The code was passing a pseudo rather than its allocated hard reg
to ira_need_caller_save_p.  Running under valgrind to reproduce
the failure also showed that ALLOCNO_CROSSED_CALLS_ABIS wasn't
being explicitly initialised.

2019-10-01  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR rtl-optimization/91948
	* ira-build.c (ira_create_allocno): Initialize
	ALLOCNO_CROSSED_CALLS_ABIS.
	* ira-color.c (allocno_reload_assign): Pass hard_regno rather
	than regno to ira_need_caller_save_p.

From-SVN: r276407