1. CS 136 Lab 2 MIPS ISA SPIM

2. Prob 2.30 sll $a2, $a2, 2 sll $a3, $a3, 2 add $v0, $zero, $zero add $t0, $zero, $zero outer:add $t4, $a0, $t0 lw $t4, 0($t4) add $t1, $zero, $zero inner:add $t3, $a1, $t1 lw $t3, 0($t3) bne $t3, $t4, skip addi $v0, $v0, 1 skip: addi $t1, $t1, 4 bne $t1, $a3, inner addi $t0, $t0, 4 bne $t0, $a2, outer

3. Prob 2.31 add, addi, sll => 1 cycle lw, bne => 2 cycles For 2GHz CPU, how much time for 1 cycle.

4. Prob 2.33 x[4] = x[5] + a; Base addr for X = 6,400,000 ten a is stored in $t3 MIPS instruction (s)?

5. Prob 2.36 for (i=0; i<=100; i=i+1) {a[i] = b[i] + c;} How many memory data references will be made during execution? –load, store How many instructions are executed during the running of this code?

6. Prob 2.39 Suppose lb $s0, 100($zero) #byte@100= 0x0F? lb $s1, 200($zero) #byte@200= 0xFF What are the values of $s0 and $s1?

7. System Calls ServiceSystem call codeArgumentsResult print_int1$a0 = integer print_float2$f12 = float print_double3$f12 = double print_string4$a0 = string read_int5integer (in $v0) read_float6float (in $f0) read_double7double (in $f0) read_string8$a0=buffer,$a1=len sbrk9$a0 = amountaddress (in $v0) exit10

8. Exercise 1.text.globl main main: li $v0, 4 la $a0, str1 syscall li $v0, 5 syscall move $t0, $v0 #print out str2 #input second integer #move the input to $t1 #code start #code end move $t1, $v0 add $t2, $t0, $t1 #print out str3 and the sum #code start #code end.data str1:.asciiz "input first integer:" str2:.asciiz "input second integer:" str3:.asciiz "the sum is:"

9. General Purpose Registers (32) Reference: A-24 $at (1), $k0 (26), and $k1 (27): reserved for the assembler and operating system. $a0–$a3 (4–7) are used to pass the first four arguments to routines. $v0(2) and $v1(3) are used to return values from functions. –What else usage?

10. General Purpose Registers (32) Registers $t0–$t9 (8–15, 24, 25) are caller-saved registers that are used to hold temporary quantities that need not be preserved across calls. Registers $s0–$s7 (16–23) are callee- saved registers that hold long-lived values that should be preserved across calls. $gp (28), $sp (29), $fp (30), $ra (31) PCSPIM…

11. Source code format.text.globl main main: [#comment] [label:] opcode [op1],[op2],[op3].data str:.asciiz “string” integer:.word 0xaf,0xffff2,0x4233 … Reference: A-47

13. Load and Store li $t0, 5#load immediate la $t0, str#load address lw $t0, 8($sp) #load word lb $t0, ($s1) #load byte sb ‘a’, ($s0) #store byte sw $a0, 100($sp) #store word

14. Prob 2.39 test code.text.globl main main: lb $s0, bb1 lb $s1, bb2.data bb1:.byte 0x0F bb2:.byte 0xFF

15. Arithmetic Instruction add $t2, $t1, $t0# $t2 = $t1 + $t0 addi $t1, $t0, 5# $t1 = $t0 + 5 sub $t2, $t1, $t0# $t2 = $t1 - $t0 mul $t2, $t1, $t0# $t2 = $t1 * $t0 div $t2, $t1, $t0# $t2 = $t1 / $t0 If we multiply two 32 bit unsigned integers… what is the size in bits of the largest possible result?

16. #calculate W=A*X^2+B*X+C #asnser should be 180.text.globl main main: #code start #code end.data X:.word 7 A:.word 3 B:.word 4 C:.word 5 W:.word 0 ans:.asciiz "answer = "

17. pseudo-instruction Instructions provided by an assembler but not implemented in hardware. li $t0, 0x40044005 –lui $t0, 4004 –ori $t0, $t0, 4005 li $t0, 0x4005 –ori $t0, $t0, 4005 move $t1, $t2 mul $t2, $t2, $t3 –mult $t4, $t1 –mflo $t4 A-51

18. Branches j beq $t0, $t1, bne $t0, $t1, slt $t1, $t2, $t3 –if (t2<t3) then t1=1, else t1=0 slti $t1, $t2, 7 –if (t2<7) then t1=1, else t1=0

19. pseudo-instruction beq $t1, small, L –li $at, small –beq $t1, $at, L beq $t2, big, L –li $at, big –beq $at, $t2, L blt $t0, $t1, L –slt $at, $t0, $t1 –bne $at, $zero, L ble $t3, $t5, L –slt $at, $t5, $t3 –beq $at, $zero, L

20. Branch Example.text.globl main main: la $t2, str li $t1, 0 nextch: lb $t0, ($t2) beqz $t0, strend add $t1, $t1, 1 add $t2, 1 j nextch strend: move $a0, $t1 li $v0, 1 syscall.data str:.asciiz "hello world!"

21. Exercise.text.globl main main: #swap all of ‘a’ from str to ‘A’ #code begin #code end strend: la $a0, str li $v0, 4 syscall.data str:.asciiz "aabbbababababbaaaabbaa"

22. void main() { char str[] = "aabbbababababbaaaabbaa"; char* t2 = str; char t1 = 'A'; char t0; do { t0 = *t2; if(t0 == 0) break; if(t0 == 'a') *t2 = t1; t2++; }while(1); printf("%s\n", str); }

23. Exercise.text.globl main main: #load the address of string to $t2 #load ‘A’ to $t1 nextch: #load byte from address ($t2) to $t0 #branch to strend if $t0 = 0 #branch to nota if $t0 != 'a' #store byte $t1 to address ($t2) nota: increment $t2 by 1 jump to nextch strend: la $a0, str li $v0, 4 syscall.data str:.asciiz "aabbbababababbaaaabbaa"

24. Booth’s Algorithm Case #Bits Instected Action performed 00 0 0>>2 10 0 1+m’cand & >>2 20 1 0+m’cand & >>2 30 1 1+2*m’cand & >>2 41 0 0-2*m’cand & >>2 51 0 1-m’cand & >>2 61 1 0-m’cand & >>2 71 1 1>>2