Mov value on floating point register to general register - c

Question

So I am using the instruction "fmov x0,d3" to move the value from d3 to x0, but for some reason the value on x0 remains unchanged.
Can someone, please, tell me how to properly move a value from a floating point register to a general register?
This is my code:
mov x0,#6 //Moves the decimal 0 value to the x0 register, which is the return register
Fadd_test_64:
fmov d1, #7.0 //Moves floating point value to the d1 register
fmov d2, #2.0
fmov d4, #14.0 //Moves the expected result to d4
fadd d3,d1,d2 //d3=d1+d2
fcmp d3, d4 //Compares w3 to w4
b.ne Fadd_error_64 //if they are different, go to Fadd_error_64
b Fadd_end_64 //if not, go to Fadd_end_64
Fadd_error_64:
fmov x0,d3 //Moves the value on the floating point register to the return register
Fadd_end_64:
ret
//Functions declaration
void mathTest_64bits(void);
UINT16 FAddition_64();
//Main function
int main(void)
{
mathTest_64bits();
return 0;
}
//Functino in C to run the assembly code
void mathTest_64bits(void)
{
int ret;
ret = FAddition_64();
if(ret!=0)
{
Print(L"64-bits Floating Point Addition test: Failed: %d",ret);
}
else
{
Print(L"64-bits Floating Point Addition test: Success ");
}
Print(L"\n");
}