Move MemoryAddress::copy (more review feedback)

Reviewed-by: psandoz

src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/MemorySegment.java

@@ -310,16 +310,16 @@
     MemorySegment fill(byte value);
 
     /**
-     * Perform bulk copy from given source segment to this segment. More specifically, the bytes at
+     * Performs a bulk copy from given source segment to this segment. More specifically, the bytes at
      * offset {@code 0} through {@code src.byteSize() - 1} in the source segment are copied into this segment
      * at offset {@code 0} through {@code src.byteSize() - 1}.
      * If the source segment overlaps with this segment, then the copying is performed as if the bytes at
      * offset {@code 0} through {@code src.byteSize() - 1} in the source segment were first copied into a
      * temporary segment with size {@code bytes}, and then the contents of the temporary segment were copied into
      * this segment at offset {@code 0} through {@code src.byteSize() - 1}.
      * <p>
-     * The result of a bulk copy is unspecified if, in the uncommon case, the source segment does not overlap with
-     * this segment, but it instead refers to an overlapping regions of the same backing storage using different addresses.
+     * The result of a bulk copy is unspecified if, in the uncommon case, the source segment and this segment
+     * do not overlap, but refer to overlapping regions of the same backing storage using different addresses.
      * For example, this may occur if the same file is {@link MemorySegment#mapFromPath mapped} to two segments.
      *
      * @param src the source segment.

src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java

@@ -122,14 +122,13 @@ public final MemorySegment fill(byte value){
     }
 
     public void copyFrom(MemorySegment src) {
-        long size = src.byteSize();
-        ((AbstractMemorySegmentImpl)src).checkRange(0, size, true);
-        checkRange(0, size, false);
-        long offsetSrc = ((AbstractMemorySegmentImpl) src).min();
-        long offsetDst = min();
-        Object baseSrc = ((AbstractMemorySegmentImpl) src).base();
-        Object baseDst = base();
-        UNSAFE.copyMemory(baseSrc, offsetSrc, baseDst, offsetDst, size);
+        AbstractMemorySegmentImpl that = (AbstractMemorySegmentImpl)src;
+        long size = that.byteSize();
+        checkRange(0, size, true);
+        that.checkRange(0, size, false);
+        UNSAFE.copyMemory(
+                that.base(), that.min(),
+                base(), min(), size);
     }
 
     @Override

test/micro/org/openjdk/bench/jdk/incubator/foreign/BulkOps.java

@@ -69,13 +69,13 @@
     @Benchmark
     @OutputTimeUnit(TimeUnit.NANOSECONDS)
     public void unsafe_fill() {
-        unsafe.setMemory(unsafe_addr, ALLOC_SIZE, (byte)0);
+        unsafe.setMemory(unsafe_addr, ALLOC_SIZE, (byte)42);
     }
 
     @Benchmark
     @OutputTimeUnit(TimeUnit.NANOSECONDS)
     public void segment_fill() {
-        segment.fill((byte)0);
+        segment.fill((byte)42);
     }
 
     @Benchmark