[src/trunk]: src/sys/arch/m68k/fpe Implement a hyperbolic arctangent (FATANH).

[isaki <isaki%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3ac7aea0c3f3
branches:  trunk
changeset: 786192:3ac7aea0c3f3
user:      isaki <isaki%NetBSD.org@localhost>
date:      Fri Apr 19 14:05:12 2013 +0000

description:
Implement a hyperbolic arctangent (FATANH).

diffstat:

 sys/arch/m68k/fpe/fpu_hyperb.c |  70 +++++++++++++++++++++++++++++++++++++++--
 1 files changed, 66 insertions(+), 4 deletions(-)

diffs (94 lines):

diff -r ccad3c515dd8 -r 3ac7aea0c3f3 sys/arch/m68k/fpe/fpu_hyperb.c
--- a/sys/arch/m68k/fpe/fpu_hyperb.c    Fri Apr 19 13:57:52 2013 +0000
+++ b/sys/arch/m68k/fpe/fpu_hyperb.c    Fri Apr 19 14:05:12 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: fpu_hyperb.c,v 1.9 2013/04/19 13:31:11 isaki Exp $     */
+/*     $NetBSD: fpu_hyperb.c,v 1.10 2013/04/19 14:05:12 isaki Exp $    */
 
 /*
  * Copyright (c) 1995  Ken Nakata
@@ -57,7 +57,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu_hyperb.c,v 1.9 2013/04/19 13:31:11 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu_hyperb.c,v 1.10 2013/04/19 14:05:12 isaki Exp $");
 
 #include "fpu_emulate.h"
 
@@ -67,11 +67,73 @@
  *     fpu_atanh(), fpu_cosh(), fpu_sinh(), and fpu_tanh()
  */
 
+/*
+ *             1       1 + x
+ * atanh(x) = ---*log(-------)
+ *             2       1 - x
+ */
 struct fpn *
 fpu_atanh(struct fpemu *fe)
 {
-       /* stub */
-       return &fe->fe_f2;
+       struct fpn x;
+       struct fpn t;
+       struct fpn *r;
+
+       if (ISNAN(&fe->fe_f2))
+               return &fe->fe_f2;
+       if (ISINF(&fe->fe_f2))
+               return fpu_newnan(fe);
+
+       /*
+        * if x is +0/-0, 68000PRM.pdf says it returns +0/-0 but
+        * my real 68882 returns +0 for both.
+        */
+       if (ISZERO(&fe->fe_f2)) {
+               fe->fe_f2.fp_sign = 0;
+               return &fe->fe_f2;
+       }
+
+       /*
+        * -INF if x == -1
+        * +INF if x ==  1
+        */
+       r = &fe->fe_f2;
+       if (r->fp_exp == 0 && r->fp_mant[0] == FP_1 &&
+           r->fp_mant[1] == 0 && r->fp_mant[2] == 0) {
+               r->fp_class = FPC_INF;
+               return r;
+       }
+
+       /* NAN if |x| > 1 */
+       if (fe->fe_f2.fp_exp >= 0)
+               return fpu_newnan(fe);
+
+       CPYFPN(&x, &fe->fe_f2);
+
+       /* t := 1 - x */
+       fpu_const(&fe->fe_f1, FPU_CONST_1);
+       fe->fe_f2.fp_sign = !fe->fe_f2.fp_sign;
+       r = fpu_add(fe);
+       CPYFPN(&t, r);
+
+       /* r := 1 + x */
+       fpu_const(&fe->fe_f1, FPU_CONST_1);
+       CPYFPN(&fe->fe_f2, &x);
+       r = fpu_add(fe);
+
+       /* (1-x)/(1+x) */
+       CPYFPN(&fe->fe_f1, r);
+       CPYFPN(&fe->fe_f2, &t);
+       r = fpu_div(fe);
+
+       /* log((1-x)/(1+x)) */
+       CPYFPN(&fe->fe_f2, r);
+       r = fpu_logn(fe);
+
+       /* r /= 2 */
+       r->fp_exp--;
+
+       return r;
 }
 
 /*