glibc/sysdeps/generic/fenv_private.h

/* Optimized inline fenv.h functions for libm.  Generic version.
   Copyright (C) 2011-2024 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.

   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 _FENV_PRIVATE_H
#define _FENV_PRIVATE_H 1

#include <fenv.h>
#include <get-rounding-mode.h>

/* The standards only specify one variant of the fenv.h interfaces.
   But at least for some architectures we can be more efficient if we
   know what operations are going to be performed.  Therefore we
   define additional interfaces.  By default they refer to the normal
   interfaces.  */

static __always_inline void
default_libc_feholdexcept (fenv_t *e)
{
  (void) __feholdexcept (e);
}

#ifndef libc_feholdexcept
# define libc_feholdexcept  default_libc_feholdexcept
#endif
#ifndef libc_feholdexceptf
# define libc_feholdexceptf default_libc_feholdexcept
#endif
#ifndef libc_feholdexceptl
# define libc_feholdexceptl default_libc_feholdexcept
#endif

static __always_inline void
default_libc_fesetround (int r)
{
  (void) __fesetround (r);
}

#ifndef libc_fesetround
# define libc_fesetround  default_libc_fesetround
#endif
#ifndef libc_fesetroundf
# define libc_fesetroundf default_libc_fesetround
#endif
#ifndef libc_fesetroundl
# define libc_fesetroundl default_libc_fesetround
#endif

static __always_inline void
default_libc_feholdexcept_setround (fenv_t *e, int r)
{
  __feholdexcept (e);
  __fesetround (r);
}

#ifndef libc_feholdexcept_setround
# define libc_feholdexcept_setround  default_libc_feholdexcept_setround
#endif
#ifndef libc_feholdexcept_setroundf
# define libc_feholdexcept_setroundf default_libc_feholdexcept_setround
#endif
#ifndef libc_feholdexcept_setroundl
# define libc_feholdexcept_setroundl default_libc_feholdexcept_setround
#endif

#ifndef libc_feholdsetround_53bit
# define libc_feholdsetround_53bit libc_feholdsetround
#endif

#ifndef libc_fetestexcept
# define libc_fetestexcept  fetestexcept
#endif
#ifndef libc_fetestexceptf
# define libc_fetestexceptf fetestexcept
#endif
#ifndef libc_fetestexceptl
# define libc_fetestexceptl fetestexcept
#endif

static __always_inline void
default_libc_fesetenv (fenv_t *e)
{
  (void) __fesetenv (e);
}

#ifndef libc_fesetenv
# define libc_fesetenv  default_libc_fesetenv
#endif
#ifndef libc_fesetenvf
# define libc_fesetenvf default_libc_fesetenv
#endif
#ifndef libc_fesetenvl
# define libc_fesetenvl default_libc_fesetenv
#endif

static __always_inline void
default_libc_feupdateenv (fenv_t *e)
{
  (void) __feupdateenv (e);
}

#ifndef libc_feupdateenv
# define libc_feupdateenv  default_libc_feupdateenv
#endif
#ifndef libc_feupdateenvf
# define libc_feupdateenvf default_libc_feupdateenv
#endif
#ifndef libc_feupdateenvl
# define libc_feupdateenvl default_libc_feupdateenv
#endif

#ifndef libc_feresetround_53bit
# define libc_feresetround_53bit libc_feresetround
#endif

static __always_inline int
default_libc_feupdateenv_test (fenv_t *e, int ex)
{
  int ret = fetestexcept (ex);
  __feupdateenv (e);
  return ret;
}

#ifndef libc_feupdateenv_test
# define libc_feupdateenv_test  default_libc_feupdateenv_test
#endif
#ifndef libc_feupdateenv_testf
# define libc_feupdateenv_testf default_libc_feupdateenv_test
#endif
#ifndef libc_feupdateenv_testl
# define libc_feupdateenv_testl default_libc_feupdateenv_test
#endif

/* Save and set the rounding mode.  The use of fenv_t to store the old mode
   allows a target-specific version of this function to avoid converting the
   rounding mode from the fpu format.  By default we have no choice but to
   manipulate the entire env.  */

#ifndef libc_feholdsetround
# define libc_feholdsetround  libc_feholdexcept_setround
#endif
#ifndef libc_feholdsetroundf
# define libc_feholdsetroundf libc_feholdexcept_setroundf
#endif
#ifndef libc_feholdsetroundl
# define libc_feholdsetroundl libc_feholdexcept_setroundl
#endif

/* ... and the reverse.  */

#ifndef libc_feresetround
# define libc_feresetround  libc_feupdateenv
#endif
#ifndef libc_feresetroundf
# define libc_feresetroundf libc_feupdateenvf
#endif
#ifndef libc_feresetroundl
# define libc_feresetroundl libc_feupdateenvl
#endif

/* ... and a version that also discards exceptions.  */

#ifndef libc_feresetround_noex
# define libc_feresetround_noex  libc_fesetenv
#endif
#ifndef libc_feresetround_noexf
# define libc_feresetround_noexf libc_fesetenvf
#endif
#ifndef libc_feresetround_noexl
# define libc_feresetround_noexl libc_fesetenvl
#endif

