diff options
Diffstat (limited to 'libm/powerpc/s_round.c')
| -rw-r--r-- | libm/powerpc/s_round.c | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/libm/powerpc/s_round.c b/libm/powerpc/s_round.c new file mode 100644 index 000000000..81f4d0fec --- /dev/null +++ b/libm/powerpc/s_round.c @@ -0,0 +1,112 @@ +#include <limits.h> +#include <math.h> + +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; + +static const unsigned long int signMask = 0x80000000ul; +static const double twoTo52 = 4503599627370496.0; + +/******************************************************************************* +* * +* The function round rounds its double argument to integral value * +* according to the "add half to the magnitude and truncate" rounding of * +* Pascal's Round function and FORTRAN's ANINT function and returns the * +* result in double format. This function signals inexact if an ordered * +* return value is not equal to the operand. * +* * +*******************************************************************************/ + +double round ( double x ) + { + DblInHex argument, OldEnvironment; + register double y, z; + register unsigned long int xHead; + register long int target; + + argument.dbl = x; + xHead = argument.words.hi & 0x7fffffffUL; // xHead <- high half of |x| + target = ( argument.words.hi < signMask ); // flag positive sign + + if ( xHead < 0x43300000ul ) +/******************************************************************************* +* Is |x| < 2.0^52? * +*******************************************************************************/ + { + if ( xHead < 0x3ff00000ul ) +/******************************************************************************* +* Is |x| < 1.0? * +*******************************************************************************/ + { + asm ("mffs %0" : "=f" (OldEnvironment.dbl)); // get environment + if ( xHead < 0x3fe00000ul ) +/******************************************************************************* +* Is |x| < 0.5? * +*******************************************************************************/ + { + if ( ( xHead | argument.words.lo ) != 0ul ) + OldEnvironment.words.lo |= 0x02000000ul; + asm ("mtfsf 255,%0" : /*NULLOUT*/ : /*IN*/ "f" ( OldEnvironment.dbl )); + if ( target ) + return ( 0.0 ); + else + return ( -0.0 ); + } +/******************************************************************************* +* Is 0.5 ² |x| < 1.0? * +*******************************************************************************/ + OldEnvironment.words.lo |= 0x02000000ul; + asm ("mtfsf 255,%0" : /*NULLOUT*/ : /*IN*/ "f" ( OldEnvironment.dbl )); + if ( target ) + return ( 1.0 ); + else + return ( -1.0 ); + } +/******************************************************************************* +* Is 1.0 < |x| < 2.0^52? * +*******************************************************************************/ + if ( target ) + { // positive x + y = ( x + twoTo52 ) - twoTo52; // round at binary point + if ( y == x ) // exact case + return ( x ); + z = x + 0.5; // inexact case + y = ( z + twoTo52 ) - twoTo52; // round at binary point + if ( y > z ) + return ( y - 1.0 ); + else + return ( y ); + } + +/******************************************************************************* +* Is x < 0? * +*******************************************************************************/ + else + { + y = ( x - twoTo52 ) + twoTo52; // round at binary point + if ( y == x ) + return ( x ); + z = x - 0.5; + y = ( z - twoTo52 ) + twoTo52; // round at binary point + if ( y < z ) + return ( y + 1.0 ); + else + return ( y ); + } + } +/******************************************************************************* +* |x| >= 2.0^52 or x is a NaN. * +*******************************************************************************/ + return ( x ); + } |