8282389: Add new vector operations to count leading and trailing zeros. #176

swati-sha · 2022-02-25T18:59:34Z

Hi All,

Added support for new vector operations CLZ (count number of leading zeros) and CTZ (could number of trailing zeros) for all the integral vector types(Byte/Short/Integer/Long).
Added validation and performance tests corresponding the these operations in existing VectorAPI JTREG/JMH suite.

Kindly review and share your feedback.

Thanks and Regards,
Swati Sharma
Intel

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Issue

JDK-8282389: Add new vector operations to count leading and trailing zeros.

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Jatin Bhateja (@jatin-bhateja - Committer) ⚠️ Review applies to eb53db7
Paul Sandoz (@PaulSandoz - Committer)

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bridgekeeper · 2022-02-25T18:59:45Z

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

swati-sha · 2022-02-25T19:00:07Z

/label add panama-dev

openjdk · 2022-02-25T19:01:55Z

@swati-sha
The label panama is not a valid label.
These labels are valid:

mlbridge · 2022-02-25T19:05:40Z

Webrevs

jatin-bhateja

LGTM.

jatin-bhateja · 2022-02-28T08:17:37Z

/sponsor

openjdk · 2022-02-28T08:18:45Z

@swati-sha 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:

8282389: Add new vector operations to count leading and trailing zeros.

Reviewed-by: jbhateja, psandoz

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 1 new commit pushed to the vectorIntrinsics branch:

d829111: Fix compilation error in perf reduction tests

Please see this link for an up-to-date comparison between the source branch of this pull request and the vectorIntrinsics branch.
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 (@jatin-bhateja, @PaulSandoz) 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 · 2022-02-28T08:20:21Z

@jatin-bhateja The change author (@swati-sha) must issue an integrate command before the integration can be sponsored.

e1iu · 2022-02-28T09:05:36Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/DoubleVector.java

@@ -1626,6 +1628,8 @@ DoubleVector abs() {



+
+


Please remove these lines.

XiaohongGong · 2022-02-28T09:10:03Z

src/hotspot/share/prims/vectorSupport.hpp

+    VECTOR_OP_CTZ     = 29,
+    VECTOR_OP_CLZ     = 30,


Seems weird, could you please either move these two to the end of this enum or set the number to "4, 5"?

XiaohongGong · 2022-02-28T09:11:27Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/ByteVector.java

@@ -1788,6 +1794,14 @@ static int bitCount(byte a) {
        return Integer.bitCount((int)a & 0xFF);
    }

+    static int numberOfTrailingZeros(byte a) {
+        return a != 0 ? Integer.numberOfTrailingZeros(a) : 8;


Integer.numberOfTrailingZeros((int)a & 0xFF) ?

Would it not return incorrect value for a=0.

This could be Integer.numberOfTrailingZeros(a | 0x100);

And I think what he meant was the calculation of the numberOfLeadingZeros below

numberOfTrailingZeros

Having a special case for zero will be better from performance perspective in slow path.
We may incur one additional comparison but given that C2 will intrinsify at a VectorSupport.unaryOp level it will not hurt compiled code performance but special handlings improve fallback code performance.

XiaohongGong · 2022-02-28T09:16:55Z

Could you please update the copyright year to "2022" for all the modified files? Thanks!

XiaohongGong · 2022-02-28T09:24:55Z

test/jdk/jdk/incubator/vector/Byte128VectorTests.java

@@ -5310,6 +5318,92 @@ static void BIT_COUNTMaskedByte128VectorTests(IntFunction<byte[]> fa,



+
+    static byte CTZ(byte a) {
+        return (byte)(CTZ_scalar(a));


Why not directly return (byte) (a != 0 ? Integer.numberOfTrailingZeros(a) : 8); in this method?

To keep minimal changes in the test generation template, we want to keep one interface which caters to all the primitive types.

PaulSandoz · 2022-02-28T21:29:05Z

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/VectorOperators.java

@@ -452,6 +452,10 @@ static boolean opKind(Operator op, int bit) {
    public static final Unary NEG = unary("NEG", "-a", VectorSupport.VECTOR_OP_NEG, VO_ALL|VO_SPECIAL);
    /** Produce {@code bitCount(a)} */
    public static final Unary BIT_COUNT = unary("BIT_COUNT", "bitCount", VectorSupport.VECTOR_OP_BIT_COUNT, VO_NOFP);
+    /** Produce {@code numberOfTrailingZeros(a)} */
+    public static final Unary CTZ = unary("CTZ", "numberOfTrailingZeros", VectorSupport.VECTOR_OP_CTZ, VO_NOFP);


I think we should be more verbose in the names, as they will not be well understood by developers. Specifically TRAILING_ZEROS_COUNT and LEADING_ZEROS_COUNT, and be consistent in other places. Internally we could shorten to VECTOR_OP_TZ_COUNT etc. to reduce the horizontal width.

swati-sha · 2022-03-06T08:07:55Z

/integrate

openjdk · 2022-03-06T08:09:26Z

@swati-sha
Your change (at version 4304bc3) is now ready to be sponsored by a Committer.

jatin-bhateja · 2022-03-06T08:09:56Z

/sponsor

openjdk · 2022-03-06T08:11:42Z

Going to push as commit 801f1fd.
Since your change was applied there has been 1 commit pushed to the vectorIntrinsics branch:

d829111: Fix compilation error in perf reduction tests

Your commit was automatically rebased without conflicts.

openjdk · 2022-03-06T08:12:00Z

@jatin-bhateja @swati-sha Pushed as commit 801f1fd.

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

8282389: Add new vector operations to count leading and trailing zeros.

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swati-sha added 2 commits March 3, 2022 05:18

8282389: Review comments resolved.

00b1247

8282389: Removed the extra lines.

4304bc3

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8282389: Add new vector operations to count leading and trailing zeros. #176

8282389: Add new vector operations to count leading and trailing zeros. #176

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		@@ -5310,6 +5318,92 @@ static void BIT_COUNTMaskedByte128VectorTests(IntFunction<byte[]> fa,




		static byte CTZ(byte a) {
		return (byte)(CTZ_scalar(a));

8282389: Add new vector operations to count leading and trailing zeros. #176

8282389: Add new vector operations to count leading and trailing zeros. #176

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