glibc/math/math-narrow.h

/* Helper macros for functions returning a narrower type.
   Copyright (C) 2018-2021 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	_MATH_NARROW_H
#define	_MATH_NARROW_H	1

#include <bits/floatn.h>
#include <bits/long-double.h>
#include <errno.h>
#include <fenv.h>
#include <ieee754.h>
#include <math-barriers.h>
#include <math_private.h>
#include <fenv_private.h>
#include <math-narrow-alias.h>

/* Carry out a computation using round-to-odd.  The computation is
   EXPR; the union type in which to store the result is UNION and the
   subfield of the "ieee" field of that union with the low part of the
   mantissa is MANTISSA; SUFFIX is the suffix for both underlying libm
   functions for the argument type (for computations where a libm
   function rather than a C operator is used when argument and result
   types are the same) and the libc_fe* macros to ensure that the
   correct rounding mode is used, for platforms with multiple rounding
   modes where those macros set only the relevant mode.  This macro
   does not work correctly if the sign of an exact zero result depends
   on the rounding mode, so that case must be checked for
   separately.  */
#define ROUND_TO_ODD(EXPR, UNION, SUFFIX, MANTISSA)			\
  ({									\
    fenv_t env;								\
    UNION u;								\
									\
    libc_feholdexcept_setround ## SUFFIX (&env, FE_TOWARDZERO);		\
    u.d = (EXPR);							\
    math_force_eval (u.d);						\
    u.ieee.MANTISSA							\
      |= libc_feupdateenv_test ## SUFFIX (&env, FE_INEXACT) != 0;	\
									\
    u.d;								\
  })

/* Check for error conditions from a narrowing add function returning
   RET with arguments X and Y and set errno as needed.  Overflow and
   underflow can occur for finite arguments and a domain error for
   infinite ones.  */
#define CHECK_NARROW_ADD(RET, X, Y)			\
  do							\
    {							\
      if (!isfinite (RET))				\
	{						\
	  if (isnan (RET))				\
	    {						\
	      if (!isnan (X) && !isnan (Y))		\
		__set_errno (EDOM);			\
	    }						\
	  else if (isfinite (X) && isfinite (Y))	\
	    __set_errno (ERANGE);			\
	}						\
      else if ((RET) == 0 && (X) != -(Y))		\
	__set_errno (ERANGE);				\
    }							\
  while (0)

/* Implement narrowing add using round-to-odd.  The arguments are X
   and Y, the return type is TYPE and UNION, MANTISSA and SUFFIX are
   as for ROUND_TO_ODD.  */
#define NARROW_ADD_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA)	\
  do									\
    {									\
      TYPE ret;								\
									\
      /* Ensure a zero result is computed in the original rounding	\
	 mode.  */							\
      if ((X) == -(Y))							\
	ret = (TYPE) ((X) + (Y));					\
      else								\
	ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) + (Y),		\
				   UNION, SUFFIX, MANTISSA);		\
									\
      CHECK_NARROW_ADD (ret, (X), (Y));					\
      return ret;							\
    }									\
  while (0)

/* Implement a narrowing add function that is not actually narrowing
   or where no attempt is made to be correctly rounding (the latter
   only applies to IBM long double).  The arguments are X and Y and
   the return type is TYPE.  */
#define NARROW_ADD_TRIVIAL(X, Y, TYPE)		\
  do						\
    {						\
      TYPE ret;					\
						\
      ret = (TYPE) ((X) + (Y));			\
      CHECK_NARROW_ADD (ret, (X), (Y));		\
      return ret;				\
    }						\
  while (0)

/* Check for error conditions from a narrowing subtract function
   returning RET with arguments X and Y and set errno as needed.
   Overflow and underflow can occur for finite arguments and a domain
   error for infinite ones.  */
#define CHECK_NARROW_SUB(RET, X, Y)			\
  do							\
    {							\
      if (!isfinite (RET))				\
	{						\
	  if (isnan (RET))				\
	    {						\
	      if (!isnan (X) && !isnan (Y))		\
		__set_errno (EDOM);			\
	    }						\
	  else if (isfinite (X) && isfinite (Y))	\
	    __set_errno (ERANGE);			\
	}						\
      else if ((RET) == 0 && (X) != (Y))		\
	__set_errno (ERANGE);				\
    }							\
  while (0)

/* Implement narrowing subtract using round-to-odd.  The arguments are
   X and Y, the return type is TYPE and UNION, MANTISSA and SUFFIX are
   as for ROUND_TO_ODD.  */
#define NARROW_SUB_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA)	\
  do									\
    {									\
      TYPE ret;								\
									\
      /* Ensure a zero result is computed in the original rounding	\
	 mode.  */							\
      if ((X) == (Y))							\
	ret = (TYPE) ((X) - (Y));					\
      else								\
	ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) - (Y),		\
				   UNION, SUFFIX, MANTISSA);		\
									\
      CHECK_NARROW_SUB (ret, (X), (Y));					\
      return ret;							\
    }									\
  while (0)

/* Implement a narrowing subtract function that is not actually
   narrowing or where no attempt is made to be correctly rounding (the
   latter only applies to IBM long double).  The arguments are X and Y
   and the return type is TYPE.  */
#define NARROW_SUB_TRIVIAL(X, Y, TYPE)		\
  do						\
    {						\
      TYPE ret;					\
						\
      ret = (TYPE) ((X) - (Y));			\
      CHECK_NARROW_SUB (ret, (X), (Y));		\
      return ret;				\
    }						\
  while (0)

