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JDK-8277496 Remove duplication in c1 Block successor lists #6614

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LudwikJaniuk
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@LudwikJaniuk LudwikJaniuk commented Nov 30, 2021

Remove BlockBegin::_successors, leaving BlockEnd::_sux as the SSOT for the successors of a block. Prior to this PR, these two lists were both tracking the same list of successors of the same block. This necessitated a lot of syncing and verification code.

With this PR, as long as a block has its end pointer assigned, its successors can always be reached by querying the BlockEnd. BlockEnd::_sux becomes the single place where the list of successors is maintained. When modified, the successor list no longer needs to be synchronized in two places, reducing complexity and confusion. Asserts on the two lists corresponding no longer need to be made.

While being created in GraphBuilder, BlockBegins don't have a BlockEnd assigned yet. To temporarily track block successors in this small interval, add a lookup structure BlockListBuilder::_bci2block_successors.

This PR affects debug printing code. If the end pointer of a BlockBegin is NULL for some reason, then the successor list can no longer be printed (for obious reasons).

This PR introduces an additional check to IR::verify to check that BlockBegin::_end is not set to null.

This PR also performs some minor refactoring, polishing, inlining, and removing of dead code around the affected areas.

The commit history has been polished to attempt to guide the reader through the changes.

hs-tier1 and hs-tier2 tests pass.


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Issue

  • JDK-8277496: Remove duplication in c1 Block successor lists

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6614/head:pull/6614
$ git checkout pull/6614

Update a local copy of the PR:
$ git checkout pull/6614
$ git pull https://git.openjdk.java.net/jdk pull/6614/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6614

View PR using the GUI difftool:
$ git pr show -t 6614

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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6614.diff

LudwikJaniuk added 28 commits Nov 30, 2021
create separate versions for two cases _end == NULL, _end != NULL. This makes it explicit that the former case is only ever used in GraphBuilder (and in the printer).
GraphBuilder accessor methods for _successors: In preparation for creating a temporary list of lists in graphbuilder
This makes it clear how weird this is. The nonnull case doesnt even set begin!
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@bridgekeeper bridgekeeper bot commented Nov 30, 2021

👋 Welcome back LudwikJaniuk! 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.

@openjdk openjdk bot added the rfr label Nov 30, 2021
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@openjdk openjdk bot commented Nov 30, 2021

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

  • hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added the hotspot-compiler label Nov 30, 2021
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@mlbridge mlbridge bot commented Nov 30, 2021

Webrevs

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@neliasso neliasso left a comment

A very nice clean up!

@@ -3338,6 +3393,10 @@ GraphBuilder::GraphBuilder(Compilation* compilation, IRScope* scope)
#ifndef PRODUCT
if (PrintCompilation && Verbose) tty->print_cr("Created %d Instructions", _instruction_count);
#endif

// JANIUK: If we iterate all the blocks in _blocks, some of them have end NULL.

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Left over comment?

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@LudwikJaniuk LudwikJaniuk Dec 1, 2021

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Indeed! Removed it

@@ -1586,6 +1586,7 @@ static void print_block(BlockBegin* x) {
}
}

if (end != NULL)
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Missing braces on if statement

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@LudwikJaniuk LudwikJaniuk Dec 1, 2021

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Corrected it

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@neliasso neliasso left a comment

Looks good! Thanks for fixing!

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@openjdk openjdk bot commented Dec 1, 2021

@LudwikJaniuk 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:

8277496: Remove duplication in c1 Block successor lists

Reviewed-by: neliasso, kvn

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 96 new commits pushed to the master branch:

  • 24e16ac: 8277617: Adjust AVX3Threshold for copy/fill stubs
  • 2b87c2b: 8277793: Support vector F2I and D2L cast operations for X86
  • e1cde19: 8278247: KeyStoreSpi::engineGetAttributes does not throws KeyStoreException
  • a729a70: 8225181: KeyStore should have a getAttributes method
  • 38f525e: 8275821: Optimize random number generators developed in JDK-8248862 using Math.unsignedMultiplyHigh()
  • 780b8b1: 8278179: Enable all doclint warnings for build of java.naming
  • 678ac58: 8278240: ProblemList containers/docker/TestJcmd.java on linux-aarch64
  • 01cb2b9: 8277529: SIGSEGV in C2 CompilerThread Node::rematerialize() compiling Packet::readUnsignedTrint
  • 660f21a: 8278119: ProblemList few headful test failing in macosx12-aarch64 system
  • 2e30fa9: 8278171: [vectorapi] Mask incorrectly computed for zero extending cast
  • ... and 86 more: https://git.openjdk.java.net/jdk/compare/a5f2a58ba4ac25f4bd66f1f1f4c036a4f0024229...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 (@neliasso, @vnkozlov) 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).

@openjdk openjdk bot added the ready label Dec 1, 2021
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@LudwikJaniuk LudwikJaniuk commented Dec 2, 2021

/integrate

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@openjdk openjdk bot commented Dec 2, 2021

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Your change (at version dbe1301) is now ready to be sponsored by a Committer.

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@vnkozlov vnkozlov left a comment

@LudwikJaniuk Please, rerun your testing. Running only -b linux-x64 is not enough - you should not specify this option at all. Testing should be done on all platforms. Also linux-x64 is product build which does not include asserts. So we may not catch possible issues.

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@vnkozlov vnkozlov left a comment

Good.
Testing results looks good too.

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@neliasso neliasso commented Dec 6, 2021

/sponsor

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@openjdk openjdk bot commented Dec 6, 2021

Going to push as commit 8d190dd.
Since your change was applied there have been 104 commits pushed to the master branch:

  • 194cdf4: 8277864: Compilation error thrown while doing a boxing conversion on selector expression
  • f39fe5b: 8154011: Make TraceDeoptimization a diagnostic flag
  • f180a45: 8278016: Add compiler tests to tier{2,3}
  • 104aa1f: 8268575: Annotations not visible on model elements before they are generated
  • 839b606: 8278143: Remove unused "argc" from ConstantPool::copy_bootstrap_arguments_at_impl
  • 267c024: 8265150: AsyncGetCallTrace crashes on ResourceMark
  • 9642629: 8276779: (ch) InputStream returned by Channels.newInputStream should have fast path for SelectableChannels
  • 02ee337: 8278175: Enable all doclint warnings for build of java.desktop
  • 24e16ac: 8277617: Adjust AVX3Threshold for copy/fill stubs
  • 2b87c2b: 8277793: Support vector F2I and D2L cast operations for X86
  • ... and 94 more: https://git.openjdk.java.net/jdk/compare/a5f2a58ba4ac25f4bd66f1f1f4c036a4f0024229...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Dec 6, 2021
@openjdk openjdk bot added integrated and removed ready rfr sponsor labels Dec 6, 2021
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@openjdk openjdk bot commented Dec 6, 2021

@neliasso @LudwikJaniuk Pushed as commit 8d190dd.

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

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