Week 13

Question 1

_____ determines the ordering of an instruction J, with respect to a branch instruction so that J is executed in both correct program order and only when it should be

Answer 1

Control dependence (Every instruction after the first branch is control dependent on some set of branches)

Question 2

True / false: An instruction that is control dependent of a branch can be scheduled before the branch

Answer 2

FALSE – if scheduled before, it would no longer be controlled by the branch

Question 3

The correct sequence of instruction execution is called the _____

Answer 3

instruction execution trace

Question 4

what, exactly, is a branch instruction?

Answer 4

a bit string that, when interpreted according to the instruction format, has a certain opcode

Question 5

_____ of instructions within a basic block cannot change program control flow

Answer 5

static scheduling

Question 6

what are some compilation techniques used to reduce stalls?

Answer 6

register allocation – use registers to reduce accesses to slower storage (SRAM, DRAM)
static instruction scheduling: reorder machine instructions from obvious compiled order to reduce depencdence-caused stalls
single assignment – reduce/eliminate false data dependences by reducing / eliminating reuse of storage locations

Question 7

what does static instruction scheduling do?

Answer 7

Reorders machine instructions from obvious compiled order to reduce dependence-caused stalls