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  1. JDK
  2. JDK-8302976

C2 Intrinsification of Float.floatToFloat16 and Float.float16ToFloat Yields Different Result than the Interpreter

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Details

    • b14
    • x86, aarch64
    • Verified

    Backports

      Description

        The following code snippet prints twice 31745 with the interpreter, and 32257 31745 with -Xcomp -XX:-TieredCompilation. This means, C2 will eliminate both intrinsifications if they are within the same compilation unit (the latter print), and return the same result as the interpreter. But if it applies the intrinsifications respectively in different compilation units and employ the underlying vcvtps2ph and vcvtph2ps instructions (the former print), then it will return a different value.


        public class Foo {
          public static short bar(float f) {
            return Float.floatToFloat16(f);
          }
          public static void main(String[] args) {
            System.out.println(bar(Float.float16ToFloat((short) 31745)));
            System.out.println(Float.floatToFloat16(Float.float16ToFloat((short) 31745)));
          }
        }

        Attachments

          1. Test.java
            0.4 kB
          2. TestAll.java
            2 kB
          3. TestAllFix.java
            3 kB
          4. TestAllFloat.java
            2 kB

          Issue Links

            backported by

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8307015 C2 Intrinsification of Float.floatToFloat16 and Float.float16ToFloat Yields Different Result than the Interpreter

            • P2 - Crashes, loss of data, severe memory leak.
            • Resolved

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8304741 C2 Intrinsification of Float.floatToFloat16 and Float.float16ToFloat Yields Different Result than the Interpreter

            • P2 - Crashes, loss of data, severe memory leak.
            • Closed

            Backport - A issue that is required to port a Bug or Feature into another product release. This issue type is generally associated with the main Bug/Feature to represent each individual release of the port. JDK-8305576 C2 Intrinsification of Float.floatToFloat16 and Float.float16ToFloat Yields Different Result than the Interpreter

            • P2 - Crashes, loss of data, severe memory leak.
            • Closed
            relates to

            Bug - A problem which impairs or prevents the functions of the product. JDK-8293991 java/lang/Float/Binary16ConversionNaN.java fails on silent NaN conversions

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved

            Enhancement - null JDK-8289551 Conversions between bit representations of half precision values and floats

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved

            Enhancement - null JDK-8289552 Make intrinsic conversions between bit representations of half precision values and floats

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved

            Enhancement - null JDK-8324724 Add Stub routines for FP16 conversions on aarch64

            • P4 - Minor loss of function, or other problem where easy workaround is present.
            • Resolved
            links to

            Commit Commit openjdk/jdk20u/59a3f4f4

            Commit Commit openjdk/jdk/8cfd74f7

            Review Review openjdk/jdk20u/21

            Review Review openjdk/jdk/12704

            Review Review openjdk/jdk/12869

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                kvn Vladimir Kozlov
                yzheng Yudi Zheng
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                Dates

                  Created:
                  Updated:
                  Resolved: