* Makefile.in (emit-rtl.o): Depend on HASHTAB_H.
	* alias.c (reg_known_value): Add comments.
	(init_alias_analysis): Likewise.
	* cse.c (exp_equiv_p): CONST_INTs are equal iff they have the same
	address.
	(cse_basic_block): Fix typo in comment.
	* emit-rtl.c: Include hashtab.h.
	(const_int_htab): New variable.
	(const_int_htab_hash): New function.
	(const_int_htab_eq): Likewise.
	(rtx_htab_mark_1): Likewise.
	(rtx_htab_mark): Likewise.
	(gen_rtx_CONST_INT): Cache all CONST_INTs.
	(unshare_all_rtx): Fix formatting.
	(init_emit_once): Initialize const_int_htab.
	* rtl.c (rtx_equal_p): CONST_INTs are equal iff they have the same
	address.
	* rtl.texi: Document the fact that all CONST_INTs with the same
	value are shared.

From-SVN: r32844