Adjust some defaults based on statistics about ranges and use pos lists

Author: tkrodriguez

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/util/IntList.java

@@ -44,7 +44,11 @@ public final class IntList {
      * @param initialCapacity
      */
     public IntList(int initialCapacity) {
-        array = new int[initialCapacity];
+        if (initialCapacity == 0) {
+            array = EMPTY_INT_ARRAY;
+        } else {
+            array = new int[initialCapacity];
+        }
     }
 
     /**

compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/alloc/lsra/Interval.java

@@ -650,8 +650,6 @@ void removeFirstUsePos() {
         usePosList.removeLowestUsePos();
     }
 
-    private static final int[] EMPTY_INT_ARRAY = new int[0];
-
     /**
      * The length of the valid portion of {@link #rangePairs}.
      */
@@ -1082,8 +1080,11 @@ int currentIntersectsAtLimit(Interval other, int limit) {
             assert isIllegal(operand) || LIRValueUtil.isVariable(operand);
         }
         this.kind = LIRKind.Illegal;
-        this.rangePairs = EMPTY_INT_ARRAY;
-        this.usePosList = new UsePosList(4);
+        // intervals only exist to contain ranges and 30% of ranges only contain a single element so
+        // start with enough space for a single range.
+        this.rangePairs = new int[2];
+        // 50% of intervals have empty UsePosLists.
+        this.usePosList = new UsePosList(0);
         this.next = intervalEndMarker;
         this.spillState = SpillState.NoDefinitionFound;
         this.spillDefinitionPos = -1;