If many (e.g., 1,000,000) iterations of this loop are executed, determine the fraction of all register reads that are useful in a 3-issue static superscalar processor. Compare this to your result for a 2-issue processor from 4.29.1.

Exercise 4.29.1

If many (e.g., 1,000,000) iterations of this loop are executed, determine the fraction of all register reads that are useful in a 2-issue static superscalar processor.

In this exercise, we consider the execution of a loop in a statically scheduled superscalar processor. To simplify the exercise, assume that any combination of instruction types can execute in the same cycle, e.g., in a 3-issue superscalar, the three instructions can be 3 ALU operations, 3 branches, 3 load/store instructions, or any combination of these instructions. Note that this only removes a resource constraint, but data and control dependences must still be handled correctly. Problems in this exercise refer to the following loop:

a. b. Loop: Loop: ADDI R1, R1,4 LW R2,0 (R1) LW R3,16(R1) ADD R2, R2, R1 ADD R2, R2, R3 BEQ R2, zero, Loop LW R1,0 (R1) AND R1, R1, R2 LW R2,0 (R2) BEQ R1,zero, Loop Loop