source: vbox/trunk/src/VBox/Runtime/common/math/x86/fenv-x86.c@ 16802

/*-
 * Copyright (c) 2004-2005 David Schultz <[email protected]>
 * 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.
 *
 * $FreeBSD: src/lib/msun/i387/fenv.c,v 1.2 2005/03/17 22:21:46 das Exp $
 */

/*#include "namespace.h"
#include <sys/cdefs.h>
#include <sys/types.h>
#include <machine/npx.h> 
#include "fenv.h"*/
#include <iprt/types.h>
#include <iprt/nocrt/fenv.h>

#if 0
const fenv_t __fe_dfl_env = {
        __INITIAL_NPXCW__,
        0x0000,
        0x0000,
        0x1f80,
        0xffffffff,
        { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
          0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff }
};
#endif 

enum __sse_support __has_sse =
#ifdef __SSE__
        __SSE_YES;
#else
        __SSE_UNK;
#endif

#define getfl(x)        __asm __volatile("pushfl\n\tpopl %0" : "=mr" (*(x)))
#define setfl(x)        __asm __volatile("pushl %0\n\tpopfl" : : "g" (x))
#define cpuid_dx(x)     __asm __volatile("pushl %%ebx\n\tmovl $1, %%eax\n\t"  \
                                         "cpuid\n\tpopl %%ebx"                \
                                        : "=d" (*(x)) : : "eax", "ecx")

/*
 * Test for SSE support on this processor.  We need to do this because
 * 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.
 */
int
__test_sse(void)
{
        int flag, nflag;
        int dx_features;

        /* Am I a 486? */
        getfl(&flag);
        nflag = flag ^ 0x200000;
        setfl(nflag);
        getfl(&nflag);
        if (flag != nflag) {
                /* Not a 486, so CPUID should work. */
                cpuid_dx(&dx_features);
                if (dx_features & 0x2000000) {
                        __has_sse = __SSE_YES;
                        return (1);
                }
        }
        __has_sse = __SSE_NO;
        return (0);
}

#if 0 /* later */
int
_STD(fesetexceptflag)(const fexcept_t *flagp, int excepts)
{
        fenv_t env;
        int mxcsr;

        __fnstenv(&env);
        env.__status &= ~excepts;
        env.__status |= *flagp & excepts;
        __fldenv(env);

        if (__HAS_SSE()) {
                __stmxcsr(&mxcsr);
                mxcsr &= ~excepts;
                mxcsr |= *flagp & excepts;
                __ldmxcsr(mxcsr);
        }

        return (0);
}

int
_STD(feraiseexcept)(int excepts)
{
        fexcept_t ex = excepts;

        fesetexceptflag(&ex, excepts);
        __fwait();
        return (0);
}

int
_STD(fegetenv)(fenv_t *envp)
{
        int control, mxcsr;

        /*
         * fnstenv masks all exceptions, so we need to save and
         * restore the control word to avoid this side effect.
         */
        __fnstcw(&control);
        __fnstenv(envp);
        if (__HAS_SSE()) {
                __stmxcsr(&mxcsr);
                __set_mxcsr(*envp, mxcsr);
        }
        __fldcw(control);
        return (0);
}

int
_STD(feholdexcept)(fenv_t *envp)
{
        int mxcsr;

        __fnstenv(envp);
        __fnclex();
        if (__HAS_SSE()) {
                __stmxcsr(&mxcsr);
                __set_mxcsr(*envp, mxcsr);
                mxcsr &= ~FE_ALL_EXCEPT;
                mxcsr |= FE_ALL_EXCEPT << _SSE_EMASK_SHIFT;
                __ldmxcsr(mxcsr);
        }
        return (0);
}

int
_STD(feupdateenv)(const fenv_t *envp)
{
        int mxcsr, status;

        __fnstsw(&status);
        if (__HAS_SSE())
                __stmxcsr(&mxcsr);
        else
                mxcsr = 0;
        fesetenv(envp);
        feraiseexcept((mxcsr | status) & FE_ALL_EXCEPT);
        return (0);
}

int
__feenableexcept(int mask)
{
        int mxcsr, control, omask;

        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)
{
        int mxcsr, control, omask;

        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);
}

__weak_reference(__feenableexcept, feenableexcept);
__weak_reference(__fedisableexcept, fedisableexcept);
#endif /* later */