1 files changed, 46 insertions, 0 deletions
diff --git a/contrib/llvm-project/compiler-rt/lib/builtins/ppc/floattitf.c b/contrib/llvm-project/compiler-rt/lib/builtins/ppc/floattitf.c
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index 000000000000..6deac6498128
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+++ b/contrib/llvm-project/compiler-rt/lib/builtins/ppc/floattitf.c
@@ -0,0 +1,46 @@
+//===-- lib/builtins/ppc/floattitf.c - Convert int128->long double -*-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 converting a signed 128 bit integer to a 128bit IBM /
+// PowerPC long double (double-double) value.
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdint.h>
+
+// Conversions from signed and unsigned 64-bit int to long double.
+long double __floatditf(int64_t);
+long double __floatunditf(uint64_t);
+
+// Convert a signed 128-bit integer to long double.
+// This uses the following property:  Let hi and lo be 64-bits each,
+// and let signed_val_k() and unsigned_val_k() be the value of the
+// argument interpreted as a signed or unsigned k-bit integer. Then,
+//
+// signed_val_128(hi,lo) = signed_val_64(hi) * 2^64 + unsigned_val_64(lo)
+// = (long double)hi * 2^64 + (long double)lo,
+//
+// where (long double)hi and (long double)lo are signed and
+// unsigned 64-bit integer to long double conversions, respectively.
+long double __floattitf(__int128_t arg) {
+  // Split the int128 argument into 64-bit high and low int64 parts.
+  int64_t ArgHiPart = (int64_t)(arg >> 64);
+  uint64_t ArgLoPart = (uint64_t)arg;
+
+  // Convert each 64-bit part into long double. The high part
+  // must be a signed conversion and the low part an unsigned conversion
+  // to ensure the correct result.
+  long double ConvertedHiPart = __floatditf(ArgHiPart);
+  long double ConvertedLoPart = __floatunditf(ArgLoPart);
+
+  // The low bit of ArgHiPart corresponds to the 2^64 bit in arg.
+  // Multiply the high part by 2^64 to undo the right shift by 64-bits
+  // done in the splitting. Then, add to the low part to obtain the
+  // final result.
+  return ((ConvertedHiPart * 0x1.0p64) + ConvertedLoPart);
+}