/* Check for error conditions from a narrowing multiply function
   returning RET with arguments X and Y and set errno as needed.
   Overflow and underflow can occur for finite arguments and a domain
   error for Inf * 0.  */
#define CHECK_NARROW_MUL(RET, X, Y)			\
  do							\
    {							\
      if (!isfinite (RET))				\
	{						\
	  if (isnan (RET))				\
	    {						\
	      if (!isnan (X) && !isnan (Y))		\
		__set_errno (EDOM);			\
	    }						\
	  else if (isfinite (X) && isfinite (Y))	\
	    __set_errno (ERANGE);			\
	}						\
      else if ((RET) == 0 && (X) != 0 && (Y) != 0)	\
	__set_errno (ERANGE);				\
    }							\
  while (0)

/* Implement narrowing multiply using round-to-odd.  The arguments are
   X and Y, the return type is TYPE and UNION, MANTISSA and SUFFIX are
   as for ROUND_TO_ODD.  */
#define NARROW_MUL_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA)	\
  do									\
    {									\
      TYPE ret;								\
									\
      ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) * (Y),		\
				 UNION, SUFFIX, MANTISSA);		\
									\
      CHECK_NARROW_MUL (ret, (X), (Y));					\
      return ret;							\
    }									\
  while (0)

/* Implement a narrowing multiply function that is not actually
   narrowing or where no attempt is made to be correctly rounding (the
   latter only applies to IBM long double).  The arguments are X and Y
   and the return type is TYPE.  */
#define NARROW_MUL_TRIVIAL(X, Y, TYPE)		\
  do						\
    {						\
      TYPE ret;					\
						\
      ret = (TYPE) ((X) * (Y));			\
      CHECK_NARROW_MUL (ret, (X), (Y));		\
      return ret;				\
    }						\
  while (0)

/* Check for error conditions from a narrowing divide function
   returning RET with arguments X and Y and set errno as needed.
   Overflow, underflow and divide-by-zero can occur for finite
   arguments and a domain error for Inf / Inf and 0 / 0.  */
#define CHECK_NARROW_DIV(RET, X, Y)			\
  do							\
    {							\
      if (!isfinite (RET))				\
	{						\
	  if (isnan (RET))				\
	    {						\
	      if (!isnan (X) && !isnan (Y))		\
		__set_errno (EDOM);			\
	    }						\
	  else if (isfinite (X))			\
	    __set_errno (ERANGE);			\
	}						\
      else if ((RET) == 0 && (X) != 0 && !isinf (Y))	\
	__set_errno (ERANGE);				\
    }							\
  while (0)

/* Implement narrowing divide using round-to-odd.  The arguments are
   X and Y, the return type is TYPE and UNION, MANTISSA and SUFFIX are
   as for ROUND_TO_ODD.  */
#define NARROW_DIV_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA)	\
  do									\
    {									\
      TYPE ret;								\
									\
      ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) / (Y),		\
				 UNION, SUFFIX, MANTISSA);		\
									\
      CHECK_NARROW_DIV (ret, (X), (Y));					\
      return ret;							\
    }									\
  while (0)

/* Implement a narrowing divide function that is not actually
   narrowing or where no attempt is made to be correctly rounding (the
   latter only applies to IBM long double).  The arguments are X and Y
   and the return type is TYPE.  */
#define NARROW_DIV_TRIVIAL(X, Y, TYPE)		\
  do						\
    {						\
      TYPE ret;					\
						\
      ret = (TYPE) ((X) / (Y));			\
      CHECK_NARROW_DIV (ret, (X), (Y));		\
      return ret;				\
    }						\
  while (0)

/* Check for error conditions from a narrowing square root function
   returning RET with argument X and set errno as needed.  Overflow
   and underflow can occur for finite positive arguments and a domain
   error for negative arguments.  */
#define CHECK_NARROW_SQRT(RET, X)		\
  do						\
    {						\
      if (!isfinite (RET))			\
	{					\
	  if (isnan (RET))			\
	    {					\
	      if (!isnan (X))			\
		__set_errno (EDOM);		\
	    }					\
	  else if (isfinite (X))		\
	    __set_errno (ERANGE);		\
	}					\
      else if ((RET) == 0 && (X) != 0)		\
	__set_errno (ERANGE);			\
    }						\
  while (0)

/* Implement narrowing square root using round-to-odd.  The argument
   is X, the return type is TYPE and UNION, MANTISSA and SUFFIX are as
   for ROUND_TO_ODD.  */
#define NARROW_SQRT_ROUND_TO_ODD(X, TYPE, UNION, SUFFIX, MANTISSA)	\
  do									\
    {									\
      TYPE ret;								\
									\
      ret = (TYPE) ROUND_TO_ODD (sqrt ## SUFFIX (math_opt_barrier (X)),	\
				 UNION, SUFFIX, MANTISSA);		\
									\
      CHECK_NARROW_SQRT (ret, (X));					\
      return ret;							\
    }									\
  while (0)

/* Implement a narrowing square root function where no attempt is made
   to be correctly rounding (this only applies to IBM long double; the
   case where the function is not actually narrowing is handled by
   aliasing other sqrt functions in libm, not using this macro).  The
   argument is X and the return type is TYPE.  */
#define NARROW_SQRT_TRIVIAL(X, TYPE, SUFFIX)	\
  do						\
    {						\
      TYPE ret;					\
						\
      ret = (TYPE) (sqrt ## SUFFIX (X));	\
      CHECK_NARROW_SQRT (ret, (X));		\
      return ret;				\
    }						\
  while (0)

#endif /* math-narrow.h.  */