Hello,

I came across these two inline assembly functions below that are not being compiled with the online compiler. Hence I tried to rewrite them as an s-File following this Cookbook answer.
But I am not quite experienced with assembly and sure about how to pass the parameters and if the result is returned correctly.

I'd appreciate it, if someone could have a look at it :)

Thank you very much in advance,
Moritz

Edit: Sorry, I just saw, that this question fits maybe better to the "Hello World!"-forum?!

static __inline__ int MULSHIFT32(int x, int y)
{
int zlow;
__asm__ volatile ("smull %0,%1,%2,%3" : "=&r" (zlow), "=r" (y) : "r" (x), "1" (y) : "cc");
return y;
}

  AREA asm_func, CODE, READONLY
; Export my_asm function location so that C compiler can find it and link
    EXPORT MULSHIFT32
MULSHIFT32
;
; ARM Assembly language function to describe the following inline assembly function:
;
; function call: extern "C" static int MULSHIFT32(int x, int y);
; --> R0 = x; R1 = y;
;  smull RdLo, RdHi, Rn, Rm [:= RdHi, RdLo = Rn * Rm]
; return RdHi
; 
; calculate Signed MULtiply Long
        SMULL R1, R0, R0, R1
; Return to C using link register (Branch and change instruction set)
	BX   LR
        END

typedef union _U64
{
	long long w64;
	struct{
		unsigned int lo32;
		signed int hi32;
	} r;
} U64;
static __inline long long MADD64(long long sum64, int x, int y)
{
	U64 u;
	u.w64 = sum64;
	__asm__ volatile ("smlal %0,%1,%2,%3" : "+&r" (u.r.lo32), "+&r" (u.r.hi32) : "r" (x), "r" (y) : "cc");
	return u.w64;
}


  AREA asm_func, CODE, READONLY
; Export my_asm function location so that C compiler can find it and link
    EXPORT MADD64
MADD64
;
; ARM Assembly language function to describe the following inline assembly function:
;
; function call: extern "C" static long long MADD64(long long sum64, int x, int y)
; --> R0, R1 = sum64 (R0 = lo32, R1 = hi32); R2 = x, R3 = y;
;  smlal RdLo, RdHi, Rn, Rm [:= RdHi,RdLo = signed(RdHi,RdLo + Rm * Rs)]
; return RdLo, RdHi
; 
; calculate Signed MuLtiply and Accumulate Long
	SMLAL R0, R1, R2, R3
; Return to C using link register (Branch and change instruction set)
	BX    LR
        END

Looks okay to me. Are there errors when compiling? Note that you can just use 64-bit vars in your program. It's very likely the compiler will use these instructions for matching operations.

Thank you for your reply.
64-bit variables are fine. I suppose there aren't any longer ones.

Edit: Ah, yes it is compiling fine. I was just unsure if there could happen any errors with wrong register etc. :)

One question still remains. There is no chance to keep these functions inline, isn't it?