- review and remove duplicate code from TimSort: merge java/util/ComparableTimSort.java and java/util/TimSort.java
 - evaluate performance {pro|re}gression from corrected mergeCollapse() method suggested in JDK-8072909 and possibly apply it:
private void mergeCollapse() {
        while (stackSize > 1) {
            int n = stackSize - 2;
            if ( n > 0 && runLen[n-1] <= runLen[n] + runLen[n+1]
                || n-1 > 0 && runLen[n-2] <= runLen[n] + runLen[n-1]) {
                if (runLen[n - 1] < runLen[n + 1])
                    n--;
            } else if (n<0 || runLen[n] > runLen[n + 1]) {
                break; // Invariant is established
            }
            mergeAt(n);
        }
    }