8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits #15164

afshin-zafari · 2023-08-04T17:41:50Z

The JVM options that are in range of int type are converted in globals.hpp and other files where affected.

Tests

tiers 1-4 passed for linux-x64, linux-x64-debug, windows-x64, windows-x64-debug
tier1 all passed.

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Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits (Enhancement - P4)

Reviewers

David Holmes (@dholmes-ora - Reviewer)
Coleen Phillimore (@coleenp - Reviewer)
Dean Long (@dean-long - Reviewer)

Reviewing

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bridgekeeper · 2023-08-04T17:42:35Z

👋 Welcome back azafari! 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 · 2023-08-04T17:43:32Z

@afshin-zafari The following labels will be automatically applied to this pull request:

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hotspot

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 · 2023-08-04T19:59:39Z

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dean-long · 2023-08-04T22:44:49Z

src/hotspot/share/runtime/globals.hpp

          "switch")                                                         \
                                                                            \
-  develop(intx, StopInterpreterAt, 0,                                       \
+  develop(int, StopInterpreterAt, 0,                                        \


Some cpu ports access this from assembly, so changing the size is gong to require cpu-specific changes. I'd rather see this and BytecodeCounter::_counter_value both changed to uint64_t.

share/interpreter/bytecodeHistogram.cpp:int BytecodeCounter::_counter_value = 0;

Maybe this should be inx instead.

The only reason to use intx is if this should be 32-bit on 32-bit and 64-bit on 64-bit. I don't think that is the case here.

The reason that this should be reverted is that to fix it, you have to fix all the platform code and that seems out of scope for fixing Wconversion warnings.

Actually this counts bytecodes, so it could easily become 64 bit on 64 bit platforms.

This is complicated. BytecodeCounter::_counter_value is an int, and StopInterpreterAt compares to that in shared code, which is fine because it'll promote the former to intx. The cpu-specific code fetches the former as int and the latter as intx, except in one place so fixing either is going to be work. The one place that complains on x86 is

src/hotspot/cpu/x86/templateInterpreterGenerator_x86.cpp:1865:12: warning: conversion from 'intx' {aka 'long int'} to 'int32_t' {aka 'int'} may change value [-Wconversion]
1865 | StopInterpreterAt,
| ^~~~~~~~~~~~~~~~~

__ cmp32(ExternalAddress((address) &BytecodeCounter::_counter_value), StopInterpreterAt, rscratch1);

We could just static_cast StopInterpreterAt to int here.

Actually this counts bytecodes, so it could easily become 64 bit on 64 bit platforms.

I thought this was the count within a method, in which case the bytecode limit is the same for 32-bit and 64-bit.

dean-long · 2023-08-04T22:45:58Z

src/hotspot/share/opto/macro.cpp

-      uint step_size = AllocatePrefetchStepSize;
-      uint distance = AllocatePrefetchDistance;
+      int step_size = AllocatePrefetchStepSize;
+      int distance = AllocatePrefetchDistance;


I think this is a step in the wrong direction. Shouldn't these remain uint?

This change also doesn't fit the PR description. There is no need to change this in this PR (or even at all).

Okay. Reverted back.

src/hotspot/share/runtime/globals.hpp

dean-long · 2023-08-04T22:51:28Z

I know HotSpot code is not very careful about distinguishing between int and uint, but shouldn't we prefer uint for values that can't be negative? The disadvantage of uint though is will we get more -Wsign-conversion warnings to fix when that warning gets turned on.

coleenp · 2023-08-05T16:19:22Z

The argument checking code gives a nice error if you pass a negative value for a parameter in the range of 0 .. positive-number if the argument is an int, and a bad one if the argument is uint. That's why in previous changes, I've preferred changing to int. We could file an RFE to improve the error message though. I don't know how hard that would be to fix.

dholmes-ora

I think the basic change from intx to int is sound - there is no reason for these flags to have a different size depending on the platform. But you need to check any other references to these flags (e.g. printing) are changed appropriately.

The issue of signed versus unsigned is a topic for a different day IMO.

