/* $NetBSD: fenv.c,v 1.7 2017/03/22 23:11:09 chs Exp $ */
/*-
* Copyright (c) 2004-2005 David Schultz <das (at) FreeBSD.ORG>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: fenv.c,v 1.7 2017/03/22 23:11:09 chs Exp $");
#include "namespace.h"
#include <assert.h>
#include <fenv.h>
#include <stddef.h>
#include <string.h>
#ifdef __weak_alias
__weak_alias(feclearexcept,_feclearexcept)
__weak_alias(fedisableexcept,_fedisableexcept)
__weak_alias(feenableexcept,_feenableexcept)
__weak_alias(fegetenv,_fegetenv)
__weak_alias(fegetexcept,_fegetexcept)
__weak_alias(fegetexceptflag,_fegetexceptflag)
__weak_alias(fegetround,_fegetround)
__weak_alias(feholdexcept,_feholdexcept)
__weak_alias(feraiseexcept,_feraiseexcept)
__weak_alias(fesetenv,_fesetenv)
__weak_alias(fesetexceptflag,_fesetexceptflag)
__weak_alias(fesetround,_fesetround)
__weak_alias(fetestexcept,_fetestexcept)
__weak_alias(feupdateenv,_feupdateenv)
#endif
/* Load x87 Control Word */
#define __fldcw(__cw) __asm__ __volatile__ \
("fldcw %0" : : "m" (__cw))
/* No-Wait Store Control Word */
#define __fnstcw(__cw) __asm__ __volatile__ \
("fnstcw %0" : "=m" (*(__cw)))
/* No-Wait Store Status Word */
#define __fnstsw(__sw) __asm__ __volatile__ \
("fnstsw %0" : "=am" (*(__sw)))
/* No-Wait Clear Exception Flags */
#define __fnclex() __asm__ __volatile__ \
("fnclex")
/* Load x87 Environment */
#define __fldenv(__env) __asm__ __volatile__ \
("fldenv %0" : : "m" (__env))
/* No-Wait Store x87 environment */
#define __fnstenv(__env) __asm__ __volatile__ \
("fnstenv %0" : "=m" (*(__env)))
/* Check for and handle pending unmasked x87 pending FPU exceptions */
#define __fwait(__env) __asm__ __volatile__ \
("fwait")
/* Load the MXCSR register */
#define __ldmxcsr(__mxcsr) __asm__ __volatile__ \
("ldmxcsr %0" : : "m" (__mxcsr))
/* Store the MXCSR register state */
#define __stmxcsr(__mxcsr) __asm__ __volatile__ \
("stmxcsr %0" : "=m" (*(__mxcsr)))
/*
* The following constant represents the default floating-point environment
* (that is, the one installed at program startup) and has type pointer to
* const-qualified fenv_t.
*
* It can be used as an argument to the functions within the <fenv.h> header
* that manage the floating-point environment, namely fesetenv() and
* feupdateenv().
*
* x87 fpu registers are 16bit wide. The upper bits, 31-16, are marked as
* RESERVED. We provide a partial floating-point environment, where we
* define only the lower bits. The reserved bits are extracted and set by
* the consumers of FE_DFL_ENV, during runtime.
*/
fenv_t __fe_dfl_env = {
{
__NetBSD_NPXCW__, /* Control word register */
0x00000000, /* Status word register */
0x0000ffff, /* Tag word register */
{
0x00000000,
0x00000000,
0x00000000,
0x00000000,
},
},
__INITIAL_MXCSR__ /* MXCSR register */
};
#define FE_DFL_ENV ((const fenv_t *) &__fe_dfl_env)
static void __init_libm(void) __attribute__ ((constructor, used));
static void __init_libm(void)
{
uint16_t control;
__fnstcw(&control);
__fe_dfl_env.x87.control = control;
}
/*
* The feclearexcept() function clears the supported floating-point exceptions
* represented by `excepts'.
*/
int
feclearexcept(int excepts)
{
fenv_t fenv;
int ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
/* Store the current x87 floating-point environment */
__fnstenv(&fenv);
/* Clear the requested floating-point exceptions */
fenv.x87.status &= ~ex;
/* Load the x87 floating-point environent */
__fldenv(fenv);
/* Same for SSE environment */
__stmxcsr(&fenv.mxcsr);
fenv.mxcsr &= ~ex;
__ldmxcsr(fenv.mxcsr);
/* Success */
return (0);
}
/*
* The fegetexceptflag() function stores an implementation-defined
* representation of the states of the floating-point status flags indicated by
* the argument excepts in the object pointed to by the argument flagp.
*/
int
fegetexceptflag(fexcept_t *flagp, int excepts)
{
uint32_t mxcsr;
uint16_t x87_status;
int ex;
_DIAGASSERT(flagp != NULL);
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
/* Store the current x87 status register */
__fnstsw(&x87_status);
/* Store the MXCSR register */
__stmxcsr(&mxcsr);
/* Store the results in flagp */
*flagp = (x87_status | mxcsr) & ex;
/* Success */
return (0);
}
/*
* The feraiseexcept() function raises the supported floating-point exceptions
* represented by the argument `excepts'.
