Backport PR c/89946 (ICE in assemble_start_function, at varasm.c:1871)

Backport PR c/89946 (ICE in assemble_start_function, at varasm.c:1871)

gcc/ChangeLog
2021-10-07  Giuliano Belinassi  <gbelinassi@suse.de>

	Backport from mainline
	2019-04-12  Jakub Jelinek  <jakub@redhat.com>

	PR c/89946
	* varasm.c (assemble_start_function): Don't use tree_fits_uhwi_p
	and gcc_unreachable if it fails, just call tree_to_uhwi which
	verifies that too.  Test TREE_CHAIN instead of list_length > 1.
	Start warning message with a lower-case letter.  Formatting fixes.

	PR rtl-optimization/90026
	* cfgcleanup.c (try_optimize_cfg): When removing empty bb with no
	successors, look for BARRIERs inside of the whole BB_FOOTER chain
	rather than just at the start of it.  If e->src BB_FOOTER is not NULL
	in cfglayout mode, use emit_barrier_after_bb.

gcc/c-family/ChangeLog
2021-10-07  Giuliano Belinassi  <gbelinassi@suse.de>

	Backport of mainline
	2019-04-12  Jakub Jelinek  <jakub@redhat.com>

	PR c/89946
	* c-attribs.c (handle_patchable_function_entry_attribute): Add
	function comment.  Warn if arguments of the attribute are not positive
	integer constants.

gcc/testsuite/ChangeLog
2021-10-07  Giuliano Belinassi  <gbelinassi@suse.de>

	Backport from mainline
	2019-04-12  Jakub Jelinek  <jakub@redhat.com>

	PR c/89946
	* c-c++-common/pr89946.c: New test.

	PR rtl-optimization/90026
	* g++.dg/opt/pr90026.C: New test.