* c-common.c (handle_noicf_attribute): New function.
	* doc/extend.texi (no_icf): Add new attribute description.
	* ipa-icf.c (sem_item_optimizer::merge_classes): Handle cases
	where the pass attempts to merge a function with no_icf attribute.
	* gcc.dg/ipa/ipa-icf-33.c: New test.

From-SVN: r219848