*
* The standard explicitly allows us to execute an instruction that has the
* exception as a side effect, but we choose to manipulate the status register
* directly.
*
* The validation of input is being deferred to fesetexceptflag().
*/
int
feraiseexcept(int excepts)
{
int ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
fesetexceptflag((unsigned int *)&ex, ex);
__fwait();
/* Success */
return (0);
}
/*
* This function sets the floating-point status flags indicated by the argument
* `excepts' to the states stored in the object pointed to by `flagp'. It does
* NOT raise any floating-point exceptions, but only sets the state of the flags.
*/
int
fesetexceptflag(const fexcept_t *flagp, int excepts)
{
fenv_t fenv;
int ex;
_DIAGASSERT(flagp != NULL);
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
/* Store the current x87 floating-point environment */
__fnstenv(&fenv);
/* Set the requested status flags */
fenv.x87.status |= *flagp & ex;
/* Load the x87 floating-point environent */
__fldenv(fenv);
/* Same for SSE environment */
__stmxcsr(&fenv.mxcsr);
fenv.mxcsr |= *flagp & ex;
__ldmxcsr(fenv.mxcsr);
/* Success */
return (0);
}
/*
* The fetestexcept() function determines which of a specified subset of the
* floating-point exception flags are currently set. The `excepts' argument
* specifies the floating-point status flags to be queried.
*/
int
fetestexcept(int excepts)
{
fenv_t fenv;
uint32_t mxcsr;
uint16_t status;
int ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
/* Store the current x87 floating-point environment */
memset(&fenv, 0, sizeof(fenv));
__fnstenv(&fenv);
__fnstsw(&status);
/* Store the MXCSR register state */
__stmxcsr(&fenv.mxcsr);
__stmxcsr(&mxcsr);
return ((fenv.x87.status | fenv.mxcsr) & ex);
}
/*
* The fegetround() function gets the current rounding direction.
*/
int
fegetround(void)
{
uint32_t mxcsr;
uint16_t control;
/*
* We check both the x87 floating-point unit _and_ the SSE unit.
* Normally, those two must agree with respect to each other. If they
* don't, it's not our fault and the result is non-determinable, in
* which case POSIX says that a negative value should be returned.
*/
__fnstcw(&control);
__stmxcsr(&mxcsr);
if ((control & _X87_ROUNDING_MASK)
!= ((mxcsr & _SSE_ROUNDING_MASK) >> 3)) {
return (-1);
}
return (control & _X87_ROUNDING_MASK);
}
/*
* The fesetround() function establishes the rounding direction represented by
* its argument `round'. If the argument is not equal to the value of a rounding
* direction macro, the rounding direction is not changed.
*/
int
fesetround(int round)
{
uint32_t mxcsr;
uint16_t control;
/* Check whether requested rounding direction is supported */
if (round & (~_X87_ROUNDING_MASK))
return (-1);
/* Store the current x87 control word register */
__fnstcw(&control);
/*
* Set the rounding direction
* Rounding Control is bits 10-11, so shift appropriately
*/
control &= ~_X87_ROUNDING_MASK;
control |= round;
/* Load the x87 control word register */
__fldcw(control);
/*
* Same for the SSE environment
* Rounding Control is bits 13-14, so shift appropriately
*/
__stmxcsr(&mxcsr);
mxcsr &= ~_SSE_ROUNDING_MASK;
mxcsr |= (round << _SSE_ROUND_SHIFT);
__ldmxcsr(mxcsr);
/* Success */
return (0);
}
/*
* The fegetenv() function attempts to store the current floating-point
* environment in the object pointed to by envp.
*/
int
fegetenv(fenv_t *envp)
{
_DIAGASSERT(envp != NULL);
/* Store the current x87 floating-point environment */
__fnstenv(envp);
/* Store the MXCSR register state */
__stmxcsr(&envp->mxcsr);
/*
* When an FNSTENV instruction is executed, all pending exceptions are
* essentially lost (either the x87 FPU status register is cleared or all
* exceptions are masked).
*
* 8.6 X87 FPU EXCEPTION SYNCHRONIZATION -
* Intel(R) 64 and IA-32 Architectures Softare Developer's Manual - Vol 1
*
*/
__fldcw(envp->x87.control);
/* Success */
return (0);
}
/*
* The feholdexcept() function saves the current floating-point environment
* in the object pointed to by envp, clears the floating-point status flags, and
* then installs a non-stop (continue on floating-point exceptions) mode, if
* available, for all floating-point exceptions.
