[SPARK-16962][CORE][SQL] Fix misaligned record accesses for SPARC architectures

## What changes were proposed in this pull request?

Made changes to record length offsets to make them uniform throughout various areas of Spark core and unsafe

## How was this patch tested?

This change affects only SPARC architectures and was tested on X86 architectures as well for regression.

Author: sumansomasundar <suman.somasundar@oracle.com>

Closes #14762 from sumansomasundar/master.

2 files changed, 82 insertions, 7 deletions

diff --git a/common/unsafe/src/main/java/org/apache/spark/unsafe/UnsafeAlignedOffset.java b/common/unsafe/src/main/java/org/apache/spark/unsafe/UnsafeAlignedOffset.java
new file mode 100644
index 0000000000..be62e40412
--- /dev/null
+++ b/common/unsafe/src/main/java/org/apache/spark/unsafe/UnsafeAlignedOffset.java
@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.unsafe;
+
+/**
+ * Class to make changes to record length offsets uniform through out
+ * various areas of Apache Spark core and unsafe.  The SPARC platform
+ * requires this because using a 4 byte Int for record lengths causes
+ * the entire record of 8 byte Items to become misaligned by 4 bytes.
+ * Using a 8 byte long for record length keeps things 8 byte aligned.
+ */
+public class UnsafeAlignedOffset {
+
+  private static final int UAO_SIZE = Platform.unaligned() ? 4 : 8;
+
+  public static int getUaoSize() {
+    return UAO_SIZE;
+  }
+
+  public static int getSize(Object object, long offset) {
+    switch (UAO_SIZE) {
+      case 4:
+        return Platform.getInt(object, offset);
+      case 8:
+        return (int)Platform.getLong(object, offset);
+      default:
+        throw new AssertionError("Illegal UAO_SIZE");
+    }
+  }
+
+  public static void putSize(Object object, long offset, int value) {
+    switch (UAO_SIZE) {
+      case 4:
+        Platform.putInt(object, offset, value);
+        break;
+      case 8:
+        Platform.putLong(object, offset, value);
+        break;
+      default:
+        throw new AssertionError("Illegal UAO_SIZE");
+    }
+  }
+}
diff --git a/common/unsafe/src/main/java/org/apache/spark/unsafe/array/ByteArrayMethods.java b/common/unsafe/src/main/java/org/apache/spark/unsafe/array/ByteArrayMethods.java
index cf42877bf9..9c551ab19e 100644
--- a/common/unsafe/src/main/java/org/apache/spark/unsafe/array/ByteArrayMethods.java
+++ b/common/unsafe/src/main/java/org/apache/spark/unsafe/array/ByteArrayMethods.java
@@ -40,6 +40,7 @@ public class ByteArrayMethods {
     }
   }
 
+  private static final boolean unaligned = Platform.unaligned();
   /**
    * Optimized byte array equality check for byte arrays.
    * @return true if the arrays are equal, false otherwise
@@ -47,17 +48,33 @@ public class ByteArrayMethods {
   public static boolean arrayEquals(
       Object leftBase, long leftOffset, Object rightBase, long rightOffset, final long length) {
     int i = 0;
-    while (i <= length - 8) {
-      if (Platform.getLong(leftBase, leftOffset + i) !=
-        Platform.getLong(rightBase, rightOffset + i)) {
-        return false;
+
+    // check if stars align and we can get both offsets to be aligned
+    if ((leftOffset % 8) == (rightOffset % 8)) {
+      while ((leftOffset + i) % 8 != 0 && i < length) {
+        if (Platform.getByte(leftBase, leftOffset + i) !=
+            Platform.getByte(rightBase, rightOffset + i)) {
+              return false;
+        }
+        i += 1;
+      }
+    }
+    // for architectures that suport unaligned accesses, chew it up 8 bytes at a time
+    if (unaligned || (((leftOffset + i) % 8 == 0) && ((rightOffset + i) % 8 == 0))) {
+      while (i <= length - 8) {
+        if (Platform.getLong(leftBase, leftOffset + i) !=
+            Platform.getLong(rightBase, rightOffset + i)) {
+              return false;
+        }
+        i += 8;
       }
-      i += 8;
     }
+    // this will finish off the unaligned comparisons, or do the entire aligned
+    // comparison whichever is needed.
     while (i < length) {
       if (Platform.getByte(leftBase, leftOffset + i) !=
-        Platform.getByte(rightBase, rightOffset + i)) {
-        return false;
+          Platform.getByte(rightBase, rightOffset + i)) {
+            return false;
       }
       i += 1;
     }