fmax-stack-var-size, was: Re: OpenMP and local arrays

[Steve Kargl]

On Fri, Aug 03, 2007 at 09:48:06AM -0700, Asher Langton wrote:
> On 8/2/07, Steve Kargl <sgk@troutmask.apl.washington.edu> wrote:
> > On Wed, Aug 01, 2007 at 11:39:29AM -0700, Asher Langton wrote:
> > >
> > > To follow up on this: Mike Kumbera pointed out the
> > > '-fmax-stack-var-size=' option.  What do you all think about adding a
> > > flag that sets gfc_option.flag_max_stack_var_size to -1?  This should
> > > be equivalent to ifort's '-auto' and pgf90's '-Mrecursive' options
> > > (see trans-decl.c:gfc_can_put_var_on_stack () ).  Then '-fopenmp'
> > > would also set  gfc_option.flag_max_stack_var_size to -1, and -- if
> > > there's a demand for it -- we could add a '-frecursive' option that
> > > does the same thing, which will allow indirect recursion to work
> > > properly.
> > >
> >
> > Given your program above and some testing I did locally, I think
> > the above suggestion with -fmax-stack-var-size seems reasonable.
> > I have no preference about a -frecursive option, but I also
> > haven't given it much thought.
> 
> The max-stack-var-size fix solves some problems we've seen when
> compiling our codes with OpenMP.  I'll put together a proper patch
> today.  I think there ought be some way to set this directly, but
> maybe it'll be enough just to make '-1' a valid argument to
> '-fmax-stack-var-size' and document this.
> 

Asher,

You can test for 'gfc_option.flag_openmp != 0' in
options.c(gfc_post_options) and then (re)set the stack
option.


  /* For thread private storage in an OpenMP code, we need
     to (not?) use the stack.  */
  if (!gfc_option.flag_openmp)
    gfc_option.flag_max_stack_var_size = -1;

I've CC'd Jakub, who may have an opinion on this matter.

-- 
Steve