[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 #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
r273783 makes this work on x86_64 (and other targets with relaxed alignment)
and sparc-solaris11 (and other strictly aligned targets) where the strlen call
in g() still isn't folded.  The difference is this between the following
MEM_REF on x86_64:

  # _4 = PHI <3355185(2), 3552564(3)>
  MEM <unsigned int> [(char * {ref-all})&a] = _4;

and this one on sparc-solaris11:

  # iftmp.0_2 = PHI <"456"(2), "123"(3)>
  MEM <unsigned char[4]> [(char * {ref-all})&a] = MEM <unsigned char[4]> [(char
* {ref-all})iftmp.0_2];
  _1 = __builtin_strlen (&a);

It should be handled but isn't.