On Fri, Jun 16, 2006 at 12:28:37AM +0900, Atsushi Nemoto wrote:
> On Wed, 14 Jun 2006 12:50:40 -0400, Daniel Jacobowitz <dan@xxxxxxxxxx> wrote:
> > > For example, in the code below, RDHWR is placed _before_ checking the
> > > error. I suppose these instructions were reordered by gcc's
> > > optimization, but the optimization would have large negative effect in
> > > this case.
> >
> > You'd have to figure out how to get GCC not to eagerly schedule the
> > rdhwr. This might be quite hard. I don't know much about this part of
> > the scheduler.
>
> I really did not understand yet how errno is bound TLS. I found some
> "rdhwr" in glibc-ports source code (tls-macros.h, nptl/tls.h). The
> RDHWR instruction in the example code comes from one of them, no?
No.
> I also found a "rdhwr" in gcc's mips.md file ("tls_get_tp_<mode>").
> Is this the origin? MD is a very foreign language for me...
Yes. Compile something like this with -O2 but without -fpic:
__thread int x;
int foo() { return x; }
It should use the IE model, which will generate a rdhwr.
--
Daniel Jacobowitz
CodeSourcery
