Chapter 5.12, Problem 5.11PP

Program Plan Intro

Given Assembly code:

a in %rdi, i in %rax, cnt in %rdx

.L5:

vmovss -4(%rsi, %rax, 4), %xmm0

vaddss (%rdi, %rax, 4), %xmm0, %xmm0

vmovss %xmm0, (%rsi, %rax, 4)

addq $1, %rax

cmpq %rdx, %rax

jne .L5

Cycles per element (CPE):

• The CPE denotes performance of program that helps in improving code.
• It helps to understand detailed level loop performance for an iterative program.
• It is appropriate for programs that use a repetitive computation.
• The processor’s activity sequencing is controlled by a clock that provides regular signal of some frequency.

Memory aliasing:

• It denotes a case where two pointers might designate to memory location that is same.
• The compiler should assume that unlike pointers might be aliased for safe optimizations.
• The program aspects that could limit chances for a compiler in generating optimized code denote optimization blockers.
• If a compiler is unable to determine whether two pointers might be aliased, it should adopt that either case would be possible.
• The possible optimization set is been limited in this case.