llvm/lib/Support/APSInt.cpp

   1 //===-- llvm/ADT/APSInt.cpp - Arbitrary Precision Signed Int ---*- C++ -*--===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the APSInt class, which is a simple class that
  10 // represents an arbitrary sized integer that knows its signedness.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/ADT/APSInt.h"
  15 #include "llvm/ADT/FoldingSet.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include <cassert>
  18
  19 using namespace llvm;
  20
  21 APSInt::APSInt(StringRef Str) {
  22   assert(!Str.empty() && "Invalid string length");
  23
  24   // (Over-)estimate the required number of bits.
  25   unsigned NumBits = ((Str.size() * 64) / 19) + 2;
  26   APInt Tmp(NumBits, Str, /*radix=*/10);
  27   if (Str[0] == '-') {
  28     unsigned MinBits = Tmp.getSignificantBits();
  29     if (MinBits < NumBits)
  30       Tmp = Tmp.trunc(std::max<unsigned>(1, MinBits));
  31     *this = APSInt(Tmp, /*isUnsigned=*/false);
  32     return;
  33   }
  34   unsigned ActiveBits = Tmp.getActiveBits();
  35   if (ActiveBits < NumBits)
  36     Tmp = Tmp.trunc(std::max<unsigned>(1, ActiveBits));
  37   *this = APSInt(Tmp, /*isUnsigned=*/true);
  38 }
  39
  40 void APSInt::Profile(FoldingSetNodeID& ID) const {
  41   ID.AddInteger((unsigned) (IsUnsigned ? 1 : 0));
  42   APInt::Profile(ID);
  43 }