8303508: Vector.lane() gets wrong value on x86

Reviewed-by: eliu, thartmann

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp

@@ -2276,6 +2276,14 @@ XMMRegister C2_MacroAssembler::get_lane(BasicType typ, XMMRegister dst, XMMRegis
   }
 }
 
+void C2_MacroAssembler::movsxl(BasicType typ, Register dst) {
+  if (typ == T_BYTE) {
+    movsbl(dst, dst);
+  } else if (typ == T_SHORT) {
+    movswl(dst, dst);
+  }
+}
+
 void C2_MacroAssembler::get_elem(BasicType typ, Register dst, XMMRegister src, int elemindex) {
   int esize =  type2aelembytes(typ);
   int elem_per_lane = 16/esize;
@@ -2287,13 +2295,11 @@ void C2_MacroAssembler::get_elem(BasicType typ, Register dst, XMMRegister src, i
       movq(dst, src);
     } else {
       movdl(dst, src);
-      if (typ == T_BYTE)
-        movsbl(dst, dst);
-      else if (typ == T_SHORT)
-        movswl(dst, dst);
+      movsxl(typ, dst);
     }
   } else {
     extract(typ, dst, src, eindex);
+    movsxl(typ, dst);
   }
 }
 

src/hotspot/cpu/x86/c2_MacroAssembler_x86.hpp

@@ -133,6 +133,7 @@
   XMMRegister get_lane(BasicType typ, XMMRegister dst, XMMRegister src, int elemindex);
   void get_elem(BasicType typ, Register dst, XMMRegister src, int elemindex);
   void get_elem(BasicType typ, XMMRegister dst, XMMRegister src, int elemindex, XMMRegister vtmp = xnoreg);
+  void movsxl(BasicType typ, Register dst);
 
   // vector test
   void vectortest(BasicType bt, XMMRegister src1, XMMRegister src2, XMMRegister vtmp, int vlen_in_bytes);

test/hotspot/jtreg/compiler/vectorapi/Test8303508.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2023, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package compiler.vectorapi;
+
+import jdk.incubator.vector.ByteVector;
+import jdk.incubator.vector.ShortVector;
+import jdk.incubator.vector.VectorSpecies;
+
+/*
+ * @test
+ * @bug 8303508
+ * @summary Vector.lane() gets wrong value on x86
+ * @modules jdk.incubator.vector
+ * @library /test/lib
+ *
+ * @run main/othervm -Xbatch -XX:-TieredCompilation -ea compiler.vectorapi.Test8303508
+ */
+public class Test8303508 {
+
+    static final VectorSpecies<Byte> BSPECIES_128 = ByteVector.SPECIES_128;
+    static final VectorSpecies<Short> SSPECIES_128 = ShortVector.SPECIES_128;
+
+    static final byte[] ba = {0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15};
+    static final short[] sa = {0, -1, -2, -3, -4, -5, -6, -7};
+
+    private static byte vec_extract_byte(int idx) {
+        var bv = ByteVector.fromArray(BSPECIES_128, ba, 0);
+        return bv.lane(idx);
+    }
+
+    private static short vec_extract_short(int idx) {
+        var sv = ShortVector.fromArray(SSPECIES_128, sa, 0);
+        return sv.lane(idx);
+    }
+
+    public static void main(String[] args) {
+        int idx = 0;
+        int actual = 0;
+        int expected = 0;
+        for (int i = 0; i < 10000; i++) {
+            idx = i & 0xF;
+            actual = vec_extract_byte(idx);
+            expected = ba[idx];
+            if (actual != expected) {
+                throw new AssertionError("incorrect result byte extraction, actual = " + actual + " expected = " + expected);
+            }
+            idx = i & 0x7;
+            actual = vec_extract_short(idx);
+            expected = sa[idx];
+            if (actual != expected) {
+                throw new AssertionError("incorrect result short extraction, actual = " + actual + " expected = " + expected);
+            }
+        }
+        System.out.println("PASS");
+    }
+}