Why doesn't code branch at BEQ after MOVS

Id really appreciate if somebody could help me.

Why doesn't code branch on the first reading of BEQ, if comparing r2 with r2. Apparently the final value in r0 is 0X0000001B. Thank you so much, im very confused and frustrated running this over and over in Keil.

    MOV r0,#1
    MOV r1, #0X3
    MOV r2,#0X3
    MOVS r2,r2
 while  
    BEQ stop    
    MUL r0,r1,r0
    SUBS r2,r2,#1
    B while

stop

Your code doesn't branch because BEQ test if Z flag is equal to 1.

• MOVS will set Z to 1 if you MOV r2, #0, or register which has a value of 0.

• If you want to set the Z flag to 1, you can use CMP to check the flags N and Z. Such will do R2-R2 = 0, Z=1

    MOV r0,#1
    MOV r1, #0X3
    MOV r2,#0X3
    CMP r2,r2
   while  
    BEQ stop    
    MUL r0,r1,r0
    SUBS r2,r2,#1
    B while
   stop  
  

• Another, less efficient method would be to use another register with SUBS, setting all the flags (NZCV).

    MOV r0,#1
    MOV r1, #0X3
    MOV r2,#0X3
    SUBS r3, r2,r2
   while  
    BEQ stop    
    MUL r0,r1,r0
    SUBS r2,r2,#1
    B while
   stop  
  

Good luck!