8330388: Remove invokedynamic cache index encoding #18819

matias9927 · 2024-04-17T15:26:52Z

Before JDK-8307190, JDK-8309673, and JDK-8301995, invokedynamic operands needed to be rewritten to encoded values to better distinguish indy entries from other cp cache entries. The above changes now distinguish between entries with to_cp_index() using the bytecode, which is now propagated by the callers.

The encoding flips the bits of the index so the encoded index is always negative, leading to access errors if there is no matching decode call. These calls are removed with some methods adjusted to distinguish between indices with the bytecode. Verified with tier 1-5 tests. The changes show no issues when tested against libgraal.

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Issue

JDK-8330388: Remove invokedynamic cache index encoding (Bug - P4)

Reviewers

Chris Plummer (@plummercj - Reviewer) ⚠️ Review applies to 87926aee
Dean Long (@dean-long - Reviewer) ⚠️ Review applies to 87926aee
Coleen Phillimore (@coleenp - Reviewer)

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/18819/head:pull/18819
$ git checkout pull/18819

Update a local copy of the PR:
$ git checkout pull/18819
$ git pull https://git.openjdk.org/jdk.git pull/18819/head

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$ git pr checkout 18819

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$ git pr show -t 18819

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https://git.openjdk.org/jdk/pull/18819.diff

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bridgekeeper · 2024-04-17T15:27:30Z

👋 Welcome back matsaave! 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 · 2024-04-17T15:27:41Z

@matias9927 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:

8330388: Remove invokedynamic cache index encoding

Reviewed-by: cjplummer, dlong, coleenp

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 78 new commits pushed to the master branch:

83c74d7: 8329717: Missing @since tags in elements in DocumentationTool and Taglet
0b9350e: 8322992: Javac fails with StackOverflowError when compiling deeply nested synchronized blocks
20be5e0: 8314846: Do not store Klass::_secondary_super_cache in CDS archive
7e421ce: 8330585: Refactor/rename forwardee handling
3e65d90: 8330820: Remove remnants of operator_new.cpp in build system
936a47d: 8330607: Deprecate -XX:+UseEmptySlotsInSupers
ee7b2e9: 8330051: Small ObjectMonitor spinning code cleanups
3e185c7: 8330154: Serial: Remove TenuredSpace::update_for_block
f889797: 8330463: Rename invalidate() to write_region() in ModRefBarrierSet
c4f5c51: 8330576: ZYoungCompactionLimit should have range check
... and 68 more: https://git.openjdk.org/jdk/compare/941bee197ff679e9b8755cad117f5172e3508ef2...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

openjdk · 2024-04-17T15:28:14Z

@matias9927 The following labels will be automatically applied to this pull request:

graal
hotspot
serviceability

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

mlbridge · 2024-04-17T18:53:24Z

Webrevs

01: Full - Incremental (3ef92512)
00: Full (87926aee)

plummercj

SA changes look good.

dean-long · 2024-04-17T22:41:08Z

src/hotspot/share/ci/ciEnv.cpp

    // process the BSM
    int pool_index = indy_info->constant_pool_index();
-    BootstrapInfo bootstrap_specifier(cp, pool_index, index);
+    BootstrapInfo bootstrap_specifier(cp, pool_index, indy_index);


Why not just change the incoming parameter name to index?

indy_index is used frequently even in functions that are only used in the context of invokedynamic. I think it helps with clarity.

dean-long · 2024-04-17T22:43:38Z

src/hotspot/share/classfile/resolutionErrors.hpp

  static const int CPCACHE_INDEX_MANGLE_VALUE = 1000000;

  // This function is used to encode an invokedynamic index to differentiate it from a
  // constant pool index.  It assumes it is being called with a index that is less than 0


Is this comment still correct?

The last sentence is no longer valid, thanks for catching this!

dean-long · 2024-04-17T22:44:59Z

src/hotspot/share/interpreter/bootstrapInfo.cpp

    return true;
  } else if (indy_entry->resolution_failed()) {
-    int encoded_index = ResolutionErrorTable::encode_indy_index(ConstantPool::encode_invokedynamic_index(_indy_index));
+    int encoded_index = ResolutionErrorTable::encode_indy_index(_indy_index);


That's an improvement, from two levels of encoding to only one!

dean-long · 2024-04-17T22:48:16Z

Did you consider minimizing changes by leaving decode_invokedynamic_index/encode_invokedynamic_index calls in place, but having the implementations not change the value?

dean-long

@dougxc should check JVMCI changes.

gilles-duboscq · 2024-04-18T07:51:37Z

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotConstantPool.java

-        } else {
-            which = rawIndex;
-        }
+        int which = rawIndex;


We could get rid of that intermediate variable now and just use rawIndex below.

dougxc · 2024-04-18T08:24:12Z

@dougxc should check JVMCI changes.

Thanks for the heads up. I've asked @matias9927 to double check these changes against libgraal which should address any concerns about how this change impacts Graal.

coleenp

To borrow @shipilev's comment from a different PR, Good Riddance!

matias9927 · 2024-04-18T15:34:59Z

Did you consider minimizing changes by leaving decode_invokedynamic_index/encode_invokedynamic_index calls in place, but having the implementations not change the value?

The intention from the start was to remove the encode/decode methods because they have been made unnecessary thanks to the changes mentioned in the description. As the author of the previously mentioned changes that overhauled the cpcache, this change should have been included in one of those PRs, but I must have forgotten! Leaving the calls in even if they did nothing would just make the code confusing and might become a red herring if other issues in the area come up.

coleenp

Still good!

matias9927 · 2024-04-23T15:02:00Z

Thanks for the reviews @dean-long @gilles-duboscq @coleenp and @plummercj!
/integrate

openjdk · 2024-04-23T15:02:29Z

Going to push as commit 383fe6e.
Since your change was applied there have been 94 commits pushed to the master branch:

2ea8926: 8330961: Remove redundant public specifier in ModRefBarrierSet
3d5eeac: 8289770: Remove Windows version macro from ShellFolder2.cpp
6158da5: 8330108: Increase CipherInputStream buffer size
a92ad03: 8329995: Restricted access to /proc can cause JFR initialization to crash
fcb4a8b: 8330578: The VM creates instance of abstract class VirtualMachineError
3bd6982: 8326150: Typo in the documentation for jdk.jshell
d9d926d: 8330145: Serial: Refactor SerialHeap::scan_evacuated_objs
1a6da3d: 8330822: Remove ModRefBarrierSet::write_ref_array_work
281f9bd: 8330735: RISC-V: No need to move sp to tmp register in set_last_Java_frame
daa5a4b: 8330802: Desugar switch in Locale::createLocale
... and 84 more: https://git.openjdk.org/jdk/compare/941bee197ff679e9b8755cad117f5172e3508ef2...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-04-23T15:02:35Z

@matias9927 Pushed as commit 383fe6e.

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

8330388: Remove invokedynamic cache index encoding

87926ae

openjdk bot added graal graal-dev@openjdk.org serviceability serviceability-dev@openjdk.org hotspot hotspot-dev@openjdk.org labels Apr 17, 2024

matias9927 marked this pull request as ready for review April 17, 2024 18:49

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8330388: Remove invokedynamic cache index encoding #18819

8330388: Remove invokedynamic cache index encoding #18819

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