303 lines
4.5 KiB
C
303 lines
4.5 KiB
C
/***
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*ieee.c - ieee control and status routines
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*
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* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* IEEE control and status routines.
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*
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*Revision History:
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*
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* 04-01-02 GDP Rewritten to use abstract control and status words
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*
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*/
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#include <trans.h>
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#include <float.h>
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static unsigned int _abstract_sw(unsigned short sw);
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static unsigned int _abstract_cw(unsigned short cw);
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static unsigned short _hw_cw(unsigned int abstr);
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/***
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* _statusfp() -
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*
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*Purpose:
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* return abstract fp status word
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned int _statusfp()
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{
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short status;
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_asm {
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fstsw status
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}
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return _abstract_sw(status);
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}
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/***
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*_clearfp() -
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*
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*Purpose:
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* return abstract status word and clear status
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned int _clearfp()
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{
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short status;
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_asm {
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fnstsw status
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fnclex
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}
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return _abstract_sw(status);
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}
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/*** _controlfp
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*() -
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*
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*Purpose:
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* return and set abstract user fp control word
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned int _controlfp(unsigned int newctrl, unsigned int mask)
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{
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short oldCw;
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short newCw;
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unsigned int oldabs;
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unsigned int newabs;
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_asm {
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fstcw oldCw
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}
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oldabs = _abstract_cw(oldCw);
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newabs = (newctrl & mask) | (oldabs & ~mask);
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newCw = _hw_cw(newabs);
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_asm {
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fldcw newCw
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}
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return newabs;
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} /* _controlfp() */
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/***
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* _abstract_cw() - abstract control word
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*
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*Purpose:
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* produce a fp control word in abstracted (machine independent) form
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*
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*Entry:
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* cw: machine control word
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned int _abstract_cw(unsigned short cw)
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{
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unsigned int abstr = 0;
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//
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// Set exception mask bits
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//
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if (cw & IEM_INVALID)
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abstr |= _EM_INVALID;
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if (cw & IEM_ZERODIVIDE)
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abstr |= _EM_ZERODIVIDE;
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if (cw & IEM_OVERFLOW)
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abstr |= _EM_OVERFLOW;
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if (cw & IEM_UNDERFLOW)
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abstr |= _EM_UNDERFLOW;
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if (cw & IEM_INEXACT)
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abstr |= _EM_INEXACT;
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//
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// Set rounding mode
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//
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switch (cw & IMCW_RC) {
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case IRC_NEAR:
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abstr |= _RC_NEAR;
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break;
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case IRC_UP:
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abstr |= _RC_UP;
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break;
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case IRC_DOWN:
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abstr |= _RC_DOWN;
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break;
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case IRC_CHOP:
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abstr |= _RC_CHOP;
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break;
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}
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//
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// Set Precision mode
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//
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switch (cw & IMCW_PC) {
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case IPC_64:
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abstr |= _PC_64;
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break;
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case IPC_53:
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abstr |= _PC_53;
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break;
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case IPC_24:
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abstr |= _PC_24;
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break;
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}
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return abstr;
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}
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/***
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* _hw_cw() - h/w control word
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*
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*Purpose:
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* produce a machine dependent fp control word
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*
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*
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*Entry:
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* abstr: abstract control word
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned short _hw_cw(unsigned int abstr)
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{
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//
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// Set standard infinity and denormal control bits
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//
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unsigned short cw = 0x1002;
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//
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// Set exception mask bits
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//
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if (abstr & _EM_INVALID)
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cw |= IEM_INVALID;
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if (abstr & _EM_ZERODIVIDE)
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cw |= IEM_ZERODIVIDE;
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if (abstr & _EM_OVERFLOW)
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cw |= IEM_OVERFLOW;
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if (abstr & _EM_UNDERFLOW)
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cw |= IEM_UNDERFLOW;
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if (abstr & _EM_INEXACT)
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cw |= IEM_INEXACT;
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//
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// Set rounding mode
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//
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switch (abstr & _MCW_RC) {
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case _RC_NEAR:
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cw |= IRC_NEAR;
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break;
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case _RC_UP:
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cw |= IRC_UP;
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break;
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case _RC_DOWN:
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cw |= IRC_DOWN;
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break;
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case _RC_CHOP:
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cw |= IRC_CHOP;
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break;
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}
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//
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// Set Precision mode
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//
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switch (abstr & _MCW_PC) {
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case _PC_64:
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cw |= IPC_64;
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break;
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case _PC_53:
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cw |= IPC_53;
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break;
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case _PC_24:
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cw |= IPC_24;
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break;
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}
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return cw;
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}
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/***
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* _abstract_sw() - abstract fp status word
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*
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*Purpose:
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* produce an abstract (machine independent) fp status word
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*
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*
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*Entry:
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* sw: machine status word
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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unsigned int _abstract_sw(unsigned short sw)
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{
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unsigned int abstr = 0;
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if (sw & ISW_INVALID)
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abstr |= _EM_INVALID;
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if (sw & ISW_ZERODIVIDE)
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abstr |= _EM_ZERODIVIDE;
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if (sw & ISW_OVERFLOW)
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abstr |= _EM_OVERFLOW;
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if (sw & ISW_UNDERFLOW)
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abstr |= _EM_UNDERFLOW;
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if (sw & ISW_INEXACT)
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abstr |= _EM_INEXACT;
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return abstr;
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}
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