how do I implement a jump address table in MIPS64? [duplicate] - mips

Question

C++ Program
# include < iostream >
# include <string >
using namespace std;
int main ()
{
int resistance ; // in Ohms
string partNum ; // Part Number
cout << " Enter resistance : " << endl ;
cin >> resistance ;
switch ( resistance )
{
case 3 : partNum = " OD30GJE "; break ;
case 10 : partNum = " OD100JE "; break ;
case 22 : partNum = " OD220JE "; break ;
default : partNum = "No match "; break ;
}
cout << " Part number : " << partNum << endl ;
return 0;
}
Translate the C code to MIPS assembly code, add to your code the capability to match the closest resistor. Be sure to use the jr instruction for the switch statement. Have your code get the resistance as input from the user and display to the console the resistor's corresponding or closest part number.
Mips Assembly Code
.data
int_value: .space 20
.align 2
input: .asciiz "Enter resistance.\n" # declaration for string variable,
string1: .asciiz "OD30GJE\n" # declaration for string variable,
string2: .asciiz "OD100JE\n"
string3: .asciiz "OD220JE\n"
string11: .asciiz "No Match\n"
string12: .asciiz "Enter resistance\n"
.text
main:
li $v0, 4
la $a0, input # print for input
syscall
la $t0, int_value
li $v0, 5 # load appropriate system call code into register $v0;
syscall # call operating system to perform operation
sw $v0, int_value # value read from keyboard returned in register $v0;
# store this in desired location
lw $s1, 0($t0)
condition1:
slt $t1, $s1, $zero # if $s1 < 0 $t1 = 1 else $t1 = 0
beq $t1, $zero, condition2 # if $t1 = 0; InvalidEntry
bne $t1, $zero, invalid_entry
condition2:
sgt $t1, $s1, -1 # if $s1 > -1 then $t1 = 1 else $t1 = 0
beq $t1, $zero, invalid_entry # if $t1 = 0; InvalidEntry
sgt $t1, $s1, 9 # if s1 > 9 t1 = 1 else $t1 = 0
bne $t1, $zero, condition3 # if $t1 does not equal = 0; condition3
li $v0, 4
la $a0, string1
syscall
j exit
condition3:
sgt $t1, $s1, 9 # if $s1 > 9 then $t1 = 1 else $t1 = 0
beq $t1, $zero, invalid_entry # if $t1 = 0; InvalidEntry
sgt $t1, $s1, 21 # if s1 > 21 t1 = 1 else $t1 = 0
bne $t1, $zero, condition3 # if $t1 does not equal = 0; condition3
li $v0, 4
la $a0, string2
syscall
j exit
invalid_entry:
li $v0, 4
la $a0, string11
syscall
j exit
exit:
li $v0, 10 # v0<- (exit)
syscall

Answer 1

The following shows how to make a jump table. The offset within the jump table is assumed to be in $s1. $s1 must be a multiple of 4 (i.e. a byte offset).
This code has not been tested!
. . . .
b 1f # jump past the jump table
nop # branch delay slot
# table of jump addresses
JTAB: .word LABEL1
.word LABEL2
.word LABEL3
1: la $t0, JTAB # load start address of the jump table
add $t0, $t0, $s1 # add offset to table address
lw $t1, 0($t0) # load the address stored at JTAB + $s1
jr $t1 # and jump to that address
nop # branch delay slot
LABEL1: # do something
b 2f # break
nop
LABEL2: # do something else
b 2f # break
nop
LABEL3: # do a different thing
b 2f # break
nop
2: # after the end of the "case statement"