[Bug tree-optimization/63989] tree-ssa-strlen.c doesn't handle constant pointer plus and array refs if constant offset is smaller than known constant string length

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 34220
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34220&action=edit
gcc5-pr63989-wip1.patch

So, for start, this untested patch deals with #c1 f1 case.  Still need to
extend handle_char_store etc.