[PATCH], RFC, add support for __float128/__ibm128 types on PowerPC

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

This patch adds support for a new type (__float128) on the PowerPC to allow
people to use the 128-bit IEEE floating point format instead of the traditional
IBM double-double that has been used in the Linux compilers.  At this time,
long double still will remain using the IBM double-double format.

There has been an undocumented option to switch long double to to IEEE 128-bit,
but right now, there are bugs I haven't ironed out on VSX systems.

In addition, I added another type (__ibm128) so that when the transition is
eventually made, people can use this type to get the old long double type.

I was wondering if people had any comments on the code so far, and things I
should different.  Note, I will be out on vacation May 6th - 14th, so I don't
expect to submit the patches until I get back.

At present, I don't have tests in the testsuite.

If you want to try it out, I have it as a svn branch:
svn+ssh://gcc.gnu.org/svn/gcc/branches/ibm/gcc-4_10-ieee

Now, some questions.  For Power server systems, we will want to always pass
IEEE 128-bit as a vector type, but I have code in here to pass it in the
traditional fashion in two FPRs if -mvsx is not used?  It is a little unclean
to have two different sets of support functions, and possibly confuse the user
if they compile some code with -mvsx and some without.  I can require -mvsx if
it is desirable to only have one ABI controlling it.  Or I can do this
selection on the ELF v2 abi switch.

Do we need -mfloat128?  Or should it just be an undocumented swtich and switch
on with VSX and/or ELF v2 abi?

Would other users besides Linux users want to use the __float128 type?

I assume I haven't broken anything on the other non-Linux environments,
particularly the ones that already have IEEE 128-bit support, but it would be
nice to know that for certain.

[gcc]
2014-04-29  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/predicates.md (int_reg_operand_not_pseudo): New
	predicate that matches hard GPR registers, but not pseudos.
	(easy_fp_constant): Add support for new floating point modes
	XFmode and JFmode.

	* config/rs6000/rs6000-cpus.def (ISA_2_6_MASKS_SERVER): Set
	-mfloat128 on by default.
	(POWERPC_MASKS): Add -mfloat128.
	(power7 cpu): Enable -mfloat128.

	* config/rs6000/rs6000.opt (-mfloat128): New option to control
	whether the __float128 (IEEE 128-bit floating point) and __ibm128
	(traditional IBM double double format for long double) types are
	enabled.

	* config/rs6000/rs6000-c.c (rs6000_target_modify_macros): If
	-mfloat128, define __FLOAT128__.

	* config/rs6000/rs6000-builtin.def (PACK_JF): Define pack/unpack
	builtin functions for __ibm128.
	(UNPACK_F): Likewise.

	* config/rs6000/rs6000.c (scalar_float_not_vector_p): New helper
	function for scalar floats that are used in traditional floating
	point registers, and not in a vector register.
	(rs6000_hard_regno_nregs_internal): Add support for __float128 on
	VSX systems to know that the value uses the full vector register
	rather than being a pair of scalar registers.
	(rs6000_hard_regno_mode_ok): Likewise.
	(rs6000_debug_reg_global): Add debugging for __float128 and
	__ibm128.
	(rs6000_init_hard_regno_mode_ok): Add support for __float128 and
	__ibm128.
	(rs6000_option_override_internal): Don't allow -mfloat128 and
	-mlong-double-64.
	(invalid_e500_subreg): Add support for __float128 and __ibm128
	floating point types.  On VSX systems, pass/return __float128 in
	vector registers.
	(reg_offset_addressing_ok_p): Likewise.
	(rs6000_legitimate_offset_address_p): Likewise.
	(rs6000_legitimize_reload_address): Likewise.
	(rs6000_legitimate_address_p): Likewise.
	(rs6000_emit_move): Likewise.
	(USE_FP_FOR_ARG_P): Likewise.
	(rs6000_aggregate_candidate): Likewise.
	(rs6000_discover_homogeneous_aggregate): Likewise.
	(rs6000_return_in_memory): Likewise.
	(init_cumulative_args): Likewise.
	(rs6000_function_arg_boundary): Likewise.
	(rs6000_function_arg_advance_1): Likewise.
	(rs6000_function_arg): Likewise.
	(rs6000_arg_partial_bytes): Likewise.
	(rs6000_pass_by_reference): Likewise.
	(rs6000_init_builtins): Initialize support for __float128 and
	__ibm128.
	(init_float128_ibm): New function to set up the library names for
	the IBM double-double 128-bit format.
	(init_float128_ieee): New function to set up the library names for
	IEEE 128-bit types.  On VSX systems, use <name>_vector, on non-VSX
	systems with -mfloat128, use <name>_fpr, and on non-Linux/BSD
	systems that default to long double == IEEE 128-bit, use the
	historic names.
	(rs6000_init_libfuncs): Move setup of the library names to
	init_float128_ibm and init_float128_ieee.
	(rs6000_cannot_change_mode_class): Add support for __float128 and
	__ibm128.
	(rs6000_generate_compare): Likewise.
	(rs6000_split_multireg_move): Likewise.
	(spe_func_has_64bit_regs_p): Likewise.
	(rs6000_output_function_epilogue): Likewise.
	(output_toc): Likewise.
	(rs6000_mangle_type): Expand mangling to use "g" for __ibm128, and
	"e" for __float128, to be compatible with defaults for long
	double.
	(rs6000_register_move_cost): Add support for __float128 and
	__ibm128.
	(rs6000_function_value): Likewise.
	(rs6000_libcall_value): Likewise.
	(rs6000_opt_masks): Add -mfloat128.

