[cft] aligning main's stack frame

[Richard Henderson]

On Mon, Oct 17, 2005 at 12:25:46PM +0200, Andi Kleen wrote:
> > main:
> >         leal    4(%esp), %ecx		# create argument pointer
> >         andl    $-16, %esp		# align stack
> >         pushl   -4(%ecx)		# copy return address
> 
> This will misaligned the call/ret stack in the CPU, leading to branch
> mispredictions on many of the following RETs. On main it's probably
> not a big issue, but for other functions it might be.

No it won't.  I don't actually use that for the return insn.

I cheat and move the CFA, and that copy satisfies the return
address at CFA-4 during the body of the function.


r~