Using Any ILP Optimization, Double the Performance of the Following

Essay

Using any ILP optimization, double the performance of the following loop, or explain why it is not possible. The machine can only do one branch per cycle, but has infinite resources otherwise.
r1 = ... ; r1 is head pointer to a linked list r3 = 0
LOOP:
r2 = M[r1 + 8]
r3 = r3 + r2 r1 = M[r1]
branch r1 != 0, LOOP
... = r3 ; r3 is used when loop complete