Misalignment of local SSE variables in thread function

[Andrew Haley]

Brian Dessent writes:
 > Jonathan Kinsey wrote:
 > 
 > > Thanks for the link, unfortunately it doesn't work _beginthread just
 > > calls _beginthreadex - unless there is a alignment argument I didn't see
 > > (I tried it anyway and no luck).
 > > 
 > > If you read the end of the post at the link it says that it doesn't fix
 > > a SSE problem that someone was having - at least I'm not on my own...
 > 
 > I did read that but I hoped it was someone having unrelated problems.  I
 > guess it's not.
 > 
 > So, neither CreateThread nor MSVCRT align the stack, so I guess you'll
 > have to do it yourself.  You should be able to do this with something
 > like:
 > 
 >   asm  __volatile__  ("andl $-16, %%esp" : : : "%esp");
 > 
 > at the beginning of your thread function.

Ouch.  I don't think that would work.

 > You could probably do this in a wrapper-function that calls your
 > actual thread function too.

That sounds like a much better idea, although it may well also be
problematic.

A pure assembly function that did the adjustment and called your
actual thread function would be the best idea.

Andrew.