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Diffstat (limited to 'libm/powerpc/s_floor.c')
| -rw-r--r-- | libm/powerpc/s_floor.c | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/libm/powerpc/s_floor.c b/libm/powerpc/s_floor.c new file mode 100644 index 000000000..f7b4534bb --- /dev/null +++ b/libm/powerpc/s_floor.c @@ -0,0 +1,109 @@ +/******************************************************************************* +* * +* File ceilfloor.c, * +* Function ceil(x) and floor(x), * +* Implementation of ceil and floor for the PowerPC. * +* * +* Copyright © 1991 Apple Computer, Inc. All rights reserved. * +* * +* Written by Ali Sazegari, started on November 1991, * +* * +* based on math.h, library code for Macintoshes with a 68881/68882 * +* by Jim Thomas. * +* * +* W A R N I N G: This routine expects a 64 bit double model. * +* * +* December 03 1992: first rs6000 port. * +* July 14 1993: comment changes and addition of #pragma fenv_access. * +* May 06 1997: port of the ibm/taligent ceil and floor routines. * +* April 11 2001: first port to os x using gcc. * +* June 13 2001: replaced __setflm with in-line assembly * +* * +*******************************************************************************/ + +static const double twoTo52 = 4503599627370496.0; +static const unsigned long signMask = 0x80000000ul; + +typedef union + { + struct { +#if defined(__BIG_ENDIAN__) + unsigned long int hi; + unsigned long int lo; +#else + unsigned long int lo; + unsigned long int hi; +#endif + } words; + double dbl; + } DblInHex; + +/******************************************************************************* +* Functions needed for the computation. * +*******************************************************************************/ + +/******************************************************************************* +* Floor(x) returns the largest integer not greater than x. * +*******************************************************************************/ + +double floor ( double x ) + { + DblInHex xInHex,OldEnvironment; + register double y; + register unsigned long int xhi; + register long int target; + + xInHex.dbl = x; + xhi = xInHex.words.hi & 0x7fffffffUL; // xhi is the high half of |x| + target = ( xInHex.words.hi < signMask ); + + if ( xhi < 0x43300000ul ) +/******************************************************************************* +* Is |x| < 2.0^52? * +*******************************************************************************/ + { + if ( xhi < 0x3ff00000ul ) +/******************************************************************************* +* Is |x| < 1.0? * +*******************************************************************************/ + { + if ( ( xhi | xInHex.words.lo ) == 0ul ) // zero x is exact case + return ( x ); + else + { // inexact case + asm ("mffs %0" : "=f" (OldEnvironment.dbl)); + OldEnvironment.words.lo |= 0x02000000ul; + asm ("mtfsf 255,%0" : /*NULLOUT*/ : /*IN*/ "f" ( OldEnvironment.dbl )); + if ( target ) + return ( 0.0 ); + else + return ( -1.0 ); + } + } +/******************************************************************************* +* Is 1.0 < |x| < 2.0^52? * +*******************************************************************************/ + if ( target ) + { + y = ( x + twoTo52 ) - twoTo52; // round at binary pt. + if ( y > x ) + return ( y - 1.0 ); + else + return ( y ); + } + + else + { + y = ( x - twoTo52 ) + twoTo52; // round at binary pt. + if ( y > x ) + return ( y - 1.0 ); + else + return ( y ); + } + } +/******************************************************************************* +* |x| >= 2.0^52 or x is a NaN. * +*******************************************************************************/ + return ( x ); + } + |