re PR middle-end/53590 (compiler fails to generate SIMD instruction for FP division)

re PR middle-end/53590 (compiler fails to generate SIMD instruction for FP division)

	PR middle-end/53590
	* common.opt (-fdelete-dead-exceptions): New switch.
	* doc/invoke.texi (Code Gen Options): Document it.
	* cse.c (count_reg_usage) <CALL_INSN>: Use !insn_nothrow_p in lieu of
	insn_could_throw_p predicate.  Do not skip an insn that could throw
	if dead exceptions can be deleted.
	(insn_live_p): Likewise, do not return true in that case.
	* dce.c (can_alter_cfg): New flag.
	(deletable_insn_p): Do not return false for an insn that can throw if
	the CFG can be altered and dead exceptions can be deleted.
	(init_dce): Set can_alter_cfg to false for fast DCE, true otherwise.
	* dse.c (scan_insn): Use !insn_nothrow_p in lieu of insn_could_throw_
	predicate. Do not preserve an insn that could throw if dead exceptions
	can be deleted.
	* function.h (struct function): Add can_delete_dead_exceptions flag.
	* function.c (allocate_struct_function): Set it.
	* lto-streamer-in.c (input_struct_function_base): Stream it.
	* lto-streamer-out.c (input_struct_function_base): Likewise.
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Do not mark a
	statement that could throw as necessary if dead exceptions can be
	deleted.
ada/
	* gcc-interface/misc.c (gnat_init_options_struct): Set
	opts->x_flag_delete_dead_exceptions to 1.

From-SVN: r188651