[RISC-V] Add support for _Bfloat16

1 At point <https://github.com/riscv/riscv-bfloat16>,
  BF16 has already been completed "post public review".

2 LLVM has also added support for RISCV BF16 in
  <https://reviews.llvm.org/D151313> and
  <https://reviews.llvm.org/D150929>.

3 According to the discussion <https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/367>,
  this use __bf16 and use DF16b in riscv_mangle_type like x86.

Below test are passed for this patch
    * The riscv fully regression test.

gcc/ChangeLog:

	* config/riscv/iterators.md: New mode iterator HFBF.
	* config/riscv/riscv-builtins.cc (riscv_init_builtin_types):
	Initialize data type _Bfloat16.
	* config/riscv/riscv-modes.def (FLOAT_MODE): New.
	(ADJUST_FLOAT_FORMAT): New.
	* config/riscv/riscv.cc (riscv_mangle_type): Support for BFmode.
	(riscv_scalar_mode_supported_p): Ditto.
	(riscv_libgcc_floating_mode_supported_p): Ditto.
	(riscv_init_libfuncs): Set the conversion method for BFmode and
	HFmode.
	(riscv_block_arith_comp_libfuncs_for_mode): Set the arithmetic
	and comparison libfuncs for the mode.
	* config/riscv/riscv.md (mode" ): Add BF.
	(movhf): Support for BFmode.
	(mov<mode>): Ditto.
	(*movhf_softfloat): Ditto.
	(*mov<mode>_softfloat): Ditto.

libgcc/ChangeLog:

	* config/riscv/sfp-machine.h (_FP_NANFRAC_B): New.
	(_FP_NANSIGN_B): Ditto.
	* config/riscv/t-softfp32: Add support for BF16 libfuncs.
	* config/riscv/t-softfp64: Ditto.
	* soft-fp/floatsibf.c: For si -> bf16.
	* soft-fp/floatunsibf.c: For unsi -> bf16.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/bf16_arithmetic.c: New test.
	* gcc.target/riscv/bf16_call.c: New test.
	* gcc.target/riscv/bf16_comparison.c: New test.
	* gcc.target/riscv/bf16_float_libcall_convert.c: New test.
	* gcc.target/riscv/bf16_integer_libcall_convert.c: New test.

Co-authored-by: Jin Ma <jinma@linux.alibaba.com>

2 files changed, 90 insertions, 0 deletions

diff --git a/libgcc/soft-fp/floatsibf.c b/libgcc/soft-fp/floatsibf.c
new file mode 100644
index 0000000..0cb05e5
--- /dev/null
+++ b/libgcc/soft-fp/floatsibf.c
@@ -0,0 +1,45 @@
+/* Software floating-point emulation.
+   Convert a 32bit signed integer to bfloat16
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file into
+   combinations with other programs, and to distribute those
+   combinations without any restriction coming from the use of this
+   file.  (The Lesser General Public License restrictions do apply in
+   other respects; for example, they cover modification of the file,
+   and distribution when not linked into a combine executable.)
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include "soft-fp.h"
+#include "brain.h"
+
+BFtype
+__floatsibf (SItype i)
+{
+  FP_DECL_EX;
+  FP_DECL_B (A);
+  BFtype a;
+
+  FP_INIT_ROUNDMODE;
+  FP_FROM_INT_B (A, i, SI_BITS, USItype);
+  FP_PACK_RAW_B (a, A);
+  FP_HANDLE_EXCEPTIONS;
+
+  return a;
+}
diff --git a/libgcc/soft-fp/floatunsibf.c b/libgcc/soft-fp/floatunsibf.c
new file mode 100644
index 0000000..cd8c4bc
--- /dev/null
+++ b/libgcc/soft-fp/floatunsibf.c
@@ -0,0 +1,45 @@
+/* Software floating-point emulation.
+   Convert a 32bit unsigned integer to bfloat16
+   Copyright (C) 2007-2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file into
+   combinations with other programs, and to distribute those
+   combinations without any restriction coming from the use of this
+   file.  (The Lesser General Public License restrictions do apply in
+   other respects; for example, they cover modification of the file,
+   and distribution when not linked into a combine executable.)
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include "soft-fp.h"
+#include "brain.h"
+
+BFtype
+__floatunsibf (USItype i)
+{
+  FP_DECL_EX;
+  FP_DECL_B (A);
+  BFtype a;
+
+  FP_INIT_ROUNDMODE;
+  FP_FROM_INT_B (A, i, SI_BITS, USItype);
+  FP_PACK_RAW_B (a, A);
+  FP_HANDLE_EXCEPTIONS;
+
+  return a;
+}