[Bug tree-optimization/91183] strlen of a strcpy result with a conditional source not folded

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91183

--- Comment #7 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch to handle the issue discussed in comment #6:
https://gcc.gnu.org/ml/gcc-patches/2019-08/msg00000.html