Soft-fp: Add brain format support

  In https://gcc.gnu.org/r13-3292 I've added brain format support
(std::bfloat16_t) on the GCC side, but as glibc has the master copy
of soft-fp, the following patch adds the files from that commit and
also from
https://gcc.gnu.org/pipermail/gcc-patches/2022-November/606398.html
to glibc.


	Jakub
  

On 09/03/23 14:54, Jakub Jelinek via Libc-alpha wrote:
> In https://gcc.gnu.org/r13-3292 I've added brain format support
> (std::bfloat16_t) on the GCC side, but as glibc has the master copy
> of soft-fp, the following patch adds the files from that commit and
> also from
> https://gcc.gnu.org/pipermail/gcc-patches/2022-November/606398.html
> to glibc.
> 

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> diff --git a/soft-fp/brain.h b/soft-fp/brain.h
> new file mode 100644
> index 0000000000..15b63a9a34
> --- /dev/null
> +++ b/soft-fp/brain.h
> @@ -0,0 +1,172 @@
> +/* Software floating-point emulation.
> +   Definitions for Brain Floating Point format (bfloat16).
> +   Copyright (C) 1997-2023 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/>.  */
> +
> +#ifndef SOFT_FP_BRAIN_H
> +#define SOFT_FP_BRAIN_H	1
> +
> +#if _FP_W_TYPE_SIZE < 32
> +# error "Here's a nickel kid.  Go buy yourself a real computer."
> +#endif
> +
> +#define _FP_FRACTBITS_B		(_FP_W_TYPE_SIZE)
> +
> +#define _FP_FRACTBITS_DW_B	(_FP_W_TYPE_SIZE)
> +
> +#define _FP_FRACBITS_B		8
> +#define _FP_FRACXBITS_B		(_FP_FRACTBITS_B - _FP_FRACBITS_B)
> +#define _FP_WFRACBITS_B		(_FP_WORKBITS + _FP_FRACBITS_B)
> +#define _FP_WFRACXBITS_B	(_FP_FRACTBITS_B - _FP_WFRACBITS_B)
> +#define _FP_EXPBITS_B		8
> +#define _FP_EXPBIAS_B		127
> +#define _FP_EXPMAX_B		255
> +
> +#define _FP_QNANBIT_B		((_FP_W_TYPE) 1 << (_FP_FRACBITS_B-2))
> +#define _FP_QNANBIT_SH_B	((_FP_W_TYPE) 1 << (_FP_FRACBITS_B-2+_FP_WORKBITS))
> +#define _FP_IMPLBIT_B		((_FP_W_TYPE) 1 << (_FP_FRACBITS_B-1))
> +#define _FP_IMPLBIT_SH_B	((_FP_W_TYPE) 1 << (_FP_FRACBITS_B-1+_FP_WORKBITS))
> +#define _FP_OVERFLOW_B		((_FP_W_TYPE) 1 << (_FP_WFRACBITS_B))
> +
> +#define _FP_WFRACBITS_DW_B	(2 * _FP_WFRACBITS_B)
> +#define _FP_WFRACXBITS_DW_B	(_FP_FRACTBITS_DW_B - _FP_WFRACBITS_DW_B)
> +#define _FP_HIGHBIT_DW_B	\
> +  ((_FP_W_TYPE) 1 << (_FP_WFRACBITS_DW_B - 1) % _FP_W_TYPE_SIZE)
> +
> +/* The implementation of _FP_MUL_MEAT_B and _FP_DIV_MEAT_B should be
> +   chosen by the target machine.  */
> +
> +typedef float BFtype __attribute__ ((mode (BF)));
> +
> +union _FP_UNION_B
> +{
> +  BFtype flt;
> +  struct _FP_STRUCT_LAYOUT
> +  {
> +#if __BYTE_ORDER == __BIG_ENDIAN
> +    unsigned sign : 1;
> +    unsigned exp  : _FP_EXPBITS_B;
> +    unsigned frac : _FP_FRACBITS_B - (_FP_IMPLBIT_B != 0);
> +#else
> +    unsigned frac : _FP_FRACBITS_B - (_FP_IMPLBIT_B != 0);
> +    unsigned exp  : _FP_EXPBITS_B;
> +    unsigned sign : 1;
