1 files changed, 103 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/floatdidf.c b/compiler-rt/lib/builtins/floatdidf.c
new file mode 100644
index 000000000000..8f887314b9e1
--- /dev/null
+++ b/compiler-rt/lib/builtins/floatdidf.c
@@ -0,0 +1,103 @@
+//===-- floatdidf.c - Implement __floatdidf -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __floatdidf for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.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.
+
+COMPILER_RT_ABI double __floatdidf(di_int a) {
+  static const double twop52 = 4503599627370496.0; // 0x1.0p52
+  static const double twop32 = 4294967296.0;       // 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.
+
+COMPILER_RT_ABI 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.s.high = ((su_int)s & 0x80000000) |        // sign
+                ((e + 1023) << 20) |              // exponent
+                ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high
+  fb.u.s.low = (su_int)a;                         // mantissa-low
+  return fb.f;
+}
+#endif
+
+#if defined(__ARM_EABI__)
+#if defined(COMPILER_RT_ARMHF_TARGET)
+AEABI_RTABI double __aeabi_l2d(di_int a) { return __floatdidf(a); }
+#else
+COMPILER_RT_ALIAS(__floatdidf, __aeabi_l2d)
+#endif
+#endif