/***
*ieee.c - ieee control and status routines
*
* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
* IEEE control and status routines.
*
*Revision History:
*
* 04-01-02 GDP Rewritten to use abstract control and status words
* 10-30-92 GDP _fpreset now resets saved fp context if called from a
* signal handler.
* 09-01-94 SKS Change include file from <nt.h> to <windows.h>
* 04-11-95 JWM _fpreset() now resets default precision.
* 05-10-96 BWT Fix POSIX build.
*
*/
#include <trans.h>
#include <float.h>
#include <windows.h>
#include <signal.h>
extern void _setdefaultprecision();
static unsigned int _abstract_sw(unsigned short sw);
static unsigned int _abstract_cw(unsigned short cw);
static unsigned short _hw_cw(unsigned int abstr);
/***
* _statusfp() -
*
*Purpose:
* return abstract fp status word
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _statusfp()
{
short status;
_asm {
fstsw status
}
return _abstract_sw(status);
}
/***
*_clearfp() -
*
*Purpose:
* return abstract status word and clear status
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _clearfp()
{
short status;
_asm {
fnstsw status
fnclex
}
return _abstract_sw(status);
}
/*** _control87
*() -
*
*Purpose:
* return and set abstract user fp control word
* can modify EM_DENORMAL mask
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _control87(unsigned int newctrl, unsigned int mask)
{
short oldCw;
short newCw;
unsigned int oldabs;
unsigned int newabs;
_asm {
fstcw oldCw
}
oldabs = _abstract_cw(oldCw);
newabs = (newctrl & mask) | (oldabs & ~mask);
newCw = _hw_cw(newabs);
_asm {
fldcw newCw
}
return newabs;
} /* _controlfp() */
/*** _controlfp
*() -
*
*Purpose:
* return and set abstract user fp control word
* cannot change denormal mask (ignores _EM_DENORMAL)
* This is done for portable IEEE behavior on all platforms
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _controlfp(unsigned int newctrl, unsigned int mask)
{
return _control87(newctrl, mask & ~_EM_DENORMAL);
}
/***
* _fpreset() - reset fp system
*
*Purpose:
* reset fp environment to the default state
* Also reset saved fp environment if invoked from a user's
* signal handler
*
*Entry:
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
#define TAG_ALL_EMPTY ((unsigned int) 0xffff);
void _fpreset()
{
#ifndef _POSIX_
PEXCEPTION_POINTERS excptrs = (PEXCEPTION_POINTERS) _pxcptinfoptrs;
#endif
_asm {
fninit
}
_setdefaultprecision(); // reset precision, usually down to 53 bits
#ifndef _POSIX_
if (excptrs &&
excptrs->ContextRecord->ContextFlags & CONTEXT_FLOATING_POINT) {
// _fpreset has been invoked by a signal handler which in turn
// has been invoked by the CRT filter routine. In this case
// the saved fp context should be cleared, so that the change take
// effect on continuation.
FLOATING_SAVE_AREA *pFloatSave = &excptrs->ContextRecord->FloatSave;
pFloatSave->StatusWord = 0;
pFloatSave->TagWord = TAG_ALL_EMPTY;
}
#endif
}
/***
* _abstract_cw() - abstract control word
*
*Purpose:
* produce a fp control word in abstracted (machine independent) form
*
*Entry:
* cw: machine control word
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _abstract_cw(unsigned short cw)
{
unsigned int abstr = 0;
//
// Set exception mask bits
//
if (cw & IEM_INVALID)
abstr |= _EM_INVALID;
if (cw & IEM_ZERODIVIDE)
abstr |= _EM_ZERODIVIDE;
if (cw & IEM_OVERFLOW)
abstr |= _EM_OVERFLOW;
if (cw & IEM_UNDERFLOW)
abstr |= _EM_UNDERFLOW;
if (cw & IEM_INEXACT)
abstr |= _EM_INEXACT;
if (cw & IEM_DENORMAL)
abstr |= _EM_DENORMAL;
//
// Set rounding mode
//
switch (cw & IMCW_RC) {
case IRC_NEAR:
abstr |= _RC_NEAR;
break;
case IRC_UP:
abstr |= _RC_UP;
break;
case IRC_DOWN:
abstr |= _RC_DOWN;
break;
case IRC_CHOP:
abstr |= _RC_CHOP;
break;
}
//
// Set Precision mode
//
switch (cw & IMCW_PC) {
case IPC_64:
abstr |= _PC_64;
break;
case IPC_53:
abstr |= _PC_53;
break;
case IPC_24:
abstr |= _PC_24;
break;
}
//
// Infinity control (bit can be programmed but has no effect)
//
if (cw & IMCW_IC) {
abstr |= _IC_AFFINE;
}
return abstr;
}
/***
* _hw_cw() - h/w control word
*
*Purpose:
* produce a machine dependent fp control word
*
*
*Entry:
* abstr: abstract control word
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned short _hw_cw(unsigned int abstr)
{
//
// Set standard infinity and denormal control bits
//
unsigned short cw = 0;
//
// Set exception mask bits
//
if (abstr & _EM_INVALID)
cw |= IEM_INVALID;
if (abstr & _EM_ZERODIVIDE)
cw |= IEM_ZERODIVIDE;
if (abstr & _EM_OVERFLOW)
cw |= IEM_OVERFLOW;
if (abstr & _EM_UNDERFLOW)
cw |= IEM_UNDERFLOW;
if (abstr & _EM_INEXACT)
cw |= IEM_INEXACT;
if (abstr & _EM_DENORMAL)
cw |= IEM_DENORMAL;
//
// Set rounding mode
//
switch (abstr & _MCW_RC) {
case _RC_NEAR:
cw |= IRC_NEAR;
break;
case _RC_UP:
cw |= IRC_UP;
break;
case _RC_DOWN:
cw |= IRC_DOWN;
break;
case _RC_CHOP:
cw |= IRC_CHOP;
break;
}
//
// Set Precision mode
//
switch (abstr & _MCW_PC) {
case _PC_64:
cw |= IPC_64;
break;
case _PC_53:
cw |= IPC_53;
break;
case _PC_24:
cw |= IPC_24;
break;
}
//
// Set Infinity mode
//
if (abstr & _MCW_IC) {
cw |= IIC_AFFINE;
}
return cw;
}
/***
* _abstract_sw() - abstract fp status word
*
*Purpose:
* produce an abstract (machine independent) fp status word
*
*
*Entry:
* sw: machine status word
*
*Exit:
*
*Exceptions:
*
*******************************************************************************/
unsigned int _abstract_sw(unsigned short sw)
{
unsigned int abstr = 0;
if (sw & ISW_INVALID)
abstr |= _SW_INVALID;
if (sw & ISW_ZERODIVIDE)
abstr |= _SW_ZERODIVIDE;
if (sw & ISW_OVERFLOW)
abstr |= _SW_OVERFLOW;
if (sw & ISW_UNDERFLOW)
abstr |= _SW_UNDERFLOW;
if (sw & ISW_INEXACT)
abstr |= _SW_INEXACT;
if (sw & ISW_DENORMAL)
abstr |= _SW_DENORMAL;
return abstr;
}