Re: Enforcing order of execution for function arguments

[Andrew Haley <aph at redhat dot com>]

Roberto COSTA writes:
 > Andrew Haley wrote:
 > > Chris Jefferson writes:
 > > 
 > >  > One thing which comes up regularly in various C and C++
 > >  > messageboards is that statements like "f() + g()" and "a(f(), g())"
 > >  > do not declare which order f() and g() will be executed in.
 > >  > 
 > >  > How hard would it be to fix the order of execution in gcc/g++?
 > >  > Could someone point me to the piece of code which must change, or
 > >  > if it is only a very small change, the actual change required? I
 > >  > would very much like to be able to benchmark this, as I can find no
 > >  > previous case where someone has tried fixing the order of execution
 > >  > to see if it actually makes any measureable difference.
 > > 
 > > The easiest way is during gimplification: you'd walk over the arglist
 > > from left to right, calling
 > > 
 > >         gimplify_expr (&arg, pre_p, post_p,
 > > 		       is_gimple_formal_tmp_var, fb_rvalue);
 > > 
 > > on each arg.
 > 
 > But would it be sufficient?

I think so.

 > I guess you would also have to make sure that further passes (i.e. 
 > out-of-ssa) do not revert what you have just done.

If any arg had side-effects that would be a bug.

Andrew.