minix/lib/libm/arch/i387/fenv.c

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/* $NetBSD: fenv.c,v 1.3 2010/08/01 06:34:38 taca Exp $ */
/*-
* Copyright (c) 2004-2005 David Schultz <das@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 1.3 2010/08/01 06:34:38 taca Exp $");
#include <sys/param.h>
#include <sys/sysctl.h>
#include <assert.h>
#include <fenv.h>
#include <stddef.h>
#include <string.h>
/* 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 */
0x0, /* Unused */
0x0000, /* Status word register */
0x0, /* Unused */
0x0000ffff, /* Tag word register */
0x0, /* Unused */
{
0x0000, 0x0000,
0x0000, 0xffff
}
},
__INITIAL_MXCSR__ /* MXCSR register */
};
/*
* Test for SSE support on this processor.
*
* We need to use ldmxcsr/stmxcsr to get correct results if any part
* of the program was compiled to use SSE floating-point, but we can't
* use SSE on older processors.
*
* In order to do so, we need to query the processor capabilities via the CPUID
* instruction. We can make it even simpler though, by querying the machdep.sse
* sysctl.
*/
static int __HAS_SSE = 0;
static void __test_sse(void) __attribute__ ((constructor));
static void __test_sse(void)
{
#ifndef __minix
size_t oldlen = sizeof(__HAS_SSE);
int rv;
rv = sysctlbyname("machdep.sse", &__HAS_SSE, &oldlen, NULL, 0);
if (rv == -1)
#endif
__HAS_SSE = 0;
}
/*
* The feclearexcept() function clears the supported floating-point exceptions
* represented by `excepts'.
*/
int
feclearexcept(int excepts)
{
fenv_t env;
uint32_t mxcsr;
int ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
/* It's ~3x faster to call fnclex, than store/load fp env */
if (ex == FE_ALL_EXCEPT) {
__fnclex();
} else {
__fnstenv(&env);
env.x87.status &= ~ex;
__fldenv(env);
}
if (__HAS_SSE) {
__stmxcsr(&mxcsr);
mxcsr &= ~ex;
__ldmxcsr(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 status;
int ex;
_DIAGASSERT(flagp != NULL);
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
__fnstsw(&status);
if (__HAS_SSE)
__stmxcsr(&mxcsr);
else
mxcsr = 0;
*flagp = (mxcsr | status) & 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)
{
fexcept_t ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
fesetexceptflag(&ex, excepts);
__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 env;
uint32_t mxcsr;
int ex;
_DIAGASSERT(flagp != NULL);
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
__fnstenv(&env);
env.x87.status &= ~ex;
env.x87.status |= *flagp & ex;
__fldenv(env);
if (__HAS_SSE) {
__stmxcsr(&mxcsr);
mxcsr &= ~ex;
mxcsr |= *flagp & ex;
__ldmxcsr(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)
{
uint32_t mxcsr;
uint16_t status;
int ex;
_DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0);
ex = excepts & FE_ALL_EXCEPT;
__fnstsw(&status);
if (__HAS_SSE)
__stmxcsr(&mxcsr);
else
mxcsr = 0;
return ((status | mxcsr) & ex);
}
int
fegetround(void)
{
uint16_t control;
/*
* We assume that the x87 and the SSE unit agree on the
* rounding mode. Reading the control word on the x87 turns
* out to be about 5 times faster than reading it on the SSE
* unit on an Opteron 244.
*/
__fnstcw(&control);
return (control & __X87_ROUND_MASK);
}
/*
* The fesetround() function shall establish 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;
if (round & ~__X87_ROUND_MASK) {
/* Failure */
return (-1);
}
__fnstcw(&control);
control &= ~__X87_ROUND_MASK;
control |= round;
__fldcw(control);
if (__HAS_SSE) {
__stmxcsr(&mxcsr);
mxcsr &= ~(__X87_ROUND_MASK << __SSE_ROUND_SHIFT);
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)
{
uint32_t mxcsr;
_DIAGASSERT(flagp != NULL);
/*
* fnstenv masks all exceptions, so we need to restore the old control
* word to avoid this side effect.
*/
__fnstenv(envp);
__fldcw(envp->x87.control);
if (__HAS_SSE) {
__stmxcsr(&mxcsr);
envp->mxcsr = mxcsr;
}
/* 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);
__fnstenv(envp);
__fnclex();
if (__HAS_SSE) {
__stmxcsr(&mxcsr);
envp->mxcsr = mxcsr;
mxcsr &= ~FE_ALL_EXCEPT;
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 env;
_DIAGASSERT(envp != NULL);
/* Store the x87 floating-point environment */
memset(&env, 0, sizeof(env));
__fnstenv(&env);
__fe_dfl_env.x87.unused1 = env.x87.unused1;
__fe_dfl_env.x87.unused2 = env.x87.unused2;
__fe_dfl_env.x87.unused3 = env.x87.unused3;
memcpy(__fe_dfl_env.x87.others,
env.x87.others,
sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t));
__fldenv(envp->x87);
if (__HAS_SSE)
__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 env;
uint32_t mxcsr;
uint16_t status;
_DIAGASSERT(envp != NULL);
/* Store the x87 floating-point environment */
memset(&env, 0, sizeof(env));
__fnstenv(&env);
__fe_dfl_env.x87.unused1 = env.x87.unused1;
__fe_dfl_env.x87.unused2 = env.x87.unused2;
__fe_dfl_env.x87.unused3 = env.x87.unused3;
memcpy(__fe_dfl_env.x87.others,
env.x87.others,
sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t));
__fnstsw(&status);
if (__HAS_SSE)
__stmxcsr(&mxcsr);
else
mxcsr = 0;
fesetenv(envp);
feraiseexcept((mxcsr | status) & 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;
mask &= FE_ALL_EXCEPT;
__fnstcw(&control);
if (__HAS_SSE)
__stmxcsr(&mxcsr);
else
mxcsr = 0;
omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
control &= ~mask;
__fldcw(control);
if (__HAS_SSE) {
mxcsr &= ~(mask << __SSE_EMASK_SHIFT);
__ldmxcsr(mxcsr);
}
return (~omask);
}
int
fedisableexcept(int mask)
{
uint32_t mxcsr, omask;
uint16_t control;
mask &= FE_ALL_EXCEPT;
__fnstcw(&control);
if (__HAS_SSE)
__stmxcsr(&mxcsr);
else
mxcsr = 0;
omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
control |= mask;
__fldcw(control);
if (__HAS_SSE) {
mxcsr |= mask << __SSE_EMASK_SHIFT;
__ldmxcsr(mxcsr);
}
return (~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);
}