first commit of the new libm!

[musl] / src / math / floor.c

diff --git a/src/math/floor.c b/src/math/floor.c
new file mode 100644 (file)
index 0000000..521a148
--- /dev/null
+++ b/src/math/floor.c
@@ -0,0 +1,82 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_floor.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/*
+ * floor(x)
+ * Return x rounded toward -inf to integral value
+ * Method:
+ *      Bit twiddling.
+ * Exception:
+ *      Inexact flag raised if x not equal to floor(x).
+ */
+
+#include "libm.h"
+
+static const double huge = 1.0e300;
+
+double floor(double x)
+{
+       int32_t i0,i1,j0;
+       uint32_t i,j;
+
+       EXTRACT_WORDS(i0, i1, x);
+       // FIXME: signed shift
+       j0 = ((i0>>20)&0x7ff) - 0x3ff;
+       if (j0 < 20) {
+               if (j0 < 0) {  /* |x| < 1 */
+                       /* raise inexact if x != 0 */
+                       if (huge+x > 0.0) {
+                               if (i0 >= 0) {  /* x >= 0 */
+                                       i0 = i1 = 0;
+                               } else if (((i0&0x7fffffff)|i1) != 0) {
+                                       i0 = 0xbff00000;
+                                       i1 = 0;
+                               }
+                       }
+               } else {
+                       i = 0x000fffff>>j0;
+                       if (((i0&i)|i1) == 0)
+                               return x; /* x is integral */
+                        /* raise inexact flag */
+                       if (huge+x > 0.0) {
+                               if (i0 < 0)
+                                       i0 += 0x00100000>>j0;
+                               i0 &= ~i;
+                               i1=0;
+                       }
+               }
+       } else if (j0 > 51) {
+               if (j0 == 0x400)
+                       return x+x; /* inf or NaN */
+               else
+                       return x;   /* x is integral */
+       } else {
+               i = ((uint32_t)(0xffffffff))>>(j0-20);
+               if ((i1&i) == 0)
+                       return x;   /* x is integral */
+               /* raise inexact flag */
+               if (huge+x > 0.0) {
+                       if (i0 < 0) {
+                               if (j0 == 20)
+                                       i0+=1;
+                               else {
+                                       j = i1+(1<<(52-j0));
+                                       if (j < i1)
+                                               i0 += 1; /* got a carry */
+                                       i1 = j;
+                               }
+                       }
+                       i1 &= ~i;
+               }
+       }
+       INSERT_WORDS(x, i0, i1);
+       return x;
+}