Initial import of compiler-rt.
-
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@74292 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/floatundidf.c b/lib/floatundidf.c
new file mode 100644
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--- /dev/null
+++ b/lib/floatundidf.c
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+//===-- floatundidf.c - Implement __floatundidf ---------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __floatundidf 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
+// du_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
+__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.
+
+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
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