re PR middle-end/12392 (very long optimized compile)

re PR middle-end/12392 (very long optimized compile)

2016-03-30  Michael Matz  <matz@suse.de>
	Richard Biener  <rguenther@suse.de>

	PR ipa/12392
	* ipa-polymorphic-call.c (struct type_change_info): Change
	speculative to an unsigned allowing to limit the work we do.
	(csftc_abort_walking_p): New inline function..
	(check_stmt_for_type_change): Limit the number of may-defs
	skipped for speculative devirtualization to
	max-speculative-devirt-maydefs.
	* params.def (max-speculative-devirt-maydefs): New param.
	* doc/invoke.texi (--param max-speculative-devirt-maydefs): Document.

Co-Authored-By: Richard Biener <rguenther@suse.de>
From-SVN: r234546