question how do I add this R0 <- c ?

Question

Question:
a = 5;
b = 10;
c;
//Create the assembly code to translate the following if statement
if ( a <= b )
{
c = a + b -3;
}
R0 <- c

AREA | .text | , CODE, READONLY
EXPORT __main

a EQU 0x20000000
b EQU 0x20000004
c EQU 0x20000008

__main
; a = 5
MOVS R0, #5
LDR R7, =a ;first address in SRAM
STR R0, [R7]
;b = 10
MOVS R1, #10
LDR R7, = b
STR R1, [R7]

; if a<=b
; then c = a+b -3
LDR R7, = a
LDR R0, [R7]
CMP R0, R1 ; if R0 is equal or less

; if it flags then jump if not do the condition c = a + b -3;
BNE endif1 ; branch not equal
;write the condition
LDR R7, =a ; load the value of a
LDR R0, [R7]
LDR R7, =b ; load the value of b
LDR R1, [R7]
ADDS R0, R1 ; a+b

SUBS R0, #3 ; (a+b) - 3
LDR R7, =c ; store result in c
STR R0, [R7]

endif1

done
B done
END

Answer 1

It should already end with c in R0, but there is a logic error that causes the program to skip the calculation and exit with 5 in R0.

Fix this conditional:
BNE endif1 ;branch not equal

It should be:
  BGT endif1    ; branch if greater than

Also, it is unnecessary to reload variable a into R0 right before the CMP because R0 still holds the value 5 from when it stored it in a. So,

LDR R7, = a
LDR R0, [R7]
CMP R0, R1

can be reduced to

CMP R0, R1

Likewise, for the addition of (a+b), the values are already in registers R0 and R1, respectively. I think you can cut out the four LDR instructions before the ADDS R0, R1 instruction.

To ensure R0 holds c for different a and b input values wherein execution skips the calculation, insert LDR R7, =c and LDR R0, [R7] after label endif1.

If there is no further requirement to use a, b, and c then ultimately you could eliminate their allocated variable space and remove all LDR R7,* and STR instructons. All calculations would be done in the registers only.