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authorPeter S. Mazinger <ps.m@gmx.net>2005-09-22 00:51:06 +0000
committerPeter S. Mazinger <ps.m@gmx.net>2005-09-22 00:51:06 +0000
commit178be753686094a0a998ab898e1f13d96626fbc9 (patch)
tree94782c457501e0d48317753fc4e4e5196a673ab9 /libm/powerpc/s_round.c
parentf8d5244380826053b8c75b3c302d39bdd1f9a121 (diff)
split out nearbyint, round, trunc from libm/powerpc/s_modf.c
Diffstat (limited to 'libm/powerpc/s_round.c')
-rw-r--r--libm/powerpc/s_round.c112
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 );
+ }