MIPS Instruction Set

contents) into register load immediate li $1,100. $1=100. Pseudo-instruction (provided by assembler, not processor!) Loads immediate value into register

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1 MIPS Instruction Set Arithmetic Instructions Instruction Example Meaning Comments add add $1,$2,$3 $1=$2+$3 subtract sub $1,$2,$3 $1=$2 – $3 add immediate addi $1,$2,100 $1=$2+100 “Immediate” means a constant number add unsigned addu $1,$2,$3 $1=$2+$3 Values are treated as unsigned integers, not two’s complement integers subtract unsigned subu $1,$2,$3 $1=$2 – $3 Values are treated as unsigned integers, not two’s complement integers add immediate unsigned addiu $1,$2,100 $1=$2+100 Values are treated as unsigned integers, not two’s complement integers Multiply (without overflow) mul $1,$2,$3 $1=$2*$3 Result is only 32 bits! Multiply mult $2,$3 $hi,$low= $2*$3 Upper 32 bits stored in special register hi Lower 32 bits stored in special register lo Divide div $2,$3 $hi,$low=$2/$3 Remainder stored in special register hi Quotient stored in special register lo

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MIPS Instruction Set 2 Logical Instruction Example Meaning Comments and and $1,$2,$3 $1=$2&$3 Bitwise AND or or $1,$2,$3 $1=$2|$3 Bitwise OR and immediate andi $1,$2,100 $1=$2&100 Bitwise AND with immediate value or immediate or $1,$2,100 $1=$2|100 Bitwise OR with immediate value shift left logical sll $1,$2,10 $1=$2<<10 Shift left by constant number of bits shift right logical srl $1,$2,10 $1=$2>>10 Shift right by constant number of bits Data Transfer Instruction Example Meaning Comments load word lw $1,100($2) $1=Memory[$2+100] Copy from memory to register store word sw $1,100($2) Memory[$2+100]=$1 Copy from register to memory load upper immediate lui $1,100 $1=100×2^16 Load constant into upper 16 bits. Lower 16 bits are set to zero. load address la $1,label $1=Address of lab el Pseudo – instruction (provided by assembler, not processor!) Loads computed address of label (not its contents) into register load immediate li $1,100 $1=100 Pseudo – instruction (provided by assembler, not processor!) Loads immediate value into register

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MIPS Instruction Set 3 move from hi mfhi $2 $2=hi Copy from special register hi to general register move from lo mflo $2 $2=lo Copy from special register lo to general register move move $1,$2 $1=$2 Pseudo – instruction (provided by assembler, not processor!) Copy from register to register. Conditional Branch Instruction Example Meaning Comments branch on equal beq $1,$2,100 if($1==$2) go to PC+4+100 Test if registers are equal branch on not equal bne $1,$2,100 if($1!=$2) go to PC+4+100 Test if registers are not equal branch on greater than bgt $1,$2,100 if($1> $2) go to PC+4+100 Pseduo – instruction branch on greater than or equal bge $1,$2,100 if($1>=$2) go to PC+4+100 Pseduo – instruction branch on less than blt $1,$2,100 if($1<$2) go to PC+4+100 Pseduo - instruction branch on less than or equal ble $1,$2,100 if($1<=$2) go to PC+4+100 Pseduo - instruction PAGE - 4 ============ MIPS Instruction Set 4 Comparison Instruction Example Meaning Comments set on less than slt $1,$2,$3 if($2<$3)$1=1; else $1=0 Test if less than. If true, set $1 to 1. Otherwise, set $1 to 0. set on less than immediate slti $1,$2,100 if($2<100)$1=1; else $1=0 Test if less than. If true, set $1 to 1. Otherwise, set $1 to 0. Unconditional Jump Instruction Example Meaning Comments jump j 1000 go to address 1000 Jump to target address jump register jr $1 go to address stored in $1 For switch, procedure return jump and link jal 1000 $ra=PC+4; go to address 1000 Use when making procedure call. This saves the return address in $ra System Calls Service Operation Code (in $v0) Arguments Results print_int Print integer number (32 bit) 1 $a0 = integer to be printed None print_float Print floating - point number (32 bit) 2 $f12 = float to be printed None print_double Print floating - point number (64 bit) 3 $f12 = double to be printed None PAGE - 5 ============ MIPS Instruction Set 5 print_string Print null - terminated character string 4 $a0 = address of string in memory None read_int Read integer number from user 5 None Integer returned in $v0 read_float Read floating - point number from user 6 None Float returned in $f0 read_double Read double floating - point number from user 7 None Double returned in $f0 read_string Works the same as Standard C Library fgets() function. 8 $a0 = memory address of string input buffer $a1 = length of string buffer (n) None sbrk Returns the address to a block of memory containing n additional bytes. (Useful for dynamic memory allocation ) 9 $a0 = amount address in $v0 exit Stop program from running 10 None None print_char Print character 11 $a0 = character to be printed None read_char Read character from user 12 None Char returned in $v0 exit2 Stops program from running and returns an integer 17 $a0 = result (integer number) None Assembler Directives Directive Result .word w1, , wn Store n 32 - bit values in successive memory words .half h1, , hn Store n 16 - bit values in successive memory words .byte b1, , bn Store n 8 - bit values in successive memory words PAGE - 6 ============ MIPS Instruction Set 6 .ascii str Store the ASCII string str in memory. Strings are in double - quotes, i.e. "Computer Science" .asciiz str Store the ASCII string str in memory and null - terminate it Strings are in double - quotes, i.e. "Computer Science" .space n Leave an empty n - byte region of memory for later use .align n Ali gn the next datum on a 2^n byte boundary. For example, .align 2 aligns the next value on a word boundary Registers Register Number Register Name Description 0 $zero The value 0 2 - 3 $v0 - $v1 ( v alues) from expression evaluation and function results 4 - 7 $a0 - $a3 ( a rguments) First four parameters for subroutine 8 - 15, 24 - 25 $t0 - $t9 T emporary variables 16 - 23 $s0 - $s7 S aved values representing final computed results 31 $ra R eturn a ddress 62 KB – 6 Pages