Module Name: src
Committed By: isaki
Date: Sat Apr 20 03:06:20 UTC 2013
Modified Files:
src/sys/arch/m68k/fpe: fpu_exp.c
Log Message:
Implement exponential and power functions.
o FETOX .. exp(x)
o FETOXM1 .. exp(x) - 1
o FTENTOX .. 10^x
o FTWOTOX .. 2^x
At last all mathematics functions of FPE were implemented.
Thanks to Yosuke Sugahara.
To generate a diff of this commit:
cvs rdiff -u -r1.5 -r1.6 src/sys/arch/m68k/fpe/fpu_exp.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/m68k/fpe/fpu_exp.c
diff -u src/sys/arch/m68k/fpe/fpu_exp.c:1.5 src/sys/arch/m68k/fpe/fpu_exp.c:1.6
--- src/sys/arch/m68k/fpe/fpu_exp.c:1.5 Mon Jul 18 07:44:30 2011
+++ src/sys/arch/m68k/fpe/fpu_exp.c Sat Apr 20 03:06:19 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: fpu_exp.c,v 1.5 2011/07/18 07:44:30 isaki Exp $ */
+/* $NetBSD: fpu_exp.c,v 1.6 2013/04/20 03:06:19 isaki Exp $ */
/*
* Copyright (c) 1995 Ken Nakata
@@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu_exp.c,v 1.5 2011/07/18 07:44:30 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu_exp.c,v 1.6 2013/04/20 03:06:19 isaki Exp $");
#include "fpu_emulate.h"
@@ -40,30 +40,146 @@ __KERNEL_RCSID(0, "$NetBSD: fpu_exp.c,v
* fpu_exp.c: defines fpu_etox(), fpu_etoxm1(), fpu_tentox(), and fpu_twotox();
*/
+/*
+ * x^2 x^3 x^4
+ * exp(x) = 1 + x + --- + --- + --- + ...
+ * 2! 3! 4!
+ */
+static struct fpn *
+fpu_etox_taylor(struct fpemu *fe)
+{
+ struct fpn res;
+ struct fpn x;
+ struct fpn s0;
+ struct fpn *s1;
+ struct fpn *r;
+ uint32_t k;
+
+ CPYFPN(&x, &fe->fe_f2);
+ CPYFPN(&s0, &fe->fe_f2);
+
+ /* res := 1 + x */
+ fpu_const(&fe->fe_f1, FPU_CONST_1);
+ r = fpu_add(fe);
+ CPYFPN(&res, r);
+
+ k = 2;
+ for (;; k++) {
+ /* s1 = s0 * x / k */
+ CPYFPN(&fe->fe_f1, &s0);
+ CPYFPN(&fe->fe_f2, &x);
+ r = fpu_mul(fe);
+
+ CPYFPN(&fe->fe_f1, r);
+ fpu_explode(fe, &fe->fe_f2, FTYPE_LNG, &k);
+ s1 = fpu_div(fe);
+
+ /* break if s1 is enough small */
+ if (ISZERO(s1))
+ break;
+ if (res.fp_exp - s1->fp_exp >= FP_NMANT)
+ break;
+
+ /* s0 := s1 for next loop */
+ CPYFPN(&s0, s1);
+
+ /* res += s1 */
+ CPYFPN(&fe->fe_f2, s1);
+ CPYFPN(&fe->fe_f1, &res);
+ r = fpu_add(fe);
+ CPYFPN(&res, r);
+ }
+
+ CPYFPN(&fe->fe_f2, &res);
+ return &fe->fe_f2;
+}
+
+/*
+ * exp(x)
+ */
struct fpn *
fpu_etox(struct fpemu *fe)
{
- /* stub */
- return &fe->fe_f2;
+ struct fpn *fp;
+
+ if (ISNAN(&fe->fe_f2))
+ return &fe->fe_f2;
+ if (ISINF(&fe->fe_f2)) {
+ if (fe->fe_f2.fp_sign)
+ fpu_const(&fe->fe_f2, FPU_CONST_0);
+ return &fe->fe_f2;
+ }
+
+ if (fe->fe_f2.fp_sign == 0) {
+ /* exp(x) */
+ fp = fpu_etox_taylor(fe);
+ } else {
+ /* 1/exp(-x) */
+ fe->fe_f2.fp_sign = 0;
+ fp = fpu_etox_taylor(fe);
+
+ CPYFPN(&fe->fe_f2, fp);
+ fpu_const(&fe->fe_f1, FPU_CONST_1);
+ fp = fpu_div(fe);
+ }
+
+ return fp;
}
+/*
+ * exp(x) - 1
+ */
struct fpn *
fpu_etoxm1(struct fpemu *fe)
{
- /* stub */
- return &fe->fe_f2;
+ struct fpn *fp;
+
+ fp = fpu_etox(fe);
+
+ CPYFPN(&fe->fe_f1, fp);
+ /* build a 1.0 */
+ fp = fpu_const(&fe->fe_f2, FPU_CONST_1);
+ fe->fe_f2.fp_sign = !fe->fe_f2.fp_sign;
+ /* fp = f2 - 1.0 */
+ fp = fpu_add(fe);
+
+ return fp;
}
+/*
+ * 10^x = exp(x * ln10)
+ */
struct fpn *
fpu_tentox(struct fpemu *fe)
{
- /* stub */
- return &fe->fe_f2;
+ struct fpn *fp;
+
+ /* build a ln10 */
+ fp = fpu_const(&fe->fe_f1, FPU_CONST_LN_10);
+ /* fp = ln10 * f2 */
+ fp = fpu_mul(fe);
+
+ /* copy the result to the src opr */
+ CPYFPN(&fe->fe_f2, fp);
+
+ return fpu_etox(fe);
}
+/*
+ * 2^x = exp(x * ln2)
+ */
struct fpn *
fpu_twotox(struct fpemu *fe)
{
- /* stub */
- return &fe->fe_f2;
+ struct fpn *fp;
+
+ /* build a ln2 */
+ fp = fpu_const(&fe->fe_f1, FPU_CONST_LN_2);
+ /* fp = ln2 * f2 */
+ fp = fpu_mul(fe);
+
+ /* copy the result to the src opr */
+ CPYFPN(&fe->fe_f2, fp);
+
+ return fpu_etox(fe);
}
