Add unpadded array allocations.

Unpadded array allocations avoid unused bytes following arrays. API conventions
follow those of newNonMovableArray.
Dalvik implementation assume dlmalloc allocation properties, ART implementation
is handled by resizing the array post-allocation:
https://android-review.googlesource.com/83670
Add VMRuntimeTest to check the properties of the array allocation routines.
Change java.lang.reflect.Array.newInstance to compare more probable array types
before less probable ones.

Bug: 13028925.

Change-Id: Icf6bfb1aa5ad4faa062b393082c689b6118a84b5

1 files changed, 7 insertions, 0 deletions

diff --git a/libart/src/main/java/dalvik/system/VMRuntime.java b/libart/src/main/java/dalvik/system/VMRuntime.java
index 39cd3263d..7bbb93ef7 100644
--- a/libart/src/main/java/dalvik/system/VMRuntime.java
+++ b/libart/src/main/java/dalvik/system/VMRuntime.java
@@ -223,6 +223,13 @@ public final class VMRuntime {
     public native Object newNonMovableArray(Class<?> componentType, int length);
 
     /**
+     * Returns an array of at least minLength, but potentially larger. The increased size comes from
+     * avoiding any padding after the array. The amount of padding varies depending on the
+     * componentType and the memory allocator implementation.
+     */
+    public native Object newUnpaddedArray(Class<?> componentType, int minLength);
+
+    /**
      * Returns the address of array[0]. This differs from using JNI in that JNI might lie and
      * give you the address of a copy of the array when in forcecopy mode.
      */