Updating an operand in RTL for a builtin function

[Mohamed Shafi]

On 5/4/07, Andrew Haley <aph-gcc@littlepinkcloud.com> wrote:
> Mohamed Shafi writes:
>
>  > I am trying to implement a builtin function __macf for a private target.
>  > I have added the required target hooks for this.
>  > Say for the following code
>  >
>  > int main()
>  > {
>  >   int operand1 = 2;
>  >   int operand2 = 3;
>  >   int operand3 = 4;
>  >   int result;
>  >
>  >    /* operand3 = operand3 + (operand1 * operand2)*/
>  >
>  >   result = __macf(operand1, operand2, operand3);
>  >
>  > }
>  >
>  > Requirement :  I need the value of operand3 and result to be same
>  > after calling the builtin.
>  > But this is not happening.
>
> What do you mean, exactly?  C only has call by value, and gcc's
> builtins can only return one value.  Builtins don't change their
> arguments.  If you want to update one of the arguments you'll have to
> pass a pointer to the builtin.
>
 After the builtin i want to have the following operations also to carried out
operand3 = result ;
Since builtins don't change their arguments and since i don't want to
pass the pointers, i will have to write some kind of wrapper function
to do that. Where should i be doing this? in target_expand_builtin
function ? or should it be done in the backend patten of macf builtin
?

Thanks in advance.

Regards,
Shafi