*/
int
feholdexcept(fenv_t *envp)
{
uint32_t mxcsr;
_DIAGASSERT(envp != NULL);
/* Store the current x87 floating-point environment */
__fnstenv(envp);
/* Clear all exception flags in FPU */
__fnclex();
/* Store the MXCSR register state */
__stmxcsr(&envp->mxcsr);
/* Clear exception flags in MXCSR XXX */
mxcsr = envp->mxcsr;
mxcsr &= ~FE_ALL_EXCEPT;
/* Mask all exceptions */
mxcsr |= FE_ALL_EXCEPT << _SSE_EMASK_SHIFT;
__ldmxcsr(mxcsr);
/* Success */
return (0);
}
/*
* The fesetenv() function attempts to establish the floating-point environment
* represented by the object pointed to by envp. The argument `envp' points
* to an object set by a call to fegetenv() or feholdexcept(), or equal a
* floating-point environment macro. The fesetenv() function does not raise
* floating-point exceptions, but only installs the state of the floating-point
* status flags represented through its argument.
*/
int
fesetenv(const fenv_t *envp)
{
fenv_t fenv;
_DIAGASSERT(envp != NULL);
/* Store the x87 floating-point environment */
memset(&fenv, 0, sizeof fenv);
__fnstenv(&fenv);
__fe_dfl_env.x87.control = (fenv.x87.control & 0xffff0000)
| (__fe_dfl_env.x87.control & 0x0000ffff);
__fe_dfl_env.x87.status = (fenv.x87.status & 0xffff0000)
| (__fe_dfl_env.x87.status & 0x0000ffff);
__fe_dfl_env.x87.tag = (fenv.x87.tag & 0xffff0000)
| (__fe_dfl_env.x87.tag & 0x0000ffff);
__fe_dfl_env.x87.others[3] = (fenv.x87.others[3] & 0xffff0000)
| (__fe_dfl_env.x87.others[3] & 0x0000ffff);
__fldenv(*envp);
/* Store the MXCSR register */
__ldmxcsr(envp->mxcsr);
/* Success */
return (0);
}
/*
* The feupdateenv() function saves the currently raised floating-point
* exceptions in its automatic storage, installs the floating-point environment
* represented by the object pointed to by `envp', and then raises the saved
* floating-point exceptions. The argument `envp' shall point to an object set
* by a call to feholdexcept() or fegetenv(), or equal a floating-point
* environment macro.
*/
int
feupdateenv(const fenv_t *envp)
{
fenv_t fenv;
uint32_t mxcsr;
uint16_t sw;
_DIAGASSERT(envp != NULL);
/* Store the x87 floating-point environment */
memset(&fenv, 0, sizeof(fenv));
__fnstenv(&fenv);
__fe_dfl_env.x87.control = (fenv.x87.control & 0xffff0000)
| (__fe_dfl_env.x87.control & 0x0000ffff);
__fe_dfl_env.x87.status = (fenv.x87.status & 0xffff0000)
| (__fe_dfl_env.x87.status & 0x0000ffff);
__fe_dfl_env.x87.tag = (fenv.x87.tag & 0xffff0000)
| (__fe_dfl_env.x87.tag & 0x0000ffff);
__fe_dfl_env.x87.others[3] = (fenv.x87.others[3] & 0xffff0000)
| (__fe_dfl_env.x87.others[3] & 0x0000ffff);
/* Store the x87 status register */
__fnstsw(&sw);
/* Store the MXCSR register */
__stmxcsr(&mxcsr);
/* Install new floating-point environment */
fesetenv(envp);
/* Raise any previously accumulated exceptions */
feraiseexcept((sw | mxcsr) & FE_ALL_EXCEPT);
/* Success */
return (0);
}
/*
* The following functions are extentions to the standard
*/
int
feenableexcept(int mask)
{
uint32_t mxcsr, omask;
uint16_t control;
_DIAGASSERT((mask & ~FE_ALL_EXCEPT) == 0);
mask &= FE_ALL_EXCEPT;
__fnstcw(&control);
__stmxcsr(&mxcsr);
omask = (control | mxcsr >> _SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
control &= ~mask;
__fldcw(control);
mxcsr &= ~(mask << _SSE_EMASK_SHIFT);
__ldmxcsr(mxcsr);
return (FE_ALL_EXCEPT & ~omask);
}
int
fedisableexcept(int mask)
{
uint32_t mxcsr, omask;
uint16_t control;
_DIAGASSERT((mask & ~FE_ALL_EXCEPT) == 0);
__fnstcw(&control);
__stmxcsr(&mxcsr);
omask = (control | mxcsr >> _SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
control |= mask;
__fldcw(control);
mxcsr |= mask << _SSE_EMASK_SHIFT;
__ldmxcsr(mxcsr);
return (FE_ALL_EXCEPT & ~omask);
}
int
fegetexcept(void)
{
uint16_t control;
/*
* We assume that the masks for the x87 and the SSE unit are
* the same.
*/
__fnstcw(&control);
return (~control & FE_ALL_EXCEPT);
}