[prev in list] [next in list] [prev in thread] [next in thread] 

List:       gcc
Subject:    Re: Would alias analysis help WRT builtin memmove -> builtin memcpy ?
From:       Jeffrey A Law <law () cygnus ! com>
Date:       2000-03-30 0:15:08
[Download RAW message or body]


  In message <200003300012.TAA03981@caip.rutgers.edu>you write:
  > I wasn't doing any casting, but the prototype of memmove may have done
  > that for me.
No, a prototype will not do a cast.  You would have to do the cast yourself.

  > Anway, here is what I am talking about.  Assume the following is in a
  > new expand_builtin_memmove() routine, where `arglist' is the tree
  > chain of parameters passed to the expanded memmove call:
  > 
  > +      tree dst = TREE_VALUE (arglist);
  > +      tree src = TREE_VALUE (TREE_CHAIN (arglist));
  > +      tree len = TREE_VALUE (TREE_CHAIN (TREE_CHAIN (arglist)));
  > +      const int dst_set = get_alias_set (dst);
  > +      const int src_set = get_alias_set (src);
  > +      const int len_set = get_alias_set (len);
  > +
  > +      fprintf (stderr, "src=%d, dst=%d, len=%d\n",
  > +              src_set, dst_set, len_set);
  > +
  > +      if (src_set <= 0 || dst_set <= 0 || src_set == dst_set)
  > +       return 0;
  > +      else
  > +       return expand_builtin_memcpy (arglist);
As I mentioned before, the aliasing code wants MEMs.  You're not even really
supposed to be calling get_alias_set like that.  You're supposed to be calling
stuff like true_dependence and the like (see alias.c).




jeff

[prev in list] [next in list] [prev in thread] [next in thread]