevs

Aug 11 '22 05:08 mlbridge[bot]

But I think we may end up just removing this anyway.

You never know for certain if this might come in handy in the future ;)

Aug 11 '22 11:08 TheShermanTanker

Technically this change seems reasonable, but I tend to agree with David that it is more likely that a better solution would be to remove this completely. Have you tried building with LTO enabled? What kind of build times do you get -- and what kind of improvements in terms of file size and performance? My gut feeling is that there is no way that the small potential improvements can counteract the huge negative impact of build times magnitudes larger.

Aug 19 '22 12:08 magicus

@TheShermanTanker This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8292226: Prepare make for better Link Time Optimization support

Reviewed-by: ihse

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 114 new commits pushed to the master branch:

79597f1ea6844f374beeeba219719cd9d5fe7d03: 8272702: Resolving URI relative path with no / may lead to incorrect toString
7b5f9edb59ef763acca80724ca37f3624d720d06: 8288966: Better handle very spiky promotion in G1
07c797720d68d5a36d438f2e9da8b72f247f22fc: 8290249: Vectorize signum on AArch64
a3ec0bb03a5de805fc4b45477925aa18b875bc79: 8253413: [REDO] [REDO] G1 incorrectly limiting young gen size when using the reserve can result in repeated full gcs
27b0f7726b70127c0ed714cfc1041d3da71a9dc3: 8292318: Memory corruption in remove_dumptime_info
9a65524e2f98c1b4e253dcb637a708cec7b591bc: 8290300: Use standard String-joining tools where applicable
f9004fe4438c30eb639e3c36e6531c306b836e36: 8292561: Make "ReplayCompiles" a diagnostic product switch
2fbb9362032df26582c389b7114cf0a215ed3afd: 8292691: Move CompilerConfig::is_xxx() inline functions out of compilerDefinitions.hpp
3601e30df794db122d8d04fb3c04868ccbaa0baf: 8290909: MemoryPoolMBean/isUsageThresholdExceeded tests failed with "isUsageThresholdExceeded() returned false, and is still false, while threshold = MMMMMMM and used peak = NNNNNNN"
37c0a13647e74fd02823a3f621e986f96904b933: 8292350: Use static methods for hashCode/toString primitives
... and 104 more: https://git.openjdk.org/jdk/compare/4b03e135e157cb6cc9ba5eebf4a1f1b6e9143f48...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@dholmes-ora, @magicus) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

Aug 22 '22 09:08 openjdk[bot]

/integrate

Aug 22 '22 10:08 TheShermanTanker

@TheShermanTanker Your change (at version cb7ef7cc541a548b69b8f32903fd13c5e15c7913) is now ready to be sponsored by a Committer.

Aug 22 '22 10:08 openjdk[bot]

/sponsor

Aug 22 '22 10:08 magicus

Going to push as commit 1ed03d82b221d6fa54b855070944aec52366c658. Since your change was applied there have been 114 commits pushed to the master branch:

79597f1ea6844f374beeeba219719cd9d5fe7d03: 8272702: Resolving URI relative path with no / may lead to incorrect toString
7b5f9edb59ef763acca80724ca37f3624d720d06: 8288966: Better handle very spiky promotion in G1
07c797720d68d5a36d438f2e9da8b72f247f22fc: 8290249: Vectorize signum on AArch64
a3ec0bb03a5de805fc4b45477925aa18b875bc79: 8253413: [REDO] [REDO] G1 incorrectly limiting young gen size when using the reserve can result in repeated full gcs
27b0f7726b70127c0ed714cfc1041d3da71a9dc3: 8292318: Memory corruption in remove_dumptime_info
9a65524e2f98c1b4e253dcb637a708cec7b591bc: 8290300: Use standard String-joining tools where applicable
f9004fe4438c30eb639e3c36e6531c306b836e36: 8292561: Make "ReplayCompiles" a diagnostic product switch
2fbb9362032df26582c389b7114cf0a215ed3afd: 8292691: Move CompilerConfig::is_xxx() inline functions out of compilerDefinitions.hpp
3601e30df794db122d8d04fb3c04868ccbaa0baf: 8290909: MemoryPoolMBean/isUsageThresholdExceeded tests failed with "isUsageThresholdExceeded() returned false, and is still false, while threshold = MMMMMMM and used peak = NNNNNNN"
37c0a13647e74fd02823a3f621e986f96904b933: 8292350: Use static methods for hashCode/toString primitives
... and 104 more: https://git.openjdk.org/jdk/compare/4b03e135e157cb6cc9ba5eebf4a1f1b6e9143f48...master

Your commit was automatically rebased without conflicts.

Aug 22 '22 11:08 openjdk[bot]

@magicus @TheShermanTanker Pushed as commit 1ed03d82b221d6fa54b855070944aec52366c658.

:bulb: You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Aug 22 '22 11:08 openjdk[bot]