Simplify LLVM's APInt and APFloat for use in Subzero.

src/IceAPFloat.h

+//===-- subzero/src/IceAPFloat.h - Constant float conversions --*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements a class to represent Subzero float and double
+/// values.
+///
+/// Note: This is a simplified version of
+/// llvm/include/llvm/ADT/APFloat.h for use with Subzero.
+//===----------------------------------------------------------------------===//
+
+#ifndef SUBZERO_SRC_ICEAPFLOAT_H
+#define SUBZERO_SRC_ICEAPFLOAT_H
+
+#include "IceAPInt.h"
+
+namespace Ice {
+
+template <typename IntType, typename FpType>
+inline FpType convertAPIntToFp(const APInt &Int) {
+  static_assert(sizeof(IntType) == sizeof(FpType),
+                "IntType and FpType should be the same width");
+  assert(Int.getBitWidth() == sizeof(IntType) * CHAR_BIT);
+  union {
+    IntType IntValue;
+    FpType FpValue;
+  } Converter;
+  Converter.IntValue = static_cast<IntType>(Int.getRawData());
+  return Converter.FpValue;
+}
+
+} // end of namespace Ice
+
+#endif //  SUBZERO_SRC_ICEAPFLOAT_H