> +#endif
> +  } bits;
> +};
> +
> +#define FP_DECL_B(X)		_FP_DECL (1, X)
> +#define FP_UNPACK_RAW_B(X, val)	_FP_UNPACK_RAW_1 (B, X, (val))
> +#define FP_UNPACK_RAW_BP(X, val)	_FP_UNPACK_RAW_1_P (B, X, (val))
> +#define FP_PACK_RAW_B(val, X)	_FP_PACK_RAW_1 (B, (val), X)
> +#define FP_PACK_RAW_BP(val, X)			\
> +  do						\
> +    {						\
> +      if (!FP_INHIBIT_RESULTS)			\
> +	_FP_PACK_RAW_1_P (B, (val), X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_UNPACK_B(X, val)			\
> +  do						\
> +    {						\
> +      _FP_UNPACK_RAW_1 (B, X, (val));		\
> +      _FP_UNPACK_CANONICAL (B, 1, X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_UNPACK_BP(X, val)			\
> +  do						\
> +    {						\
> +      _FP_UNPACK_RAW_1_P (B, X, (val));		\
> +      _FP_UNPACK_CANONICAL (B, 1, X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_UNPACK_SEMIRAW_B(X, val)		\
> +  do						\
> +    {						\
> +      _FP_UNPACK_RAW_1 (B, X, (val));		\
> +      _FP_UNPACK_SEMIRAW (B, 1, X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_UNPACK_SEMIRAW_BP(X, val)		\
> +  do						\
> +    {						\
> +      _FP_UNPACK_RAW_1_P (B, X, (val));		\
> +      _FP_UNPACK_SEMIRAW (B, 1, X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_PACK_B(val, X)			\
> +  do						\
> +    {						\
> +      _FP_PACK_CANONICAL (B, 1, X);		\
> +      _FP_PACK_RAW_1 (B, (val), X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_PACK_BP(val, X)			\
> +  do						\
> +    {						\
> +      _FP_PACK_CANONICAL (B, 1, X);		\
> +      if (!FP_INHIBIT_RESULTS)			\
> +	_FP_PACK_RAW_1_P (B, (val), X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_PACK_SEMIRAW_B(val, X)		\
> +  do						\
> +    {						\
> +      _FP_PACK_SEMIRAW (B, 1, X);		\
> +      _FP_PACK_RAW_1 (B, (val), X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_PACK_SEMIRAW_BP(val, X)		\
> +  do						\
> +    {						\
> +      _FP_PACK_SEMIRAW (B, 1, X);		\
> +      if (!FP_INHIBIT_RESULTS)			\
> +	_FP_PACK_RAW_1_P (B, (val), X);		\
> +    }						\
> +  while (0)
> +
> +#define FP_TO_INT_B(r, X, rsz, rsg)	_FP_TO_INT (B, 1, (r), X, (rsz), (rsg))
> +#define FP_TO_INT_ROUND_B(r, X, rsz, rsg)	\
> +  _FP_TO_INT_ROUND (B, 1, (r), X, (rsz), (rsg))
> +#define FP_FROM_INT_B(X, r, rs, rt)	_FP_FROM_INT (B, 1, X, (r), (rs), rt)
> +
> +/* BFmode arithmetic is not implemented.  */
> +
> +#define _FP_FRAC_HIGH_B(X)	_FP_FRAC_HIGH_1 (X)
> +#define _FP_FRAC_HIGH_RAW_B(X)	_FP_FRAC_HIGH_1 (X)
> +#define _FP_FRAC_HIGH_DW_B(X)	_FP_FRAC_HIGH_1 (X)
> +
> +#define FP_CMP_EQ_B(r, X, Y, ex)       _FP_CMP_EQ (B, 1, (r), X, Y, (ex))
> +
> +#endif /* !SOFT_FP_BRAIN_H */
> diff --git a/soft-fp/extendbfsf2.c b/soft-fp/extendbfsf2.c
> new file mode 100644
> index 0000000000..3589e57e31
> --- /dev/null
> +++ b/soft-fp/extendbfsf2.c
> @@ -0,0 +1,49 @@
> +/* Software floating-point emulation.
