1 files changed, 76 insertions, 0 deletions
diff --git a/lib/floatundisf.c b/lib/floatundisf.c
new file mode 100644
index 000000000000..79b4b82e3a03
--- /dev/null
+++ b/lib/floatundisf.c
@@ -0,0 +1,76 @@
+/*===-- floatundisf.c - Implement __floatundisf ---------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __floatundisf for the compiler_rt library.
+ *
+ *===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+#include <float.h>
+
+/* Returns: convert a to a float, rounding toward even. */
+
+/* Assumption: float is a IEEE 32 bit floating point type 
+ *            du_int is a 64 bit integral type
+ */
+
+/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */
+
+float
+__floatundisf(du_int a)
+{
+    if (a == 0)
+        return 0.0F;
+    const unsigned N = sizeof(du_int) * CHAR_BIT;
+    int sd = N - __builtin_clzll(a);  /* number of significant digits */
+    int e = sd - 1;             /* 8 exponent */
+    if (sd > FLT_MANT_DIG)
+    {
+        /*  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
+         *  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
+         *                                                12345678901234567890123456
+         *  1 = msb 1 bit
+         *  P = bit FLT_MANT_DIG-1 bits to the right of 1
+         *  Q = bit FLT_MANT_DIG bits to the right of 1
+         *  R = "or" of all bits to the right of Q
+         */
+        switch (sd)
+        {
+        case FLT_MANT_DIG + 1:
+            a <<= 1;
+            break;
+        case FLT_MANT_DIG + 2:
+            break;
+        default:
+            a = (a >> (sd - (FLT_MANT_DIG+2))) |
+                ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0);
+        };
+        /* finish: */
+        a |= (a & 4) != 0;  /* Or P into R */
+        ++a;  /* round - this step may add a significant bit */
+        a >>= 2;  /* dump Q and R */
+        /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */
+        if (a & ((du_int)1 << FLT_MANT_DIG))
+        {
+            a >>= 1;
+            ++e;
+        }
+        /* a is now rounded to FLT_MANT_DIG bits */
+    }
+    else
+    {
+        a <<= (FLT_MANT_DIG - sd);
+        /* a is now rounded to FLT_MANT_DIG bits */
+    }
+    float_bits fb;
+    fb.u = ((e + 127) << 23)       |  /* exponent */
+           ((su_int)a & 0x007FFFFF);  /* mantissa */
+    return fb.f;
+}