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MIPS Instructions and System Calls for CPU Management

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Learn about MIPS ISA instructions, CPU cycles, memory operations, and system calls for efficient CPU management in assembly programming.

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MIPS Instructions and System Calls for CPU Management

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  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 = 6,400,000ten • 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

  8. Exercise 1 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:" .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

  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

  12. 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

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

  14. 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?

  15. #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 = "

  16. 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

  17. Branches • j <addr> • beq $t0, $t1, <addr> • bne $t0, $t1, <addr> • 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

  18. 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

  19. 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!"

  20. 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"

  21. 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); }

  22. 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"

  23. Booth’s Algorithm

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