gcc/ChangeLog:

	PR tree-optimization/83075
	* tree-ssa-strlen.c (handle_builtin_stxncpy): Avoid assuming
	strncat/strncpy don't change length of source string.

gcc/testsuite/ChangeLog:

	PR tree-optimization/83075
	* gcc.dg/tree-ssa/strncat.c: New test.
	* gcc.dg/tree-ssa/strncpy-2.c: Same.

From-SVN: r255446