MatMul

    AREA    MatMul, CODE, READONLY
    IMPORT  main
    EXPORT  start

start
    LDR R0, =matR
    LDR R1, =matA
    LDR R2, =matB
    ;LDR    R3, =N
    ;LDR R3, [R3]
    LDR R3, =4              ; N

    LDR R4, =0              ; i
    LDR R5, =0              ; j
    LDR R6, =0              ; k

    LDR R7, =0              ; r(esult)
    LDR R8, =0              ; value A
    LDR R9, =0              ; value B
    LDR R10, =0             ; temporary index

iFor
    CMP R4, R3              ; while (i < N)
    BEQ endIFor             ; {
    LDR R5, =0              ;   j =0

jFor
    CMP R5, R3              ;   while (j < N)
    BEQ endJFor             ;   {
    LDR R6, =0;             ;       k = 0
    LDR R7, =0;             ;       reset (r)esult
kFor
    LDR R10, =0             ;       clear temporary value
    CMP R6, R3              ;       while (k < N)
    BEQ endKFor             ;       {

    ; value in a
    MUL R10, R4, R3         ;           index = (row*row size)
    ADD R10, R10, R6        ;                    +  column
    MUL R10, R3, R10
    ;LDR R8, [R1, R10, LSL #2] ;            address = base address + offset
    LDR R8, [R1, R10] ;         address = base address + offset
    ; value in b
    MUL R10, R6, R3         ;           index = (row*row size)
    ADD R10, R10, R5        ;                    +  column
    MUL R10, R3, R10
    ;LDR R9, [R2, R10, LSL #2] ;            address = base address + offset
    LDR R9, [R2, R10] ;         address = base address + offset

    MUL R11, R8, R9         ;           mul = a*b
    ADD R7, R7, R11         ;           r = r + mul
    ADD R6, R6, #1          ;           k++
    B kFor                  ;       }

endKFor
    ; index in R
    MUL R10, R4, R3         ;           index = (row*row size)
    ADD R10, R10, R5        ;                    +  column
    MUL R10, R3, R10
    ;STR R7, [R0, R10, LSL #2] ;            store result in (address = base address + offset)
    STR R7, [R0, R10] ;         store result in (address = base address + offset)
    ADD R5, R5, #1          ;           j++
    B jFor                  ;   }

endJFor
    ADD R4, R4, #1          ;   i++
    B iFor                  ; }

endIFor

stop    B   stop


    AREA    TestArray, DATA, READWRITE

N   EQU 4

matA
    DCD 5,4,3,2
    DCD 3,4,3,4
    DCD 2,3,4,5
    DCD 4,3,4,3

matB
    DCD 5,4,3,2
    DCD 3,4,3,4
    DCD 2,3,4,5
    DCD 4,3,4,3

matR    SPACE   64

    END