Chapter 4, Problem 4.48HW

Program Plan Intro

Given Y86-64 code:

.pos 0

 irmovq stack, %rsp

 call main

 halt

.align 8

data:

  .quad 0x0000000000000004

  .quad 0x0000000000000003

  .quad 0x0000000000000002

data_end:

  .quad 0x0000000000000001

main:

  irmovq data,%rdi

  irmovq data_end,%rsi

  call ysBubbleP

  ret

ysBubbleP:

  jmp L2

L4:

  mrmovq 8(%rax), %r9

  mrmovq (%rax), %r10

  rrmovq %r9, %r8

  subq %r10, %r8

  jge L3

  rmmovq %r10, 8(%rax)

  rmmovq %r9, (%rax)

L3:

  irmovq $8, %r8

  addq %r8, %rax

  jmp L5

L6:

  rrmovq %rdi, %rax

L5:

  rrmovq %rsi, %r8

  subq %rax, %r8

  jg L4

  irmovq $8, %r8

  subq %r8, %rsi

L2:

  rrmovq %rsi, %r8

  subq %rdi, %r8

  jg L6

    ret

.pos 0x200

stack:

Data movement instructions:

• The different instructions are been grouped as “instruction classes”.
• The instructions in a class performs same operation but with different sizes of operand.
• The “Mov” class denotes data movement instructions that copy data from a source location to a destination.
• The class has 4 instructions that includes:
  • movb:
    • It copies data from a source location to a destination.
    • It denotes an instruction that operates on 1 byte data size.
  • movw: 
    • It copies data from a source location to a destination.
    • It denotes an instruction that operates on 2 bytes data size.
  • movl:
    • It copies data from a source location to a destination.
    • It denotes an instruction that operates on 4 bytes data size.
  • movq:
    • It copies data from a source location to a destination.
    • It denotes an instruction that operates on 8 bytes data size.

Unary and Binary Operations:

• The details of unary operations includes:
  • The single operand functions as both source as well as destination.
  • It can either be a memory location or a register.
  • The instruction “incq” causes 8 byte element on stack top to be incremented.
  • The instruction “decq” causes 8 byte element on stack top to be decremented.
• The details of binary operations includes:
  • The first operand denotes the source.
  • The second operand works as both source as well as destination.
  • The first operand can either be an immediate value, memory location or register.
  • The second operand can either be a register or a memory location.

Jump Instruction:

• The “jump” instruction causes execution to switch to an entirely new position in program.
• The “label” indicates jump destinations in assembly code.
• The “je” instruction denotes “jump if equal” or “jump if zero”.
  • The comparison operation is performed.
  • If result of comparison is either equal or zero, then jump operation takes place.
• The “ja” instruction denotes “jump if above”.
  • The comparison operation is performed.
  • If result of comparison is greater, then jump operation takes place.
• The “pop” instruction resumes execution of jump instruction.
• The “jmpq” instruction jumps to given address. It denotes a direct jump.