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