> +   Return an bfloat16 converted to IEEE single
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#define FP_NO_EXACT_UNDERFLOW
> +#include "soft-fp.h"
> +#include "brain.h"
> +#include "single.h"
> +
> +SFtype
> +__extendbfsf2 (BFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_B (A);
> +  FP_DECL_S (R);
> +  SFtype r;
> +
> +  FP_INIT_EXCEPTIONS;
> +  FP_UNPACK_RAW_B (A, a);
> +  FP_EXTEND (S, B, 1, 1, R, A);
> +  FP_PACK_RAW_S (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/floattibf.c b/soft-fp/floattibf.c
> new file mode 100644
> index 0000000000..f3336a95b0
> --- /dev/null
> +++ b/soft-fp/floattibf.c
> @@ -0,0 +1,45 @@
> +/* Software floating-point emulation.
> +   Convert a 128bit signed integer to bfloat16
> +   Copyright (C) 2007-2023 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
> +__floattibf (TItype i)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_B (A);
> +  BFtype a;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_FROM_INT_B (A, i, TI_BITS, UTItype);
> +  FP_PACK_RAW_B (a, A);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return a;
> +}
> diff --git a/soft-fp/floatuntibf.c b/soft-fp/floatuntibf.c
> new file mode 100644
> index 0000000000..362b0f6c1b
> --- /dev/null
> +++ b/soft-fp/floatuntibf.c
> @@ -0,0 +1,45 @@
> +/* Software floating-point emulation.
> +   Convert a 128bit unsigned integer to bfloat16
> +   Copyright (C) 2007-2023 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
> +__floatuntibf (UTItype i)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_B (A);
> +  BFtype a;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_FROM_INT_B (A, i, TI_BITS, UTItype);
> +  FP_PACK_RAW_B (a, A);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return a;
> +}
> diff --git a/soft-fp/truncbfhf2.c b/soft-fp/truncbfhf2.c
> new file mode 100644
> index 0000000000..655c5f45ef
> --- /dev/null
> +++ b/soft-fp/truncbfhf2.c
> @@ -0,0 +1,75 @@
> +/* Software floating-point emulation.
> +   Truncate bfloat16 into IEEE half.
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "soft-fp.h"
> +#include "half.h"
> +#include "brain.h"
> +#include "single.h"
> +
> +/* BFtype and HFtype are unordered, neither is a superset or subset
> +   of each other.  Convert BFtype to SFtype (lossless) and then
> +   truncate to HFtype.  */
> +
> +HFtype
> +__truncbfhf2 (BFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_H (A);
> +  FP_DECL_S (B);
> +  FP_DECL_B (R);
> +  SFtype b;
> +  HFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  /* Optimize BFtype to SFtype conversion to simple left shift
> +     by 16 if possible, we don't need to raise exceptions on sNaN
> +     here as the SFtype to HFtype truncation should do that too.  */
> +  if (sizeof (BFtype) == 2
> +      && sizeof (unsigned short) == 2
> +      && sizeof (SFtype) == 4
> +      && sizeof (unsigned int) == 4)
> +    {
> +      union { BFtype a; unsigned short b; } u1;
> +      union { SFtype a; unsigned int b; } u2;
> +      u1.a = a;
> +      u2.b = (u1.b << 8) << 8;
> +      b = u2.a;
> +    }
> +  else
> +    {
> +      FP_UNPACK_RAW_B (A, a);
> +      FP_EXTEND (S, B, 1, 1, B, A);
> +      FP_PACK_RAW_S (b, B);
> +    }
> +  FP_UNPACK_SEMIRAW_S (B, b);
> +  FP_TRUNC (H, S, 1, 1, R, B);
> +  FP_PACK_SEMIRAW_H (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/truncdfbf2.c b/soft-fp/truncdfbf2.c
> new file mode 100644
> index 0000000000..fd3ff525a1
> --- /dev/null
> +++ b/soft-fp/truncdfbf2.c
> @@ -0,0 +1,52 @@
> +/* Software floating-point emulation.
> +   Truncate IEEE double into bfloat16.