Thanks.

dholmes-ora · 2023-08-07T02:01:17Z

src/hotspot/share/opto/macro.cpp

-      uint step_size = AllocatePrefetchStepSize;
-      uint distance = AllocatePrefetchDistance;
+      int step_size = AllocatePrefetchStepSize;
+      int distance = AllocatePrefetchDistance;


This change also doesn't fit the PR description. There is no need to change this in this PR (or even at all).

dholmes-ora · 2023-08-07T02:01:55Z

src/hotspot/share/opto/macro.cpp

+      int step_size = AllocatePrefetchStepSize;
+      int distance = AllocatePrefetchDistance;


Ditto no need to change

Okay.
Reverted back.

src/hotspot/share/runtime/globals.hpp

dholmes-ora · 2023-08-07T02:07:22Z

src/hotspot/share/runtime/globals.hpp

          "switch")                                                         \
                                                                            \
-  develop(intx, StopInterpreterAt, 0,                                       \
+  develop(int, StopInterpreterAt, 0,                                        \


The only reason to use intx is if this should be 32-bit on 32-bit and 64-bit on 64-bit. I don't think that is the case here.

coleenp

This looks good with the minor issue of removing a blank space.

coleenp · 2023-08-08T12:12:38Z

src/hotspot/share/runtime/globals.hpp

          "switch")                                                         \
                                                                            \
-  develop(intx, StopInterpreterAt, 0,                                       \
+  develop(intx, StopInterpreterAt, 0,                                        \


Does this add a blank? Should be aligned.

openjdk · 2023-08-08T12:15:09Z

@afshin-zafari 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:

8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits

Reviewed-by: dholmes, coleenp, dlong

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 25 new commits pushed to the master branch:

43462a3: 8313224: Avoid calling JavaThread::current() in MemAllocator::Allocation constructor
9abb2a5: 8312461: JNI warnings in SunMSCApi provider
42758cb: 8312882: Update the CONTRIBUTING.md with pointers to lifecycle of a PR
88b4e3b: 8304292: Memory leak related to ClassLoader::update_class_path_entry_list
6f5c903: 8313899: JVMCI exception Translation can fail in TranslatedException.
d97de82: 8313633: [macOS] java/awt/dnd/NextDropActionTest/NextDropActionTest.java fails with java.lang.RuntimeException: wrong next drop action!
79be8d9: 8312259: StatusResponseManager unused code clean up
1875b28: 8314061: [JVMCI] DeoptimizeALot stress logic breaks deferred barriers
bd1b942: 8313905: Checked_cast assert in CDS compare_by_loader
9b53251: 8313654: Test WaitNotifySuspendedVThreadTest.java timed out
... and 15 more: https://git.openjdk.org/jdk/compare/360f65d7b15b327e2f160c42f318945cc6548bda...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.

coleenp · 2023-08-08T19:54:01Z

Hi, I thought you were going to change this one too: LogEventsBufferEntries ?

dholmes-ora

I only checked the last two flags but in both cases found related changes. Please make sure all the uses of these flags has been checked. Thanks.

dholmes-ora · 2023-08-09T07:13:38Z

src/hotspot/share/runtime/globals.hpp

+  product(int, PerfDataSamplingInterval, 50,                                \
          "Data sampling interval (in milliseconds)")                       \
          range(PeriodicTask::min_interval, max_jint)                       \
          constraint(PerfDataSamplingIntervalFunc, AfterErgo)               \


You need to change the type of the PerfDataSamplingIntervalFunc as well.

I changed this and checked for the other options I changed.

dholmes-ora · 2023-08-09T07:17:32Z

src/hotspot/share/runtime/globals.hpp

          "Hit breakpoint when mallocing/freeing this pointer")             \
                                                                            \
-  develop(intx, StackPrintLimit, 100,                                       \
+  develop(int, StackPrintLimit, 100,                                        \


You can remove this cast now:

./share/utilities/vmError.cpp: const int limit = max_frames == -1 ? StackPrintLimit : MIN2(max_frames, (int)StackPrintLimit);

openjdk · 2023-08-09T11:14:09Z

@afshin-zafari this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout wconv_jvm_options
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

afshin-zafari · 2023-08-09T14:41:45Z

I also changed the type of LogEventsBufferEntries in runtime/globals.hpp which fixes the Wconversion warnings in utilities/events.hpp.

dholmes-ora

Updates look good.

Thanks

dholmes-ora · 2023-08-09T22:10:05Z

src/hotspot/share/runtime/globals.hpp

          "Enable the various ring buffer event logs")                      \
                                                                            \
-  product(uintx, LogEventsBufferEntries, 20, DIAGNOSTIC,                    \
+  product(int, LogEventsBufferEntries, 20, DIAGNOSTIC,                      \


I was going to say this should keep its unsignedness but it is treated as an int everywhere anyway.

dholmes-ora

Just noticed that AllocatePrefetchStyle should also be included in this.

