Chapter 3, Problem 3.60HW

A.

Explanation of Solution

Registers for holding values:

• The parameter “x” is been passed to function in register “%rdi”.
• The parameter “n” is been passed to function in register “%esi”.
• The register “%rax” is initialized to variable “result”...

B.

Explanation of Solution

Initial values of result and mask:

• The instruction “movl $1, %edx” sets value of “mask” to 1...

C.

Explanation of Solution

Test condition for mask:

• The instruction “testq %rdx, %rdx” denotes test condition for “mask”...

D.

Explanation of Solution

Condition to update mask:

• The instruction “salq %cl, %rdx” performs left shift on “mask”...

E.

Explanation of Solution

Condition to update result:

• The instruction “orq %r8, %rax” performs “OR” operation on “result”...

F.

Explanation of Solution

Given assembly code:

long loop(long x, int n)

x in %rdi, n in %esi

loop:

movl %esi, %ecx

movl $1, %edx

movl $0, %eax

jmp .L2

.L3:

movq %rdi, %r8

andq %rdx, %r8

orq %r8, %rax

`salq %cl, %rdx

.L2:

testq %rdx, %rdx

jne .L3

Rep; ret

Load Effective Address:

• The load effective address instruction “leaq” is a variant of “movq” instruction.
• The instruction form reads memory to a register, but memory is not been referenced at all.
• The first operand of instruction is a memory reference; the effective address is been copied to destination.
• The pointers could be generated for later references of memory.
• The common arithmetic operations could be described compactly using this instruction.
• The operand in destination should be a register.

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.

Comparison Instruction:

• The “CMP” instruction sets condition code according to differences of their two operands.
• The working pattern is same as “SUB” instruction but it sets condition code without updating destinations.
• The zero flag is been set if two operands are equal.
• The ordering relations between operands could be determined using other flags.
• The “cmpl” instruction compares values that are double word.

Unary and Binary Operations:

• The details of unary operations includes:
  • The single operand functions as both source as well as destination...