8356634: VectorShape#largestShapeFor should have public access

Reviewed-by: psandoz

Author: Ian Graves

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -208,13 +208,22 @@ static VectorShape ofSwitchKey(int sk) {
         }
     }
 
-    // non-public support for computing preferred shapes
-
-    /*package-private*/
-    static VectorShape largestShapeFor(Class<?> etype) {
+    /**
+     * Finds the largest vector shape supported by the current
+     * platform for the element type {@code etype}.
+     *
+     * @param etype the element type
+     * @return the largest vector shape supported by the platform
+     *         for {@code etype}
+     * @throws IllegalArgumentException if no such vector shape exists
+     *         for the element type or the type is not a valid {@code ETYPE}.
+     */
+    public static VectorShape largestShapeFor(Class<?> etype) {
         return VectorShape.forBitSize(getMaxVectorBitSize(etype));
     }
 
+    // non-public support for computing preferred shapes
+
     /**
      * Finds the vector shape preferred by the current platform
      * for all vector element types.

test/jdk/jdk/incubator/vector/PreferredSpeciesTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -29,6 +29,7 @@
 
 /**
  * @test
+ * @bug 8356549
  * @modules jdk.incubator.vector java.base/jdk.internal.vm.vector
  * @run testng PreferredSpeciesTest
  */
@@ -126,4 +127,45 @@ void testVectorShape(Class<?> c) {
         Assert.assertEquals(largestSpecies.length(), maxLaneCount);
         Assert.assertEquals(largestSpecies.length(), Math.max(species.length(), maxLaneCount));
     }
+
+    // Testing VectorShape.largestShapeFor() for 8356549
+    @Test(dataProvider = "classesProvider")
+    void testLargestShapeFor(Class<?> c) {
+        final int S_64_BITS = 64;
+        int elemSize = 0;
+        VectorSpecies<?> maxVectorSpecies;
+        if (c == byte.class) {
+            elemSize = Byte.SIZE;
+            maxVectorSpecies = ByteVector.SPECIES_MAX;
+        } else if (c == short.class) {
+            elemSize = Short.SIZE;
+            maxVectorSpecies = ShortVector.SPECIES_MAX;
+        } else if (c == int.class) {
+            elemSize = Integer.SIZE;
+            maxVectorSpecies = IntVector.SPECIES_MAX;
+        } else if (c == long.class) {
+            elemSize = Long.SIZE;
+            maxVectorSpecies = LongVector.SPECIES_MAX;
+        } else if (c == float.class) {
+            elemSize = Float.SIZE;
+            maxVectorSpecies = FloatVector.SPECIES_MAX;
+        } else if (c == double.class) {
+            elemSize = Double.SIZE;
+            maxVectorSpecies = DoubleVector.SPECIES_MAX;
+        } else {
+            throw new IllegalArgumentException("Bad vector element type: " + c.getName());
+        }
+
+        VectorShape vs = VectorShape.largestShapeFor(c);
+
+        int maxLaneCount = VectorSupport.getMaxLaneCount(c);
+        int max = Math.max(maxLaneCount * elemSize, S_64_BITS);
+
+        //Assert we're using the same element when comparing shapes
+        Assert.assertEquals(c, maxVectorSpecies.elementType());
+
+        Assert.assertEquals(vs.vectorBitSize(), max);
+        Assert.assertEquals(vs.vectorBitSize(), maxVectorSpecies.vectorBitSize());
+
+    }
 }