[Bug fortran/43665] Optimization of libgfortran calls: function annotations for noclobber/noescape arguments

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2010-04-06 13:50 -------
Some more quotes:

> You can mark parameters 1) unused, 2) pointed-to read-only,
> 3) not escaping, 4) only once dereferenced (thus, access only
> *p, not **p)
>
> You can mark return values as being a direct copy of arguments
> or as non-aliasing (similar to the malloc attribute).

+       attr = lookup_attribute ("fnspec", TYPE_ATTRIBUTES (type));

+   switch (TREE_STRING_POINTER (attr)[1 + arg])
+     {
+     case 'x':
+     case 'X':
+       return EAF_UNUSED;
+ 
+     case 'R':
+       return EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE;
+ 
+     case 'r':
+       return EAF_NOCLOBBER | EAF_NOESCAPE;
+ 
+     case 'W':
+       return EAF_DIRECT | EAF_NOESCAPE;
+ 
+     case 'w':
+       return EAF_NOESCAPE;


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43665