vendor/compiler-rt/compiler-rt-r224034

1 files changed, 106 insertions, 0 deletions

diff --git a/lib/builtins/floatundidf.c b/lib/builtins/floatundidf.c
new file mode 100644
index 000000000000..73b8bac1c1a1
--- /dev/null
+++ b/lib/builtins/floatundidf.c
@@ -0,0 +1,106 @@
+/* ===-- floatundidf.c - Implement __floatundidf ---------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __floatundidf for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+/* Returns: convert a to a double, rounding toward even. */
+
+/* Assumption: double is a IEEE 64 bit floating point type 
+ *             du_int is a 64 bit integral type
+ */
+
+/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */
+
+#include "int_lib.h"
+
+ARM_EABI_FNALIAS(ul2d, floatundidf)
+
+#ifndef __SOFT_FP__
+/* Support for systems that have hardware floating-point; we'll set the inexact flag
+ * as a side-effect of this computation.
+ */
+
+COMPILER_RT_ABI double
+__floatundidf(du_int a)
+{
+	static const double twop52 = 0x1.0p52;
+	static const double twop84 = 0x1.0p84;
+	static const double twop84_plus_twop52 = 0x1.00000001p84;
+	
+	union { uint64_t x; double d; } high = { .d = twop84 };
+	union { uint64_t x; double d; } low = { .d = twop52 };
+	
+	high.x |= a >> 32;
+	low.x |= a & UINT64_C(0x00000000ffffffff);
+	
+	const double result = (high.d - twop84_plus_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.
+ */ 
+
+COMPILER_RT_ABI double
+__floatundidf(du_int a)
+{
+    if (a == 0)
+        return 0.0;
+    const unsigned N = sizeof(du_int) * CHAR_BIT;
+    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 = (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 = ((e + 1023) << 20)      |        /* exponent */
+                ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */
+    fb.u.low = (su_int)a;                         /* mantissa-low  */
+    return fb.f;
+}
+#endif