import newlib-2000-02-17 snapshot

1 files changed, 44 insertions, 0 deletions

diff --git a/newlib/libc/machine/i386/f_pow.c b/newlib/libc/machine/i386/f_pow.c
new file mode 100644
index 000000000..ac7dcfe26
--- /dev/null
+++ b/newlib/libc/machine/i386/f_pow.c
@@ -0,0 +1,44 @@
+/*
+ * ====================================================
+ * Copyright (C) 1998 by Cygnus Solutions. All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+/*
+Fast version of pow using Intel float instructions.
+
+   double _f_pow (double x, double y);
+
+Function calculates x to power of y.
+The function optimizes the case where x is >0.0 and y is finite.
+In such a case, there is no error checking or setting of errno.
+All other cases defer to normal pow() function which will
+set errno as normal.
+*/
+
+#include <math.h>
+#include <ieeefp.h>
+#include "f_math.h"
+
+double _f_pow (double x, double y)
+{
+  /* following sequence handles the majority of cases for pow() */
+  if (x > 0.0 && check_finite(y))
+    {
+      double result;
+      /* calculate x ** y as 2 ** (y log2(x)).  On Intel, can only
+         raise 2 to an integer or a small fraction, thus, we have
+         to perform two steps 2**integer portion * 2**fraction. */
+      asm ("fldl 8(%%ebp); fyl2x; fld %%st; frndint; fsub %%st,%%st(1);" \
+           "fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\
+           "fmulp" : "=t" (result) : "0" (y));
+      return result;
+    }
+  else /* all other strange cases, defer to normal pow() */
+    return pow (x,y);
+}
+