Assignment #3: Assembly Code Basics

Assigned: Wednesday, March 1
Due: Wednesday, March 8 by the start of class

Overview

Topic: Basic assembly code: registers, instructions, translating small statements to and from assembly
Related Reading: Class lecture slides, Chapter 3 pp.166-191

Problems to be Submitted (25 points)

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Answers without work will recieve zero credit.

(1.5 points each) Match the following assembly code sections with their equivalent C expressions

(1)						(a) y = 0;
 movl x, %eax					(b) y = 8 * x + 5;
 incl %eax					(c) y = (4 * x) + (x % 16)
 shll $3, %eax					(d) y = (8 * x) + 1;
 subl $3, %eax					(e) y = ~x;
 movl %eax, y					(f) y = 23 * x;
						(g) y = (x / 4) + (x % 16);
(2)						(h) y = (x / 4) << x;
 movl $25, %eax					(i) y = 5 * x / 2;
 sarl $3, %eax					(j) y = (3 * x) << x;
 addl $-2, %eax					(k) y = (8 * x) - (x - 3);
 movl %eax, y					(l) y = -25 * x;
						(m) y = (4 * x) - (x / 16);
(3)						(n) y = (8 * x) << x;
 movl x, %eax					(o) y = (x - 3) << 4;
 xorl $0xffffffff, %eax				(p) y = (16 * x) - (x / 4);
 movl %eax, y					(q) y = -3 * x;
						(r) y = 1;
(4)						(s) y = -23 * x;
 movl x, %eax					(t) y = 8 * x - 3;
 movl %eax, %ebx				(u) y = (x - 3) << x;
 shll $4, %ebx					(v) y = 4 * x - 3;
 sarl $2, %eax
 subl %eax, %ebx
 movl %ebx, y

(5)
 movl x, %eax
 movl %eax, %ecx
 subl $3, %eax
 shll %ecx, %eax
 movl %eax, y

(6)
 movl x, %eax
 movl %eax, %ebx
 shll $1, %ebx
 addl %eax, %ebx
 shll $3, %ebx
 subll %ebx, %eax
 movl %eax, y


(3 points each)
For each instruction below, indicate:
  * whether the data for that operand is found/stored in:
    o register
    o memory
    o in the instruction itself
  * size of the data (1, 2, 4, or 8 bytes)
  * what addressing mode is used for each operand (see table below)
  * give an english description of the instruction (example: "add five to register EAX")

(7) addl $5, %eax 		Operand 1:		
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Operand 2:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Describe:


(8) subw var, %cx 		Operand 1:
 					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Operand 2:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Describe:


(9) movl $ptr, %edx 		Operand 1:
					found/stored in: ___________________________
					of data: ___________________________________
					addressing mode: ___________________________
				Operand 2:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Describe:


(10) movb %cl, 8(%esp) 		Operand 1:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Operand 2:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Describe:


(11) addw 6(%ebx, %eax, 4), %si 
				Operand 1:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________
				Operand 2:
					data found/stored in: ______________________
					size of data: ______________________________
					addressing mode: ___________________________ 
				Describe:



Figure 3.3 from Computer Systems: A Programmer's Perspective, 3rd Ed.
----------------------------------------------------------------------------------
Type		Form		Operand value			Name
----------------------------------------------------------------------------------
Immediate	$Imm		Imm				Immedaite

Register	r		R[r]				Register

Memory		Imm		M[Imm]				Absolute
Memory		(r)		M[ R[r] ]			Indirect
Memory		Imm(b)		M[ Imm + R[b] ]			Base + Displacement
Memory		(b,i)		M[ R[b] + R[i] ]		Indexed
Memory		Imm(b,i)	M[ Imm + R[b] + R[i] ]		Indexed
Memory		(,i,s)		M[ R[i]*s ]			Scaled Indexed
Memory		Imm(,i,s)	M[ Imm + R[i]*s ]		Scaled Indexed
Memory		(b,i,s)		M[ R[b] + R[i]*s ]		Scaled Indexed
Memory		Imm(b,i,s)	M[ Imm + R[b] + R[i]*s ]	Scaled Indexed