Import libcompiler_rt into HEAD and add Makefiles.

Obtained from:	user/ed/compiler-rt

1 files changed, 107 insertions, 0 deletions

diff --git a/contrib/compiler-rt/lib/floatdidf.c b/contrib/compiler-rt/lib/floatdidf.c
new file mode 100644
index 0000000..a0f501b
--- /dev/null
+++ b/contrib/compiler-rt/lib/floatdidf.c
@@ -0,0 +1,107 @@
+/*===-- floatdidf.c - Implement __floatdidf -------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ *===----------------------------------------------------------------------===
+ *
+ * This file implements __floatdidf for the compiler_rt library.
+ *
+ *===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+#include <float.h>
+
+/* Returns: convert a to a double, rounding toward even. */
+
+/* Assumption: double is a IEEE 64 bit floating point type 
+ *             di_int is a 64 bit integral type
+ */
+
+/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
+
+#ifndef __SOFT_FP__
+/* Support for systems that have hardware floating-point; we'll set the inexact flag
+ * as a side-effect of this computation.
+ */
+#include <stdint.h>
+
+double
+__floatdidf(di_int a)
+{
+	static const double twop52 = 0x1.0p52;
+	static const double twop32 = 0x1.0p32;
+	
+	union { int64_t x; double d; } low = { .d = twop52 };
+	
+	const double high = (int32_t)(a >> 32) * twop32;
+	low.x |= a & INT64_C(0x00000000ffffffff);
+	
+	const double result = (high - twop52) + low.d;
+	return result;
+}
+
+#else
+/* Support for systems that don't have hardware floating-point; there are no flags to
+ * set, and we don't want to code-gen to an unknown soft-float implementation.
+ */
+
+double
+__floatdidf(di_int a)
+{
+    if (a == 0)
+        return 0.0;
+    const unsigned N = sizeof(di_int) * CHAR_BIT;
+    const di_int s = a >> (N-1);
+    a = (a ^ s) - s;
+    int sd = N - __builtin_clzll(a);  /* number of significant digits */
+    int e = sd - 1;             /* exponent */
+    if (sd > DBL_MANT_DIG)
+    {
+        /*  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
+         *  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
+         *                                                12345678901234567890123456
+         *  1 = msb 1 bit
+         *  P = bit DBL_MANT_DIG-1 bits to the right of 1
+         * Q = bit DBL_MANT_DIG bits to the right of 1
+         *  R = "or" of all bits to the right of Q
+        */
+        switch (sd)
+        {
+        case DBL_MANT_DIG + 1:
+            a <<= 1;
+            break;
+        case DBL_MANT_DIG + 2:
+            break;
+        default:
+            a = ((du_int)a >> (sd - (DBL_MANT_DIG+2))) |
+                ((a & ((du_int)(-1) >> ((N + DBL_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 DBL_MANT_DIG or DBL_MANT_DIG+1 bits */
+        if (a & ((du_int)1 << DBL_MANT_DIG))
+        {
+            a >>= 1;
+            ++e;
+        }
+        /* a is now rounded to DBL_MANT_DIG bits */
+    }
+    else
+    {
+        a <<= (DBL_MANT_DIG - sd);
+        /* a is now rounded to DBL_MANT_DIG bits */
+    }
+    double_bits fb;
+    fb.u.high = ((su_int)s & 0x80000000) |        /* sign */
+                ((e + 1023) << 20)      |        /* exponent */
+                ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */
+    fb.u.low = (su_int)a;                         /* mantissa-low */
+    return fb.f;
+}
+#endif