1 files changed, 75 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/floatuntitf.c b/compiler-rt/lib/builtins/floatuntitf.c
new file mode 100644
index 000000000000..d308d3118d03
--- /dev/null
+++ b/compiler-rt/lib/builtins/floatuntitf.c
@@ -0,0 +1,75 @@
+//===-- lib/floatuntitf.c - uint128 -> quad-precision conversion --*- C -*-===//
+//
+// 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 tu_int to quad-precision conversion for the
+// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
+// mode.
+//
+//===----------------------------------------------------------------------===//
+
+#define QUAD_PRECISION
+#include "fp_lib.h"
+#include "int_lib.h"
+
+// Returns: convert a tu_int to a fp_t, rounding toward even.
+
+// Assumption: fp_t is a IEEE 128 bit floating point type
+//             tu_int is a 128 bit integral type
+
+// seee eeee eeee eeee mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm
+// mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm
+// mmmm mmmm mmmm
+
+#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
+COMPILER_RT_ABI fp_t __floatuntitf(tu_int a) {
+  if (a == 0)
+    return 0.0;
+  const unsigned N = sizeof(tu_int) * CHAR_BIT;
+  int sd = N - __clzti2(a); // number of significant digits
+  int e = sd - 1;           // exponent
+  if (sd > LDBL_MANT_DIG) {
+    //  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
+    //  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
+    //                                                12345678901234567890123456
+    //  1 = msb 1 bit
+    //  P = bit LDBL_MANT_DIG-1 bits to the right of 1
+    //  Q = bit LDBL_MANT_DIG bits to the right of 1
+    //  R = "or" of all bits to the right of Q
+    switch (sd) {
+    case LDBL_MANT_DIG + 1:
+      a <<= 1;
+      break;
+    case LDBL_MANT_DIG + 2:
+      break;
+    default:
+      a = (a >> (sd - (LDBL_MANT_DIG + 2))) |
+          ((a & ((tu_int)(-1) >> ((N + LDBL_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 LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits
+    if (a & ((tu_int)1 << LDBL_MANT_DIG)) {
+      a >>= 1;
+      ++e;
+    }
+    // a is now rounded to LDBL_MANT_DIG bits
+  } else {
+    a <<= (LDBL_MANT_DIG - sd);
+    // a is now rounded to LDBL_MANT_DIG bits
+  }
+
+  long_double_bits fb;
+  fb.u.high.all = (du_int)(e + 16383) << 48             // exponent
+                  | ((a >> 64) & 0x0000ffffffffffffLL); // significand
+  fb.u.low.all = (du_int)(a);
+  return fb.f;
+}
+
+#endif