On Wed, Jun 07, 2006 at 05:17:39PM -0500, Menezes, Evandro wrote: > > > > We have several choices for stack alignment requirement > > > > > > > > 1. Leave it unchanged. Gcc can do > > > > a. Nothing. Let the program crash. > > > > b. Align stack to 16byte if XMM registers are used locally and > > > > aren't passed down as function arguments. > > > > > > Why not so if the XMM registers are passed down as arguments? > > > > When calling a function with XMM register arguments, doesn't caller > > have to align stack to 16byte for callee? > > Not necessarily, I think. Just like the caller aligned its stack to 16 > bytes, the callee can do the same while still assuming the 4-byte alignment. > And it's an even lesser problem with -msseregparm or the sseregparam > attribute.
How are XMM arguments passed by default? What happens when there are more 16 XMM parameters? Is XMM supported with variable argument list? H.J.
