Helix mp3 end Keil

I work with the STM32F407 board I want to make an MP3 player there are good examples on the internet, The problem is that I cannot compile helix library to decode mp3 files in keil due to the fact that there are some functions in assembler, I think the options are to encode this function in C or compile assembler in keil.
Someone can code this function in C !!

MADD64(sum, x, y)   (Windows only) sum [64-bit] += x [32-bit] * y [32-bit]

typedef union _U64 {
Word64 w64;
struct {
/ * ARM ADS = little endian * /
unsigned int lo32;
signed int hi32;
} r;
} U64;

static __inline Word64 MADD64 (Word64 sum64, int x, int y)
{
U64 u;
u.w64 = sum64;

__asm__ volatile ("smlal% 0,% 1,% 2,% 3": "+ & r" (urlo32), "+ & r" (urhi32): "r" (x), "r" (y): "DC");

return u.w64;
}