Thanks

coleenp · 2023-08-10T01:50:45Z

The criteria for choosing flags was whether they were causing -Wconversion warnings, which this one doesn't. That said, it would be consistent to change this one since other AllocatePrefetch flags are changed. There are likely many other flags that can be int not intx. They can be changed in a different patch.

dholmes-ora · 2023-08-10T04:50:24Z

The criteria for choosing flags was whether they were causing -Wconversion warnings,

There is nothing in the PR or JBS to indicate this is the case. I assumed this would fix all oversized flags as the title indicates. If this is only a restricted subset perhaps the title and description should be updated to reflect that. Thanks.

coleenp

Still good.

iklam · 2023-08-10T16:07:14Z

src/hotspot/share/jvmci/jvmciCompilerToVMInit.cpp

+  do_int_flag(AllocateInstancePrefetchLines)                               \
+  do_int_flag(AllocatePrefetchDistance)                                    \
  do_intx_flag(AllocatePrefetchInstr)                                      \
-  do_intx_flag(AllocatePrefetchLines)                                      \
-  do_intx_flag(AllocatePrefetchStepSize)                                   \
-  do_intx_flag(AllocatePrefetchStyle)                                      \
+  do_int_flag(AllocatePrefetchLines)                                       \
+  do_int_flag(AllocatePrefetchStepSize)                                    \
+  do_int_flag(AllocatePrefetchStyle)                                       \


Why is AllocatePrefetchInstr not changed? It seems to use 0-3 only.

Looks like from the constraints, it's allowed to be max_intx on some platforms, so changing this would be a functional change.

JVMFlag::Error AllocatePrefetchInstrConstraintFunc(intx value, bool verbose) { intx max_value = max_intx; #if defined(X86) max_value = 3; #endif

OK, that sounds reasonable.

Fwiw, only x86 uses AllocatePrefetchInstr. Other platforms never use it, so its value for those is meaningless.

afshin-zafari · 2023-08-14T11:55:20Z

Thank you Coleen, Dean, David, Thomas and Ioi for your comments.
/integrate

openjdk · 2023-08-14T11:57:19Z

Going to push as commit 823f5b9.
Since your change was applied there have been 40 commits pushed to the master branch:

5bfb82e: 8314119: G1: Fix -Wconversion warnings in G1CardSetInlinePtr::card_pos_for
06aa3c5: 8314118: Update JMH devkit to 1.37
4164693: 8313372: [JVMCI] Export vmIntrinsics::is_intrinsic_available results to JVMCI compilers.
049b55f: 8314019: Add gc logging to jdk/jfr/event/gc/detailed/TestZAllocationStallEvent.java
a39ed10: 8314116: C2: assert(false) failed: malformed control flow after JDK-8305636
1de5bf1: 8314106: C2: assert(is_valid()) failed: must be valid after JDK-8305636
5c91622: 8314117: RISC-V: Incorrect VMReg encoding in RISCV64Frame.java
6bbcef5: 8313948: Remove unnecessary static fields defaultUpper/defaultLower in sun.net.PortConfig
b88c273: 8313743: Make fields final in sun.nio.ch
ec0cc63: 8313904: [macos] All signing tests which verifies unsigned app images are failing
... and 30 more: https://git.openjdk.org/jdk/compare/360f65d7b15b327e2f160c42f318945cc6548bda...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-08-14T11:57:25Z

@afshin-zafari Pushed as commit 823f5b9.

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

Fixed intx->int for Wconversion warnings.

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openjdk bot added graal graal-dev@openjdk.org hotspot hotspot-dev@openjdk.org labels Aug 4, 2023

afshin-zafari marked this pull request as ready for review August 4, 2023 19:53

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backslash aligned

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checked all usages of changed options.

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afshin-zafari added 2 commits August 9, 2023 14:19

Matched with master.

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Merge branch 'master' into wconv_jvm_options

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afshin-zafari changed the title ~~8308850: Change JVM options with small ranges from 64 to 32 bits, for globals.hpp~~ Change JVM options with small ranges from 64 to 32 bits that get -Wconversion warnings Aug 10, 2023

afshin-zafari changed the title ~~Change JVM options with small ranges from 64 to 32 bits that get -Wconversion warnings~~ Change JVM options with small ranges that get -Wconversion warnings to 32 bits Aug 10, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Aug 10, 2023

Fixed a missed option.

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afshin-zafari changed the title ~~Change JVM options with small ranges that get -Wconversion warnings to 32 bits~~ 8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits Aug 10, 2023

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afshin-zafari deleted the wconv_jvm_options branch June 13, 2025 10:17

		int step_size = AllocatePrefetchStepSize;
		int distance = AllocatePrefetchDistance;

8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits #15164

8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits #15164

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