[sdiy] help...no make8() function in Arduino...converting PIC to AVR

[Olivier Gillet]

There's a cost associated to calling "proper" functions - parameters
being pushed to the stack or moved to the right register, then a jump,
the body of the function, a return, and moving the result from the
output register to whatever register the result should be in. You
don't want such small things to be functions - and that's probably why
they were defined as macros in the first place! So you either have to
define those as macro ; or as inline functions, using something like
__attribute__((always_inline)) in the declaration. gcc might be smart
enough to inline them without being forced to do so with the
__attribute__, but it's not a very good thing to make such
assumptions.

Olivier

On Wed, Apr 11, 2012 at 6:47 PM, dan snazelle <subjectivity at hotmail.com> wrote:
> ok so if
>
>
>  make8  = (((var >> (offset*8)) & 0xff)
>  _mul  value = (int)( a1*val1>>8);
>
>
>
> then since i dont quite understand the parentheses in define I could make 2 functions
>
>
>
> byte make8(int var, byte offset)
> {
> byte result=(((var >> (offset*8)) & 0xff);
> return result;}
>
>
>
> and for the other function  (_mul)
>
>
> int _mul (byte a1, byte val) {
>
> int result=(int)( a1*val1>>8);
> return result;
> }
>
>
>
> do those look right?
>
>
> thanks
>
>
>
>
>
> On Apr 11, 2012, at 12:00 PM, Martin Klang wrote:
>
>>
>> what do they do on the pic?
>>
>> make8 I found in the PIC C Compiler Reference:
>> i8 = MAKE8(var, offset)
>> Same as: i8 = (((var >> (offset*8)) & 0xff)
>>
>> so that
>>> tmpbyte1 = make8(tmp1, 1);
>>
>> would be
>> tmpbyte1 = (tmp1 >> 8) & 0xff;
>>
>> and _mul() multiplies, right?
>>
>> Looks like the code is specifically optimised for the pic instructions set -
>> tmp1 is 16 bit, right? acc1 and val1 8-bit unsigned integers?
>>
>> Presumably you can replace the two lines with
>> uint8_t value = (uint8_t)( acc1*val1>>8);
>> depending on data types, but would have to see some more code to know.
>>
>>
>> hth,
>>
>> /m
>>
>> On 11 Apr 2012, at 16:25, dan snazelle wrote:
>>
>>> can someone help me ?
>>>
>>> i am trying to convert some PIC code to AVR
>>>
>>> it is going fine except for 2 things
>>>
>>> there is no make8() function and there is no _mul()
>>>
>>>
>>> so code lines like this:
>>>
>>>
>>> tmp1 = _mul (acc1, val1);
>>>
>>> tmpbyte1 = make8(tmp1, 1);
>>>
>>>
>>> do not work
>>>
>>>
>>>
>>> i have been looking for the make8 function online so i can just write that function into my code but no luck
>>>
>>>
>>> thanks for any help!
>>
>>
>
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