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "soft-fp.h"
> +#include "brain.h"
> +#include "double.h"
> +
> +BFtype
> +__truncdfbf2 (DFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_D (A);
> +  FP_DECL_B (R);
> +  BFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_UNPACK_SEMIRAW_D (A, a);
> +#if _FP_W_TYPE_SIZE < _FP_FRACBITS_D
> +  FP_TRUNC (B, D, 1, 2, R, A);
> +#else
> +  FP_TRUNC (B, D, 1, 1, R, A);
> +#endif
> +  FP_PACK_SEMIRAW_B (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/trunchfbf2.c b/soft-fp/trunchfbf2.c
> new file mode 100644
> index 0000000000..248bed830c
> --- /dev/null
> +++ b/soft-fp/trunchfbf2.c
> @@ -0,0 +1,58 @@
> +/* Software floating-point emulation.
> +   Truncate IEEE half into bfloat16.
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "soft-fp.h"
> +#include "brain.h"
> +#include "half.h"
> +#include "single.h"
> +
> +/* BFtype and HFtype are unordered, neither is a superset or subset
> +   of each other.  Convert HFtype to SFtype (lossless) and then
> +   truncate to BFtype.  */
> +
> +BFtype
> +__trunchfbf2 (HFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_H (A);
> +  FP_DECL_S (B);
> +  FP_DECL_B (R);
> +  SFtype b;
> +  BFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_UNPACK_RAW_H (A, a);
> +  FP_EXTEND (S, H, 1, 1, B, A);
> +  FP_PACK_RAW_S (b, B);
> +  FP_UNPACK_SEMIRAW_S (B, b);
> +  FP_TRUNC (B, S, 1, 1, R, B);
> +  FP_PACK_SEMIRAW_B (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/truncsfbf2.c b/soft-fp/truncsfbf2.c
> new file mode 100644
> index 0000000000..9a5a9a0648
> --- /dev/null
> +++ b/soft-fp/truncsfbf2.c
> @@ -0,0 +1,48 @@
> +/* Software floating-point emulation.
> +   Truncate IEEE single into bfloat16.
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "soft-fp.h"
> +#include "brain.h"
> +#include "single.h"
> +
> +BFtype
> +__truncsfbf2 (SFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_S (A);
> +  FP_DECL_B (R);
> +  BFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_UNPACK_SEMIRAW_S (A, a);
> +  FP_TRUNC (B, S, 1, 1, R, A);
> +  FP_PACK_SEMIRAW_B (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/trunctfbf2.c b/soft-fp/trunctfbf2.c
> new file mode 100644
> index 0000000000..9b6bf93bbb
> --- /dev/null
> +++ b/soft-fp/trunctfbf2.c
> @@ -0,0 +1,52 @@
> +/* Software floating-point emulation.
> +   Truncate IEEE quad into bfloat16.
> +   Copyright (C) 2022-2023 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"
> +#include "quad.h"
> +
> +BFtype
> +__trunctfbf2 (TFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_Q (A);
> +  FP_DECL_B (R);
> +  BFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_UNPACK_SEMIRAW_Q (A, a);
> +#if _FP_W_TYPE_SIZE < 64
> +  FP_TRUNC (B, Q, 1, 4, R, A);
> +#else
> +  FP_TRUNC (B, Q, 1, 2, R, A);
> +#endif
> +  FP_PACK_SEMIRAW_B (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> diff --git a/soft-fp/truncxfbf2.c b/soft-fp/truncxfbf2.c
> new file mode 100644
> index 0000000000..2c3f288c92
> --- /dev/null
> +++ b/soft-fp/truncxfbf2.c
> @@ -0,0 +1,52 @@
> +/* Software floating-point emulation.
> +   Truncate IEEE extended into bfloat16.
> +   Copyright (C) 2022-2023 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include "soft-fp.h"
> +#include "brain.h"
> +#include "extended.h"
> +
> +BFtype
> +__truncxfbf2 (XFtype a)
> +{
> +  FP_DECL_EX;
> +  FP_DECL_E (A);
> +  FP_DECL_B (R);
> +  BFtype r;
> +
> +  FP_INIT_ROUNDMODE;
> +  FP_UNPACK_SEMIRAW_E (A, a);
> +#if _FP_W_TYPE_SIZE < 64
> +  FP_TRUNC (B, E, 1, 4, R, A);
> +#else
> +  FP_TRUNC (B, E, 1, 2, R, A);
> +#endif
> +  FP_PACK_SEMIRAW_B (r, R);
> +  FP_HANDLE_EXCEPTIONS;
> +
> +  return r;
> +}
> 
> 	Jakub
>