/*** *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 to * 04-11-95 JWM _fpreset() now resets default precision. * 05-10-96 BWT Fix POSIX build. * */ #include #include #include #include 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; }