Question

Find the shortest sequence of MIPS instructions that extracts bits 16 down to 11 from register \(t0 and uses the value of this field to replace bits 31 down to 26 in register \)t1 without changing the other 26 bits of register $t1.

Short answer

MIPS instructions that extract bits 16 down to 11 from $t0 and uses the value to replace bits 31 down to 26 in $t1 is as follows:

srl $t0,$t0,11

sll $t0,$t0,26

ori $t2,$0,0x03ff

sll $t2,$t2,16

ori $t2,$t2,0xffff

and $t1,$t1,$t2

or $t1,$t1,$t0

Step-by-step solution

Define MIPS instructions.

The MIPS assembly language use 32 registers, namely $s0-$s7 and $t0-$t9, $zero, $a0-$a3 etc. MIPS uses byte addresses, that allow memory to hold data structures, arrays, and registers. MIPS logical shift instructions will shift the bits in the registers to right and left and perform logical operations.

Determine the MIPS instruction

srl $t0,$t0,11

sll $t0,$t0,26

ori $t2,$0,0x03ff

sll $t2,$t2,16

ori $t2,$t2,0xffff

and $t1,$t1,$t2

or $t1,$t1,$t0

Explanation:

For a register, there exist 32 bits by default. Now to extract bits 16 down to 11 from register $t0, shift the bits to the right to 11. Then the shift left to 26 which makes the 16 bits down to 11.

Then the logical OR will be done with the immediate value of 0x03ff with 0 and store the result at $t2.Now, shift left 16 on $t2 and perform logical OR operation with immediate 0xffff. Now perform AND on $t1,$t2 and store on $t1. Finally, $t1 and $t0 will be performed with OR and store the result to $t1.