8262096: Vector API fails to work due to VectorShape initialization e…

…xception

Reviewed-by: psandoz, vlivanov

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2021, 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
@@ -60,7 +60,7 @@ public enum VectorShape {
     /** Shape of length 512 bits */
     S_512_BIT(512),
     /** Shape of maximum length supported on the platform */
-    S_Max_BIT(VectorSupport.getMaxLaneCount(byte.class) * Byte.SIZE);
+    S_Max_BIT(getMaxVectorBitSize(byte.class));
 
     final int vectorBitSize;
     final int vectorBitSizeLog2;
@@ -211,10 +211,7 @@ static VectorShape ofSwitchKey(int sk) {
 
     /*package-private*/
     static VectorShape largestShapeFor(Class<?> etype) {
-        int laneCount = VectorSupport.getMaxLaneCount(etype);
-        int elementSize = LaneType.of(etype).elementSize;
-        int vectorBitSize = laneCount * elementSize;
-        return VectorShape.forBitSize(vectorBitSize);
+        return VectorShape.forBitSize(getMaxVectorBitSize(etype));
     }
 
     /**
@@ -244,23 +241,32 @@ private static VectorShape computePreferredShape() {
         int prefBitSize = Integer.MAX_VALUE;
         for (LaneType type : LaneType.values()) {
             Class<?> etype = type.elementType;
-            int maxLaneCount = VectorSupport.getMaxLaneCount(etype);
-            int maxSize = type.elementSize * maxLaneCount;
-            // FIXME: Consider removing, since unlikely to occur on modern hardware
-            if (maxSize < Double.SIZE) {
-                String msg = "shape unavailable for lane type: " + etype.getName();
-                throw new UnsupportedOperationException(msg);
-            }
-            prefBitSize = Math.min(prefBitSize, maxSize);
+            prefBitSize = Math.min(prefBitSize, getMaxVectorBitSize(etype));
         }
         // If these assertions fail, we must reconsider our API portability assumptions.
         assert(prefBitSize >= Double.SIZE && prefBitSize < Integer.MAX_VALUE / Long.SIZE);
-        assert(prefBitSize/Byte.SIZE == VectorSupport.getMaxLaneCount(byte.class));
+        assert(prefBitSize == getMaxVectorBitSize(byte.class));
         VectorShape shape = VectorShape.forBitSize(prefBitSize);
         PREFERRED_SHAPE = shape;
         return shape;
     }
 
+    /**
+     * Returns the maximum vector bit size for a given element type.
+     *
+     * @param etype the element type.
+     * @return the maximum vector bit.
+     */
+     /*package-private*/
+    static int getMaxVectorBitSize(Class<?> etype) {
+        // VectorSupport.getMaxLaneCount may return -1 if C2 is not enabled,
+        // or a value smaller than the S_64_BIT.vectorBitSize / elementSizeInBits if MaxVectorSize < 16
+        // If so default to S_64_BIT
+        int maxLaneCount = VectorSupport.getMaxLaneCount(etype);
+        int elementSizeInBits = LaneType.of(etype).elementSize;
+        return Math.max(maxLaneCount * elementSizeInBits, S_64_BIT.vectorBitSize);
+    }
+
     private static @Stable VectorShape PREFERRED_SHAPE;
 
     // ==== JROSE NAME CHANGES ====

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2021, 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
@@ -33,6 +33,16 @@
  * @run testng PreferredSpeciesTest
  */
 
+/**
+ * @test
+ * @bug 8262096
+ * @requires vm.compiler2.enabled
+ * @summary Test the initialization of vector shapes
+ * @modules jdk.incubator.vector java.base/jdk.internal.vm.vector
+ * @run testng/othervm -XX:MaxVectorSize=8 PreferredSpeciesTest
+ * @run testng/othervm -XX:MaxVectorSize=4 PreferredSpeciesTest
+ */
+
 public class PreferredSpeciesTest {
     @DataProvider
     public static Object[][] classesProvider() {
@@ -49,26 +59,35 @@ public static Object[][] classesProvider() {
     @Test(dataProvider = "classesProvider")
     void testVectorLength(Class<?> c) {
         VectorSpecies<?> species = null;
+        int elemSize = 0;
         if (c == byte.class) {
             species = ByteVector.SPECIES_PREFERRED;
+            elemSize = Byte.SIZE;
         } else if (c == short.class) {
             species = ShortVector.SPECIES_PREFERRED;
+            elemSize = Short.SIZE;
         } else if (c == int.class) {
             species = IntVector.SPECIES_PREFERRED;
+            elemSize = Integer.SIZE;
         } else if (c == long.class) {
             species = LongVector.SPECIES_PREFERRED;
+            elemSize = Long.SIZE;
         } else if (c == float.class) {
             species = FloatVector.SPECIES_PREFERRED;
+            elemSize = Float.SIZE;
         } else if (c == double.class) {
             species = DoubleVector.SPECIES_PREFERRED;
+            elemSize = Double.SIZE;
         } else {
             throw new IllegalArgumentException("Bad vector element type: " + c.getName());
         }
         VectorShape shape = VectorShape.preferredShape();
 
-        System.out.println("class = "+c+"; preferred shape"+shape+"; preferred species = "+species+"; maxSize="+VectorSupport.getMaxLaneCount(c));
+        int maxLaneCount = Math.max(VectorSupport.getMaxLaneCount(c), 64 / elemSize);
+
+        System.out.println("class = "+c+"; preferred shape"+shape+"; preferred species = "+species+"; maxSize="+maxLaneCount);
         Assert.assertEquals(species.vectorShape(), shape);
-        Assert.assertEquals(species.length(), Math.min(species.length(), VectorSupport.getMaxLaneCount(c)));
+        Assert.assertEquals(species.length(), Math.min(species.length(), maxLaneCount));
     }
 
     @Test(dataProvider = "classesProvider")
@@ -96,12 +115,15 @@ void testVectorShape(Class<?> c) {
         } else {
             throw new IllegalArgumentException("Bad vector element type: " + c.getName());
         }
+
+        int maxLaneCount = Math.max(VectorSupport.getMaxLaneCount(c), 64 / elemSize);
+
         VectorSpecies largestSpecies = VectorSpecies.ofLargestShape(c);
-        VectorShape largestShape = VectorShape.forBitSize(VectorSupport.getMaxLaneCount(c) * elemSize);
+        VectorShape largestShape = VectorShape.forBitSize(maxLaneCount * elemSize);
 
-        System.out.println("class = "+c+"; largest species = "+largestSpecies+"; maxSize="+VectorSupport.getMaxLaneCount(c));
+        System.out.println("class = "+c+"; largest species = "+largestSpecies+"; maxSize="+maxLaneCount);
         Assert.assertEquals(largestSpecies.vectorShape(), largestShape);
-        Assert.assertEquals(largestSpecies.length(), VectorSupport.getMaxLaneCount(c));
-        Assert.assertEquals(largestSpecies.length(), Math.max(species.length(), VectorSupport.getMaxLaneCount(c)));
+        Assert.assertEquals(largestSpecies.length(), maxLaneCount);
+        Assert.assertEquals(largestSpecies.length(), Math.max(species.length(), maxLaneCount));
     }
 }