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/* Helper macros for functions returning a narrower type.
Copyright (C) 2018-2025 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>
#include <stdbool.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.
CLEAR_UNDERFLOW indicates whether underflow exceptions must be
cleared (in the case where a round-toward-zero underflow might not
indicate an underflow after narrowing, when that narrowing only
reduces precision not exponent range and the architecture uses
before-rounding tininess detection). 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, CLEAR_UNDERFLOW) \
({ \
fenv_t env; \
UNION u; \
\
libc_feholdexcept_setround ## SUFFIX (&env, FE_TOWARDZERO); \
u.d = (EXPR); \
math_force_eval (u.d); \
if (CLEAR_UNDERFLOW) \
feclearexcept (FE_UNDERFLOW); \
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, false); \
\
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, false); \
\
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, SUFFIX and
CLEAR_UNDERFLOW are as for ROUND_TO_ODD. */
#define NARROW_MUL_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA, \
CLEAR_UNDERFLOW) \
do \
{ \
TYPE ret; \
\
ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) * (Y), \
UNION, SUFFIX, MANTISSA, \
CLEAR_UNDERFLOW); \
\
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, SUFFIX and
CLEAR_UNDERFLOW are as for ROUND_TO_ODD. */
#define NARROW_DIV_ROUND_TO_ODD(X, Y, TYPE, UNION, SUFFIX, MANTISSA, \
CLEAR_UNDERFLOW) \
do \
{ \
TYPE ret; \
\
ret = (TYPE) ROUND_TO_ODD (math_opt_barrier (X) / (Y), \
UNION, SUFFIX, MANTISSA, \
CLEAR_UNDERFLOW); \
\
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, false); \
\
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)
/* Check for error conditions from a narrowing fused multiply-add
function returning RET with arguments X, Y and Z and set errno as
needed. Checking for error conditions for fma (either narrowing or
not) and setting errno is not currently implemented. See bug
6801. */
#define CHECK_NARROW_FMA(RET, X, Y, Z) \
do \
{ \
} \
while (0)
/* Implement narrowing fused multiply-add using round-to-odd. The
arguments are X, Y and Z, the return type is TYPE and UNION,
MANTISSA, SUFFIX and CLEAR_UNDERFLOW are as for ROUND_TO_ODD. */
#define NARROW_FMA_ROUND_TO_ODD(X, Y, Z, TYPE, UNION, SUFFIX, MANTISSA, \
CLEAR_UNDERFLOW) \
do \
{ \
typeof (X) tmp; \
TYPE ret; \
\
tmp = ROUND_TO_ODD (fma ## SUFFIX (math_opt_barrier (X), (Y), \
(Z)), \
UNION, SUFFIX, MANTISSA, CLEAR_UNDERFLOW); \
/* If the round-to-odd result is zero, the result is an exact \
zero and must be recomputed in the original rounding mode. */ \
if (tmp == 0) \
ret = (TYPE) (math_opt_barrier (X) * (Y) + (Z)); \
else \
ret = (TYPE) tmp; \
\
CHECK_NARROW_FMA (ret, (X), (Y), (Z)); \
return ret; \
} \
while (0)
/* Implement a narrowing fused multiply-add 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 fma functions in libm, not using this
macro). The arguments are X, Y and Z and the return type is
TYPE. */
#define NARROW_FMA_TRIVIAL(X, Y, Z, TYPE, SUFFIX) \
do \
{ \
TYPE ret; \
\
ret = (TYPE) (fma ## SUFFIX ((X), (Y), (Z))); \
CHECK_NARROW_FMA (ret, (X), (Y), (Z)); \
return ret; \
} \
while (0)
#endif /* math-narrow.h. */
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