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phoenix |
/*******************************************************************************
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* *
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* File ceilfloor.c, *
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* Function ceil(x) and floor(x), *
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* Implementation of ceil and floor for the PowerPC. *
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* *
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* Copyright © 1991 Apple Computer, Inc. All rights reserved. *
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* *
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* Written by Ali Sazegari, started on November 1991, *
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* *
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* based on math.h, library code for Macintoshes with a 68881/68882 *
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* by Jim Thomas. *
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* *
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* W A R N I N G: This routine expects a 64 bit double model. *
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* *
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* December 03 1992: first rs6000 port. *
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* July 14 1993: comment changes and addition of #pragma fenv_access. *
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* May 06 1997: port of the ibm/taligent ceil and floor routines. *
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* April 11 2001: first port to os x using gcc. *
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* June 13 2001: replaced __setflm with in-line assembly *
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* *
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*******************************************************************************/
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static const double twoTo52 = 4503599627370496.0;
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static const unsigned long signMask = 0x80000000ul;
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typedef union
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{
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struct {
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#if defined(__BIG_ENDIAN__)
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unsigned long int hi;
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unsigned long int lo;
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#else
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unsigned long int lo;
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unsigned long int hi;
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#endif
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} words;
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double dbl;
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} DblInHex;
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/*******************************************************************************
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* Functions needed for the computation. *
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*******************************************************************************/
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/*******************************************************************************
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* Floor(x) returns the largest integer not greater than x. *
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*******************************************************************************/
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double floor ( double x )
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{
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DblInHex xInHex,OldEnvironment;
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register double y;
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register unsigned long int xhi;
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register long int target;
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xInHex.dbl = x;
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xhi = xInHex.words.hi & 0x7fffffffUL; // xhi is the high half of |x|
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target = ( xInHex.words.hi < signMask );
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if ( xhi < 0x43300000ul )
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/*******************************************************************************
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* Is |x| < 2.0^52? *
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*******************************************************************************/
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{
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if ( xhi < 0x3ff00000ul )
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/*******************************************************************************
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* Is |x| < 1.0? *
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*******************************************************************************/
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{
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if ( ( xhi | xInHex.words.lo ) == 0ul ) // zero x is exact case
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return ( x );
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else
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{ // inexact case
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asm ("mffs %0" : "=f" (OldEnvironment.dbl));
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OldEnvironment.words.lo |= 0x02000000ul;
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asm ("mtfsf 255,%0" : /*NULLOUT*/ : /*IN*/ "f" ( OldEnvironment.dbl ));
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if ( target )
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return ( 0.0 );
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else
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return ( -1.0 );
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}
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}
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/*******************************************************************************
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* Is 1.0 < |x| < 2.0^52? *
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*******************************************************************************/
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if ( target )
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{
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y = ( x + twoTo52 ) - twoTo52; // round at binary pt.
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if ( y > x )
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return ( y - 1.0 );
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else
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return ( y );
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}
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else
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{
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y = ( x - twoTo52 ) + twoTo52; // round at binary pt.
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if ( y > x )
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return ( y - 1.0 );
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else
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return ( y );
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}
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}
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/*******************************************************************************
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* |x| >= 2.0^52 or x is a NaN. *
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*******************************************************************************/
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return ( x );
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}
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