8299181: PaddingLayout unable to return byteAlignment value #766

minborg · 2023-01-11T10:25:47Z

This PR proposes bit-aligning PaddingLayout to 8 by default as opposed to the current value of 1.

More generally, the PR restricts PaddingLayout bit-alignment to non-negative values that are an even multiple of 8 (i.e. 0, 8, 16, ...). There are no mechanism to derive VarHandle objects for sub-byte access anyhow and trying to obtain a miss-aligned VarHandle would throw an exception.

If integrated, all MemoryLayout types would be byte-aligned.

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Issue

JDK-8299181: PaddingLayout unable to return byteAlignment value

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Maurizio Cimadamore (@mcimadamore - Committer)

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bridgekeeper · 2023-01-11T10:27:22Z

👋 Welcome back pminborg! A progress list of the required criteria for merging this PR into foreign-memaccess+abi will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

mlbridge · 2023-01-16T13:52:29Z

Webrevs

mcimadamore · 2023-01-16T14:03:28Z

src/java.base/share/classes/java/lang/foreign/MemoryLayout.java

-        MemoryLayoutUtil.checkSize(size);
-        return PaddingLayoutImpl.of(size);
+    static PaddingLayout paddingLayout(long bitSize) {
+        if (bitSize < 0 || bitSize % 8 != 0) {


If I'm not mistaken, this is the same check that should be applied when we call withBitAlignment, right? It might be useful to consolidate (both impl-wise and doc-wise).

mcimadamore · 2023-01-16T14:07:09Z

src/java.base/share/classes/java/lang/foreign/MemoryLayout.java

-                StructLayoutImpl.of(Stream.of(elements)
-                        .map(Objects::requireNonNull)
-                        .toList()));
+        return wrapOverflow(() -> StructLayoutImpl.of(List.of(elements)));


Why was Objects.requireNonNull dropped? I believe that NPE will be thrown deeper inside the implementation - which is why we had the eager check (to make stack trace more readable).

mcimadamore · 2023-01-16T14:10:00Z

src/java.base/share/classes/jdk/internal/foreign/layout/AbstractLayout.java

-        if (((alignmentBitCount & (alignmentBitCount - 1)) != 0L) || //alignment must be a power of two
-                (alignmentBitCount < 8)) { //alignment must be greater than 8
-            throw new IllegalArgumentException("Invalid alignment: " + alignmentBitCount);
+    private static long requirePowerOfTwoAndGreaterOrEqualToEight(long value) {


Should this stay here, or be merged inside MemoryLayoutUtil? It seems the same as requireBitSizeValid, except for the zero behavior?

This method also checks if the parameter is an even power of two.

mcimadamore · 2023-01-16T14:12:21Z

test/jdk/java/foreign/TestLayouts.java

+
+    @Test
+    public void testNullMember() {
+        var illegalLayouts = new MemoryLayout[]{JAVA_INT, null, JAVA_INT};


this is covered by TestNulls. That test will try to pass null values to all API methods accepting arrays, or collections, and will do so in an automatic fashion.

openjdk · 2023-01-17T10:24:31Z

@minborg 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:

8299181: PaddingLayout unable to return byteAlignment value

Reviewed-by: mcimadamore

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 180 new commits pushed to the foreign-memaccess+abi branch:

cad8645: Merge master
d7a8621: Automatic merge of jdk:master into master
be8e6d0: 8299957: Enhance error logging in instrument coding with additional jplis_assert_msg
640eff6: 8300040: TypeOopPtr::make_from_klass_common calls itself with args in wrong order
19628e3: 8300068: UBSan CFLAGS/LDFLAGS not passed when building ADLC
9887047: Merge
4b92fb0: 8299918: Update Xcode11.3.1-MacOSX10.15 devkit at Oracle
6a4a874: 8299034: Runtime::exec clarification of inherited environment
752a370: 8299439: java/text/Format/NumberFormat/CurrencyFormat.java fails for hr_HR
3918f9f: 8299090: Specify coordinate order for additional CaptureCallState parameters on class as well
... and 170 more: https://git.openjdk.org/panama-foreign/compare/23d1e3748f0e6575b2dc1cf99fb59773fc4472f7...foreign-memaccess+abi

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 foreign-memaccess+abi branch, type /integrate in a new comment.

minborg · 2023-01-17T11:49:40Z

/integrate

openjdk · 2023-01-17T11:51:27Z

Going to push as commit 477cc26.
Since your change was applied there have been 180 commits pushed to the foreign-memaccess+abi branch:

cad8645: Merge master
d7a8621: Automatic merge of jdk:master into master
be8e6d0: 8299957: Enhance error logging in instrument coding with additional jplis_assert_msg
640eff6: 8300040: TypeOopPtr::make_from_klass_common calls itself with args in wrong order
19628e3: 8300068: UBSan CFLAGS/LDFLAGS not passed when building ADLC
9887047: Merge
4b92fb0: 8299918: Update Xcode11.3.1-MacOSX10.15 devkit at Oracle
6a4a874: 8299034: Runtime::exec clarification of inherited environment
752a370: 8299439: java/text/Format/NumberFormat/CurrencyFormat.java fails for hr_HR
3918f9f: 8299090: Specify coordinate order for additional CaptureCallState parameters on class as well
... and 170 more: https://git.openjdk.org/panama-foreign/compare/23d1e3748f0e6575b2dc1cf99fb59773fc4472f7...foreign-memaccess+abi

Your commit was automatically rebased without conflicts.

openjdk · 2023-01-17T11:51:49Z

@minborg Pushed as commit 477cc26.

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

Make PaddingLayout always align to byte boundaries

6072961

minborg added 4 commits January 11, 2023 11:43

Allow zero PaddingLayout elements

dddc6c7

Require all bitSizes to be dividable by 8

616d3a3

Use byte to store MemoryLayout variables

f3ccafb

Add copyright years

fc444c0

minborg marked this pull request as ready for review January 16, 2023 13:46

openjdk bot added the rfr Ready for review label Jan 16, 2023

mcimadamore reviewed Jan 16, 2023

View reviewed changes

minborg added 2 commits January 16, 2023 16:13

Improve after comments

e3f7fcc

Cleanup

ab8af25

mcimadamore approved these changes Jan 17, 2023

View reviewed changes

openjdk bot added the ready Ready to be integrated label Jan 17, 2023

openjdk bot added the integrated Pull request has been integrated label Jan 17, 2023

openjdk bot closed this Jan 17, 2023

openjdk bot removed ready Ready to be integrated rfr Ready for review labels Jan 17, 2023

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