[Bug tree-optimization/58806] New attribute for functions that access memory only through their arguments

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58806

--- Comment #5 from Marc Glisse <glisse at gcc dot gnu.org> ---
Created attachment 31074
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31074&action=edit
experimental patch

This optimizes the testcase in comment #0 if I mark g with the attribute
"no_global_write" and use some way of marking g's argument as EAF_DIRECT. Maybe
it would be easier to have the no_global_write attribute (possibly with a
different name) imply EAF_DIRECT on the arguments, as it gets tricky trying to
see what we may alias by following an arbitrary chain starting at a given
pointer.