[PowerPC] Calling a Function

//Tutorial by Bad Luck Brian

Calling a function


in C# we call our functions like this: Example(arg1, arg2, arg3);
example: MessageBox.Show("Bad Luck Brian", "title here");

in powerpc its a bit more complicated but its still simple ^^

we will use 'bl'

bl is like 'b', it jumps to a location but bl will continue to the next line with the returned value

example of 'b'

:0 li r3, 0x15
:1 b 6
:2 //Not executed
:3 //Not executed
:4 //Not executed
:5 //Not executed
:6 //stuff goes here, its a function..executed


:0 li r3, 0x15
:1 bl :6 //goto :6 and when done with it continue at :2
:2 // executed
:3 // executed
:4 // executed
:5 // executed
:6 //executed


calling functions in powerpc is a must and we will use it really often.
i will make some examples later on calling functions


There is another way of calling functions, we will use pointers.

we use mtctr and bctrl

we use mtctr like this:

mtctr REGISTER

Register = register containing the address to call

and to call it we just use bctrl


example:

Code:
//0x2100000 contains:  00 12 34 56   (0x123456),
//0x123456 = function i wanna call

lis r3, 0x210   //loads the address: 0x2100000 in r3
lwz r3, r3        //read at: 0x2100000  and store the value in r3 (4 bytes)
mtctr r3           //store r3 in the count register
bctrl               //call the value in the count register