Given a pattern like:

  (define_insn "aarch64_frecpe<mode>" ...)

the SVE ACLE implementation wants to generate the pattern for a
particular (non-constant) mode.  This patch automatically generates
helpers to do that, specifically:

  // Return CODE_FOR_nothing on failure.
  insn_code maybe_code_for_aarch64_frecpe (machine_mode);

  // Assert that the code exists.
  insn_code code_for_aarch64_frecpe (machine_mode);

  // Return NULL_RTX on failure.
  rtx maybe_gen_aarch64_frecpe (machine_mode, rtx, rtx);

  // Assert that generation succeeds.
  rtx gen_aarch64_frecpe (machine_mode, rtx, rtx);

Many patterns don't have sensible names when all <...>s are removed.
E.g. "<optab><mode>2" would give a base name "2".  The new functions
therefore require explicit opt-in, which should also help to reduce
code bloat.

The (arbitrary) opt-in syntax I went for was to prefix the pattern
name with '@', similarly to the existing '*' marker.

The patch also makes config/aarch64 use the new routines in cases where
they obviously apply.  This was mostly straight-forward, but it seemed
odd that we defined:

   aarch64_reload_movcp<...><P:mode>

but then only used it with DImode, never SImode.  If we should be
using Pmode instead of DImode, then that's a simple change,
but should probably be a separate patch.

2018-08-02  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* doc/md.texi: Expand the documentation of instruction names
	to mention port-local uses.  Document '@' in pattern names.
	* read-md.h (overloaded_instance, overloaded_name): New structs.
	(mapping): Declare.
	(md_reader::handle_overloaded_name): New member function.
	(md_reader::get_overloads): Likewise.
	(md_reader::m_first_overload): New member variable.
	(md_reader::m_next_overload_ptr): Likewise.
	(md_reader::m_overloads_htab): Likewise.
	* read-md.c (md_reader::md_reader): Initialize m_first_overload,
	m_next_overload_ptr and m_overloads_htab.
	* read-rtl.c (iterator_group): Add "type" and "get_c_token" fields.
	(get_mode_token, get_code_token, get_int_token): New functions.
	(map_attr_string): Add an optional argument that passes back
	the associated iterator.
	(overloaded_name_hash, overloaded_name_eq_p, named_rtx_p):
	(md_reader::handle_overloaded_name, add_overload_instance): New
	functions.
	(apply_iterators): Handle '@' names.  Report an error if '@'
	is used without iterators.
	(initialize_iterators): Initialize the new iterator_group fields.
	* genopinit.c (handle_overloaded_code_for)
	(handle_overloaded_gen): New functions.
	(main): Use them to print declarations of maybe_code_for_* and
	maybe_gen_* functions, and inline definitions of code_for_* and gen_*.
	* genemit.c (print_overload_arguments, print_overload_test)
	(handle_overloaded_code_for, handle_overloaded_gen): New functions.
	(main): Use it to print definitions of maybe_code_for_* and
	maybe_gen_* functions.
	* config/aarch64/aarch64.c (aarch64_split_128bit_move): Use
	gen_aarch64_mov{low,high}_di and gen_aarch64_movdi_{low,high}
	instead of explicit mode checks.
	(aarch64_split_simd_combine): Likewise gen_aarch64_simd_combine.
	(aarch64_split_simd_move): Likewise gen_aarch64_split_simd_mov.
	(aarch64_emit_load_exclusive): Likewise gen_aarch64_load_exclusive.
	(aarch64_emit_store_exclusive): Likewise gen_aarch64_store_exclusive.
	(aarch64_expand_compare_and_swap): Likewise
	gen_aarch64_compare_and_swap and gen_aarch64_compare_and_swap_lse
	(aarch64_gen_atomic_cas): Likewise gen_aarch64_atomic_cas.
	(aarch64_emit_atomic_swap): Likewise gen_aarch64_atomic_swp.
	(aarch64_constant_pool_reload_icode): Delete.
	(aarch64_secondary_reload): Use code_for_aarch64_reload_movcp
	instead of aarch64_constant_pool_reload_icode.  Use
	code_for_aarch64_reload_mov instead of explicit mode checks.
	(rsqrte_type, get_rsqrte_type, rsqrts_type, get_rsqrts_type): Delete.
	(aarch64_emit_approx_sqrt): Use gen_aarch64_rsqrte instead of
	get_rsqrte_type and gen_aarch64_rsqrts instead of gen_rqrts_type.
	(recpe_type, get_recpe_type, recps_type, get_recps_type): Delete.
	(aarch64_emit_approx_div): Use gen_aarch64_frecpe instead of
	get_recpe_type and gen_aarch64_frecps instead of get_recps_type.
	(aarch64_atomic_load_op_code): Delete.
	(aarch64_emit_atomic_load_op): Likewise.
	(aarch64_gen_atomic_ldop): Use UNSPECV_ATOMIC_* instead of
	aarch64_atomic_load_op_code.  Use gen_aarch64_atomic_load
	instead of aarch64_emit_atomic_load_op.
	* config/aarch64/aarch64.md (aarch64_reload_movcp<GPF_TF:mode><P:mode>)
	(aarch64_reload_movcp<VALL:mode><P:mode>, aarch64_reload_mov<mode>)
	(aarch64_movdi_<mode>low, aarch64_movdi_<mode>high)
	(aarch64_mov<mode>high_di, aarch64_mov<mode>low_di): Add a '@'
	character before the pattern name.
	* config/aarch64/aarch64-simd.md (aarch64_split_simd_mov<mode>)
	(aarch64_rsqrte<mode>, aarch64_rsqrts<mode>)
	(aarch64_simd_combine<mode>, aarch64_frecpe<mode>)
	(aarch64_frecps<mode>): Likewise.
	* config/aarch64/atomics.md (atomic_compare_and_swap<mode>)
	(aarch64_compare_and_swap<mode>, aarch64_compare_and_swap<mode>_lse)
	(aarch64_load_exclusive<mode>, aarch64_store_exclusive<mode>)
	(aarch64_atomic_swp<mode>, aarch64_atomic_cas<mode>)
	(aarch64_atomic_load<atomic_ldop><mode>): Likewise.

From-SVN: r263251