--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/llvm/lib/Support/APSInt.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,42 @@
+//===-- llvm/ADT/APSInt.cpp - Arbitrary Precision Signed Int ---*- 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 the APSInt class, which is a simple class that
+// represents an arbitrary sized integer that knows its signedness.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/APSInt.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/StringRef.h"
+
+using namespace llvm;
+
+APSInt::APSInt(StringRef Str) {
+  assert(!Str.empty() && "Invalid string length");
+
+  // (Over-)estimate the required number of bits.
+  unsigned NumBits = ((Str.size() * 64) / 19) + 2;
+  APInt Tmp(NumBits, Str, /*radix=*/10);
+  if (Str[0] == '-') {
+    unsigned MinBits = Tmp.getMinSignedBits();
+    if (MinBits > 0 && MinBits < NumBits)
+      Tmp = Tmp.trunc(MinBits);
+    *this = APSInt(Tmp, /*isUnsigned=*/false);
+    return;
+  }
+  unsigned ActiveBits = Tmp.getActiveBits();
+  if (ActiveBits > 0 && ActiveBits < NumBits)
+    Tmp = Tmp.trunc(ActiveBits);
+  *this = APSInt(Tmp, /*isUnsigned=*/true);
+}
+
+void APSInt::Profile(FoldingSetNodeID& ID) const {
+  ID.AddInteger((unsigned) (IsUnsigned ? 1 : 0));
+  APInt::Profile(ID);
+}