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Re: Apple's -fast option for gcc
On Tue, Sep 16, 2003 at 10:22:56PM -0500, Bradley Lucier wrote:
>
> On Tuesday, September 16, 2003, at 09:05 PM, Alan Modra wrote:
>
> >On Tue, Sep 16, 2003 at 02:30:36PM -0500, Bradley Lucier wrote:
> >>-malign-natural
> >
> >Be cautious with this one. It may affect structure layout.
>
> Aahhh. So is -fast good for anything beside running standalone
> programs that must go really, really fast?
Well, the structure layout change only affects structures and unions
that contain doubles. If you don't have any of these in what you're
compiling, then you're OK. An example of a struct that changes is:
struct A { int i; double d; };
which is 12 bytes without, and 16 bytes with -malign-natural.
--
Alan Modra
IBM OzLabs - Linux Technology Centre