Problem with Keil

Sorry, i need to do the next c function in asm

;int atoi (char *string){
;       int i;
;       int tmp;
;       int dato;
;       dato = 0;
;       for (i=0; i<=4; i++){
;               tmp=*(string+i);
;               if (tmp=='\0' || tmp=='\r'){
;                       return dato;
;               }
;               else{
;                       if ((tmp>=48) && (tmp<=57)){
;                               tmp=tmp-48;
;                       }
;                       else{
;                               return 0;
;                       }
;                       dato=dato*10+tmp;
;               }
;       }
;       return dato;
;}

This is my implementation...

        AREA    ATOI2,CODE,READONLY
        EXPORT  ATOI

ATOI    STMFD   sp!,{R4,lr}
        MOV     R1,#5
        MOV     R4,#10
        MOV     R3,#0
INICIO  LDRB    R2,[R0],#1
        CMP     R2,#&D      ;D ==> \r
        BEQ     SALIR
        CMP     R2,#0   ;0 ==> \0
        BEQ     SALIR
        CMP     R2,#48
        BCC     SINO
        CMP     R2,#57
        BHI     SINO
        SUB     R2,R2,#48
        ;MLA    R3,R3,R4,R2   ;Keil error
        MUL     R3,R3,R4      ;Keil error
        ADD     R3,R3,R2
        SUB     R1,R1,#1
        CMP     R1,#0
        BNE     INICIO
        B       SALIR
SINO    MOV     R3,#0
SALIR   MOV     R0,R3
        LDMFD   sp!,{R4,pc}
        END

And the error is...
atoi.s(46): error: A1477W: This register combination results in UNPREDICTABLE behaviour

i need to do the next c function in asm

No, you don't. You may believe you need that, but you don't. You just need to compile it. That's what you have a compiler for.

Now, some highly skilled people might be able to improve over what the compiler generates for this function. But you're rather obviously not anywhere near that skill level, yet.

the poor man only wants to write a little assembly - let's help him a little!

are you using thumb mode, not ARM? if so, that might limit your access to SP. what happens if you compile this code in ARM mode? also, are you sure that you have copy-pasted the exact code you are using?

"You may believe you need that, but you don't."

Actually, he might "need" it in that his homework assignment is, "create an assembler function that performs the equivalent of the standard atoi library function".

;-)

Other than that, I agree!

have you tried to compare your implementation with the code generated via compiler optimization level 0?

"This register combination results in UNPREDICTABLE behaviour"

So, have you consulted the ARM documentation to see which register combinations are acceptable?

Thanks for help...

I don't using Thumb mode and yes, I has consulted the ARM documentation and its say that only i don't use r15...

Looking for error in documentation says

For ARM: Warning: A1786W: This instruction using SP is deprecated in ARMv7
For Thumb: Error: A1477W: This register combination results in UNPREDICTABLE behaviour

But i use the arm mode, not thumb mode... (this is in options for target,target,code generation => ARM Mode)

this is in options for target,target,code generation => ARM Mode

And how likely, do you think, is it that this option has any effect on an assembler source file?

I do not understand your question ... I am using Microvision 4 and not let me use either the MUL or MLA instruction, anyone can tell me why?

Hans means that your code is not generated by the compiler. it is already in assembly, thus this particular setting has no effect on it.

anyone can tell me why?

It's because in contrast to your statement, you rather obviously are using Thumb mode --- otherwise you wouldn't be getting a Thumb-only error message.

It's clear you don't know how you ended up in Thumb mode, but there you are.

All of this only strengthens my argument that at least right now you need to not do this in assembly. You need to learn the tools first, and you need to learn the finer points of ARM and Thumb assembly language. By then you hopefully will have learned how to decide what should be done in assembly and what shouldn't.

Real ARM programmers assemble it themselves.