PR tree-optimization/86043 - strlen after memcpy partially overwriting a string not...

PR tree-optimization/86043 - strlen after memcpy partially overwriting a string not optimized
PR tree-optimization/86042 - missing strlen optimization after second strcpy

gcc/ChangeLog:

	PR tree-optimization/86043
	PR tree-optimization/86042
	* tree-ssa-strlen.c (handle_builtin_memcpy): Handle strict overlaps.
	(get_string_cst_length): Rename...
	(get_min_string_length): ...to this.  Add argument.
	(handle_char_store): Extend to handle multi-character stores by
	MEM_REF.
	* tree.c (initializer_zerop): Use new argument.  Handle MEM_REF.
	* tree.h (initializer_zerop): Add argument.

gcc/testsuite/ChangeLog:

	PR tree-optimization/86043
	PR tree-optimization/86042
	* gcc/testsuite/gcc.dg/attr-nonstring-2.c: Xfail test cases due to
	pr86688.
	* gcc.dg/strlenopt-44.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263018 138bc75d-0d04-0410-961f-82ee72b054a4