ipa: Adjust cgraph verifier to materialization on demand (PR 98222)

ipa: Adjust cgraph verifier to materialization on demand (PR 98222)

after switching to materialization of clones on demand, the verifier
can happen to see edges leading to a clone of a materialized clone.
This means its clone_of is NULL and former_clone_of needs to be
checked in order to verify that the callee is a clone of the original
decl, which it did not do and reported edges to pointing to a wrong
place.

Fixed with the following patch, which has been pre-approved by Honza.
Bootstrapped and tested on x86_64-linux, pushed to master.

Martin

gcc/ChangeLog:

2021-01-15  Martin Jambor  <mjambor@suse.cz>

	PR ipa/98222
	* cgraph.c (clone_of_p): Check also former_clone_of as we climb
	the clone tree.

gcc/testsuite/ChangeLog:

2021-01-15  Martin Jambor  <mjambor@suse.cz>

	PR ipa/98222
	* gcc.dg/ipa/pr98222.c: New test.