re PR c/87028 (false positive -Wstringop-truncation strncpy with global variable...

re PR c/87028 (false positive -Wstringop-truncation strncpy with global variable source string)

	PR c/87028
	* calls.c (get_attr_nonstring_decl): Avoid setting *REF to
	SSA_NAME_VAR.
	* gcc/gimple-low.c (lower_stmt): Fold builtin calls here.
	* gimplify (maybe_fold_stmt): Avoid folding builtin calls.

	PR c/87028
	* c-c++-common/Wstringop-truncation.c: Remove xfails.
	* gcc.dg/Wstringop-truncation-5.c: New test.
	* gcc.dg/strcmpopt_1.c: Adjust.
	* gcc.dg/tree-ssa/pr79697.c: Same.

From-SVN: r266833