# Lab1: R32I Simulator
###### tags: `RISC-V`

[Ripes](https://github.com/mortbopet/Ripes) is a graphical 5-stage RISC-V pipeline simulator & assembly editor.

Definition of lucas number : https://en.wikipedia.org/wiki/Lucas_number


Breifly, I set n = 7 in this sample to practice iterative loop in risc-v implementation.

we got 2 ALU, left is for program count, left is for branch intruction, and the mux int the leftest is to choose hump or not.
And we got an imm part, it is for we call a data such as addi, subi, which is not in memory.
and we got two mux, the up one is for choosing write back or reg1, down on is for reg2 for instead.
and the unequal part is for comparing, for branch.


EX
we got 4 muxs,left 2 muxes are about forwarding, we can choose data from reg or forwarding.
right two muxes are for choosing data from re1 or reg2.

MEM
mux is for forwarding mechanism.

WB
mux is for choosing data from memory, alu or reg.

#include<stdio.h>

int main() {
    int n = 7, a1 = 2, a2 = 1, tmp;
    for(int i = 0; i<n-2; i++){
        tmp = a1 + a2;
        a1 = a2;
        a2 = tmp;
    }
    return a2;
}

.data
argument: .word 7 # Number to find the lucas number value of
str1: .string "lucus number of "
str2: .string " is "

.text
main:
        lw       a0, argument   # Load argument from static data
        mv       a1, a0
        li       a2, 0
        li       a3, 0
        jal      ra, iter       
        ecall
back:
        # Print the result to console
        mv       a1, a0
        #mv       a2, zero
        #mv       a3, zero
        lw       a0, argument
        jal      ra, printResult
        ecall

        # Exit program
        li       a0, 10
        ecall

iter:
        li       a2, 2
        li       a3, 1
        bgt      a2, a1, exit
        addi     a1, a1, -1
        jal      for
        #ecall
exit:
        bnez     a1, zeta
        mv       a4, a3
        ret
zeta:
        mv       a4, a2
        ret
for:
        add      a4, a2, a3
        mv       a2, a3
        mv       a3, a4
        addi     a1, a1, -1
        bne      a1, zero, for
        jal      back


# expects:
printResult:
        mv       t0, a0
        mv       t1, a4

        la       a1, str1
        li       a0, 4
        ecall

        mv       a1, t0
        li       a0, 1
        ecall

        la       a1, str2
        li       a0, 4
        ecall

        mv       a1, t1
        li       a0, 1
        #ecall

        ret