re PR middle-end/54146 (Very slow compile with attribute((flatten)))

re PR middle-end/54146 (Very slow compile with attribute((flatten)))

	PR middle-end/54146
	* ira.c (init_live_subregs): Take live_subregs_used as a bitmap.
	(build_insn_chain): Make live_subregs_used a bitmap.
	Use SBITMAP_SIZE to ignore the paradoxical bytes of subregs.
	Use sbitmap_free to free the live_subreg sbitmaps.

From-SVN: r190223