> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of > Dave Korn > Sent: Friday, May 11, 2007 11:32 AM > To: 'Paul Brook'; gcc@gcc.gnu.org > Cc: 'Mohamed Shafi'; 'Andrew Haley' > Subject: RE: Updating an operand in RTL for a builtin function > > > On 11 May 2007 19:27, Paul Brook wrote: > > >>> > 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 ; > > > > Why do you want this to happen? > > I think what he means is he wants operand 3 and operand > zero to be placed in > the same register, hence the "0" constraint. As to quite why it's not > working, I don't know. A very similar pattern, only with > "=&" modifiers on > operand zero, works fine for me under 3.4.4. > > > cheers, > DaveK > -- > Can't think of a witty .sigline today.... > >
> >>> > result = __macf(operand1, operand2, operand3); > Since operand3 is passed by value, operand3 should not be changed for the above code. Could you re-write your code as this: "operand3 = __macf(operand1, operand2, operand3);" ? Then, operand3 will be updated. Regards, Chaoy-ing
