Hi, On Wed, 13 Feb 2008, H.J. Lu wrote:
> We need a callee-saved register for stack alignment. Can you expand on why? > In 64bit, our choices are rbx, and r12-r15. r12-r15 need the REX byte > and r12 also needs the SIB byte. So I'd like to use rbx. x86-64 psABI > says rbx is callee-saved and optionally used as base pointer. However, I > couldn't find an example where rbx is used as base pointer. Is this a > carryover from i386 psABI where ebx is used to hold GOT? In the large memory model you need a base pointer for the GOT. Of course we could do the same as in recent i386 and chose an arbitrary register as GOT pointer. Ciao, Michael.