#ifndef HAVE_RM_CTX
# define HAVE_RM_CTX 0
#endif


/* Default implementation using standard fenv functions.
   Avoid unnecessary rounding mode changes by first checking the
   current rounding mode.  Note the use of __glibc_unlikely is
   important for performance.  */

static __always_inline void
default_libc_feholdsetround_ctx (struct rm_ctx *ctx, int round)
{
  ctx->updated_status = false;

  /* Update rounding mode only if different.  */
  if (__glibc_unlikely (round != get_rounding_mode ()))
    {
      ctx->updated_status = true;
      __fegetenv (&ctx->env);
      __fesetround (round);
    }
}

static __always_inline void
default_libc_feresetround_ctx (struct rm_ctx *ctx)
{
  /* Restore the rounding mode if updated.  */
  if (__glibc_unlikely (ctx->updated_status))
    __feupdateenv (&ctx->env);
}

static __always_inline void
default_libc_feholdsetround_noex_ctx (struct rm_ctx *ctx, int round)
{
  /* Save exception flags and rounding mode, and disable exception
     traps.  */
  __feholdexcept (&ctx->env);

  /* Update rounding mode only if different.  */
  if (__glibc_unlikely (round != get_rounding_mode ()))
    __fesetround (round);
}

static __always_inline void
default_libc_feresetround_noex_ctx (struct rm_ctx *ctx)
{
  /* Restore exception flags and rounding mode.  */
  __fesetenv (&ctx->env);
}

#if HAVE_RM_CTX
/* Set/Restore Rounding Modes only when necessary.  If defined, these functions
   set/restore floating point state only if the state needed within the lexical
   block is different from the current state.  This saves a lot of time when
   the floating point unit is much slower than the fixed point units.  */

# ifndef libc_feholdsetround_noex_ctx
#   define libc_feholdsetround_noex_ctx  libc_feholdsetround_ctx
# endif
# ifndef libc_feholdsetround_noexf_ctx
#   define libc_feholdsetround_noexf_ctx libc_feholdsetroundf_ctx
# endif
# ifndef libc_feholdsetround_noexl_ctx
#   define libc_feholdsetround_noexl_ctx libc_feholdsetroundl_ctx
# endif

# ifndef libc_feresetround_noex_ctx
#   define libc_feresetround_noex_ctx  libc_fesetenv_ctx
# endif
# ifndef libc_feresetround_noexf_ctx
#   define libc_feresetround_noexf_ctx libc_fesetenvf_ctx
# endif
# ifndef libc_feresetround_noexl_ctx
#   define libc_feresetround_noexl_ctx libc_fesetenvl_ctx
# endif

#else

# define libc_feholdsetround_ctx      default_libc_feholdsetround_ctx
# define libc_feresetround_ctx        default_libc_feresetround_ctx
# define libc_feholdsetround_noex_ctx default_libc_feholdsetround_noex_ctx
# define libc_feresetround_noex_ctx   default_libc_feresetround_noex_ctx

# define libc_feholdsetroundf_ctx libc_feholdsetround_ctx
# define libc_feholdsetroundl_ctx libc_feholdsetround_ctx
# define libc_feresetroundf_ctx   libc_feresetround_ctx
# define libc_feresetroundl_ctx   libc_feresetround_ctx

# define libc_feholdsetround_noexf_ctx libc_feholdsetround_noex_ctx
# define libc_feholdsetround_noexl_ctx libc_feholdsetround_noex_ctx
# define libc_feresetround_noexf_ctx   libc_feresetround_noex_ctx
# define libc_feresetround_noexl_ctx   libc_feresetround_noex_ctx

#endif

#ifndef libc_feholdsetround_53bit_ctx
#  define libc_feholdsetround_53bit_ctx libc_feholdsetround_ctx
#endif
#ifndef libc_feresetround_53bit_ctx
#  define libc_feresetround_53bit_ctx libc_feresetround_ctx
#endif

#define SET_RESTORE_ROUND_GENERIC(RM,ROUNDFUNC,CLEANUPFUNC) \
  struct rm_ctx ctx __attribute__((cleanup (CLEANUPFUNC ## _ctx))); \
  ROUNDFUNC ## _ctx (&ctx, (RM))

/* Set the rounding mode within a lexical block.  Restore the rounding mode to
   the value at the start of the block.  The exception mode must be preserved.
   Exceptions raised within the block must be set in the exception flags.
   Non-stop mode may be enabled inside the block.  */

#define SET_RESTORE_ROUND(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround, libc_feresetround)
#define SET_RESTORE_ROUNDF(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetroundf, libc_feresetroundf)
#define SET_RESTORE_ROUNDL(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetroundl, libc_feresetroundl)

/* Set the rounding mode within a lexical block.  Restore the rounding mode to
   the value at the start of the block.  The exception mode must be preserved.
   Exceptions raised within the block must be discarded, and exception flags
   are restored to the value at the start of the block.
   Non-stop mode must be enabled inside the block.  */

#define SET_RESTORE_ROUND_NOEX(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_noex, \
			     libc_feresetround_noex)
#define SET_RESTORE_ROUND_NOEXF(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_noexf, \
			     libc_feresetround_noexf)
#define SET_RESTORE_ROUND_NOEXL(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_noexl, \
			     libc_feresetround_noexl)

/* Like SET_RESTORE_ROUND, but also set rounding precision to 53 bits.  */
#define SET_RESTORE_ROUND_53BIT(RM) \
  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_53bit,	      \
			     libc_feresetround_53bit)

#endif /* fenv_private.h.  */