[patch, fortran] Handling of .and. and .or. expressions

[graham stott via fortran]

if i read this correctly it appears that IMPURE/PURE are not the normal pure attribute used by gcc but some entirely diff attribute specific to FORTANso people are taking about different things

-------- Original message --------
From: Steve Kargl <sgk@troutmask.apl.washington.edu> 
Date: 16/06/2018  17:38  (GMT+00:00) 
To: Janus Weil <janus@gcc.gnu.org> 
Cc: Janne Blomqvist <blomqvist.janne@gmail.com>, Thomas Koenig <tkoenig@netcologne.de>, fortran@gcc.gnu.org, gcc-patches <gcc-patches@gcc.gnu.org> 
Subject: Re: [patch, fortran] Handling of .and. and .or. expressions 

On Sat, Jun 16, 2018 at 01:09:36PM +0200, Janus Weil wrote:
> 
> 
> Am 15. Juni 2018 20:38:17 MESZ schrieb Steve Kargl <sgk@troutmask.apl.washington.edu>:
> >> But at least for pure functions, this optimization looks Ok.
> >> 
> >
> >Why is everyone fixated on PURE vs IMPURE functions?
> 
> Simply because it makes a difference in this context!

It does not!  A function marked as PURE by a programmer
must meet certain requirement of the Fortran standard.
An unmarked function or a function marked as IMPURE can
still meet those same requirements.  Marking something as 
IMPURE has only a single requirement in the standard.

   An impure elemental procedure processes array arguments
   in array element order.

That's it.  Marking a function as IMPURE does not mean 
the function has side effects.  It does not mean that
a function must be evaluated for each reference.  Are
you advocating that gfortran must evaluate ping() 
twice for

  impure real function ping()
  end function ping
  
  x = ping() + 0 * ping()
  end

-- 
Steve