	* config/rs6000/rs6000.h (FLOAT128_IEEE_P): New macro to identify
	types that map to IEEE 128-bit floating point.
	(FLOAT128_IBM_P): New macro to identify types that map to the
	traditional IBM double-double 128-bit floating point.
	(FLOAT128_VECTOR_P): New macro to identify 128-bit floating point
	types that take a single vector register.
	(FLOAT128_2REG_P): New macro to identify 128-bit floating point
	types that take 2 adjacent scalar registers.
	(MASK_FLOAT128): Map to OPTION_MASK_FLOAT128.
	(SLOW_UNALIGNED_ACCESS): Add support for __float182 and __ibm128.
	(HARD_REGNO_CALLER_SAVE_MODE): Likewise.
	(HARD_REGNO_CALL_PART_CLOBBERED): Likewise.
	(VSX_VECTOR_MODE): Spacing.
	(ALTIVEC_VECTOR_MODE): Add __float128 in vector registers.
	(MODES_TIEABLE_P): Move vectors higher than scalar floating point,
	so that __float128 in vector registers ties with vectors and not
	with other floating point values.
	(struct rs6000_args): Add libcall argument so that we can tell
	when we calling a library support function for __float128.
	(enum rs6000_builtin_type_index): Add __float128 and __ibm128
	support.
	(ieee128_float_type_node): Likewise.
	(ibm128_float_type_node): Likewise.

	* config/rs6000/altivec.md (VM): Add support for IEEE 128-bit
	floating point types that goes in a vector.
	(VM2): Likewise.

	* config/rs6000/rs6000.md (FMOVE128): Add supprt for __float128
	and __ibm128.
	(FMOVE128_GPR): Likewise.
	(mov<mode>_64bit, FMOVE128 types): Likewise.
	(mov<mode>_32bit, FMOVE128 types): Likewise.
	(FP128_64): Likewise.
	(unpack<mode>): Add support to pack/unpack __ibm128 types.  Delete
	old insns just for TFmode.  Don't pack/unpack 128-bit types in a
	vector register.
	(TF_JF): Likewise.
	(unpack<mode>_0): Likewise.
	(unpacktf_0): Likewise.
	(unpack<mode>_1): Likewise.
	(unpacktf_1): Likewise.
	(unpack<mode>_dm): Likewise.
	(unpack<mode>_nodm): Likewise.
	(pack<mode>): Likewise.

	* config/rs6000/vector.md (VEC_L): Add XFmode to vector modes.
	(VEC_R): Likewise.

	* config/rs6000/rs6000-modes.def (XFmode): Add new modes to
	support __float128 and __ibm128 types.
	(JFmode): Likewise.

	* config/rs6000/vsx.md (VSX_L): Add XFmode to vector modes.
	(VSX_M): Likewise.
	(VSX_M2): Likewise.

	* doc/extend.texi (Floating Types): Document __float128 and
	__ibm128 on PowerPC.
	(PowerPC Built-in Functions): Document pack, unpack builtins for
	__ibm128.

	* doc/invoke.texi (RS/6000 and PowerPC Options): Add -mfloat128.

[libgcc]
2014-04-29  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config/rs6000/float128-vsx.h: New files to add support to build
	the IEEE 128-bit support functions on the PowerPC.  Build two
	versions of the IEEE 128-bit support, one version that uses the
	traditional floating point registers, and passes the type as two
	scalar registers, and the other that passes the type in a single
	vector register.
	* config/rs6000/float128-novsx.h: Likewise.
	* config/rs6000/t-float128: Likewise.

	* soft-fp/quad.h (TFmode): If TFmode is defined, don't use the
	normal TF mode definition.

	* config.host (powerpc*-linux*): Add support for building the IEEE
	128-bit floating point support functions.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797

Attachment: gcc-power8.patch104b
Description: Text document