Assembly Language

1
Assembly Language

• Integer Arithmetic

2
Flags

• MUL
• Carry and Overflow 1, if the upper half of the
  product is not equal to zero.
• IMUL
• One-Operand Format
• Carry and Overflow 1, if the upper half of the
  product is not a sign extension of the lower half
• Two-Operand Formats, Three-Operand Formats
• Carry and Overflow 1, if significant digits are
  lost

3
IMUL Instruction

• One-Operand Formats
• IMUL r/m8 AXALr/m byte
• IMUL r/m16 DXAXAXr/m word
• IMUL r/m32 EDXEAXEAXr/m doubleword
• Two-Operand Formats
• The product is the first operand. The first
  operand must be a register.
• IMUL r16, r/m16
• IMUL r16, imm8
• IMUL r16, imm16

4
IMUL Instruction

• Two-Operand Formats
• IMUL r32, r/m32
• IMUL r32, imm8
• IMUL r32, imm16
• Three-Operand Formats
• The product is stored at the first operand. The
  first operand is a register, the second operand
  can be a register or memory, and the third is an
  immediate value

5
IMUL Instruction

• IMUL r16, r/m16, imm8
• IMUL r16, r/m16, imm16
• IMUL r32, r/m32, imm8
• IMUL r32, r/m32, imm32

6
Assembly Language

• Advanced Procedures

7
Examples

• ArryFill.asm
• Csum.asm
• Fact.asm

8
Exercise 1

• Write a recursive implementation of Euclid's
  algorithm for finding the greatest common divisor
  (GCD) of two integers. Note we will only test
  this procedure with nonnegative integers.
• The GCD algorithm involves integer division using
  a recursive implementation, described by the
  following C code
• int GCD(int x, int y)
• n x y
• if (n 0)
• return y
• else
• return GCD(y, n)

9

• Implement this function in assembly language and
  write a test program that calls the function
  several times, passing it different values.
  Display all results on the screen.
• ch08_05.exe

10

• Due date 95/12/21
• ftp//eec751_at_ftp.csie.nuk.edu.tw
• Zip your files as a09xxxxx_951214.zip

11
Assembly Language

• Structures and Macros

12
Examples

• List.asm
• Walk.asm